initial commit

ayu-highlight.css

@@ -0,0 +1,71 @@
+/*
+Based off of the Ayu theme
+Original by Dempfi (https://github.com/dempfi/ayu)
+*/
+
+.hljs {
+  display: block;
+  overflow-x: auto;
+  background: #191f26;
+  color: #e6e1cf;
+  padding: 0.5em;
+}
+
+.hljs-comment,
+.hljs-quote,
+.hljs-meta {
+  color: #5c6773;
+  font-style: italic;
+}
+
+.hljs-variable,
+.hljs-template-variable,
+.hljs-attribute,
+.hljs-attr,
+.hljs-regexp,
+.hljs-link,
+.hljs-selector-id,
+.hljs-selector-class {
+  color: #ff7733;
+}
+
+.hljs-number,
+.hljs-builtin-name,
+.hljs-literal,
+.hljs-type,
+.hljs-params {
+  color: #ffee99;
+}
+
+.hljs-string,
+.hljs-bullet {
+  color: #b8cc52;
+}
+
+.hljs-title,
+.hljs-built_in,
+.hljs-section {
+  color: #ffb454;
+}
+
+.hljs-keyword,
+.hljs-selector-tag,
+.hljs-symbol {
+  color: #ff7733;
+}
+
+.hljs-name {
+    color: #36a3d9;
+}
+
+.hljs-tag {
+    color: #00568d;
+}
+
+.hljs-emphasis {
+  font-style: italic;
+}
+
+.hljs-strong {
+  font-weight: bold;
+}

book.js

@@ -0,0 +1,611 @@
+"use strict";
+
+// Fix back button cache problem
+window.onunload = function () { };
+
+// Global variable, shared between modules
+function playpen_text(playpen) {
+    let code_block = playpen.querySelector("code");
+
+    if (window.ace && code_block.classList.contains("editable")) {
+        let editor = window.ace.edit(code_block);
+        return editor.getValue();
+    } else {
+        return code_block.textContent;
+    }
+}
+
+(function codeSnippets() {
+    // Hide Rust code lines prepended with a specific character
+    var hiding_character = "#";
+
+    function fetch_with_timeout(url, options, timeout = 6000) {
+        return Promise.race([
+            fetch(url, options),
+            new Promise((_, reject) => setTimeout(() => reject(new Error('timeout')), timeout))
+        ]);
+    }
+
+    var playpens = Array.from(document.querySelectorAll(".playpen"));
+    if (playpens.length > 0) {
+        fetch_with_timeout("https://play.rust-lang.org/meta/crates", {
+            headers: {
+                'Content-Type': "application/json",
+            },
+            method: 'POST',
+            mode: 'cors',
+        })
+        .then(response => response.json())
+        .then(response => {
+            // get list of crates available in the rust playground
+            let playground_crates = response.crates.map(item => item["id"]);
+            playpens.forEach(block => handle_crate_list_update(block, playground_crates));
+        });
+    }
+
+    function handle_crate_list_update(playpen_block, playground_crates) {
+        // update the play buttons after receiving the response
+        update_play_button(playpen_block, playground_crates);
+
+        // and install on change listener to dynamically update ACE editors
+        if (window.ace) {
+            let code_block = playpen_block.querySelector("code");
+            if (code_block.classList.contains("editable")) {
+                let editor = window.ace.edit(code_block);
+                editor.addEventListener("change", function (e) {
+                    update_play_button(playpen_block, playground_crates);
+                });
+            }
+        }
+    }
+
+    // updates the visibility of play button based on `no_run` class and
+    // used crates vs ones available on http://play.rust-lang.org
+    function update_play_button(pre_block, playground_crates) {
+        var play_button = pre_block.querySelector(".play-button");
+
+        // skip if code is `no_run`
+        if (pre_block.querySelector('code').classList.contains("no_run")) {
+            play_button.classList.add("hidden");
+            return;
+        }
+
+        // get list of `extern crate`'s from snippet
+        var txt = playpen_text(pre_block);
+        var re = /extern\s+crate\s+([a-zA-Z_0-9]+)\s*;/g;
+        var snippet_crates = [];
+        var item;
+        while (item = re.exec(txt)) {
+            snippet_crates.push(item[1]);
+        }
+
+        // check if all used crates are available on play.rust-lang.org
+        var all_available = snippet_crates.every(function (elem) {
+            return playground_crates.indexOf(elem) > -1;
+        });
+
+        if (all_available) {
+            play_button.classList.remove("hidden");
+        } else {
+            play_button.classList.add("hidden");
+        }
+    }
+
+    function run_rust_code(code_block) {
+        var result_block = code_block.querySelector(".result");
+        if (!result_block) {
+            result_block = document.createElement('code');
+            result_block.className = 'result hljs language-bash';
+
+            code_block.append(result_block);
+        }
+
+        let text = playpen_text(code_block);
+
+        var params = {
+            channel: "stable",
+            mode: "debug",
+            edition: "2018",
+            crateType: "bin",
+            tests: false,
+            code: text
+        };
+
+        if (text.indexOf("#![feature") !== -1) {
+            params.channel = "nightly";
+        }
+
+        if (text.indexOf("#[test]") !== -1) {
+            params.tests = "true";
+        }
+
+        if (text.indexOf("#![crate_type=\"lib\"]") !== -1) {
+            params.crateType = "lib";
+        }
+
+        result_block.innerText = "Running...";
+
+        fetch_with_timeout("https://play.rust-lang.org/execute", {
+            headers: {
+                'Content-Type': "application/json",
+            },
+            method: 'POST',
+            mode: 'cors',
+            body: JSON.stringify(params)
+        })
+        .then(response => response.json())
+        .then(response => result_block.innerText = response.stderr + "\n\n" + response.stdout)
+        .catch(error => result_block.innerText = "Playground Communication: " + error.message);
+    }
+
+    // Syntax highlighting Configuration
+    hljs.configure({
+        tabReplace: '    ', // 4 spaces
+        languages: [],      // Languages used for auto-detection
+    });
+
+    if (window.ace) {
+        // language-rust class needs to be removed for editable
+        // blocks or highlightjs will capture events
+        Array
+            .from(document.querySelectorAll('code.editable'))
+            .forEach(function (block) { block.classList.remove('language-rust'); });
+
+        Array
+            .from(document.querySelectorAll('code:not(.editable)'))
+            .forEach(function (block) { hljs.highlightBlock(block); });
+    } else {
+        Array
+            .from(document.querySelectorAll('code'))
+            .forEach(function (block) { hljs.highlightBlock(block); });
+    }
+
+    // Adding the hljs class gives code blocks the color css
+    // even if highlighting doesn't apply
+    Array
+        .from(document.querySelectorAll('code'))
+        .forEach(function (block) { block.classList.add('hljs'); });
+
+    Array.from(document.querySelectorAll("code.language-rust")).forEach(function (block) {
+
+        var code_block = block;
+        var pre_block = block.parentNode;
+        // hide lines
+        var lines = code_block.innerHTML.split("\n");
+        var first_non_hidden_line = false;
+        var lines_hidden = false;
+        var trimmed_line = "";
+
+        for (var n = 0; n < lines.length; n++) {
+            trimmed_line = lines[n].trim();
+            if (trimmed_line[0] == hiding_character && trimmed_line[1] != hiding_character) {
+                if (first_non_hidden_line) {
+                    lines[n] = "<span class=\"hidden\">" + "\n" + lines[n].replace(/(\s*)# ?/, "$1") + "</span>";
+                }
+                else {
+                    lines[n] = "<span class=\"hidden\">" + lines[n].replace(/(\s*)# ?/, "$1") + "\n" + "</span>";
+                }
+                lines_hidden = true;
+            }
+            else if (first_non_hidden_line) {
+                lines[n] = "\n" + lines[n];
+            }
+            else {
+                first_non_hidden_line = true;
+            }
+            if (trimmed_line[0] == hiding_character && trimmed_line[1] == hiding_character) {
+                lines[n] = lines[n].replace("##", "#")
+            }
+        }
+        code_block.innerHTML = lines.join("");
+
+        // If no lines were hidden, return
+        if (!lines_hidden) { return; }
+
+        var buttons = document.createElement('div');
+        buttons.className = 'buttons';
+        buttons.innerHTML = "<button class=\"fa fa-expand\" title=\"Show hidden lines\" aria-label=\"Show hidden lines\"></button>";
+
+        // add expand button
+        pre_block.insertBefore(buttons, pre_block.firstChild);
+
+        pre_block.querySelector('.buttons').addEventListener('click', function (e) {
+            if (e.target.classList.contains('fa-expand')) {
+                var lines = pre_block.querySelectorAll('span.hidden');
+
+                e.target.classList.remove('fa-expand');
+                e.target.classList.add('fa-compress');
+                e.target.title = 'Hide lines';
+                e.target.setAttribute('aria-label', e.target.title);
+
+                Array.from(lines).forEach(function (line) {
+                    line.classList.remove('hidden');
+                    line.classList.add('unhidden');
+                });
+            } else if (e.target.classList.contains('fa-compress')) {
+                var lines = pre_block.querySelectorAll('span.unhidden');
+
+                e.target.classList.remove('fa-compress');
+                e.target.classList.add('fa-expand');
+                e.target.title = 'Show hidden lines';
+                e.target.setAttribute('aria-label', e.target.title);
+
+                Array.from(lines).forEach(function (line) {
+                    line.classList.remove('unhidden');
+                    line.classList.add('hidden');
+                });
+            }
+        });
+    });
+
+    Array.from(document.querySelectorAll('pre code')).forEach(function (block) {
+        var pre_block = block.parentNode;
+        if (!pre_block.classList.contains('playpen')) {
+            var buttons = pre_block.querySelector(".buttons");
+            if (!buttons) {
+                buttons = document.createElement('div');
+                buttons.className = 'buttons';
+                pre_block.insertBefore(buttons, pre_block.firstChild);
+            }
+
+            var clipButton = document.createElement('button');
+            clipButton.className = 'fa fa-copy clip-button';
+            clipButton.title = 'Copy to clipboard';
+            clipButton.setAttribute('aria-label', clipButton.title);
+            clipButton.innerHTML = '<i class=\"tooltiptext\"></i>';
+
+            buttons.insertBefore(clipButton, buttons.firstChild);
+        }
+    });
+
+    // Process playpen code blocks
+    Array.from(document.querySelectorAll(".playpen")).forEach(function (pre_block) {
+        // Add play button
+        var buttons = pre_block.querySelector(".buttons");
+        if (!buttons) {
+            buttons = document.createElement('div');
+            buttons.className = 'buttons';
+            pre_block.insertBefore(buttons, pre_block.firstChild);
+        }
+
+        var runCodeButton = document.createElement('button');
+        runCodeButton.className = 'fa fa-play play-button';
+        runCodeButton.hidden = true;
+        runCodeButton.title = 'Run this code';
+        runCodeButton.setAttribute('aria-label', runCodeButton.title);
+
+        var copyCodeClipboardButton = document.createElement('button');
+        copyCodeClipboardButton.className = 'fa fa-copy clip-button';
+        copyCodeClipboardButton.innerHTML = '<i class="tooltiptext"></i>';
+        copyCodeClipboardButton.title = 'Copy to clipboard';
+        copyCodeClipboardButton.setAttribute('aria-label', copyCodeClipboardButton.title);
+
+        buttons.insertBefore(runCodeButton, buttons.firstChild);
+        buttons.insertBefore(copyCodeClipboardButton, buttons.firstChild);
+
+        runCodeButton.addEventListener('click', function (e) {
+            run_rust_code(pre_block);
+        });
+
+        let code_block = pre_block.querySelector("code");
+        if (window.ace && code_block.classList.contains("editable")) {
+            var undoChangesButton = document.createElement('button');
+            undoChangesButton.className = 'fa fa-history reset-button';
+            undoChangesButton.title = 'Undo changes';
+            undoChangesButton.setAttribute('aria-label', undoChangesButton.title);
+
+            buttons.insertBefore(undoChangesButton, buttons.firstChild);
+
+            undoChangesButton.addEventListener('click', function () {
+                let editor = window.ace.edit(code_block);
+                editor.setValue(editor.originalCode);
+                editor.clearSelection();
+            });
+        }
+    });
+})();
+
+(function themes() {
+    var html = document.querySelector('html');
+    var themeToggleButton = document.getElementById('theme-toggle');
+    var themePopup = document.getElementById('theme-list');
+    var themeColorMetaTag = document.querySelector('meta[name="theme-color"]');
+    var stylesheets = {
+        ayuHighlight: document.querySelector("[href$='ayu-highlight.css']"),
+        tomorrowNight: document.querySelector("[href$='tomorrow-night.css']"),
+        highlight: document.querySelector("[href$='highlight.css']"),
+    };
+
+    function showThemes() {
+        themePopup.style.display = 'block';
+        themeToggleButton.setAttribute('aria-expanded', true);
+        themePopup.querySelector("button#" + document.body.className).focus();
+    }
+
+    function hideThemes() {
+        themePopup.style.display = 'none';
+        themeToggleButton.setAttribute('aria-expanded', false);
+        themeToggleButton.focus();
+    }
+
+    function set_theme(theme) {
+        let ace_theme;
+
+        if (theme == 'coal' || theme == 'navy') {
+            stylesheets.ayuHighlight.disabled = true;
+            stylesheets.tomorrowNight.disabled = false;
+            stylesheets.highlight.disabled = true;
+
+            ace_theme = "ace/theme/tomorrow_night";
+        } else if (theme == 'ayu') {
+            stylesheets.ayuHighlight.disabled = false;
+            stylesheets.tomorrowNight.disabled = true;
+            stylesheets.highlight.disabled = true;
+
+            ace_theme = "ace/theme/tomorrow_night";
+        } else {
+            stylesheets.ayuHighlight.disabled = true;
+            stylesheets.tomorrowNight.disabled = true;
+            stylesheets.highlight.disabled = false;
+
+            ace_theme = "ace/theme/dawn";
+        }
+
+        setTimeout(function () {
+            themeColorMetaTag.content = getComputedStyle(document.body).backgroundColor;
+        }, 1);
+
+        if (window.ace && window.editors) {
+            window.editors.forEach(function (editor) {
+                editor.setTheme(ace_theme);
+            });
+        }
+
+        var previousTheme;
+        try { previousTheme = localStorage.getItem('mdbook-theme'); } catch (e) { }
+        if (previousTheme === null || previousTheme === undefined) { previousTheme = default_theme; }
+
+        try { localStorage.setItem('mdbook-theme', theme); } catch (e) { }
+
+        document.body.className = theme;
+        html.classList.remove(previousTheme);
+        html.classList.add(theme);
+    }
+
+    // Set theme
+    var theme;
+    try { theme = localStorage.getItem('mdbook-theme'); } catch(e) { }
+    if (theme === null || theme === undefined) { theme = default_theme; }
+
+    set_theme(theme);
+
+    themeToggleButton.addEventListener('click', function () {
+        if (themePopup.style.display === 'block') {
+            hideThemes();
+        } else {
+            showThemes();
+        }
+    });
+
+    themePopup.addEventListener('click', function (e) {
+        var theme = e.target.id || e.target.parentElement.id;
+        set_theme(theme);
+    });
+
+    themePopup.addEventListener('focusout', function(e) {
+        // e.relatedTarget is null in Safari and Firefox on macOS (see workaround below)
+        if (!!e.relatedTarget && !themeToggleButton.contains(e.relatedTarget) && !themePopup.contains(e.relatedTarget)) {
+            hideThemes();
+        }
+    });
+
+    // Should not be needed, but it works around an issue on macOS & iOS: https://github.com/rust-lang-nursery/mdBook/issues/628
+    document.addEventListener('click', function(e) {
+        if (themePopup.style.display === 'block' && !themeToggleButton.contains(e.target) && !themePopup.contains(e.target)) {
+            hideThemes();
+        }
+    });
+
+    document.addEventListener('keydown', function (e) {
+        if (e.altKey || e.ctrlKey || e.metaKey || e.shiftKey) { return; }
+        if (!themePopup.contains(e.target)) { return; }
+
+        switch (e.key) {
+            case 'Escape':
+                e.preventDefault();
+                hideThemes();
+                break;
+            case 'ArrowUp':
+                e.preventDefault();
+                var li = document.activeElement.parentElement;
+                if (li && li.previousElementSibling) {
+                    li.previousElementSibling.querySelector('button').focus();
+                }
+                break;
+            case 'ArrowDown':
+                e.preventDefault();
+                var li = document.activeElement.parentElement;
+                if (li && li.nextElementSibling) {
+                    li.nextElementSibling.querySelector('button').focus();
+                }
+                break;
+            case 'Home':
+                e.preventDefault();
+                themePopup.querySelector('li:first-child button').focus();
+                break;
+            case 'End':
+                e.preventDefault();
+                themePopup.querySelector('li:last-child button').focus();
+                break;
+        }
+    });
+})();
+
+(function sidebar() {
+    var html = document.querySelector("html");
+    var sidebar = document.getElementById("sidebar");
+    var sidebarLinks = document.querySelectorAll('#sidebar a');
+    var sidebarToggleButton = document.getElementById("sidebar-toggle");
+    var firstContact = null;
+
+    function showSidebar() {
+        html.classList.remove('sidebar-hidden')
+        html.classList.add('sidebar-visible');
+        Array.from(sidebarLinks).forEach(function (link) {
+            link.setAttribute('tabIndex', 0);
+        });
+        sidebarToggleButton.setAttribute('aria-expanded', true);
+        sidebar.setAttribute('aria-hidden', false);
+        try { localStorage.setItem('mdbook-sidebar', 'visible'); } catch (e) { }
+    }
+
+    function hideSidebar() {
+        html.classList.remove('sidebar-visible')
+        html.classList.add('sidebar-hidden');
+        Array.from(sidebarLinks).forEach(function (link) {
+            link.setAttribute('tabIndex', -1);
+        });
+        sidebarToggleButton.setAttribute('aria-expanded', false);
+        sidebar.setAttribute('aria-hidden', true);
+        try { localStorage.setItem('mdbook-sidebar', 'hidden'); } catch (e) { }
+    }
+
+    // Toggle sidebar
+    sidebarToggleButton.addEventListener('click', function sidebarToggle() {
+        if (html.classList.contains("sidebar-hidden")) {
+            showSidebar();
+        } else if (html.classList.contains("sidebar-visible")) {
+            hideSidebar();
+        } else {
+            if (getComputedStyle(sidebar)['transform'] === 'none') {
+                hideSidebar();
+            } else {
+                showSidebar();
+            }
+        }
+    });
+
+    document.addEventListener('touchstart', function (e) {
+        firstContact = {
+            x: e.touches[0].clientX,
+            time: Date.now()
+        };
+    }, { passive: true });
+
+    document.addEventListener('touchmove', function (e) {
+        if (!firstContact)
+            return;
+
+        var curX = e.touches[0].clientX;
+        var xDiff = curX - firstContact.x,
+            tDiff = Date.now() - firstContact.time;
+
+        if (tDiff < 250 && Math.abs(xDiff) >= 150) {
+            if (xDiff >= 0 && firstContact.x < Math.min(document.body.clientWidth * 0.25, 300))
+                showSidebar();
+            else if (xDiff < 0 && curX < 300)
+                hideSidebar();
+
+            firstContact = null;
+        }
+    }, { passive: true });
+
+    // Scroll sidebar to current active section
+    var activeSection = sidebar.querySelector(".active");
+    if (activeSection) {
+        sidebar.scrollTop = activeSection.offsetTop;
+    }
+})();
+
+(function chapterNavigation() {
+    document.addEventListener('keydown', function (e) {
+        if (e.altKey || e.ctrlKey || e.metaKey || e.shiftKey) { return; }
+        if (window.search && window.search.hasFocus()) { return; }
+
+        switch (e.key) {
+            case 'ArrowRight':
+                e.preventDefault();
+                var nextButton = document.querySelector('.nav-chapters.next');
+                if (nextButton) {
+                    window.location.href = nextButton.href;
+                }
+                break;
+            case 'ArrowLeft':
+                e.preventDefault();
+                var previousButton = document.querySelector('.nav-chapters.previous');
+                if (previousButton) {
+                    window.location.href = previousButton.href;
+                }
+                break;
+        }
+    });
+})();
+
+(function clipboard() {
+    var clipButtons = document.querySelectorAll('.clip-button');
+
+    function hideTooltip(elem) {
+        elem.firstChild.innerText = "";
+        elem.className = 'fa fa-copy clip-button';
+    }
+
+    function showTooltip(elem, msg) {
+        elem.firstChild.innerText = msg;
+        elem.className = 'fa fa-copy tooltipped';
+    }
+
+    var clipboardSnippets = new Clipboard('.clip-button', {
+        text: function (trigger) {
+            hideTooltip(trigger);
+            let playpen = trigger.closest("pre");
+            return playpen_text(playpen);
+        }
+    });
+
+    Array.from(clipButtons).forEach(function (clipButton) {
+        clipButton.addEventListener('mouseout', function (e) {
+            hideTooltip(e.currentTarget);
+        });
+    });
+
+    clipboardSnippets.on('success', function (e) {
+        e.clearSelection();
+        showTooltip(e.trigger, "Copied!");
+    });
+
+    clipboardSnippets.on('error', function (e) {
+        showTooltip(e.trigger, "Clipboard error!");
+    });
+})();
+
+(function scrollToTop () {
+    var menuTitle = document.querySelector('.menu-title');
+
+    menuTitle.addEventListener('click', function () {
+        document.scrollingElement.scrollTo({ top: 0, behavior: 'smooth' });
+    });
+})();
+
+(function autoHideMenu() {
+    var menu = document.getElementById('menu-bar');
+
+    var previousScrollTop = document.scrollingElement.scrollTop;
+
+    document.addEventListener('scroll', function () {
+        if (menu.classList.contains('folded') && document.scrollingElement.scrollTop < previousScrollTop) {
+            menu.classList.remove('folded');
+        } else if (!menu.classList.contains('folded') && document.scrollingElement.scrollTop > previousScrollTop) {
+            menu.classList.add('folded');
+        }
+
+        if (!menu.classList.contains('bordered') && document.scrollingElement.scrollTop > 0) {
+            menu.classList.add('bordered');
+        }
+
+        if (menu.classList.contains('bordered') && document.scrollingElement.scrollTop === 0) {
+            menu.classList.remove('bordered');
+        }
+
+        previousScrollTop = document.scrollingElement.scrollTop;
+    }, { passive: true });
+})();

css/chrome.css

@@ -0,0 +1,420 @@
+/* CSS for UI elements (a.k.a. chrome) */
+
+@import 'variables.css';
+
+::-webkit-scrollbar {
+    background: var(--bg);
+}
+::-webkit-scrollbar-thumb {
+    background: var(--scrollbar);
+}
+
+#searchresults a,
+.content a:link,
+a:visited,
+a > .hljs {
+    color: var(--links);
+}
+
+/* Menu Bar */
+
+#menu-bar {
+    position: -webkit-sticky;
+    position: sticky;
+    top: 0;
+    z-index: 101;
+    margin: auto calc(0px - var(--page-padding));
+}
+#menu-bar > #menu-bar-sticky-container {
+    display: flex;
+    flex-wrap: wrap;
+    background-color: var(--bg);
+    border-bottom-color: var(--bg);
+    border-bottom-width: 1px;
+    border-bottom-style: solid;
+}
+.js #menu-bar > #menu-bar-sticky-container {
+    transition: transform 0.3s;
+}
+#menu-bar.bordered > #menu-bar-sticky-container  {
+    border-bottom-color: var(--table-border-color);
+}
+#menu-bar i, #menu-bar .icon-button {
+    position: relative;
+    padding: 0 8px;
+    z-index: 10;
+    line-height: 50px;
+    cursor: pointer;
+    transition: color 0.5s;
+}
+@media only screen and (max-width: 420px) {
+    #menu-bar i, #menu-bar .icon-button {
+        padding: 0 5px;
+    }
+}
+
+.icon-button {
+    border: none;
+    background: none;
+    padding: 0;
+    color: inherit;
+}
+.icon-button i {
+    margin: 0;
+}
+
+.right-buttons {
+    margin: 0 15px;
+}
+.right-buttons a {
+    text-decoration: none;
+}
+
+html:not(.sidebar-visible) #menu-bar:not(:hover).folded > #menu-bar-sticky-container {
+    transform: translateY(-60px);
+}
+
+.left-buttons {
+    display: flex;
+    margin: 0 5px;
+}
+.no-js .left-buttons { 
+    display: none;
+}
+
+.menu-title {
+    display: inline-block;
+    font-weight: 200;
+    font-size: 20px;
+    line-height: 50px;
+    text-align: center;
+    margin: 0;
+    flex: 1;
+    white-space: nowrap;
+    overflow: hidden;
+    text-overflow: ellipsis;
+}
+.js .menu-title {
+    cursor: pointer;
+}
+
+.menu-bar,
+.menu-bar:visited,
+.nav-chapters,
+.nav-chapters:visited,
+.mobile-nav-chapters,
+.mobile-nav-chapters:visited,
+.menu-bar .icon-button,
+.menu-bar a i {
+    color: var(--icons);
+}
+
+.menu-bar i:hover,
+.menu-bar .icon-button:hover,
+.nav-chapters:hover,
+.mobile-nav-chapters i:hover {
+    color: var(--icons-hover);
+}
+
+/* Nav Icons */
+
+.nav-chapters {
+    font-size: 2.5em;
+    text-align: center;
+    text-decoration: none;
+
+    position: fixed;
+    top: 50px; /* Height of menu-bar */
+    bottom: 0;
+    margin: 0;
+    max-width: 150px;
+    min-width: 90px;
+
+    display: flex;
+    justify-content: center;
+    align-content: center;
+    flex-direction: column;
+
+    transition: color 0.5s;
+}
+
+.nav-chapters:hover { text-decoration: none; }
+
+.nav-wrapper {
+    margin-top: 50px;
+    display: none;
+}
+
+.mobile-nav-chapters { 
+    font-size: 2.5em;
+    text-align: center;
+    text-decoration: none;
+    width: 90px;
+    border-radius: 5px;
+    background-color: var(--sidebar-bg);
+}
+
+.previous {
+    float: left;
+}
+
+.next {
+    float: right;
+    right: var(--page-padding);
+}
+
+@media only screen and (max-width: 1080px) {
+    .nav-wide-wrapper { display: none; }
+    .nav-wrapper { display: block; }
+}
+
+@media only screen and (max-width: 1380px) {
+    .sidebar-visible .nav-wide-wrapper { display: none; }
+    .sidebar-visible .nav-wrapper { display: block; }
+}
+
+/* Inline code */
+
+:not(pre) > .hljs {
+    display: inline-block;
+    vertical-align: middle;
+    padding: 0.1em 0.3em;
+    border-radius: 3px;
+    color: var(--inline-code-color);
+}
+
+a:hover > .hljs {
+    text-decoration: underline;
+}
+
+pre {
+    position: relative;
+}
+pre > .buttons {
+    position: absolute;
+    z-index: 100;
+    right: 5px;
+    top: 5px;
+
+    color: var(--sidebar-fg);
+    cursor: pointer;
+}
+pre > .buttons :hover {
+    color: var(--sidebar-active);
+}
+pre > .buttons i {
+    margin-left: 8px;
+}
+pre > .buttons button {
+    color: inherit;
+    background: transparent;
+    border: none;
+    cursor: inherit;
+}
+pre > .result {
+    margin-top: 10px;
+}
+
+/* Search */
+
+#searchresults a {
+    text-decoration: none;
+}
+
+mark {
+    border-radius: 2px;
+    padding: 0 3px 1px 3px;
+    margin: 0 -3px -1px -3px;
+    background-color: var(--search-mark-bg);
+    transition: background-color 300ms linear;
+    cursor: pointer;
+}
+
+mark.fade-out {
+    background-color: rgba(0,0,0,0) !important;
+    cursor: auto;
+}
+
+.searchbar-outer {
+    margin-left: auto;
+    margin-right: auto;
+    max-width: var(--content-max-width);
+}
+
+#searchbar {
+    width: 100%;
+    margin: 5px auto 0px auto;
+    padding: 10px 16px;
+    transition: box-shadow 300ms ease-in-out;
+    border: 1px solid var(--searchbar-border-color);
+    border-radius: 3px;
+    background-color: var(--searchbar-bg);
+    color: var(--searchbar-fg);
+}
+#searchbar:focus,
+#searchbar.active {
+    box-shadow: 0 0 3px var(--searchbar-shadow-color);
+}
+
+.searchresults-header {
+    font-weight: bold;
+    font-size: 1em;
+    padding: 18px 0 0 5px;
+    color: var(--searchresults-header-fg);
+}
+
+.searchresults-outer {
+    margin-left: auto;
+    margin-right: auto;
+    max-width: var(--content-max-width);
+    border-bottom: 1px dashed var(--searchresults-border-color);
+}
+
+ul#searchresults {
+    list-style: none;
+    padding-left: 20px;
+}
+ul#searchresults li {
+    margin: 10px 0px;
+    padding: 2px;
+    border-radius: 2px;
+}
+ul#searchresults li.focus {
+    background-color: var(--searchresults-li-bg);
+}
+ul#searchresults span.teaser {
+    display: block;
+    clear: both;
+    margin: 5px 0 0 20px;
+    font-size: 0.8em;
+}
+ul#searchresults span.teaser em {
+    font-weight: bold;
+    font-style: normal;
+}
+
+/* Sidebar */
+
+.sidebar {
+    position: fixed;
+    left: 0;
+    top: 0;
+    bottom: 0;
+    width: var(--sidebar-width);
+    overflow-y: auto;
+    padding: 10px 10px;
+    font-size: 0.875em;
+    box-sizing: border-box;
+    -webkit-overflow-scrolling: touch;
+    overscroll-behavior-y: contain;
+    background-color: var(--sidebar-bg);
+    color: var(--sidebar-fg);
+}
+.js .sidebar {
+    transition: transform 0.3s; /* Animation: slide away */
+}
+.sidebar code {
+    line-height: 2em;
+}
+.sidebar-hidden .sidebar {
+    transform: translateX(calc(0px - var(--sidebar-width)));
+}
+.sidebar::-webkit-scrollbar {
+    background: var(--sidebar-bg);
+}
+.sidebar::-webkit-scrollbar-thumb {
+    background: var(--scrollbar);
+}
+
+.sidebar-visible .page-wrapper {
+    transform: translateX(var(--sidebar-width));
+}
+@media only screen and (min-width: 620px) {
+    .sidebar-visible .page-wrapper {
+        transform: none;
+        margin-left: var(--sidebar-width);
+    }
+}
+
+.chapter {
+    list-style: none outside none;
+    padding-left: 0;
+    line-height: 2.2em;
+}
+.chapter li {
+    color: var(--sidebar-non-existant);
+}
+.chapter li a {
+    color: var(--sidebar-fg);
+    display: block;
+    padding: 0;
+    text-decoration: none;
+}
+.chapter li a:hover { text-decoration: none }
+.chapter li .active,
+a:hover {
+    /* Animate color change */
+    color: var(--sidebar-active);
+}
+
+.spacer {
+    width: 100%;
+    height: 3px;
+    margin: 5px 0px;
+}
+.chapter .spacer {
+    background-color: var(--sidebar-spacer);
+}
+
+@media (-moz-touch-enabled: 1), (pointer: coarse) { 
+    .chapter li a { padding: 5px 0; }
+    .spacer { margin: 10px 0; }
+}
+
+.section {
+    list-style: none outside none;
+    padding-left: 20px;
+    line-height: 1.9em;
+}
+
+/* Theme Menu Popup */
+
+.theme-popup {
+    position: absolute;
+    left: 10px;
+    top: 50px;
+    z-index: 1000;
+    border-radius: 4px;
+    font-size: 0.7em;
+    color: var(--fg);
+    background: var(--theme-popup-bg);
+    border: 1px solid var(--theme-popup-border);
+    margin: 0;
+    padding: 0;
+    list-style: none;
+    display: none;
+}
+.theme-popup .default {
+    color: var(--icons);
+}
+.theme-popup .theme {
+    width: 100%;
+    border: 0;
+    margin: 0;
+    padding: 2px 10px;
+    line-height: 25px;
+    white-space: nowrap;
+    text-align: left;
+    cursor: pointer;
+    color: inherit;
+    background: inherit;
+    font-size: inherit;
+}
+.theme-popup .theme:hover {
+    background-color: var(--theme-hover);
+}
+.theme-popup .theme:hover:first-child,
+.theme-popup .theme:hover:last-child {
+    border-top-left-radius: inherit;
+    border-top-right-radius: inherit;
+}

css/general.css

@@ -0,0 +1,144 @@
+/* Base styles and content styles */
+
+@import 'variables.css';
+
+html {
+    font-family: "Open Sans", sans-serif;
+    color: var(--fg);
+    background-color: var(--bg);
+    text-size-adjust: none;
+}
+
+body {
+    margin: 0;
+    font-size: 1rem;
+    overflow-x: hidden;
+}
+
+code {
+    font-family: "Source Code Pro", Consolas, "Ubuntu Mono", Menlo, "DejaVu Sans Mono", monospace, monospace;
+    font-size: 0.875em; /* please adjust the ace font size accordingly in editor.js */
+}
+
+.left { float: left; }
+.right { float: right; }
+.hidden { display: none; }
+.play-button.hidden { display: none; }
+
+h2, h3 { margin-top: 2.5em; }
+h4, h5 { margin-top: 2em; }
+
+.header + .header h3,
+.header + .header h4,
+.header + .header h5 { 
+    margin-top: 1em;
+}
+
+a.header:target h1:before,
+a.header:target h2:before,
+a.header:target h3:before,
+a.header:target h4:before {
+    display: inline-block;
+    content: "»";
+    margin-left: -30px;
+    width: 30px;
+}
+
+.page {
+    outline: 0;
+    padding: 0 var(--page-padding);
+}
+.page-wrapper {
+    box-sizing: border-box;
+}
+.js .page-wrapper {
+    transition: margin-left 0.3s ease, transform 0.3s ease; /* Animation: slide away */
+}
+
+.content {
+    overflow-y: auto;
+    padding: 0 15px;
+    padding-bottom: 50px;
+}
+.content main {
+    margin-left: auto;
+    margin-right: auto;
+    max-width: var(--content-max-width);
+}
+.content a { text-decoration: none; }
+.content a:hover { text-decoration: underline; }
+.content img { max-width: 100%; }
+.content .header:link,
+.content .header:visited {
+    color: var(--fg);
+}
+.content .header:link,
+.content .header:visited:hover {
+    text-decoration: none;
+}
+
+table {
+    margin: 0 auto;
+    border-collapse: collapse;
+}
+table td {
+    padding: 3px 20px;
+    border: 1px var(--table-border-color) solid;
+}
+table thead {
+    background: var(--table-header-bg);
+}
+table thead td {
+    font-weight: 700;
+    border: none;
+}
+table thead tr {
+    border: 1px var(--table-header-bg) solid;
+}
+/* Alternate background colors for rows */
+table tbody tr:nth-child(2n) {
+    background: var(--table-alternate-bg);
+}
+
+
+blockquote {
+    margin: 20px 0;
+    padding: 0 20px;
+    color: var(--fg);
+    background-color: var(--quote-bg);
+    border-top: .1em solid var(--quote-border);
+    border-bottom: .1em solid var(--quote-border);
+}
+
+
+:not(.footnote-definition) + .footnote-definition,
+.footnote-definition + :not(.footnote-definition) {
+    margin-top: 2em;
+}
+.footnote-definition {
+    font-size: 0.9em;
+    margin: 0.5em 0;
+}
+.footnote-definition p {
+    display: inline;
+}
+
+.tooltiptext {
+    position: absolute;
+    visibility: hidden;
+    color: #fff;
+    background-color: #333;
+    transform: translateX(-50%); /* Center by moving tooltip 50% of its width left */
+    left: -8px; /* Half of the width of the icon */
+    top: -35px;
+    font-size: 0.8em;
+    text-align: center;
+    border-radius: 6px;
+    padding: 5px 8px;
+    margin: 5px;
+    z-index: 1000;
+}
+.tooltipped .tooltiptext {
+    visibility: visible;
+}
+  

css/print.css

@@ -0,0 +1,54 @@
+
+#sidebar,
+#menu-bar,
+.nav-chapters,
+.mobile-nav-chapters {
+    display: none;
+}
+
+#page-wrapper.page-wrapper {
+    transform: none;
+    margin-left: 0px;
+    overflow-y: initial;
+}
+
+#content {
+    max-width: none;
+    margin: 0;
+    padding: 0;
+}
+
+.page {
+    overflow-y: initial;
+}
+
+code {
+    background-color: #666666;
+    border-radius: 5px;
+
+    /* Force background to be printed in Chrome */
+    -webkit-print-color-adjust: exact;
+}
+
+pre > .buttons {
+    z-index: 2;
+}
+
+a, a:visited, a:active, a:hover {
+    color: #4183c4;
+    text-decoration: none;
+}
+
+h1, h2, h3, h4, h5, h6 {
+    page-break-inside: avoid;
+    page-break-after: avoid;
+}
+
+pre, code {
+    page-break-inside: avoid;
+    white-space: pre-wrap;
+}
+
+.fa {
+    display: none !important;
+}

css/variables.css

@@ -0,0 +1,210 @@
+
+/* Globals */
+
+:root {
+    --sidebar-width: 300px;
+    --page-padding: 15px;
+    --content-max-width: 750px;
+}
+
+/* Themes */
+
+.ayu {
+    --bg: hsl(210, 25%, 8%);
+    --fg: #c5c5c5;
+
+    --sidebar-bg: #14191f;
+    --sidebar-fg: #c8c9db;
+    --sidebar-non-existant: #5c6773;
+    --sidebar-active: #ffb454;
+    --sidebar-spacer: #2d334f;
+
+    --scrollbar: var(--sidebar-fg);
+
+    --icons: #737480;
+    --icons-hover: #b7b9cc;
+
+    --links: #0096cf;
+
+    --inline-code-color: #ffb454;
+
+    --theme-popup-bg: #14191f;
+    --theme-popup-border: #5c6773;
+    --theme-hover: #191f26;
+
+    --quote-bg: hsl(226, 15%, 17%);
+    --quote-border: hsl(226, 15%, 22%);
+
+    --table-border-color: hsl(210, 25%, 13%);
+    --table-header-bg: hsl(210, 25%, 28%);
+    --table-alternate-bg: hsl(210, 25%, 11%);
+
+    --searchbar-border-color: #848484;
+    --searchbar-bg: #424242;
+    --searchbar-fg: #fff;
+    --searchbar-shadow-color: #d4c89f;
+    --searchresults-header-fg: #666;
+    --searchresults-border-color: #888;
+    --searchresults-li-bg: #252932;
+    --search-mark-bg: #e3b171;
+}
+
+.coal {
+    --bg: hsl(200, 7%, 8%);
+    --fg: #98a3ad;
+
+    --sidebar-bg: #292c2f;
+    --sidebar-fg: #a1adb8;
+    --sidebar-non-existant: #505254;
+    --sidebar-active: #3473ad;
+    --sidebar-spacer: #393939;
+
+    --scrollbar: var(--sidebar-fg);
+
+    --icons: #43484d;
+    --icons-hover: #b3c0cc;
+
+    --links: #2b79a2;
+
+    --inline-code-color: #c5c8c6;;
+
+    --theme-popup-bg: #141617;
+    --theme-popup-border: #43484d;
+    --theme-hover: #1f2124;
+
+    --quote-bg: hsl(234, 21%, 18%);
+    --quote-border: hsl(234, 21%, 23%);
+
+    --table-border-color: hsl(200, 7%, 13%);
+    --table-header-bg: hsl(200, 7%, 28%);
+    --table-alternate-bg: hsl(200, 7%, 11%);
+
+    --searchbar-border-color: #aaa;
+    --searchbar-bg: #b7b7b7;
+    --searchbar-fg: #000;
+    --searchbar-shadow-color: #aaa;
+    --searchresults-header-fg: #666;
+    --searchresults-border-color: #98a3ad;
+    --searchresults-li-bg: #2b2b2f;
+    --search-mark-bg: #355c7d;
+}
+
+.light {
+    --bg: hsl(0, 0%, 100%);
+    --fg: #333333;
+
+    --sidebar-bg: #fafafa;
+    --sidebar-fg: #364149;
+    --sidebar-non-existant: #aaaaaa;
+    --sidebar-active: #008cff;
+    --sidebar-spacer: #f4f4f4;
+
+    --scrollbar: #cccccc;
+
+    --icons: #cccccc;
+    --icons-hover: #333333;
+
+    --links: #4183c4;
+
+    --inline-code-color: #6e6b5e;
+
+    --theme-popup-bg: #fafafa;
+    --theme-popup-border: #cccccc;
+    --theme-hover: #e6e6e6;
+
+    --quote-bg: hsl(197, 37%, 96%);
+    --quote-border: hsl(197, 37%, 91%);
+
+    --table-border-color: hsl(0, 0%, 95%);
+    --table-header-bg: hsl(0, 0%, 80%);
+    --table-alternate-bg: hsl(0, 0%, 97%);
+
+    --searchbar-border-color: #aaa;
+    --searchbar-bg: #fafafa;
+    --searchbar-fg: #000;
+    --searchbar-shadow-color: #aaa;
+    --searchresults-header-fg: #666;
+    --searchresults-border-color: #888;
+    --searchresults-li-bg: #e4f2fe;
+    --search-mark-bg: #a2cff5;
+}
+
+.navy {
+    --bg: hsl(226, 23%, 11%);
+    --fg: #bcbdd0;
+
+    --sidebar-bg: #282d3f;
+    --sidebar-fg: #c8c9db;
+    --sidebar-non-existant: #505274;
+    --sidebar-active: #2b79a2;
+    --sidebar-spacer: #2d334f;
+
+    --scrollbar: var(--sidebar-fg);
+
+    --icons: #737480;
+    --icons-hover: #b7b9cc;
+
+    --links: #2b79a2;
+
+    --inline-code-color: #c5c8c6;;
+
+    --theme-popup-bg: #161923;
+    --theme-popup-border: #737480;
+    --theme-hover: #282e40;
+
+    --quote-bg: hsl(226, 15%, 17%);
+    --quote-border: hsl(226, 15%, 22%);
+
+    --table-border-color: hsl(226, 23%, 16%);
+    --table-header-bg: hsl(226, 23%, 31%);
+    --table-alternate-bg: hsl(226, 23%, 14%);
+
+    --searchbar-border-color: #aaa;
+    --searchbar-bg: #aeaec6;
+    --searchbar-fg: #000;
+    --searchbar-shadow-color: #aaa;
+    --searchresults-header-fg: #5f5f71;
+    --searchresults-border-color: #5c5c68;
+    --searchresults-li-bg: #242430;
+    --search-mark-bg: #a2cff5;
+}
+
+.rust {
+    --bg: hsl(60, 9%, 87%);
+    --fg: #262625;
+
+    --sidebar-bg: #3b2e2a;
+    --sidebar-fg: #c8c9db;
+    --sidebar-non-existant: #505254;
+    --sidebar-active: #e69f67;
+    --sidebar-spacer: #45373a;
+
+    --scrollbar: var(--sidebar-fg);
+
+    --icons: #737480;
+    --icons-hover: #262625;
+
+    --links: #2b79a2;
+
+    --inline-code-color: #6e6b5e;
+
+    --theme-popup-bg: #e1e1db;
+    --theme-popup-border: #b38f6b;
+    --theme-hover: #99908a;
+
+    --quote-bg: hsl(60, 5%, 75%);
+    --quote-border: hsl(60, 5%, 70%);
+
+    --table-border-color: hsl(60, 9%, 82%);
+    --table-header-bg: #b3a497;
+    --table-alternate-bg: hsl(60, 9%, 84%);
+
+    --searchbar-border-color: #aaa;
+    --searchbar-bg: #fafafa;
+    --searchbar-fg: #000;
+    --searchbar-shadow-color: #aaa;
+    --searchresults-header-fg: #666;
+    --searchresults-border-color: #888;
+    --searchresults-li-bg: #dec2a2;
+    --search-mark-bg: #e69f67;
+}

docs/.nojekyll

@@ -0,0 +1 @@
+This file makes sure that Github Pages doesn't process mdBook's output.

editor.js

@@ -0,0 +1,27 @@
+"use strict";
+window.editors = [];
+(function(editors) {
+    if (typeof(ace) === 'undefined' || !ace) {
+        return;
+    }
+
+    Array.from(document.querySelectorAll('.editable')).forEach(function(editable) {
+        let editor = ace.edit(editable);
+            editor.setOptions({
+            highlightActiveLine: false,
+            showPrintMargin: false,
+            showLineNumbers: false,
+            showGutter: false,
+            maxLines: Infinity,
+            fontSize: "0.875em" // please adjust the font size of the code in general.styl
+        });
+
+        editor.$blockScrolling = Infinity;
+
+        editor.getSession().setMode("ace/mode/rust");
+
+        editor.originalCode = editor.getValue();
+
+        editors.push(editor);
+    });
+})(window.editors);

highlight.css

@@ -0,0 +1,69 @@
+/* Base16 Atelier Dune Light - Theme */
+/* by Bram de Haan (http://atelierbram.github.io/syntax-highlighting/atelier-schemes/dune) */
+/* Original Base16 color scheme by Chris Kempson (https://github.com/chriskempson/base16) */
+
+/* Atelier-Dune Comment */
+.hljs-comment,
+.hljs-quote {
+  color: #AAA;
+}
+
+/* Atelier-Dune Red */
+.hljs-variable,
+.hljs-template-variable,
+.hljs-attribute,
+.hljs-tag,
+.hljs-name,
+.hljs-regexp,
+.hljs-link,
+.hljs-name,
+.hljs-selector-id,
+.hljs-selector-class {
+  color: #d73737;
+}
+
+/* Atelier-Dune Orange */
+.hljs-number,
+.hljs-meta,
+.hljs-built_in,
+.hljs-builtin-name,
+.hljs-literal,
+.hljs-type,
+.hljs-params {
+  color: #b65611;
+}
+
+/* Atelier-Dune Green */
+.hljs-string,
+.hljs-symbol,
+.hljs-bullet {
+  color: #60ac39;
+}
+
+/* Atelier-Dune Blue */
+.hljs-title,
+.hljs-section {
+  color: #6684e1;
+}
+
+/* Atelier-Dune Purple */
+.hljs-keyword,
+.hljs-selector-tag {
+  color: #b854d4;
+}
+
+.hljs {
+  display: block;
+  overflow-x: auto;
+  background: #f1f1f1;
+  color: #6e6b5e;
+  padding: 0.5em;
+}
+
+.hljs-emphasis {
+  font-style: italic;
+}
+
+.hljs-strong {
+  font-weight: bold;
+}

index.html

@@ -0,0 +1,219 @@
+<!DOCTYPE HTML>
+<html lang="en" class="sidebar-visible no-js">
+    <head>
+        <!-- Book generated using mdBook -->
+        <meta charset="UTF-8">
+        <title>Chapter 1 - chainerror</title>
+        <meta content="text/html; charset=utf-8" http-equiv="Content-Type">
+        <meta name="description" content="">
+        <meta name="viewport" content="width=device-width, initial-scale=1">
+        <meta name="theme-color" content="#ffffff" />
+
+        <link rel="shortcut icon" href="favicon.png">
+        <link rel="stylesheet" href="css/variables.css">
+        <link rel="stylesheet" href="css/general.css">
+        <link rel="stylesheet" href="css/chrome.css">
+        <link rel="stylesheet" href="css/print.css" media="print">
+
+        <!-- Fonts -->
+        <link rel="stylesheet" href="FontAwesome/css/font-awesome.css">
+        <link href="https://fonts.googleapis.com/css?family=Open+Sans:300italic,400italic,600italic,700italic,800italic,400,300,600,700,800" rel="stylesheet" type="text/css">
+        <link href="https://fonts.googleapis.com/css?family=Source+Code+Pro:500" rel="stylesheet" type="text/css">
+
+        <!-- Highlight.js Stylesheets -->
+        <link rel="stylesheet" href="highlight.css">
+        <link rel="stylesheet" href="tomorrow-night.css">
+        <link rel="stylesheet" href="ayu-highlight.css">
+
+        <!-- Custom theme stylesheets -->
+        
+
+        
+    </head>
+    <body class="light">
+        <!-- Provide site root to javascript -->
+        <script type="text/javascript">
+            var path_to_root = "";
+            var default_theme = "light";
+        </script>
+
+        <!-- Work around some values being stored in localStorage wrapped in quotes -->
+        <script type="text/javascript">
+            try {
+                var theme = localStorage.getItem('mdbook-theme');
+                var sidebar = localStorage.getItem('mdbook-sidebar');
+
+                if (theme.startsWith('"') && theme.endsWith('"')) {
+                    localStorage.setItem('mdbook-theme', theme.slice(1, theme.length - 1));
+                }
+
+                if (sidebar.startsWith('"') && sidebar.endsWith('"')) {
+                    localStorage.setItem('mdbook-sidebar', sidebar.slice(1, sidebar.length - 1));
+                }
+            } catch (e) { }
+        </script>
+
+        <!-- Set the theme before any content is loaded, prevents flash -->
+        <script type="text/javascript">
+            var theme;
+            try { theme = localStorage.getItem('mdbook-theme'); } catch(e) { } 
+            if (theme === null || theme === undefined) { theme = default_theme; }
+            document.body.className = theme;
+            document.querySelector('html').className = theme + ' js';
+        </script>
+
+        <!-- Hide / unhide sidebar before it is displayed -->
+        <script type="text/javascript">
+            var html = document.querySelector('html');
+            var sidebar = 'hidden';
+            if (document.body.clientWidth >= 1080) {
+                try { sidebar = localStorage.getItem('mdbook-sidebar'); } catch(e) { }
+                sidebar = sidebar || 'visible';
+            }
+            html.classList.remove('sidebar-visible');
+            html.classList.add("sidebar-" + sidebar);
+        </script>
+
+        <nav id="sidebar" class="sidebar" aria-label="Table of contents">
+            <ol class="chapter"><li><a href="tutorial1.html"><strong aria-hidden="true">1.</strong> Chapter 1</a></li><li><a href="tutorial2.html"><strong aria-hidden="true">2.</strong> Chapter 2</a></li><li><a href="tutorial3.html"><strong aria-hidden="true">3.</strong> Chapter 3</a></li><li><a href="tutorial4.html"><strong aria-hidden="true">4.</strong> Chapter 4</a></li><li><a href="tutorial5.html"><strong aria-hidden="true">5.</strong> Chapter 5</a></li><li><a href="tutorial6.html"><strong aria-hidden="true">6.</strong> Chapter 6</a></li><li><a href="tutorial7.html"><strong aria-hidden="true">7.</strong> Chapter 7</a></li><li><a href="tutorial8.html"><strong aria-hidden="true">8.</strong> Chapter 8</a></li><li><a href="tutorial9.html"><strong aria-hidden="true">9.</strong> Chapter 9</a></li><li><a href="tutorial10.html"><strong aria-hidden="true">10.</strong> Chapter 10</a></li><li><a href="tutorial11.html"><strong aria-hidden="true">11.</strong> Chapter 11</a></li></ol>
+        </nav>
+
+        <div id="page-wrapper" class="page-wrapper">
+
+            <div class="page">
+                
+                <div id="menu-bar" class="menu-bar">
+                    <div id="menu-bar-sticky-container">
+                        <div class="left-buttons">
+                            <button id="sidebar-toggle" class="icon-button" type="button" title="Toggle Table of Contents" aria-label="Toggle Table of Contents" aria-controls="sidebar">
+                                <i class="fa fa-bars"></i>
+                            </button>
+                            <button id="theme-toggle" class="icon-button" type="button" title="Change theme" aria-label="Change theme" aria-haspopup="true" aria-expanded="false" aria-controls="theme-list">
+                                <i class="fa fa-paint-brush"></i>
+                            </button>
+                            <ul id="theme-list" class="theme-popup" aria-label="Themes" role="menu">
+                                <li role="none"><button role="menuitem" class="theme" id="light">Light (default)</button></li>
+                                <li role="none"><button role="menuitem" class="theme" id="rust">Rust</button></li>
+                                <li role="none"><button role="menuitem" class="theme" id="coal">Coal</button></li>
+                                <li role="none"><button role="menuitem" class="theme" id="navy">Navy</button></li>
+                                <li role="none"><button role="menuitem" class="theme" id="ayu">Ayu</button></li>
+                            </ul>
+                            
+                            <button id="search-toggle" class="icon-button" type="button" title="Search. (Shortkey: s)" aria-label="Toggle Searchbar" aria-expanded="false" aria-keyshortcuts="S" aria-controls="searchbar">
+                                <i class="fa fa-search"></i>
+                            </button>
+                            
+                        </div>
+
+                        <h1 class="menu-title">chainerror</h1> 
+
+                        <div class="right-buttons">
+                            <a href="print.html" title="Print this book" aria-label="Print this book">
+                                <i id="print-button" class="fa fa-print"></i>
+                            </a>
+                            
+                        </div>
+                    </div>
+                </div>
+
+                
+                <div id="search-wrapper" class="hidden">
+                    <form id="searchbar-outer" class="searchbar-outer">
+                        <input type="search" name="search" id="searchbar" name="searchbar" placeholder="Search this book ..." aria-controls="searchresults-outer" aria-describedby="searchresults-header">
+                    </form>
+                    <div id="searchresults-outer" class="searchresults-outer hidden">
+                        <div id="searchresults-header" class="searchresults-header"></div>
+                        <ul id="searchresults">
+                        </ul>
+                    </div>
+                </div>
+                
+
+                <!-- Apply ARIA attributes after the sidebar and the sidebar toggle button are added to the DOM -->
+                <script type="text/javascript">
+                    document.getElementById('sidebar-toggle').setAttribute('aria-expanded', sidebar === 'visible');
+                    document.getElementById('sidebar').setAttribute('aria-hidden', sidebar !== 'visible');
+                    Array.from(document.querySelectorAll('#sidebar a')).forEach(function(link) {
+                        link.setAttribute('tabIndex', sidebar === 'visible' ? 0 : -1);
+                    });
+                </script>
+
+                <div id="content" class="content">
+                    <main>
+                        <pre><pre class="playpen"><code class="language-rust">use std::error::Error;
+use std::result::Result;
+
+fn do_some_io() -&gt; Result&lt;(), Box&lt;Error&gt;&gt; {
+    Err(&quot;do_some_io error&quot;)?;
+    Ok(())
+}
+
+fn func2() -&gt; Result&lt;(), Box&lt;Error&gt;&gt; {
+    if let Err(_) = do_some_io() {
+        Err(&quot;func2 error&quot;)?;
+    }
+    Ok(())
+}
+
+fn func1() -&gt; Result&lt;(), Box&lt;Error&gt;&gt; {
+    if let Err(_) = func2() {
+        Err(&quot;func1 error&quot;)?;
+    }
+    Ok(())
+}
+
+fn main() -&gt; Result&lt;(), Box&lt;Error&gt;&gt; {
+    func1()
+}
+</code></pre></pre>
+
+                    </main>
+
+                    <nav class="nav-wrapper" aria-label="Page navigation">
+                        <!-- Mobile navigation buttons -->
+                        
+
+                        
+
+                        <div style="clear: both"></div>
+                    </nav>
+                </div>
+            </div>
+
+            <nav class="nav-wide-wrapper" aria-label="Page navigation">
+                
+
+                
+            </nav>
+
+        </div>
+
+        
+
+        
+
+        
+        <script src="ace.js" type="text/javascript" charset="utf-8"></script>
+        <script src="editor.js" type="text/javascript" charset="utf-8"></script>
+        <script src="mode-rust.js" type="text/javascript" charset="utf-8"></script>
+        <script src="theme-dawn.js" type="text/javascript" charset="utf-8"></script>
+        <script src="theme-tomorrow_night.js" type="text/javascript" charset="utf-8"></script>
+        
+
+        
+        <script src="elasticlunr.min.js" type="text/javascript" charset="utf-8"></script>
+        <script src="mark.min.js" type="text/javascript" charset="utf-8"></script>
+        <script src="searcher.js" type="text/javascript" charset="utf-8"></script>
+        
+
+        <script src="clipboard.min.js" type="text/javascript" charset="utf-8"></script>
+        <script src="highlight.js" type="text/javascript" charset="utf-8"></script>
+        <script src="book.js" type="text/javascript" charset="utf-8"></script>
+
+        <!-- Custom JS scripts -->
+        
+
+        
+
+    </body>
+</html>

searcher.js

@@ -0,0 +1,477 @@
+"use strict";
+window.search = window.search || {};
+(function search(search) {
+    // Search functionality
+    //
+    // You can use !hasFocus() to prevent keyhandling in your key
+    // event handlers while the user is typing their search.
+
+    if (!Mark || !elasticlunr) {
+        return;
+    }
+
+    //IE 11 Compatibility from https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/startsWith
+    if (!String.prototype.startsWith) {
+        String.prototype.startsWith = function(search, pos) {
+            return this.substr(!pos || pos < 0 ? 0 : +pos, search.length) === search;
+        };
+    }
+
+    var search_wrap = document.getElementById('search-wrapper'),
+        searchbar = document.getElementById('searchbar'),
+        searchbar_outer = document.getElementById('searchbar-outer'),
+        searchresults = document.getElementById('searchresults'),
+        searchresults_outer = document.getElementById('searchresults-outer'),
+        searchresults_header = document.getElementById('searchresults-header'),
+        searchicon = document.getElementById('search-toggle'),
+        content = document.getElementById('content'),
+
+        searchindex = null,
+        doc_urls = [],
+        results_options = {
+            teaser_word_count: 30,
+            limit_results: 30,
+        },
+        search_options = {
+            bool: "AND",
+            expand: true,
+            fields: {
+                title: {boost: 1},
+                body: {boost: 1},
+                breadcrumbs: {boost: 0}
+            }
+        },
+        mark_exclude = [],
+        marker = new Mark(content),
+        current_searchterm = "",
+        URL_SEARCH_PARAM = 'search',
+        URL_MARK_PARAM = 'highlight',
+        teaser_count = 0,
+
+        SEARCH_HOTKEY_KEYCODE = 83,
+        ESCAPE_KEYCODE = 27,
+        DOWN_KEYCODE = 40,
+        UP_KEYCODE = 38,
+        SELECT_KEYCODE = 13;
+
+    function hasFocus() {
+        return searchbar === document.activeElement;
+    }
+
+    function removeChildren(elem) {
+        while (elem.firstChild) {
+            elem.removeChild(elem.firstChild);
+        }
+    }
+
+    // Helper to parse a url into its building blocks.
+    function parseURL(url) {
+        var a =  document.createElement('a');
+        a.href = url;
+        return {
+            source: url,
+            protocol: a.protocol.replace(':',''),
+            host: a.hostname,
+            port: a.port,
+            params: (function(){
+                var ret = {};
+                var seg = a.search.replace(/^\?/,'').split('&');
+                var len = seg.length, i = 0, s;
+                for (;i<len;i++) {
+                    if (!seg[i]) { continue; }
+                    s = seg[i].split('=');
+                    ret[s[0]] = s[1];
+                }
+                return ret;
+            })(),
+            file: (a.pathname.match(/\/([^/?#]+)$/i) || [,''])[1],
+            hash: a.hash.replace('#',''),
+            path: a.pathname.replace(/^([^/])/,'/$1')
+        };
+    }
+    
+    // Helper to recreate a url string from its building blocks.
+    function renderURL(urlobject) {
+        var url = urlobject.protocol + "://" + urlobject.host;
+        if (urlobject.port != "") {
+            url += ":" + urlobject.port;
+        }
+        url += urlobject.path;
+        var joiner = "?";
+        for(var prop in urlobject.params) {
+            if(urlobject.params.hasOwnProperty(prop)) {
+                url += joiner + prop + "=" + urlobject.params[prop];
+                joiner = "&";
+            }
+        }
+        if (urlobject.hash != "") {
+            url += "#" + urlobject.hash;
+        }
+        return url;
+    }
+    
+    // Helper to escape html special chars for displaying the teasers
+    var escapeHTML = (function() {
+        var MAP = {
+            '&': '&amp;',
+            '<': '&lt;',
+            '>': '&gt;',
+            '"': '&#34;',
+            "'": '&#39;'
+        };
+        var repl = function(c) { return MAP[c]; };
+        return function(s) {
+            return s.replace(/[&<>'"]/g, repl);
+        };
+    })();
+    
+    function formatSearchMetric(count, searchterm) {
+        if (count == 1) {
+            return count + " search result for '" + searchterm + "':";
+        } else if (count == 0) {
+            return "No search results for '" + searchterm + "'.";
+        } else {
+            return count + " search results for '" + searchterm + "':";
+        }
+    }
+    
+    function formatSearchResult(result, searchterms) {
+        var teaser = makeTeaser(escapeHTML(result.doc.body), searchterms);
+        teaser_count++;
+
+        // The ?URL_MARK_PARAM= parameter belongs inbetween the page and the #heading-anchor
+        var url = doc_urls[result.ref].split("#");
+        if (url.length == 1) { // no anchor found
+            url.push("");
+        }
+
+        return '<a href="' + path_to_root + url[0] + '?' + URL_MARK_PARAM + '=' + searchterms + '#' + url[1]
+            + '" aria-details="teaser_' + teaser_count + '">' + result.doc.breadcrumbs + '</a>'
+            + '<span class="teaser" id="teaser_' + teaser_count + '" aria-label="Search Result Teaser">' 
+            + teaser + '</span>';
+    }
+    
+    function makeTeaser(body, searchterms) {
+        // The strategy is as follows:
+        // First, assign a value to each word in the document:
+        //  Words that correspond to search terms (stemmer aware): 40
+        //  Normal words: 2
+        //  First word in a sentence: 8
+        // Then use a sliding window with a constant number of words and count the
+        // sum of the values of the words within the window. Then use the window that got the
+        // maximum sum. If there are multiple maximas, then get the last one.
+        // Enclose the terms in <em>.
+        var stemmed_searchterms = searchterms.map(function(w) {
+            return elasticlunr.stemmer(w.toLowerCase());
+        });
+        var searchterm_weight = 40;
+        var weighted = []; // contains elements of ["word", weight, index_in_document]
+        // split in sentences, then words
+        var sentences = body.toLowerCase().split('. ');
+        var index = 0;
+        var value = 0;
+        var searchterm_found = false;
+        for (var sentenceindex in sentences) {
+            var words = sentences[sentenceindex].split(' ');
+            value = 8;
+            for (var wordindex in words) {
+                var word = words[wordindex];
+                if (word.length > 0) {
+                    for (var searchtermindex in stemmed_searchterms) {
+                        if (elasticlunr.stemmer(word).startsWith(stemmed_searchterms[searchtermindex])) {
+                            value = searchterm_weight;
+                            searchterm_found = true;
+                        }
+                    };
+                    weighted.push([word, value, index]);
+                    value = 2;
+                }
+                index += word.length;
+                index += 1; // ' ' or '.' if last word in sentence
+            };
+            index += 1; // because we split at a two-char boundary '. '
+        };
+
+        if (weighted.length == 0) {
+            return body;
+        }
+
+        var window_weight = [];
+        var window_size = Math.min(weighted.length, results_options.teaser_word_count);
+
+        var cur_sum = 0;
+        for (var wordindex = 0; wordindex < window_size; wordindex++) {
+            cur_sum += weighted[wordindex][1];
+        };
+        window_weight.push(cur_sum);
+        for (var wordindex = 0; wordindex < weighted.length - window_size; wordindex++) {
+            cur_sum -= weighted[wordindex][1];
+            cur_sum += weighted[wordindex + window_size][1];
+            window_weight.push(cur_sum);
+        };
+
+        if (searchterm_found) {
+            var max_sum = 0;
+            var max_sum_window_index = 0;
+            // backwards
+            for (var i = window_weight.length - 1; i >= 0; i--) {
+                if (window_weight[i] > max_sum) {
+                    max_sum = window_weight[i];
+                    max_sum_window_index = i;
+                }
+            };
+        } else {
+            max_sum_window_index = 0;
+        }
+
+        // add <em/> around searchterms
+        var teaser_split = [];
+        var index = weighted[max_sum_window_index][2];
+        for (var i = max_sum_window_index; i < max_sum_window_index+window_size; i++) {
+            var word = weighted[i];
+            if (index < word[2]) {
+                // missing text from index to start of `word`
+                teaser_split.push(body.substring(index, word[2]));
+                index = word[2];
+            }
+            if (word[1] == searchterm_weight) {
+                teaser_split.push("<em>")
+            }
+            index = word[2] + word[0].length;
+            teaser_split.push(body.substring(word[2], index));
+            if (word[1] == searchterm_weight) {
+                teaser_split.push("</em>")
+            }
+        };
+
+        return teaser_split.join('');
+    }
+
+    function init(config) {
+        results_options = config.results_options;
+        search_options = config.search_options;
+        searchbar_outer = config.searchbar_outer;
+        doc_urls = config.doc_urls;
+        searchindex = elasticlunr.Index.load(config.index);
+
+        // Set up events
+        searchicon.addEventListener('click', function(e) { searchIconClickHandler(); }, false);
+        searchbar.addEventListener('keyup', function(e) { searchbarKeyUpHandler(); }, false);
+        document.addEventListener('keydown', function(e) { globalKeyHandler(e); }, false);
+        // If the user uses the browser buttons, do the same as if a reload happened
+        window.onpopstate = function(e) { doSearchOrMarkFromUrl(); };
+        // Suppress "submit" events so the page doesn't reload when the user presses Enter
+        document.addEventListener('submit', function(e) { e.preventDefault(); }, false);
+
+        // If reloaded, do the search or mark again, depending on the current url parameters
+        doSearchOrMarkFromUrl();
+    }
+    
+    function unfocusSearchbar() {
+        // hacky, but just focusing a div only works once
+        var tmp = document.createElement('input');
+        tmp.setAttribute('style', 'position: absolute; opacity: 0;');
+        searchicon.appendChild(tmp);
+        tmp.focus();
+        tmp.remove();
+    }
+    
+    // On reload or browser history backwards/forwards events, parse the url and do search or mark
+    function doSearchOrMarkFromUrl() {
+        // Check current URL for search request
+        var url = parseURL(window.location.href);
+        if (url.params.hasOwnProperty(URL_SEARCH_PARAM)
+            && url.params[URL_SEARCH_PARAM] != "") {
+            showSearch(true);
+            searchbar.value = decodeURIComponent(
+                (url.params[URL_SEARCH_PARAM]+'').replace(/\+/g, '%20'));
+            searchbarKeyUpHandler(); // -> doSearch()
+        } else {
+            showSearch(false);
+        }
+
+        if (url.params.hasOwnProperty(URL_MARK_PARAM)) {
+            var words = url.params[URL_MARK_PARAM].split(' ');
+            marker.mark(words, {
+                exclude: mark_exclude
+            });
+
+            var markers = document.querySelectorAll("mark");
+            function hide() {
+                for (var i = 0; i < markers.length; i++) {
+                    markers[i].classList.add("fade-out");
+                    window.setTimeout(function(e) { marker.unmark(); }, 300);
+                }
+            }
+            for (var i = 0; i < markers.length; i++) {
+                markers[i].addEventListener('click', hide);
+            }
+        }
+    }
+    
+    // Eventhandler for keyevents on `document`
+    function globalKeyHandler(e) {
+        if (e.altKey || e.ctrlKey || e.metaKey || e.shiftKey || e.target.type === 'textarea') { return; }
+
+        if (e.keyCode === ESCAPE_KEYCODE) {
+            e.preventDefault();
+            searchbar.classList.remove("active");
+            setSearchUrlParameters("",
+                (searchbar.value.trim() !== "") ? "push" : "replace");
+            if (hasFocus()) {
+                unfocusSearchbar();
+            }
+            showSearch(false);
+            marker.unmark();
+        } else if (!hasFocus() && e.keyCode === SEARCH_HOTKEY_KEYCODE) {
+            e.preventDefault();
+            showSearch(true);
+            window.scrollTo(0, 0);
+            searchbar.select();
+        } else if (hasFocus() && e.keyCode === DOWN_KEYCODE) {
+            e.preventDefault();
+            unfocusSearchbar();
+            searchresults.firstElementChild.classList.add("focus");
+        } else if (!hasFocus() && (e.keyCode === DOWN_KEYCODE
+                                || e.keyCode === UP_KEYCODE
+                                || e.keyCode === SELECT_KEYCODE)) {
+            // not `:focus` because browser does annoying scrolling
+            var focused = searchresults.querySelector("li.focus");
+            if (!focused) return;
+            e.preventDefault();
+            if (e.keyCode === DOWN_KEYCODE) {
+                var next = focused.nextElementSibling;
+                if (next) {
+                    focused.classList.remove("focus");
+                    next.classList.add("focus");
+                }
+            } else if (e.keyCode === UP_KEYCODE) {
+                focused.classList.remove("focus");
+                var prev = focused.previousElementSibling;
+                if (prev) {
+                    prev.classList.add("focus");
+                } else {
+                    searchbar.select();
+                }
+            } else { // SELECT_KEYCODE
+                window.location.assign(focused.querySelector('a'));
+            }
+        }
+    }
+    
+    function showSearch(yes) {
+        if (yes) {
+            search_wrap.classList.remove('hidden');
+            searchicon.setAttribute('aria-expanded', 'true');
+        } else {
+            search_wrap.classList.add('hidden');
+            searchicon.setAttribute('aria-expanded', 'false');
+            var results = searchresults.children;
+            for (var i = 0; i < results.length; i++) {
+                results[i].classList.remove("focus");
+            }
+        }
+    }
+
+    function showResults(yes) {
+        if (yes) {
+            searchresults_outer.classList.remove('hidden');
+        } else {
+            searchresults_outer.classList.add('hidden');
+        }
+    }
+
+    // Eventhandler for search icon
+    function searchIconClickHandler() {
+        if (search_wrap.classList.contains('hidden')) {
+            showSearch(true);
+            window.scrollTo(0, 0);
+            searchbar.select();
+        } else {
+            showSearch(false);
+        }
+    }
+    
+    // Eventhandler for keyevents while the searchbar is focused
+    function searchbarKeyUpHandler() {
+        var searchterm = searchbar.value.trim();
+        if (searchterm != "") {
+            searchbar.classList.add("active");
+            doSearch(searchterm);
+        } else {
+            searchbar.classList.remove("active");
+            showResults(false);
+            removeChildren(searchresults);
+        }
+
+        setSearchUrlParameters(searchterm, "push_if_new_search_else_replace");
+
+        // Remove marks
+        marker.unmark();
+    }
+    
+    // Update current url with ?URL_SEARCH_PARAM= parameter, remove ?URL_MARK_PARAM and #heading-anchor .
+    // `action` can be one of "push", "replace", "push_if_new_search_else_replace"
+    // and replaces or pushes a new browser history item.
+    // "push_if_new_search_else_replace" pushes if there is no `?URL_SEARCH_PARAM=abc` yet.
+    function setSearchUrlParameters(searchterm, action) {
+        var url = parseURL(window.location.href);
+        var first_search = ! url.params.hasOwnProperty(URL_SEARCH_PARAM);
+        if (searchterm != "" || action == "push_if_new_search_else_replace") {
+            url.params[URL_SEARCH_PARAM] = searchterm;
+            delete url.params[URL_MARK_PARAM];
+            url.hash = "";
+        } else {
+            delete url.params[URL_SEARCH_PARAM];
+        }
+        // A new search will also add a new history item, so the user can go back
+        // to the page prior to searching. A updated search term will only replace
+        // the url.
+        if (action == "push" || (action == "push_if_new_search_else_replace" && first_search) ) {
+            history.pushState({}, document.title, renderURL(url));
+        } else if (action == "replace" || (action == "push_if_new_search_else_replace" && !first_search) ) {
+            history.replaceState({}, document.title, renderURL(url));
+        }
+    }
+    
+    function doSearch(searchterm) {
+
+        // Don't search the same twice
+        if (current_searchterm == searchterm) { return; }
+        else { current_searchterm = searchterm; }
+
+        if (searchindex == null) { return; }
+
+        // Do the actual search
+        var results = searchindex.search(searchterm, search_options);
+        var resultcount = Math.min(results.length, results_options.limit_results);
+
+        // Display search metrics
+        searchresults_header.innerText = formatSearchMetric(resultcount, searchterm);
+
+        // Clear and insert results
+        var searchterms  = searchterm.split(' ');
+        removeChildren(searchresults);
+        for(var i = 0; i < resultcount ; i++){
+            var resultElem = document.createElement('li');
+            resultElem.innerHTML = formatSearchResult(results[i], searchterms);
+            searchresults.appendChild(resultElem);
+        }
+
+        // Display results
+        showResults(true);
+    }
+
+    fetch(path_to_root + 'searchindex.json')
+        .then(response => response.json())
+        .then(json => init(json))        
+        .catch(error => { // Try to load searchindex.js if fetch failed
+            var script = document.createElement('script');
+            script.src = path_to_root + 'searchindex.js';
+            script.onload = () => init(window.search);
+            document.head.appendChild(script);
+        });
+
+    // Exported functions
+    search.hasFocus = hasFocus;
+})(window.search);

searchindex.js

@@ -0,0 +1 @@
+window.search = {"doc_urls":[],"index":{"documentStore":{"docInfo":{},"docs":{},"length":0,"save":true},"fields":["title","body","breadcrumbs"],"index":{"body":{"root":{"df":0,"docs":{}}},"breadcrumbs":{"root":{"df":0,"docs":{}}},"title":{"root":{"df":0,"docs":{}}}},"pipeline":["trimmer","stopWordFilter","stemmer"],"ref":"id","version":"0.9.5"},"results_options":{"limit_results":30,"teaser_word_count":30},"search_options":{"bool":"OR","expand":true,"fields":{"body":{"boost":1},"breadcrumbs":{"boost":1},"title":{"boost":2}}}};

searchindex.json

@@ -0,0 +1 @@
+{"doc_urls":[],"index":{"documentStore":{"docInfo":{},"docs":{},"length":0,"save":true},"fields":["title","body","breadcrumbs"],"index":{"body":{"root":{"df":0,"docs":{}}},"breadcrumbs":{"root":{"df":0,"docs":{}}},"title":{"root":{"df":0,"docs":{}}}},"pipeline":["trimmer","stopWordFilter","stemmer"],"ref":"id","version":"0.9.5"},"results_options":{"limit_results":30,"teaser_word_count":30},"search_options":{"bool":"OR","expand":true,"fields":{"body":{"boost":1},"breadcrumbs":{"boost":1},"title":{"boost":2}}}}

theme-dawn.js

@@ -0,0 +1 @@
+ace.define("ace/theme/dawn",["require","exports","module","ace/lib/dom"],function(e,t,n){t.isDark=!1,t.cssClass="ace-dawn",t.cssText=".ace-dawn .ace_gutter {background: #ebebeb;color: #333}.ace-dawn .ace_print-margin {width: 1px;background: #e8e8e8}.ace-dawn {background-color: #F9F9F9;color: #080808}.ace-dawn .ace_cursor {color: #000000}.ace-dawn .ace_marker-layer .ace_selection {background: rgba(39, 95, 255, 0.30)}.ace-dawn.ace_multiselect .ace_selection.ace_start {box-shadow: 0 0 3px 0px #F9F9F9;}.ace-dawn .ace_marker-layer .ace_step {background: rgb(255, 255, 0)}.ace-dawn .ace_marker-layer .ace_bracket {margin: -1px 0 0 -1px;border: 1px solid rgba(75, 75, 126, 0.50)}.ace-dawn .ace_marker-layer .ace_active-line {background: rgba(36, 99, 180, 0.12)}.ace-dawn .ace_gutter-active-line {background-color : #dcdcdc}.ace-dawn .ace_marker-layer .ace_selected-word {border: 1px solid rgba(39, 95, 255, 0.30)}.ace-dawn .ace_invisible {color: rgba(75, 75, 126, 0.50)}.ace-dawn .ace_keyword,.ace-dawn .ace_meta {color: #794938}.ace-dawn .ace_constant,.ace-dawn .ace_constant.ace_character,.ace-dawn .ace_constant.ace_character.ace_escape,.ace-dawn .ace_constant.ace_other {color: #811F24}.ace-dawn .ace_invalid.ace_illegal {text-decoration: underline;font-style: italic;color: #F8F8F8;background-color: #B52A1D}.ace-dawn .ace_invalid.ace_deprecated {text-decoration: underline;font-style: italic;color: #B52A1D}.ace-dawn .ace_support {color: #691C97}.ace-dawn .ace_support.ace_constant {color: #B4371F}.ace-dawn .ace_fold {background-color: #794938;border-color: #080808}.ace-dawn .ace_list,.ace-dawn .ace_markup.ace_list,.ace-dawn .ace_support.ace_function {color: #693A17}.ace-dawn .ace_storage {font-style: italic;color: #A71D5D}.ace-dawn .ace_string {color: #0B6125}.ace-dawn .ace_string.ace_regexp {color: #CF5628}.ace-dawn .ace_comment {font-style: italic;color: #5A525F}.ace-dawn .ace_heading,.ace-dawn .ace_markup.ace_heading {color: #19356D}.ace-dawn .ace_variable {color: #234A97}.ace-dawn .ace_indent-guide {background: url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAACCAYAAACZgbYnAAAAEklEQVQImWNgYGBgYLh/5+x/AAizA4hxNNsZAAAAAElFTkSuQmCC) right repeat-y}";var r=e("../lib/dom");r.importCssString(t.cssText,t.cssClass)})

theme-tomorrow_night.js

@@ -0,0 +1 @@
+ace.define("ace/theme/tomorrow_night",["require","exports","module","ace/lib/dom"],function(e,t,n){t.isDark=!0,t.cssClass="ace-tomorrow-night",t.cssText=".ace-tomorrow-night .ace_gutter {background: #25282c;color: #C5C8C6}.ace-tomorrow-night .ace_print-margin {width: 1px;background: #25282c}.ace-tomorrow-night {background-color: #1D1F21;color: #C5C8C6}.ace-tomorrow-night .ace_cursor {color: #AEAFAD}.ace-tomorrow-night .ace_marker-layer .ace_selection {background: #373B41}.ace-tomorrow-night.ace_multiselect .ace_selection.ace_start {box-shadow: 0 0 3px 0px #1D1F21;}.ace-tomorrow-night .ace_marker-layer .ace_step {background: rgb(102, 82, 0)}.ace-tomorrow-night .ace_marker-layer .ace_bracket {margin: -1px 0 0 -1px;border: 1px solid #4B4E55}.ace-tomorrow-night .ace_marker-layer .ace_active-line {background: #282A2E}.ace-tomorrow-night .ace_gutter-active-line {background-color: #282A2E}.ace-tomorrow-night .ace_marker-layer .ace_selected-word {border: 1px solid #373B41}.ace-tomorrow-night .ace_invisible {color: #4B4E55}.ace-tomorrow-night .ace_keyword,.ace-tomorrow-night .ace_meta,.ace-tomorrow-night .ace_storage,.ace-tomorrow-night .ace_storage.ace_type,.ace-tomorrow-night .ace_support.ace_type {color: #B294BB}.ace-tomorrow-night .ace_keyword.ace_operator {color: #8ABEB7}.ace-tomorrow-night .ace_constant.ace_character,.ace-tomorrow-night .ace_constant.ace_language,.ace-tomorrow-night .ace_constant.ace_numeric,.ace-tomorrow-night .ace_keyword.ace_other.ace_unit,.ace-tomorrow-night .ace_support.ace_constant,.ace-tomorrow-night .ace_variable.ace_parameter {color: #DE935F}.ace-tomorrow-night .ace_constant.ace_other {color: #CED1CF}.ace-tomorrow-night .ace_invalid {color: #CED2CF;background-color: #DF5F5F}.ace-tomorrow-night .ace_invalid.ace_deprecated {color: #CED2CF;background-color: #B798BF}.ace-tomorrow-night .ace_fold {background-color: #81A2BE;border-color: #C5C8C6}.ace-tomorrow-night .ace_entity.ace_name.ace_function,.ace-tomorrow-night .ace_support.ace_function,.ace-tomorrow-night .ace_variable {color: #81A2BE}.ace-tomorrow-night .ace_support.ace_class,.ace-tomorrow-night .ace_support.ace_type {color: #F0C674}.ace-tomorrow-night .ace_heading,.ace-tomorrow-night .ace_markup.ace_heading,.ace-tomorrow-night .ace_string {color: #B5BD68}.ace-tomorrow-night .ace_entity.ace_name.ace_tag,.ace-tomorrow-night .ace_entity.ace_other.ace_attribute-name,.ace-tomorrow-night .ace_meta.ace_tag,.ace-tomorrow-night .ace_string.ace_regexp,.ace-tomorrow-night .ace_variable {color: #CC6666}.ace-tomorrow-night .ace_comment {color: #969896}.ace-tomorrow-night .ace_indent-guide {background: url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAACCAYAAACZgbYnAAAAEklEQVQImWNgYGBgYHB3d/8PAAOIAdULw8qMAAAAAElFTkSuQmCC) right repeat-y}";var r=e("../lib/dom");r.importCssString(t.cssText,t.cssClass)})

tomorrow-night.css

@@ -0,0 +1,96 @@
+/* Tomorrow Night Theme */
+/* http://jmblog.github.com/color-themes-for-google-code-highlightjs */
+/* Original theme - https://github.com/chriskempson/tomorrow-theme */
+/* http://jmblog.github.com/color-themes-for-google-code-highlightjs */
+
+/* Tomorrow Comment */
+.hljs-comment {
+  color: #969896;
+}
+
+/* Tomorrow Red */
+.hljs-variable,
+.hljs-attribute,
+.hljs-tag,
+.hljs-regexp,
+.ruby .hljs-constant,
+.xml .hljs-tag .hljs-title,
+.xml .hljs-pi,
+.xml .hljs-doctype,
+.html .hljs-doctype,
+.css .hljs-id,
+.css .hljs-class,
+.css .hljs-pseudo {
+  color: #cc6666;
+}
+
+/* Tomorrow Orange */
+.hljs-number,
+.hljs-preprocessor,
+.hljs-pragma,
+.hljs-built_in,
+.hljs-literal,
+.hljs-params,
+.hljs-constant {
+  color: #de935f;
+}
+
+/* Tomorrow Yellow */
+.ruby .hljs-class .hljs-title,
+.css .hljs-rule .hljs-attribute {
+  color: #f0c674;
+}
+
+/* Tomorrow Green */
+.hljs-string,
+.hljs-value,
+.hljs-inheritance,
+.hljs-header,
+.hljs-name,
+.ruby .hljs-symbol,
+.xml .hljs-cdata {
+  color: #b5bd68;
+}
+
+/* Tomorrow Aqua */
+.hljs-title,
+.css .hljs-hexcolor {
+  color: #8abeb7;
+}
+
+/* Tomorrow Blue */
+.hljs-function,
+.python .hljs-decorator,
+.python .hljs-title,
+.ruby .hljs-function .hljs-title,
+.ruby .hljs-title .hljs-keyword,
+.perl .hljs-sub,
+.javascript .hljs-title,
+.coffeescript .hljs-title {
+  color: #81a2be;
+}
+
+/* Tomorrow Purple */
+.hljs-keyword,
+.javascript .hljs-function {
+  color: #b294bb;
+}
+
+.hljs {
+  display: block;
+  overflow-x: auto;
+  background: #1d1f21;
+  color: #c5c8c6;
+  padding: 0.5em;
+  -webkit-text-size-adjust: none;
+}
+
+.coffeescript .javascript,
+.javascript .xml,
+.tex .hljs-formula,
+.xml .javascript,
+.xml .vbscript,
+.xml .css,
+.xml .hljs-cdata {
+  opacity: 0.5;
+}

tutorial1.html

@@ -0,0 +1,227 @@
+<!DOCTYPE HTML>
+<html lang="en" class="sidebar-visible no-js">
+    <head>
+        <!-- Book generated using mdBook -->
+        <meta charset="UTF-8">
+        <title>Chapter 1 - chainerror</title>
+        <meta content="text/html; charset=utf-8" http-equiv="Content-Type">
+        <meta name="description" content="">
+        <meta name="viewport" content="width=device-width, initial-scale=1">
+        <meta name="theme-color" content="#ffffff" />
+
+        <link rel="shortcut icon" href="favicon.png">
+        <link rel="stylesheet" href="css/variables.css">
+        <link rel="stylesheet" href="css/general.css">
+        <link rel="stylesheet" href="css/chrome.css">
+        <link rel="stylesheet" href="css/print.css" media="print">
+
+        <!-- Fonts -->
+        <link rel="stylesheet" href="FontAwesome/css/font-awesome.css">
+        <link href="https://fonts.googleapis.com/css?family=Open+Sans:300italic,400italic,600italic,700italic,800italic,400,300,600,700,800" rel="stylesheet" type="text/css">
+        <link href="https://fonts.googleapis.com/css?family=Source+Code+Pro:500" rel="stylesheet" type="text/css">
+
+        <!-- Highlight.js Stylesheets -->
+        <link rel="stylesheet" href="highlight.css">
+        <link rel="stylesheet" href="tomorrow-night.css">
+        <link rel="stylesheet" href="ayu-highlight.css">
+
+        <!-- Custom theme stylesheets -->
+        
+
+        
+    </head>
+    <body class="light">
+        <!-- Provide site root to javascript -->
+        <script type="text/javascript">
+            var path_to_root = "";
+            var default_theme = "light";
+        </script>
+
+        <!-- Work around some values being stored in localStorage wrapped in quotes -->
+        <script type="text/javascript">
+            try {
+                var theme = localStorage.getItem('mdbook-theme');
+                var sidebar = localStorage.getItem('mdbook-sidebar');
+
+                if (theme.startsWith('"') && theme.endsWith('"')) {
+                    localStorage.setItem('mdbook-theme', theme.slice(1, theme.length - 1));
+                }
+
+                if (sidebar.startsWith('"') && sidebar.endsWith('"')) {
+                    localStorage.setItem('mdbook-sidebar', sidebar.slice(1, sidebar.length - 1));
+                }
+            } catch (e) { }
+        </script>
+
+        <!-- Set the theme before any content is loaded, prevents flash -->
+        <script type="text/javascript">
+            var theme;
+            try { theme = localStorage.getItem('mdbook-theme'); } catch(e) { } 
+            if (theme === null || theme === undefined) { theme = default_theme; }
+            document.body.className = theme;
+            document.querySelector('html').className = theme + ' js';
+        </script>
+
+        <!-- Hide / unhide sidebar before it is displayed -->
+        <script type="text/javascript">
+            var html = document.querySelector('html');
+            var sidebar = 'hidden';
+            if (document.body.clientWidth >= 1080) {
+                try { sidebar = localStorage.getItem('mdbook-sidebar'); } catch(e) { }
+                sidebar = sidebar || 'visible';
+            }
+            html.classList.remove('sidebar-visible');
+            html.classList.add("sidebar-" + sidebar);
+        </script>
+
+        <nav id="sidebar" class="sidebar" aria-label="Table of contents">
+            <ol class="chapter"><li><a href="tutorial1.html" class="active"><strong aria-hidden="true">1.</strong> Chapter 1</a></li><li><a href="tutorial2.html"><strong aria-hidden="true">2.</strong> Chapter 2</a></li><li><a href="tutorial3.html"><strong aria-hidden="true">3.</strong> Chapter 3</a></li><li><a href="tutorial4.html"><strong aria-hidden="true">4.</strong> Chapter 4</a></li><li><a href="tutorial5.html"><strong aria-hidden="true">5.</strong> Chapter 5</a></li><li><a href="tutorial6.html"><strong aria-hidden="true">6.</strong> Chapter 6</a></li><li><a href="tutorial7.html"><strong aria-hidden="true">7.</strong> Chapter 7</a></li><li><a href="tutorial8.html"><strong aria-hidden="true">8.</strong> Chapter 8</a></li><li><a href="tutorial9.html"><strong aria-hidden="true">9.</strong> Chapter 9</a></li><li><a href="tutorial10.html"><strong aria-hidden="true">10.</strong> Chapter 10</a></li><li><a href="tutorial11.html"><strong aria-hidden="true">11.</strong> Chapter 11</a></li></ol>
+        </nav>
+
+        <div id="page-wrapper" class="page-wrapper">
+
+            <div class="page">
+                
+                <div id="menu-bar" class="menu-bar">
+                    <div id="menu-bar-sticky-container">
+                        <div class="left-buttons">
+                            <button id="sidebar-toggle" class="icon-button" type="button" title="Toggle Table of Contents" aria-label="Toggle Table of Contents" aria-controls="sidebar">
+                                <i class="fa fa-bars"></i>
+                            </button>
+                            <button id="theme-toggle" class="icon-button" type="button" title="Change theme" aria-label="Change theme" aria-haspopup="true" aria-expanded="false" aria-controls="theme-list">
+                                <i class="fa fa-paint-brush"></i>
+                            </button>
+                            <ul id="theme-list" class="theme-popup" aria-label="Themes" role="menu">
+                                <li role="none"><button role="menuitem" class="theme" id="light">Light (default)</button></li>
+                                <li role="none"><button role="menuitem" class="theme" id="rust">Rust</button></li>
+                                <li role="none"><button role="menuitem" class="theme" id="coal">Coal</button></li>
+                                <li role="none"><button role="menuitem" class="theme" id="navy">Navy</button></li>
+                                <li role="none"><button role="menuitem" class="theme" id="ayu">Ayu</button></li>
+                            </ul>
+                            
+                            <button id="search-toggle" class="icon-button" type="button" title="Search. (Shortkey: s)" aria-label="Toggle Searchbar" aria-expanded="false" aria-keyshortcuts="S" aria-controls="searchbar">
+                                <i class="fa fa-search"></i>
+                            </button>
+                            
+                        </div>
+
+                        <h1 class="menu-title">chainerror</h1> 
+
+                        <div class="right-buttons">
+                            <a href="print.html" title="Print this book" aria-label="Print this book">
+                                <i id="print-button" class="fa fa-print"></i>
+                            </a>
+                            
+                        </div>
+                    </div>
+                </div>
+
+                
+                <div id="search-wrapper" class="hidden">
+                    <form id="searchbar-outer" class="searchbar-outer">
+                        <input type="search" name="search" id="searchbar" name="searchbar" placeholder="Search this book ..." aria-controls="searchresults-outer" aria-describedby="searchresults-header">
+                    </form>
+                    <div id="searchresults-outer" class="searchresults-outer hidden">
+                        <div id="searchresults-header" class="searchresults-header"></div>
+                        <ul id="searchresults">
+                        </ul>
+                    </div>
+                </div>
+                
+
+                <!-- Apply ARIA attributes after the sidebar and the sidebar toggle button are added to the DOM -->
+                <script type="text/javascript">
+                    document.getElementById('sidebar-toggle').setAttribute('aria-expanded', sidebar === 'visible');
+                    document.getElementById('sidebar').setAttribute('aria-hidden', sidebar !== 'visible');
+                    Array.from(document.querySelectorAll('#sidebar a')).forEach(function(link) {
+                        link.setAttribute('tabIndex', sidebar === 'visible' ? 0 : -1);
+                    });
+                </script>
+
+                <div id="content" class="content">
+                    <main>
+                        <pre><pre class="playpen"><code class="language-rust">use std::error::Error;
+use std::result::Result;
+
+fn do_some_io() -&gt; Result&lt;(), Box&lt;Error&gt;&gt; {
+    Err(&quot;do_some_io error&quot;)?;
+    Ok(())
+}
+
+fn func2() -&gt; Result&lt;(), Box&lt;Error&gt;&gt; {
+    if let Err(_) = do_some_io() {
+        Err(&quot;func2 error&quot;)?;
+    }
+    Ok(())
+}
+
+fn func1() -&gt; Result&lt;(), Box&lt;Error&gt;&gt; {
+    if let Err(_) = func2() {
+        Err(&quot;func1 error&quot;)?;
+    }
+    Ok(())
+}
+
+fn main() -&gt; Result&lt;(), Box&lt;Error&gt;&gt; {
+    func1()
+}
+</code></pre></pre>
+
+                    </main>
+
+                    <nav class="nav-wrapper" aria-label="Page navigation">
+                        <!-- Mobile navigation buttons -->
+                        
+
+                        
+                            <a rel="next" href="tutorial2.html" class="mobile-nav-chapters next" title="Next chapter" aria-label="Next chapter" aria-keyshortcuts="Right">
+                                <i class="fa fa-angle-right"></i>
+                            </a>
+                        
+
+                        <div style="clear: both"></div>
+                    </nav>
+                </div>
+            </div>
+
+            <nav class="nav-wide-wrapper" aria-label="Page navigation">
+                
+
+                
+                    <a href="tutorial2.html" class="nav-chapters next" title="Next chapter" aria-label="Next chapter" aria-keyshortcuts="Right">
+                        <i class="fa fa-angle-right"></i>
+                    </a>
+                
+            </nav>
+
+        </div>
+
+        
+
+        
+
+        
+        <script src="ace.js" type="text/javascript" charset="utf-8"></script>
+        <script src="editor.js" type="text/javascript" charset="utf-8"></script>
+        <script src="mode-rust.js" type="text/javascript" charset="utf-8"></script>
+        <script src="theme-dawn.js" type="text/javascript" charset="utf-8"></script>
+        <script src="theme-tomorrow_night.js" type="text/javascript" charset="utf-8"></script>
+        
+
+        
+        <script src="elasticlunr.min.js" type="text/javascript" charset="utf-8"></script>
+        <script src="mark.min.js" type="text/javascript" charset="utf-8"></script>
+        <script src="searcher.js" type="text/javascript" charset="utf-8"></script>
+        
+
+        <script src="clipboard.min.js" type="text/javascript" charset="utf-8"></script>
+        <script src="highlight.js" type="text/javascript" charset="utf-8"></script>
+        <script src="book.js" type="text/javascript" charset="utf-8"></script>
+
+        <!-- Custom JS scripts -->
+        
+
+        
+
+    </body>
+</html>

tutorial10.html

@@ -0,0 +1,546 @@
+<!DOCTYPE HTML>
+<html lang="en" class="sidebar-visible no-js">
+    <head>
+        <!-- Book generated using mdBook -->
+        <meta charset="UTF-8">
+        <title>Chapter 10 - chainerror</title>
+        <meta content="text/html; charset=utf-8" http-equiv="Content-Type">
+        <meta name="description" content="">
+        <meta name="viewport" content="width=device-width, initial-scale=1">
+        <meta name="theme-color" content="#ffffff" />
+
+        <link rel="shortcut icon" href="favicon.png">
+        <link rel="stylesheet" href="css/variables.css">
+        <link rel="stylesheet" href="css/general.css">
+        <link rel="stylesheet" href="css/chrome.css">
+        <link rel="stylesheet" href="css/print.css" media="print">
+
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+                        <h1 class="menu-title">chainerror</h1> 
+
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+                <div id="content" class="content">
+                    <main>
+                        <pre><pre class="playpen"><code class="language-rust">use crate::chainerror::*;
+use std::error::Error;
+use std::io;
+use std::result::Result;
+
+fn do_some_io() -&gt; Result&lt;(), Box&lt;Error&gt;&gt; {
+    Err(io::Error::from(io::ErrorKind::NotFound))?;
+    Ok(())
+}
+
+derive_str_cherr!(Func2Error);
+
+fn func2() -&gt; Result&lt;(), Box&lt;Error&gt;&gt; {
+    let filename = &quot;foo.txt&quot;;
+    do_some_io().map_err(mstrerr!(Func2Error, &quot;Error reading '{}'&quot;, filename))?;
+    Ok(())
+}
+
+#[derive(Debug)]
+enum Func1Error {
+    Func2,
+    IO(String),
+}
+
+impl ::std::fmt::Display for Func1Error {
+    fn fmt(&amp;self, f: &amp;mut ::std::fmt::Formatter) -&gt; ::std::fmt::Result {
+        match self {
+            Func1Error::Func2 =&gt; write!(f, &quot;func1 error calling func2&quot;),
+            Func1Error::IO(filename) =&gt; write!(f, &quot;Error reading '{}'&quot;, filename),
+        }
+    }
+}
+
+fn func1() -&gt; ChainResult&lt;(), Func1Error&gt; {
+    func2().map_err(|e| cherr!(e, Func1Error::Func2))?;
+    let filename = String::from(&quot;bar.txt&quot;);
+    do_some_io().map_err(|e| cherr!(e, Func1Error::IO(filename)))?;
+    Ok(())
+}
+
+fn main() -&gt; Result&lt;(), Box&lt;Error&gt;&gt; {
+    if let Err(e) = func1() {
+        match e.kind() {
+            Func1Error::Func2 =&gt; eprintln!(&quot;Main Error Report: func1 error calling func2&quot;),
+            Func1Error::IO(filename) =&gt; {
+                eprintln!(&quot;Main Error Report: func1 error reading '{}'&quot;, filename)
+            }
+        }
+
+        if let Some(e) = e.find_chain_cause::&lt;Func2Error&gt;() {
+            eprintln!(&quot;Error reported by Func2Error: {}&quot;, e)
+        }
+
+        eprintln!(&quot;\nDebug Error:\n{:?}&quot;, e);
+    }
+    Ok(())
+}
+# #[allow(dead_code)]
+# mod chainerror {
+# use std::error::Error;
+# use std::fmt::{Debug, Display, Formatter, Result};
+# use std::result::Result as StdResult;
+# 
+# pub struct ChainError&lt;T&gt; {
+#     #[cfg(not(feature = &quot;no-fileline&quot;))]
+#     occurrence: Option&lt;(u32, &amp;'static str)&gt;,
+#     kind: T,
+#     error_cause: Option&lt;Box&lt;dyn Error + 'static&gt;&gt;,
+# }
+# 
+# pub type ChainResult&lt;O, E&gt; = StdResult&lt;O, ChainError&lt;E&gt;&gt;;
+# 
+# impl&lt;T: 'static + Display + Debug&gt; ChainError&lt;T&gt; {
+#     #[cfg(not(feature = &quot;no-fileline&quot;))]
+#     pub fn new(
+#         kind: T,
+#         error_cause: Option&lt;Box&lt;dyn Error + 'static&gt;&gt;,
+#         occurrence: Option&lt;(u32, &amp;'static str)&gt;,
+#     ) -&gt; Self {
+#         Self {
+#             occurrence,
+#             kind,
+#             error_cause,
+#         }
+#     }
+# 
+#     #[cfg(feature = &quot;no-fileline&quot;)]
+#     pub fn new(
+#         kind: T,
+#         error_cause: Option&lt;Box&lt;dyn Error + 'static&gt;&gt;,
+#         _occurrence: Option&lt;(u32, &amp;'static str)&gt;,
+#     ) -&gt; Self {
+#         Self { kind, error_cause }
+#     }
+# 
+#     pub fn root_cause(&amp;self) -&gt; Option&lt;&amp;(dyn Error + 'static)&gt; {
+#         let mut cause = self as &amp;(dyn Error + 'static);
+#         while let Some(c) = cause.source() {
+#             cause = c;
+#         }
+#         Some(cause)
+#     }
+# 
+#     pub fn find_cause&lt;U: Error + 'static&gt;(&amp;self) -&gt; Option&lt;&amp;U&gt; {
+#         let mut cause = self as &amp;(dyn Error + 'static);
+#         loop {
+#             if cause.is::&lt;U&gt;() {
+#                 return cause.downcast_ref::&lt;U&gt;();
+#             }
+# 
+#             match cause.source() {
+#                 Some(c) =&gt; cause = c,
+#                 None =&gt; return None,
+#             }
+#         }
+#     }
+# 
+#     pub fn find_chain_cause&lt;U: Error + 'static&gt;(&amp;self) -&gt; Option&lt;&amp;ChainError&lt;U&gt;&gt; {
+#         let mut cause = self as &amp;(dyn Error + 'static);
+#         loop {
+#             if cause.is::&lt;ChainError&lt;U&gt;&gt;() {
+#                 return cause.downcast_ref::&lt;ChainError&lt;U&gt;&gt;();
+#             }
+# 
+#             match cause.source() {
+#                 Some(c) =&gt; cause = c,
+#                 None =&gt; return None,
+#             }
+#         }
+#     }
+# 
+#     pub fn kind&lt;'a&gt;(&amp;'a self) -&gt; &amp;'a T {
+#         &amp;self.kind
+#     }
+# }
+# 
+# pub trait ChainErrorDown {
+#     fn is_chain&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; bool;
+#     fn downcast_chain_ref&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; Option&lt;&amp;ChainError&lt;T&gt;&gt;;
+#     fn downcast_chain_mut&lt;T: 'static + Display + Debug&gt;(&amp;mut self) -&gt; Option&lt;&amp;mut ChainError&lt;T&gt;&gt;;
+# }
+# 
+# use std::any::TypeId;
+# 
+# impl&lt;U: 'static + Display + Debug&gt; ChainErrorDown for ChainError&lt;U&gt; {
+#     fn is_chain&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; bool {
+#         TypeId::of::&lt;T&gt;() == TypeId::of::&lt;U&gt;()
+#     }
+# 
+#     fn downcast_chain_ref&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; Option&lt;&amp;ChainError&lt;T&gt;&gt; {
+#         if self.is_chain::&lt;T&gt;() {
+#             unsafe { Some(&amp;*(self as *const dyn Error as *const &amp;ChainError&lt;T&gt;)) }
+#         } else {
+#             None
+#         }
+#     }
+# 
+#     fn downcast_chain_mut&lt;T: 'static + Display + Debug&gt;(&amp;mut self) -&gt; Option&lt;&amp;mut ChainError&lt;T&gt;&gt; {
+#         if self.is_chain::&lt;T&gt;() {
+#             unsafe { Some(&amp;mut *(self as *mut dyn Error as *mut &amp;mut ChainError&lt;T&gt;)) }
+#         } else {
+#             None
+#         }
+#     }
+# }
+# 
+# impl ChainErrorDown for dyn Error + 'static {
+#     fn is_chain&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; bool {
+#         self.is::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# 
+#     fn downcast_chain_ref&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; Option&lt;&amp;ChainError&lt;T&gt;&gt; {
+#         self.downcast_ref::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# 
+#     fn downcast_chain_mut&lt;T: 'static + Display + Debug&gt;(&amp;mut self) -&gt; Option&lt;&amp;mut ChainError&lt;T&gt;&gt; {
+#         self.downcast_mut::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# }
+# 
+# impl ChainErrorDown for dyn Error + 'static + Send {
+#     fn is_chain&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; bool {
+#         self.is::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# 
+#     fn downcast_chain_ref&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; Option&lt;&amp;ChainError&lt;T&gt;&gt; {
+#         self.downcast_ref::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# 
+#     fn downcast_chain_mut&lt;T: 'static + Display + Debug&gt;(&amp;mut self) -&gt; Option&lt;&amp;mut ChainError&lt;T&gt;&gt; {
+#         self.downcast_mut::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# }
+# 
+# impl ChainErrorDown for dyn Error + 'static + Send + Sync {
+#     fn is_chain&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; bool {
+#         self.is::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# 
+#     fn downcast_chain_ref&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; Option&lt;&amp;ChainError&lt;T&gt;&gt; {
+#         self.downcast_ref::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# 
+#     fn downcast_chain_mut&lt;T: 'static + Display + Debug&gt;(&amp;mut self) -&gt; Option&lt;&amp;mut ChainError&lt;T&gt;&gt; {
+#         self.downcast_mut::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# }
+# 
+# impl&lt;T: 'static + Display + Debug&gt; Error for ChainError&lt;T&gt; {
+#     fn source(&amp;self) -&gt; Option&lt;&amp;(dyn Error + 'static)&gt; {
+#         if let Some(ref e) = self.error_cause {
+#             Some(e.as_ref())
+#         } else {
+#             None
+#         }
+#     }
+# }
+# 
+# impl&lt;T: 'static + Display + Debug&gt; Error for &amp;ChainError&lt;T&gt; {
+#     fn source(&amp;self) -&gt; Option&lt;&amp;(dyn Error + 'static)&gt; {
+#         if let Some(ref e) = self.error_cause {
+#             Some(e.as_ref())
+#         } else {
+#             None
+#         }
+#     }
+# }
+# 
+# impl&lt;T: 'static + Display + Debug&gt; Error for &amp;mut ChainError&lt;T&gt; {
+#     fn source(&amp;self) -&gt; Option&lt;&amp;(dyn Error + 'static)&gt; {
+#         if let Some(ref e) = self.error_cause {
+#             Some(e.as_ref())
+#         } else {
+#             None
+#         }
+#     }
+# }
+# 
+# impl&lt;T: 'static + Display + Debug&gt; Display for ChainError&lt;T&gt; {
+#     fn fmt(&amp;self, f: &amp;mut Formatter) -&gt; Result {
+#         write!(f, &quot;{}&quot;, self.kind)?;
+# 
+#         #[cfg(feature = &quot;display-cause&quot;)]
+#         {
+#             if let Some(e) = self.source() {
+#                 writeln!(f, &quot;\nCaused by:&quot;)?;
+#                 Display::fmt(&amp;e, f)?;
+#             }
+#         }
+#         Ok(())
+#     }
+# }
+# 
+# impl&lt;T: 'static + Display + Debug&gt; Debug for ChainError&lt;T&gt; {
+#     fn fmt(&amp;self, f: &amp;mut Formatter) -&gt; Result {
+#         #[cfg(not(feature = &quot;no-fileline&quot;))]
+#         {
+#             if let Some(o) = self.occurrence {
+#                 write!(f, &quot;{}:{}: &quot;, o.1, o.0)?;
+#             }
+#         }
+# 
+#         Debug::fmt(&amp;self.kind, f)?;
+# 
+#         #[cfg(not(feature = &quot;no-debug-cause&quot;))]
+#         {
+#             if let Some(e) = self.source() {
+#                 writeln!(f, &quot;\nCaused by:&quot;)?;
+#                 Debug::fmt(&amp;e, f)?;
+#             }
+#         }
+#         Ok(())
+#     }
+# }
+# 
+# #[macro_export]
+# macro_rules! cherr {
+#     ( $k:expr ) =&gt; {
+#         ChainError::&lt;_&gt;::new($k, None, Some((line!(), file!())))
+#     };
+#     ( $e:expr, $k:expr ) =&gt; {
+#         ChainError::&lt;_&gt;::new($k, Some(Box::from($e)), Some((line!(), file!())))
+#     };
+# }
+# 
+# #[macro_export]
+# macro_rules! mstrerr {
+#     ( $t:ident, $v:expr $(, $more:expr)* ) =&gt; {
+#         |e| cherr!(e, $t (format!($v, $( $more , )* )))
+#     };
+#     ( $t:path, $v:expr $(, $more:expr)* ) =&gt; {
+#         |e| cherr!(e, $t (format!($v, $( $more , )* )))
+#     };
+#     ( $v:expr $(, $more:expr)* ) =&gt; {
+#         |e| cherr!(e, format!($v, $( $more , )* ))
+#     };
+# }
+# 
+# #[macro_export]
+# macro_rules! derive_str_cherr {
+#     ($e:ident) =&gt; {
+#         struct $e(String);
+#         impl ::std::fmt::Display for $e {
+#             fn fmt(&amp;self, f: &amp;mut ::std::fmt::Formatter) -&gt; ::std::fmt::Result {
+#                 write!(f, &quot;{}&quot;, self.0)
+#             }
+#         }
+#         impl ::std::fmt::Debug for $e {
+#             fn fmt(&amp;self, f: &amp;mut ::std::fmt::Formatter) -&gt; ::std::fmt::Result {
+#                 write!(f, &quot;{}({})&quot;, stringify!($e), self.0)
+#             }
+#         }
+#         impl ::std::error::Error for $e {}
+#     };
+# }
+# 
+# #[macro_export]
+# macro_rules! try_cherr_ref {
+#     ( $e:expr, $t:ident ) =&gt; {
+#         $e.downcast_ref::&lt;ChainError&lt;$t&gt;&gt;()
+#     };
+#     ( $e:expr, $t:path ) =&gt; {
+#         $e.downcast_ref::&lt;ChainError&lt;$t&gt;&gt;()
+#     };
+# }
+# 
+# #[macro_export]
+# macro_rules! try_cherr_mut {
+#     ( $e:expr, $t:ident ) =&gt; {
+#         $e.downcast_mut::&lt;ChainError&lt;$t&gt;&gt;()
+#     };
+#     ( $e:expr, $t:path ) =&gt; {
+#         $e.downcast_mut::&lt;ChainError&lt;$t&gt;&gt;()
+#     };
+# }
+# }
+</code></pre></pre>
+
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+                    <main>
+                        <pre><pre class="playpen"><code class="language-rust">use crate::chainerror::*;
+use std::error::Error;
+use std::io;
+use std::result::Result;
+
+fn do_some_io() -&gt; Result&lt;(), Box&lt;Error&gt;&gt; {
+    Err(io::Error::from(io::ErrorKind::NotFound))?;
+    Ok(())
+}
+
+derive_str_cherr!(Func2Error);
+
+fn func2() -&gt; Result&lt;(), Box&lt;Error&gt;&gt; {
+    let filename = &quot;foo.txt&quot;;
+    do_some_io().map_err(mstrerr!(Func2Error, &quot;Error reading '{}'&quot;, filename))?;
+    Ok(())
+}
+
+enum Func1Error {
+    Func2,
+    IO(String),
+}
+
+impl ::std::fmt::Display for Func1Error {
+    fn fmt(&amp;self, f: &amp;mut ::std::fmt::Formatter) -&gt; ::std::fmt::Result {
+        match self {
+            Func1Error::Func2 =&gt; write!(f, &quot;func1 error calling func2&quot;),
+            Func1Error::IO(filename) =&gt; write!(f, &quot;Error reading '{}'&quot;, filename),
+        }
+    }
+}
+
+impl ::std::fmt::Debug for Func1Error {
+    fn fmt(&amp;self, f: &amp;mut ::std::fmt::Formatter) -&gt; ::std::fmt::Result {
+        write!(f, &quot;{}&quot;, self)
+    }
+}
+
+fn func1() -&gt; ChainResult&lt;(), Func1Error&gt; {
+    func2().map_err(|e| cherr!(e, Func1Error::Func2))?;
+    let filename = String::from(&quot;bar.txt&quot;);
+    do_some_io().map_err(|e| cherr!(e, Func1Error::IO(filename)))?;
+    Ok(())
+}
+
+fn main() -&gt; Result&lt;(), Box&lt;Error&gt;&gt; {
+    if let Err(e) = func1() {
+        match e.kind() {
+            Func1Error::Func2 =&gt; eprintln!(&quot;Main Error Report: func1 error calling func2&quot;),
+            Func1Error::IO(filename) =&gt; {
+                eprintln!(&quot;Main Error Report: func1 error reading '{}'&quot;, filename)
+            }
+        }
+
+        if let Some(e) = e.find_chain_cause::&lt;Func2Error&gt;() {
+            eprintln!(&quot;Error reported by Func2Error: {}&quot;, e)
+        }
+
+        eprintln!(&quot;\nDebug Error:\n{:?}&quot;, e);
+    }
+    Ok(())
+}
+# #[allow(dead_code)]
+# mod chainerror {
+# use std::error::Error;
+# use std::fmt::{Debug, Display, Formatter, Result};
+# use std::result::Result as StdResult;
+# 
+# pub struct ChainError&lt;T&gt; {
+#     #[cfg(not(feature = &quot;no-fileline&quot;))]
+#     occurrence: Option&lt;(u32, &amp;'static str)&gt;,
+#     kind: T,
+#     error_cause: Option&lt;Box&lt;dyn Error + 'static&gt;&gt;,
+# }
+# 
+# pub type ChainResult&lt;O, E&gt; = StdResult&lt;O, ChainError&lt;E&gt;&gt;;
+# 
+# impl&lt;T: 'static + Display + Debug&gt; ChainError&lt;T&gt; {
+#     #[cfg(not(feature = &quot;no-fileline&quot;))]
+#     pub fn new(
+#         kind: T,
+#         error_cause: Option&lt;Box&lt;dyn Error + 'static&gt;&gt;,
+#         occurrence: Option&lt;(u32, &amp;'static str)&gt;,
+#     ) -&gt; Self {
+#         Self {
+#             occurrence,
+#             kind,
+#             error_cause,
+#         }
+#     }
+# 
+#     #[cfg(feature = &quot;no-fileline&quot;)]
+#     pub fn new(
+#         kind: T,
+#         error_cause: Option&lt;Box&lt;dyn Error + 'static&gt;&gt;,
+#         _occurrence: Option&lt;(u32, &amp;'static str)&gt;,
+#     ) -&gt; Self {
+#         Self { kind, error_cause }
+#     }
+# 
+#     pub fn root_cause(&amp;self) -&gt; Option&lt;&amp;(dyn Error + 'static)&gt; {
+#         let mut cause = self as &amp;(dyn Error + 'static);
+#         while let Some(c) = cause.source() {
+#             cause = c;
+#         }
+#         Some(cause)
+#     }
+# 
+#     pub fn find_cause&lt;U: Error + 'static&gt;(&amp;self) -&gt; Option&lt;&amp;U&gt; {
+#         let mut cause = self as &amp;(dyn Error + 'static);
+#         loop {
+#             if cause.is::&lt;U&gt;() {
+#                 return cause.downcast_ref::&lt;U&gt;();
+#             }
+# 
+#             match cause.source() {
+#                 Some(c) =&gt; cause = c,
+#                 None =&gt; return None,
+#             }
+#         }
+#     }
+# 
+#     pub fn find_chain_cause&lt;U: Error + 'static&gt;(&amp;self) -&gt; Option&lt;&amp;ChainError&lt;U&gt;&gt; {
+#         let mut cause = self as &amp;(dyn Error + 'static);
+#         loop {
+#             if cause.is::&lt;ChainError&lt;U&gt;&gt;() {
+#                 return cause.downcast_ref::&lt;ChainError&lt;U&gt;&gt;();
+#             }
+# 
+#             match cause.source() {
+#                 Some(c) =&gt; cause = c,
+#                 None =&gt; return None,
+#             }
+#         }
+#     }
+# 
+#     pub fn kind&lt;'a&gt;(&amp;'a self) -&gt; &amp;'a T {
+#         &amp;self.kind
+#     }
+# }
+# 
+# pub trait ChainErrorDown {
+#     fn is_chain&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; bool;
+#     fn downcast_chain_ref&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; Option&lt;&amp;ChainError&lt;T&gt;&gt;;
+#     fn downcast_chain_mut&lt;T: 'static + Display + Debug&gt;(&amp;mut self) -&gt; Option&lt;&amp;mut ChainError&lt;T&gt;&gt;;
+# }
+# 
+# use std::any::TypeId;
+# 
+# impl&lt;U: 'static + Display + Debug&gt; ChainErrorDown for ChainError&lt;U&gt; {
+#     fn is_chain&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; bool {
+#         TypeId::of::&lt;T&gt;() == TypeId::of::&lt;U&gt;()
+#     }
+# 
+#     fn downcast_chain_ref&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; Option&lt;&amp;ChainError&lt;T&gt;&gt; {
+#         if self.is_chain::&lt;T&gt;() {
+#             unsafe { Some(&amp;*(self as *const dyn Error as *const &amp;ChainError&lt;T&gt;)) }
+#         } else {
+#             None
+#         }
+#     }
+# 
+#     fn downcast_chain_mut&lt;T: 'static + Display + Debug&gt;(&amp;mut self) -&gt; Option&lt;&amp;mut ChainError&lt;T&gt;&gt; {
+#         if self.is_chain::&lt;T&gt;() {
+#             unsafe { Some(&amp;mut *(self as *mut dyn Error as *mut &amp;mut ChainError&lt;T&gt;)) }
+#         } else {
+#             None
+#         }
+#     }
+# }
+# 
+# impl ChainErrorDown for dyn Error + 'static {
+#     fn is_chain&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; bool {
+#         self.is::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# 
+#     fn downcast_chain_ref&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; Option&lt;&amp;ChainError&lt;T&gt;&gt; {
+#         self.downcast_ref::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# 
+#     fn downcast_chain_mut&lt;T: 'static + Display + Debug&gt;(&amp;mut self) -&gt; Option&lt;&amp;mut ChainError&lt;T&gt;&gt; {
+#         self.downcast_mut::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# }
+# 
+# impl ChainErrorDown for dyn Error + 'static + Send {
+#     fn is_chain&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; bool {
+#         self.is::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# 
+#     fn downcast_chain_ref&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; Option&lt;&amp;ChainError&lt;T&gt;&gt; {
+#         self.downcast_ref::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# 
+#     fn downcast_chain_mut&lt;T: 'static + Display + Debug&gt;(&amp;mut self) -&gt; Option&lt;&amp;mut ChainError&lt;T&gt;&gt; {
+#         self.downcast_mut::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# }
+# 
+# impl ChainErrorDown for dyn Error + 'static + Send + Sync {
+#     fn is_chain&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; bool {
+#         self.is::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# 
+#     fn downcast_chain_ref&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; Option&lt;&amp;ChainError&lt;T&gt;&gt; {
+#         self.downcast_ref::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# 
+#     fn downcast_chain_mut&lt;T: 'static + Display + Debug&gt;(&amp;mut self) -&gt; Option&lt;&amp;mut ChainError&lt;T&gt;&gt; {
+#         self.downcast_mut::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# }
+# 
+# impl&lt;T: 'static + Display + Debug&gt; Error for ChainError&lt;T&gt; {
+#     fn source(&amp;self) -&gt; Option&lt;&amp;(dyn Error + 'static)&gt; {
+#         if let Some(ref e) = self.error_cause {
+#             Some(e.as_ref())
+#         } else {
+#             None
+#         }
+#     }
+# }
+# 
+# impl&lt;T: 'static + Display + Debug&gt; Error for &amp;ChainError&lt;T&gt; {
+#     fn source(&amp;self) -&gt; Option&lt;&amp;(dyn Error + 'static)&gt; {
+#         if let Some(ref e) = self.error_cause {
+#             Some(e.as_ref())
+#         } else {
+#             None
+#         }
+#     }
+# }
+# 
+# impl&lt;T: 'static + Display + Debug&gt; Error for &amp;mut ChainError&lt;T&gt; {
+#     fn source(&amp;self) -&gt; Option&lt;&amp;(dyn Error + 'static)&gt; {
+#         if let Some(ref e) = self.error_cause {
+#             Some(e.as_ref())
+#         } else {
+#             None
+#         }
+#     }
+# }
+# 
+# impl&lt;T: 'static + Display + Debug&gt; Display for ChainError&lt;T&gt; {
+#     fn fmt(&amp;self, f: &amp;mut Formatter) -&gt; Result {
+#         write!(f, &quot;{}&quot;, self.kind)?;
+# 
+#         #[cfg(feature = &quot;display-cause&quot;)]
+#         {
+#             if let Some(e) = self.source() {
+#                 writeln!(f, &quot;\nCaused by:&quot;)?;
+#                 Display::fmt(&amp;e, f)?;
+#             }
+#         }
+#         Ok(())
+#     }
+# }
+# 
+# impl&lt;T: 'static + Display + Debug&gt; Debug for ChainError&lt;T&gt; {
+#     fn fmt(&amp;self, f: &amp;mut Formatter) -&gt; Result {
+#         #[cfg(not(feature = &quot;no-fileline&quot;))]
+#         {
+#             if let Some(o) = self.occurrence {
+#                 write!(f, &quot;{}:{}: &quot;, o.1, o.0)?;
+#             }
+#         }
+# 
+#         Debug::fmt(&amp;self.kind, f)?;
+# 
+#         #[cfg(not(feature = &quot;no-debug-cause&quot;))]
+#         {
+#             if let Some(e) = self.source() {
+#                 writeln!(f, &quot;\nCaused by:&quot;)?;
+#                 Debug::fmt(&amp;e, f)?;
+#             }
+#         }
+#         Ok(())
+#     }
+# }
+# 
+# #[macro_export]
+# macro_rules! cherr {
+#     ( $k:expr ) =&gt; {
+#         ChainError::&lt;_&gt;::new($k, None, Some((line!(), file!())))
+#     };
+#     ( $e:expr, $k:expr ) =&gt; {
+#         ChainError::&lt;_&gt;::new($k, Some(Box::from($e)), Some((line!(), file!())))
+#     };
+# }
+# 
+# #[macro_export]
+# macro_rules! mstrerr {
+#     ( $t:ident, $v:expr $(, $more:expr)* ) =&gt; {
+#         |e| cherr!(e, $t (format!($v, $( $more , )* )))
+#     };
+#     ( $t:path, $v:expr $(, $more:expr)* ) =&gt; {
+#         |e| cherr!(e, $t (format!($v, $( $more , )* )))
+#     };
+#     ( $v:expr $(, $more:expr)* ) =&gt; {
+#         |e| cherr!(e, format!($v, $( $more , )* ))
+#     };
+# }
+# 
+# #[macro_export]
+# macro_rules! derive_str_cherr {
+#     ($e:ident) =&gt; {
+#         struct $e(String);
+#         impl ::std::fmt::Display for $e {
+#             fn fmt(&amp;self, f: &amp;mut ::std::fmt::Formatter) -&gt; ::std::fmt::Result {
+#                 write!(f, &quot;{}&quot;, self.0)
+#             }
+#         }
+#         impl ::std::fmt::Debug for $e {
+#             fn fmt(&amp;self, f: &amp;mut ::std::fmt::Formatter) -&gt; ::std::fmt::Result {
+#                 write!(f, &quot;{}({})&quot;, stringify!($e), self.0)
+#             }
+#         }
+#         impl ::std::error::Error for $e {}
+#     };
+# }
+# 
+# #[macro_export]
+# macro_rules! try_cherr_ref {
+#     ( $e:expr, $t:ident ) =&gt; {
+#         $e.downcast_ref::&lt;ChainError&lt;$t&gt;&gt;()
+#     };
+#     ( $e:expr, $t:path ) =&gt; {
+#         $e.downcast_ref::&lt;ChainError&lt;$t&gt;&gt;()
+#     };
+# }
+# 
+# #[macro_export]
+# macro_rules! try_cherr_mut {
+#     ( $e:expr, $t:ident ) =&gt; {
+#         $e.downcast_mut::&lt;ChainError&lt;$t&gt;&gt;()
+#     };
+#     ( $e:expr, $t:path ) =&gt; {
+#         $e.downcast_mut::&lt;ChainError&lt;$t&gt;&gt;()
+#     };
+# }
+# }
+</code></pre></pre>
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+                        <h1 class="menu-title">chainerror</h1> 
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+                        <pre><pre class="playpen"><code class="language-rust">use crate::chainerror::*;
+use std::error::Error;
+use std::result::Result;
+
+fn do_some_io() -&gt; Result&lt;(), Box&lt;Error&gt;&gt; {
+    Err(&quot;do_some_io error&quot;)?;
+    Ok(())
+}
+
+fn func2() -&gt; Result&lt;(), Box&lt;Error&gt;&gt; {
+    if let Err(e) = do_some_io() {
+        Err(cherr!(e, &quot;func2 error&quot;))?;
+    }
+    Ok(())
+}
+
+fn func1() -&gt; Result&lt;(), Box&lt;Error&gt;&gt; {
+    if let Err(e) = func2() {
+        Err(cherr!(e, &quot;func1 error&quot;))?;
+    }
+    Ok(())
+}
+
+fn main() -&gt; Result&lt;(), Box&lt;Error&gt;&gt; {
+    func1()
+}
+# #[allow(dead_code)]
+# mod chainerror {
+# use std::error::Error;
+# use std::fmt::{Debug, Display, Formatter, Result};
+# use std::result::Result as StdResult;
+# 
+# pub struct ChainError&lt;T&gt; {
+#     #[cfg(not(feature = &quot;no-fileline&quot;))]
+#     occurrence: Option&lt;(u32, &amp;'static str)&gt;,
+#     kind: T,
+#     error_cause: Option&lt;Box&lt;dyn Error + 'static&gt;&gt;,
+# }
+# 
+# pub type ChainResult&lt;O, E&gt; = StdResult&lt;O, ChainError&lt;E&gt;&gt;;
+# 
+# impl&lt;T: 'static + Display + Debug&gt; ChainError&lt;T&gt; {
+#     #[cfg(not(feature = &quot;no-fileline&quot;))]
+#     pub fn new(
+#         kind: T,
+#         error_cause: Option&lt;Box&lt;dyn Error + 'static&gt;&gt;,
+#         occurrence: Option&lt;(u32, &amp;'static str)&gt;,
+#     ) -&gt; Self {
+#         Self {
+#             occurrence,
+#             kind,
+#             error_cause,
+#         }
+#     }
+# 
+#     #[cfg(feature = &quot;no-fileline&quot;)]
+#     pub fn new(
+#         kind: T,
+#         error_cause: Option&lt;Box&lt;dyn Error + 'static&gt;&gt;,
+#         _occurrence: Option&lt;(u32, &amp;'static str)&gt;,
+#     ) -&gt; Self {
+#         Self { kind, error_cause }
+#     }
+# 
+#     pub fn root_cause(&amp;self) -&gt; Option&lt;&amp;(dyn Error + 'static)&gt; {
+#         let mut cause = self as &amp;(dyn Error + 'static);
+#         while let Some(c) = cause.source() {
+#             cause = c;
+#         }
+#         Some(cause)
+#     }
+# 
+#     pub fn find_cause&lt;U: Error + 'static&gt;(&amp;self) -&gt; Option&lt;&amp;U&gt; {
+#         let mut cause = self as &amp;(dyn Error + 'static);
+#         loop {
+#             if cause.is::&lt;U&gt;() {
+#                 return cause.downcast_ref::&lt;U&gt;();
+#             }
+# 
+#             match cause.source() {
+#                 Some(c) =&gt; cause = c,
+#                 None =&gt; return None,
+#             }
+#         }
+#     }
+# 
+#     pub fn find_chain_cause&lt;U: Error + 'static&gt;(&amp;self) -&gt; Option&lt;&amp;ChainError&lt;U&gt;&gt; {
+#         let mut cause = self as &amp;(dyn Error + 'static);
+#         loop {
+#             if cause.is::&lt;ChainError&lt;U&gt;&gt;() {
+#                 return cause.downcast_ref::&lt;ChainError&lt;U&gt;&gt;();
+#             }
+# 
+#             match cause.source() {
+#                 Some(c) =&gt; cause = c,
+#                 None =&gt; return None,
+#             }
+#         }
+#     }
+# 
+#     pub fn kind&lt;'a&gt;(&amp;'a self) -&gt; &amp;'a T {
+#         &amp;self.kind
+#     }
+# }
+# 
+# pub trait ChainErrorDown {
+#     fn is_chain&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; bool;
+#     fn downcast_chain_ref&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; Option&lt;&amp;ChainError&lt;T&gt;&gt;;
+#     fn downcast_chain_mut&lt;T: 'static + Display + Debug&gt;(&amp;mut self) -&gt; Option&lt;&amp;mut ChainError&lt;T&gt;&gt;;
+# }
+# 
+# use std::any::TypeId;
+# 
+# impl&lt;U: 'static + Display + Debug&gt; ChainErrorDown for ChainError&lt;U&gt; {
+#     fn is_chain&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; bool {
+#         TypeId::of::&lt;T&gt;() == TypeId::of::&lt;U&gt;()
+#     }
+# 
+#     fn downcast_chain_ref&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; Option&lt;&amp;ChainError&lt;T&gt;&gt; {
+#         if self.is_chain::&lt;T&gt;() {
+#             unsafe { Some(&amp;*(self as *const dyn Error as *const &amp;ChainError&lt;T&gt;)) }
+#         } else {
+#             None
+#         }
+#     }
+# 
+#     fn downcast_chain_mut&lt;T: 'static + Display + Debug&gt;(&amp;mut self) -&gt; Option&lt;&amp;mut ChainError&lt;T&gt;&gt; {
+#         if self.is_chain::&lt;T&gt;() {
+#             unsafe { Some(&amp;mut *(self as *mut dyn Error as *mut &amp;mut ChainError&lt;T&gt;)) }
+#         } else {
+#             None
+#         }
+#     }
+# }
+# 
+# impl ChainErrorDown for dyn Error + 'static {
+#     fn is_chain&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; bool {
+#         self.is::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# 
+#     fn downcast_chain_ref&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; Option&lt;&amp;ChainError&lt;T&gt;&gt; {
+#         self.downcast_ref::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# 
+#     fn downcast_chain_mut&lt;T: 'static + Display + Debug&gt;(&amp;mut self) -&gt; Option&lt;&amp;mut ChainError&lt;T&gt;&gt; {
+#         self.downcast_mut::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# }
+# 
+# impl ChainErrorDown for dyn Error + 'static + Send {
+#     fn is_chain&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; bool {
+#         self.is::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# 
+#     fn downcast_chain_ref&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; Option&lt;&amp;ChainError&lt;T&gt;&gt; {
+#         self.downcast_ref::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# 
+#     fn downcast_chain_mut&lt;T: 'static + Display + Debug&gt;(&amp;mut self) -&gt; Option&lt;&amp;mut ChainError&lt;T&gt;&gt; {
+#         self.downcast_mut::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# }
+# 
+# impl ChainErrorDown for dyn Error + 'static + Send + Sync {
+#     fn is_chain&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; bool {
+#         self.is::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# 
+#     fn downcast_chain_ref&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; Option&lt;&amp;ChainError&lt;T&gt;&gt; {
+#         self.downcast_ref::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# 
+#     fn downcast_chain_mut&lt;T: 'static + Display + Debug&gt;(&amp;mut self) -&gt; Option&lt;&amp;mut ChainError&lt;T&gt;&gt; {
+#         self.downcast_mut::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# }
+# 
+# impl&lt;T: 'static + Display + Debug&gt; Error for ChainError&lt;T&gt; {
+#     fn source(&amp;self) -&gt; Option&lt;&amp;(dyn Error + 'static)&gt; {
+#         if let Some(ref e) = self.error_cause {
+#             Some(e.as_ref())
+#         } else {
+#             None
+#         }
+#     }
+# }
+# 
+# impl&lt;T: 'static + Display + Debug&gt; Error for &amp;ChainError&lt;T&gt; {
+#     fn source(&amp;self) -&gt; Option&lt;&amp;(dyn Error + 'static)&gt; {
+#         if let Some(ref e) = self.error_cause {
+#             Some(e.as_ref())
+#         } else {
+#             None
+#         }
+#     }
+# }
+# 
+# impl&lt;T: 'static + Display + Debug&gt; Error for &amp;mut ChainError&lt;T&gt; {
+#     fn source(&amp;self) -&gt; Option&lt;&amp;(dyn Error + 'static)&gt; {
+#         if let Some(ref e) = self.error_cause {
+#             Some(e.as_ref())
+#         } else {
+#             None
+#         }
+#     }
+# }
+# 
+# impl&lt;T: 'static + Display + Debug&gt; Display for ChainError&lt;T&gt; {
+#     fn fmt(&amp;self, f: &amp;mut Formatter) -&gt; Result {
+#         write!(f, &quot;{}&quot;, self.kind)?;
+# 
+#         #[cfg(feature = &quot;display-cause&quot;)]
+#         {
+#             if let Some(e) = self.source() {
+#                 writeln!(f, &quot;\nCaused by:&quot;)?;
+#                 Display::fmt(&amp;e, f)?;
+#             }
+#         }
+#         Ok(())
+#     }
+# }
+# 
+# impl&lt;T: 'static + Display + Debug&gt; Debug for ChainError&lt;T&gt; {
+#     fn fmt(&amp;self, f: &amp;mut Formatter) -&gt; Result {
+#         #[cfg(not(feature = &quot;no-fileline&quot;))]
+#         {
+#             if let Some(o) = self.occurrence {
+#                 write!(f, &quot;{}:{}: &quot;, o.1, o.0)?;
+#             }
+#         }
+# 
+#         Debug::fmt(&amp;self.kind, f)?;
+# 
+#         #[cfg(not(feature = &quot;no-debug-cause&quot;))]
+#         {
+#             if let Some(e) = self.source() {
+#                 writeln!(f, &quot;\nCaused by:&quot;)?;
+#                 Debug::fmt(&amp;e, f)?;
+#             }
+#         }
+#         Ok(())
+#     }
+# }
+# 
+# #[macro_export]
+# macro_rules! cherr {
+#     ( $k:expr ) =&gt; {
+#         ChainError::&lt;_&gt;::new($k, None, Some((line!(), file!())))
+#     };
+#     ( $e:expr, $k:expr ) =&gt; {
+#         ChainError::&lt;_&gt;::new($k, Some(Box::from($e)), Some((line!(), file!())))
+#     };
+# }
+# 
+# #[macro_export]
+# macro_rules! mstrerr {
+#     ( $t:ident, $v:expr $(, $more:expr)* ) =&gt; {
+#         |e| cherr!(e, $t (format!($v, $( $more , )* )))
+#     };
+#     ( $t:path, $v:expr $(, $more:expr)* ) =&gt; {
+#         |e| cherr!(e, $t (format!($v, $( $more , )* )))
+#     };
+#     ( $v:expr $(, $more:expr)* ) =&gt; {
+#         |e| cherr!(e, format!($v, $( $more , )* ))
+#     };
+# }
+# 
+# #[macro_export]
+# macro_rules! derive_str_cherr {
+#     ($e:ident) =&gt; {
+#         struct $e(String);
+#         impl ::std::fmt::Display for $e {
+#             fn fmt(&amp;self, f: &amp;mut ::std::fmt::Formatter) -&gt; ::std::fmt::Result {
+#                 write!(f, &quot;{}&quot;, self.0)
+#             }
+#         }
+#         impl ::std::fmt::Debug for $e {
+#             fn fmt(&amp;self, f: &amp;mut ::std::fmt::Formatter) -&gt; ::std::fmt::Result {
+#                 write!(f, &quot;{}({})&quot;, stringify!($e), self.0)
+#             }
+#         }
+#         impl ::std::error::Error for $e {}
+#     };
+# }
+# 
+# #[macro_export]
+# macro_rules! try_cherr_ref {
+#     ( $e:expr, $t:ident ) =&gt; {
+#         $e.downcast_ref::&lt;ChainError&lt;$t&gt;&gt;()
+#     };
+#     ( $e:expr, $t:path ) =&gt; {
+#         $e.downcast_ref::&lt;ChainError&lt;$t&gt;&gt;()
+#     };
+# }
+# 
+# #[macro_export]
+# macro_rules! try_cherr_mut {
+#     ( $e:expr, $t:ident ) =&gt; {
+#         $e.downcast_mut::&lt;ChainError&lt;$t&gt;&gt;()
+#     };
+#     ( $e:expr, $t:path ) =&gt; {
+#         $e.downcast_mut::&lt;ChainError&lt;$t&gt;&gt;()
+#     };
+# }
+# }
+</code></pre></pre>
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+                        <h1 class="menu-title">chainerror</h1> 
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+                        <pre><pre class="playpen"><code class="language-rust">use crate::chainerror::*;
+use std::error::Error;
+use std::result::Result;
+
+fn do_some_io() -&gt; Result&lt;(), Box&lt;Error&gt;&gt; {
+    Err(&quot;do_some_io error&quot;)?;
+    Ok(())
+}
+
+fn func2() -&gt; Result&lt;(), Box&lt;Error&gt;&gt; {
+    do_some_io().map_err(|e| cherr!(e, &quot;func2 error&quot;))?;
+    Ok(())
+}
+
+fn func1() -&gt; Result&lt;(), Box&lt;Error&gt;&gt; {
+    func2().map_err(|e| cherr!(e, &quot;func1 error&quot;))?;
+    Ok(())
+}
+
+fn main() -&gt; Result&lt;(), Box&lt;Error&gt;&gt; {
+    if let Err(e) = func1() {
+        eprintln!(&quot;{:?}&quot;, e);
+    }
+    Ok(())
+}
+# #[allow(dead_code)]
+# mod chainerror {
+# use std::error::Error;
+# use std::fmt::{Debug, Display, Formatter, Result};
+# use std::result::Result as StdResult;
+# 
+# pub struct ChainError&lt;T&gt; {
+#     #[cfg(not(feature = &quot;no-fileline&quot;))]
+#     occurrence: Option&lt;(u32, &amp;'static str)&gt;,
+#     kind: T,
+#     error_cause: Option&lt;Box&lt;dyn Error + 'static&gt;&gt;,
+# }
+# 
+# pub type ChainResult&lt;O, E&gt; = StdResult&lt;O, ChainError&lt;E&gt;&gt;;
+# 
+# impl&lt;T: 'static + Display + Debug&gt; ChainError&lt;T&gt; {
+#     #[cfg(not(feature = &quot;no-fileline&quot;))]
+#     pub fn new(
+#         kind: T,
+#         error_cause: Option&lt;Box&lt;dyn Error + 'static&gt;&gt;,
+#         occurrence: Option&lt;(u32, &amp;'static str)&gt;,
+#     ) -&gt; Self {
+#         Self {
+#             occurrence,
+#             kind,
+#             error_cause,
+#         }
+#     }
+# 
+#     #[cfg(feature = &quot;no-fileline&quot;)]
+#     pub fn new(
+#         kind: T,
+#         error_cause: Option&lt;Box&lt;dyn Error + 'static&gt;&gt;,
+#         _occurrence: Option&lt;(u32, &amp;'static str)&gt;,
+#     ) -&gt; Self {
+#         Self { kind, error_cause }
+#     }
+# 
+#     pub fn root_cause(&amp;self) -&gt; Option&lt;&amp;(dyn Error + 'static)&gt; {
+#         let mut cause = self as &amp;(dyn Error + 'static);
+#         while let Some(c) = cause.source() {
+#             cause = c;
+#         }
+#         Some(cause)
+#     }
+# 
+#     pub fn find_cause&lt;U: Error + 'static&gt;(&amp;self) -&gt; Option&lt;&amp;U&gt; {
+#         let mut cause = self as &amp;(dyn Error + 'static);
+#         loop {
+#             if cause.is::&lt;U&gt;() {
+#                 return cause.downcast_ref::&lt;U&gt;();
+#             }
+# 
+#             match cause.source() {
+#                 Some(c) =&gt; cause = c,
+#                 None =&gt; return None,
+#             }
+#         }
+#     }
+# 
+#     pub fn find_chain_cause&lt;U: Error + 'static&gt;(&amp;self) -&gt; Option&lt;&amp;ChainError&lt;U&gt;&gt; {
+#         let mut cause = self as &amp;(dyn Error + 'static);
+#         loop {
+#             if cause.is::&lt;ChainError&lt;U&gt;&gt;() {
+#                 return cause.downcast_ref::&lt;ChainError&lt;U&gt;&gt;();
+#             }
+# 
+#             match cause.source() {
+#                 Some(c) =&gt; cause = c,
+#                 None =&gt; return None,
+#             }
+#         }
+#     }
+# 
+#     pub fn kind&lt;'a&gt;(&amp;'a self) -&gt; &amp;'a T {
+#         &amp;self.kind
+#     }
+# }
+# 
+# pub trait ChainErrorDown {
+#     fn is_chain&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; bool;
+#     fn downcast_chain_ref&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; Option&lt;&amp;ChainError&lt;T&gt;&gt;;
+#     fn downcast_chain_mut&lt;T: 'static + Display + Debug&gt;(&amp;mut self) -&gt; Option&lt;&amp;mut ChainError&lt;T&gt;&gt;;
+# }
+# 
+# use std::any::TypeId;
+# 
+# impl&lt;U: 'static + Display + Debug&gt; ChainErrorDown for ChainError&lt;U&gt; {
+#     fn is_chain&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; bool {
+#         TypeId::of::&lt;T&gt;() == TypeId::of::&lt;U&gt;()
+#     }
+# 
+#     fn downcast_chain_ref&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; Option&lt;&amp;ChainError&lt;T&gt;&gt; {
+#         if self.is_chain::&lt;T&gt;() {
+#             unsafe { Some(&amp;*(self as *const dyn Error as *const &amp;ChainError&lt;T&gt;)) }
+#         } else {
+#             None
+#         }
+#     }
+# 
+#     fn downcast_chain_mut&lt;T: 'static + Display + Debug&gt;(&amp;mut self) -&gt; Option&lt;&amp;mut ChainError&lt;T&gt;&gt; {
+#         if self.is_chain::&lt;T&gt;() {
+#             unsafe { Some(&amp;mut *(self as *mut dyn Error as *mut &amp;mut ChainError&lt;T&gt;)) }
+#         } else {
+#             None
+#         }
+#     }
+# }
+# 
+# impl ChainErrorDown for dyn Error + 'static {
+#     fn is_chain&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; bool {
+#         self.is::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# 
+#     fn downcast_chain_ref&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; Option&lt;&amp;ChainError&lt;T&gt;&gt; {
+#         self.downcast_ref::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# 
+#     fn downcast_chain_mut&lt;T: 'static + Display + Debug&gt;(&amp;mut self) -&gt; Option&lt;&amp;mut ChainError&lt;T&gt;&gt; {
+#         self.downcast_mut::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# }
+# 
+# impl ChainErrorDown for dyn Error + 'static + Send {
+#     fn is_chain&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; bool {
+#         self.is::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# 
+#     fn downcast_chain_ref&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; Option&lt;&amp;ChainError&lt;T&gt;&gt; {
+#         self.downcast_ref::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# 
+#     fn downcast_chain_mut&lt;T: 'static + Display + Debug&gt;(&amp;mut self) -&gt; Option&lt;&amp;mut ChainError&lt;T&gt;&gt; {
+#         self.downcast_mut::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# }
+# 
+# impl ChainErrorDown for dyn Error + 'static + Send + Sync {
+#     fn is_chain&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; bool {
+#         self.is::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# 
+#     fn downcast_chain_ref&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; Option&lt;&amp;ChainError&lt;T&gt;&gt; {
+#         self.downcast_ref::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# 
+#     fn downcast_chain_mut&lt;T: 'static + Display + Debug&gt;(&amp;mut self) -&gt; Option&lt;&amp;mut ChainError&lt;T&gt;&gt; {
+#         self.downcast_mut::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# }
+# 
+# impl&lt;T: 'static + Display + Debug&gt; Error for ChainError&lt;T&gt; {
+#     fn source(&amp;self) -&gt; Option&lt;&amp;(dyn Error + 'static)&gt; {
+#         if let Some(ref e) = self.error_cause {
+#             Some(e.as_ref())
+#         } else {
+#             None
+#         }
+#     }
+# }
+# 
+# impl&lt;T: 'static + Display + Debug&gt; Error for &amp;ChainError&lt;T&gt; {
+#     fn source(&amp;self) -&gt; Option&lt;&amp;(dyn Error + 'static)&gt; {
+#         if let Some(ref e) = self.error_cause {
+#             Some(e.as_ref())
+#         } else {
+#             None
+#         }
+#     }
+# }
+# 
+# impl&lt;T: 'static + Display + Debug&gt; Error for &amp;mut ChainError&lt;T&gt; {
+#     fn source(&amp;self) -&gt; Option&lt;&amp;(dyn Error + 'static)&gt; {
+#         if let Some(ref e) = self.error_cause {
+#             Some(e.as_ref())
+#         } else {
+#             None
+#         }
+#     }
+# }
+# 
+# impl&lt;T: 'static + Display + Debug&gt; Display for ChainError&lt;T&gt; {
+#     fn fmt(&amp;self, f: &amp;mut Formatter) -&gt; Result {
+#         write!(f, &quot;{}&quot;, self.kind)?;
+# 
+#         #[cfg(feature = &quot;display-cause&quot;)]
+#         {
+#             if let Some(e) = self.source() {
+#                 writeln!(f, &quot;\nCaused by:&quot;)?;
+#                 Display::fmt(&amp;e, f)?;
+#             }
+#         }
+#         Ok(())
+#     }
+# }
+# 
+# impl&lt;T: 'static + Display + Debug&gt; Debug for ChainError&lt;T&gt; {
+#     fn fmt(&amp;self, f: &amp;mut Formatter) -&gt; Result {
+#         #[cfg(not(feature = &quot;no-fileline&quot;))]
+#         {
+#             if let Some(o) = self.occurrence {
+#                 write!(f, &quot;{}:{}: &quot;, o.1, o.0)?;
+#             }
+#         }
+# 
+#         Debug::fmt(&amp;self.kind, f)?;
+# 
+#         #[cfg(not(feature = &quot;no-debug-cause&quot;))]
+#         {
+#             if let Some(e) = self.source() {
+#                 writeln!(f, &quot;\nCaused by:&quot;)?;
+#                 Debug::fmt(&amp;e, f)?;
+#             }
+#         }
+#         Ok(())
+#     }
+# }
+# 
+# #[macro_export]
+# macro_rules! cherr {
+#     ( $k:expr ) =&gt; {
+#         ChainError::&lt;_&gt;::new($k, None, Some((line!(), file!())))
+#     };
+#     ( $e:expr, $k:expr ) =&gt; {
+#         ChainError::&lt;_&gt;::new($k, Some(Box::from($e)), Some((line!(), file!())))
+#     };
+# }
+# 
+# #[macro_export]
+# macro_rules! mstrerr {
+#     ( $t:ident, $v:expr $(, $more:expr)* ) =&gt; {
+#         |e| cherr!(e, $t (format!($v, $( $more , )* )))
+#     };
+#     ( $t:path, $v:expr $(, $more:expr)* ) =&gt; {
+#         |e| cherr!(e, $t (format!($v, $( $more , )* )))
+#     };
+#     ( $v:expr $(, $more:expr)* ) =&gt; {
+#         |e| cherr!(e, format!($v, $( $more , )* ))
+#     };
+# }
+# 
+# #[macro_export]
+# macro_rules! derive_str_cherr {
+#     ($e:ident) =&gt; {
+#         struct $e(String);
+#         impl ::std::fmt::Display for $e {
+#             fn fmt(&amp;self, f: &amp;mut ::std::fmt::Formatter) -&gt; ::std::fmt::Result {
+#                 write!(f, &quot;{}&quot;, self.0)
+#             }
+#         }
+#         impl ::std::fmt::Debug for $e {
+#             fn fmt(&amp;self, f: &amp;mut ::std::fmt::Formatter) -&gt; ::std::fmt::Result {
+#                 write!(f, &quot;{}({})&quot;, stringify!($e), self.0)
+#             }
+#         }
+#         impl ::std::error::Error for $e {}
+#     };
+# }
+# 
+# #[macro_export]
+# macro_rules! try_cherr_ref {
+#     ( $e:expr, $t:ident ) =&gt; {
+#         $e.downcast_ref::&lt;ChainError&lt;$t&gt;&gt;()
+#     };
+#     ( $e:expr, $t:path ) =&gt; {
+#         $e.downcast_ref::&lt;ChainError&lt;$t&gt;&gt;()
+#     };
+# }
+# 
+# #[macro_export]
+# macro_rules! try_cherr_mut {
+#     ( $e:expr, $t:ident ) =&gt; {
+#         $e.downcast_mut::&lt;ChainError&lt;$t&gt;&gt;()
+#     };
+#     ( $e:expr, $t:path ) =&gt; {
+#         $e.downcast_mut::&lt;ChainError&lt;$t&gt;&gt;()
+#     };
+# }
+# }
+</code></pre></pre>
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+                        <h1 class="menu-title">chainerror</h1> 
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+                        <pre><pre class="playpen"><code class="language-rust">use crate::chainerror::*;
+use std::error::Error;
+use std::result::Result;
+
+fn do_some_io() -&gt; Result&lt;(), Box&lt;Error&gt;&gt; {
+    Err(&quot;do_some_io error&quot;)?;
+    Ok(())
+}
+
+fn func2() -&gt; Result&lt;(), Box&lt;Error&gt;&gt; {
+    do_some_io().map_err(mstrerr!(&quot;func2 error&quot;))?;
+    Ok(())
+}
+
+fn func1() -&gt; Result&lt;(), Box&lt;Error&gt;&gt; {
+    func2().map_err(mstrerr!(&quot;func1 error&quot;))?;
+    Ok(())
+}
+
+fn main() -&gt; Result&lt;(), Box&lt;Error&gt;&gt; {
+    if let Err(e) = func1() {
+        eprintln!(&quot;{:?}&quot;, e);
+    }
+    Ok(())
+}
+# #[allow(dead_code)]
+# mod chainerror {
+# use std::error::Error;
+# use std::fmt::{Debug, Display, Formatter, Result};
+# use std::result::Result as StdResult;
+# 
+# pub struct ChainError&lt;T&gt; {
+#     #[cfg(not(feature = &quot;no-fileline&quot;))]
+#     occurrence: Option&lt;(u32, &amp;'static str)&gt;,
+#     kind: T,
+#     error_cause: Option&lt;Box&lt;dyn Error + 'static&gt;&gt;,
+# }
+# 
+# pub type ChainResult&lt;O, E&gt; = StdResult&lt;O, ChainError&lt;E&gt;&gt;;
+# 
+# impl&lt;T: 'static + Display + Debug&gt; ChainError&lt;T&gt; {
+#     #[cfg(not(feature = &quot;no-fileline&quot;))]
+#     pub fn new(
+#         kind: T,
+#         error_cause: Option&lt;Box&lt;dyn Error + 'static&gt;&gt;,
+#         occurrence: Option&lt;(u32, &amp;'static str)&gt;,
+#     ) -&gt; Self {
+#         Self {
+#             occurrence,
+#             kind,
+#             error_cause,
+#         }
+#     }
+# 
+#     #[cfg(feature = &quot;no-fileline&quot;)]
+#     pub fn new(
+#         kind: T,
+#         error_cause: Option&lt;Box&lt;dyn Error + 'static&gt;&gt;,
+#         _occurrence: Option&lt;(u32, &amp;'static str)&gt;,
+#     ) -&gt; Self {
+#         Self { kind, error_cause }
+#     }
+# 
+#     pub fn root_cause(&amp;self) -&gt; Option&lt;&amp;(dyn Error + 'static)&gt; {
+#         let mut cause = self as &amp;(dyn Error + 'static);
+#         while let Some(c) = cause.source() {
+#             cause = c;
+#         }
+#         Some(cause)
+#     }
+# 
+#     pub fn find_cause&lt;U: Error + 'static&gt;(&amp;self) -&gt; Option&lt;&amp;U&gt; {
+#         let mut cause = self as &amp;(dyn Error + 'static);
+#         loop {
+#             if cause.is::&lt;U&gt;() {
+#                 return cause.downcast_ref::&lt;U&gt;();
+#             }
+# 
+#             match cause.source() {
+#                 Some(c) =&gt; cause = c,
+#                 None =&gt; return None,
+#             }
+#         }
+#     }
+# 
+#     pub fn find_chain_cause&lt;U: Error + 'static&gt;(&amp;self) -&gt; Option&lt;&amp;ChainError&lt;U&gt;&gt; {
+#         let mut cause = self as &amp;(dyn Error + 'static);
+#         loop {
+#             if cause.is::&lt;ChainError&lt;U&gt;&gt;() {
+#                 return cause.downcast_ref::&lt;ChainError&lt;U&gt;&gt;();
+#             }
+# 
+#             match cause.source() {
+#                 Some(c) =&gt; cause = c,
+#                 None =&gt; return None,
+#             }
+#         }
+#     }
+# 
+#     pub fn kind&lt;'a&gt;(&amp;'a self) -&gt; &amp;'a T {
+#         &amp;self.kind
+#     }
+# }
+# 
+# pub trait ChainErrorDown {
+#     fn is_chain&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; bool;
+#     fn downcast_chain_ref&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; Option&lt;&amp;ChainError&lt;T&gt;&gt;;
+#     fn downcast_chain_mut&lt;T: 'static + Display + Debug&gt;(&amp;mut self) -&gt; Option&lt;&amp;mut ChainError&lt;T&gt;&gt;;
+# }
+# 
+# use std::any::TypeId;
+# 
+# impl&lt;U: 'static + Display + Debug&gt; ChainErrorDown for ChainError&lt;U&gt; {
+#     fn is_chain&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; bool {
+#         TypeId::of::&lt;T&gt;() == TypeId::of::&lt;U&gt;()
+#     }
+# 
+#     fn downcast_chain_ref&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; Option&lt;&amp;ChainError&lt;T&gt;&gt; {
+#         if self.is_chain::&lt;T&gt;() {
+#             unsafe { Some(&amp;*(self as *const dyn Error as *const &amp;ChainError&lt;T&gt;)) }
+#         } else {
+#             None
+#         }
+#     }
+# 
+#     fn downcast_chain_mut&lt;T: 'static + Display + Debug&gt;(&amp;mut self) -&gt; Option&lt;&amp;mut ChainError&lt;T&gt;&gt; {
+#         if self.is_chain::&lt;T&gt;() {
+#             unsafe { Some(&amp;mut *(self as *mut dyn Error as *mut &amp;mut ChainError&lt;T&gt;)) }
+#         } else {
+#             None
+#         }
+#     }
+# }
+# 
+# impl ChainErrorDown for dyn Error + 'static {
+#     fn is_chain&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; bool {
+#         self.is::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# 
+#     fn downcast_chain_ref&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; Option&lt;&amp;ChainError&lt;T&gt;&gt; {
+#         self.downcast_ref::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# 
+#     fn downcast_chain_mut&lt;T: 'static + Display + Debug&gt;(&amp;mut self) -&gt; Option&lt;&amp;mut ChainError&lt;T&gt;&gt; {
+#         self.downcast_mut::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# }
+# 
+# impl ChainErrorDown for dyn Error + 'static + Send {
+#     fn is_chain&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; bool {
+#         self.is::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# 
+#     fn downcast_chain_ref&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; Option&lt;&amp;ChainError&lt;T&gt;&gt; {
+#         self.downcast_ref::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# 
+#     fn downcast_chain_mut&lt;T: 'static + Display + Debug&gt;(&amp;mut self) -&gt; Option&lt;&amp;mut ChainError&lt;T&gt;&gt; {
+#         self.downcast_mut::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# }
+# 
+# impl ChainErrorDown for dyn Error + 'static + Send + Sync {
+#     fn is_chain&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; bool {
+#         self.is::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# 
+#     fn downcast_chain_ref&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; Option&lt;&amp;ChainError&lt;T&gt;&gt; {
+#         self.downcast_ref::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# 
+#     fn downcast_chain_mut&lt;T: 'static + Display + Debug&gt;(&amp;mut self) -&gt; Option&lt;&amp;mut ChainError&lt;T&gt;&gt; {
+#         self.downcast_mut::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# }
+# 
+# impl&lt;T: 'static + Display + Debug&gt; Error for ChainError&lt;T&gt; {
+#     fn source(&amp;self) -&gt; Option&lt;&amp;(dyn Error + 'static)&gt; {
+#         if let Some(ref e) = self.error_cause {
+#             Some(e.as_ref())
+#         } else {
+#             None
+#         }
+#     }
+# }
+# 
+# impl&lt;T: 'static + Display + Debug&gt; Error for &amp;ChainError&lt;T&gt; {
+#     fn source(&amp;self) -&gt; Option&lt;&amp;(dyn Error + 'static)&gt; {
+#         if let Some(ref e) = self.error_cause {
+#             Some(e.as_ref())
+#         } else {
+#             None
+#         }
+#     }
+# }
+# 
+# impl&lt;T: 'static + Display + Debug&gt; Error for &amp;mut ChainError&lt;T&gt; {
+#     fn source(&amp;self) -&gt; Option&lt;&amp;(dyn Error + 'static)&gt; {
+#         if let Some(ref e) = self.error_cause {
+#             Some(e.as_ref())
+#         } else {
+#             None
+#         }
+#     }
+# }
+# 
+# impl&lt;T: 'static + Display + Debug&gt; Display for ChainError&lt;T&gt; {
+#     fn fmt(&amp;self, f: &amp;mut Formatter) -&gt; Result {
+#         write!(f, &quot;{}&quot;, self.kind)?;
+# 
+#         #[cfg(feature = &quot;display-cause&quot;)]
+#         {
+#             if let Some(e) = self.source() {
+#                 writeln!(f, &quot;\nCaused by:&quot;)?;
+#                 Display::fmt(&amp;e, f)?;
+#             }
+#         }
+#         Ok(())
+#     }
+# }
+# 
+# impl&lt;T: 'static + Display + Debug&gt; Debug for ChainError&lt;T&gt; {
+#     fn fmt(&amp;self, f: &amp;mut Formatter) -&gt; Result {
+#         #[cfg(not(feature = &quot;no-fileline&quot;))]
+#         {
+#             if let Some(o) = self.occurrence {
+#                 write!(f, &quot;{}:{}: &quot;, o.1, o.0)?;
+#             }
+#         }
+# 
+#         Debug::fmt(&amp;self.kind, f)?;
+# 
+#         #[cfg(not(feature = &quot;no-debug-cause&quot;))]
+#         {
+#             if let Some(e) = self.source() {
+#                 writeln!(f, &quot;\nCaused by:&quot;)?;
+#                 Debug::fmt(&amp;e, f)?;
+#             }
+#         }
+#         Ok(())
+#     }
+# }
+# 
+# #[macro_export]
+# macro_rules! cherr {
+#     ( $k:expr ) =&gt; {
+#         ChainError::&lt;_&gt;::new($k, None, Some((line!(), file!())))
+#     };
+#     ( $e:expr, $k:expr ) =&gt; {
+#         ChainError::&lt;_&gt;::new($k, Some(Box::from($e)), Some((line!(), file!())))
+#     };
+# }
+# 
+# #[macro_export]
+# macro_rules! mstrerr {
+#     ( $t:ident, $v:expr $(, $more:expr)* ) =&gt; {
+#         |e| cherr!(e, $t (format!($v, $( $more , )* )))
+#     };
+#     ( $t:path, $v:expr $(, $more:expr)* ) =&gt; {
+#         |e| cherr!(e, $t (format!($v, $( $more , )* )))
+#     };
+#     ( $v:expr $(, $more:expr)* ) =&gt; {
+#         |e| cherr!(e, format!($v, $( $more , )* ))
+#     };
+# }
+# 
+# #[macro_export]
+# macro_rules! derive_str_cherr {
+#     ($e:ident) =&gt; {
+#         struct $e(String);
+#         impl ::std::fmt::Display for $e {
+#             fn fmt(&amp;self, f: &amp;mut ::std::fmt::Formatter) -&gt; ::std::fmt::Result {
+#                 write!(f, &quot;{}&quot;, self.0)
+#             }
+#         }
+#         impl ::std::fmt::Debug for $e {
+#             fn fmt(&amp;self, f: &amp;mut ::std::fmt::Formatter) -&gt; ::std::fmt::Result {
+#                 write!(f, &quot;{}({})&quot;, stringify!($e), self.0)
+#             }
+#         }
+#         impl ::std::error::Error for $e {}
+#     };
+# }
+# 
+# #[macro_export]
+# macro_rules! try_cherr_ref {
+#     ( $e:expr, $t:ident ) =&gt; {
+#         $e.downcast_ref::&lt;ChainError&lt;$t&gt;&gt;()
+#     };
+#     ( $e:expr, $t:path ) =&gt; {
+#         $e.downcast_ref::&lt;ChainError&lt;$t&gt;&gt;()
+#     };
+# }
+# 
+# #[macro_export]
+# macro_rules! try_cherr_mut {
+#     ( $e:expr, $t:ident ) =&gt; {
+#         $e.downcast_mut::&lt;ChainError&lt;$t&gt;&gt;()
+#     };
+#     ( $e:expr, $t:path ) =&gt; {
+#         $e.downcast_mut::&lt;ChainError&lt;$t&gt;&gt;()
+#     };
+# }
+# }
+</code></pre></pre>
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+                        <h1 class="menu-title">chainerror</h1> 
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+                    <main>
+                        <pre><pre class="playpen"><code class="language-rust">use crate::chainerror::*;
+use std::error::Error;
+use std::io;
+use std::result::Result;
+
+fn do_some_io() -&gt; Result&lt;(), Box&lt;Error&gt;&gt; {
+    Err(io::Error::from(io::ErrorKind::NotFound))?;
+    Ok(())
+}
+
+fn func2() -&gt; Result&lt;(), Box&lt;Error&gt;&gt; {
+    let filename = &quot;foo.txt&quot;;
+    do_some_io().map_err(mstrerr!(&quot;Error reading '{}'&quot;, filename))?;
+    Ok(())
+}
+
+fn func1() -&gt; Result&lt;(), Box&lt;Error&gt;&gt; {
+    if let Err(e) = func2() {
+        if let Some(s) = e.source() {
+            eprintln!(&quot;func2 failed because of '{}'&quot;, s);
+            Err(e).map_err(mstrerr!(&quot;func1 error&quot;))?;
+        }
+    }
+    Ok(())
+}
+
+fn main() -&gt; Result&lt;(), Box&lt;Error&gt;&gt; {
+    if let Err(e) = func1() {
+        eprintln!(&quot;{}&quot;, e);
+    }
+    Ok(())
+}
+# #[allow(dead_code)]
+# mod chainerror {
+# use std::error::Error;
+# use std::fmt::{Debug, Display, Formatter, Result};
+# use std::result::Result as StdResult;
+# 
+# pub struct ChainError&lt;T&gt; {
+#     #[cfg(not(feature = &quot;no-fileline&quot;))]
+#     occurrence: Option&lt;(u32, &amp;'static str)&gt;,
+#     kind: T,
+#     error_cause: Option&lt;Box&lt;dyn Error + 'static&gt;&gt;,
+# }
+# 
+# pub type ChainResult&lt;O, E&gt; = StdResult&lt;O, ChainError&lt;E&gt;&gt;;
+# 
+# impl&lt;T: 'static + Display + Debug&gt; ChainError&lt;T&gt; {
+#     #[cfg(not(feature = &quot;no-fileline&quot;))]
+#     pub fn new(
+#         kind: T,
+#         error_cause: Option&lt;Box&lt;dyn Error + 'static&gt;&gt;,
+#         occurrence: Option&lt;(u32, &amp;'static str)&gt;,
+#     ) -&gt; Self {
+#         Self {
+#             occurrence,
+#             kind,
+#             error_cause,
+#         }
+#     }
+# 
+#     #[cfg(feature = &quot;no-fileline&quot;)]
+#     pub fn new(
+#         kind: T,
+#         error_cause: Option&lt;Box&lt;dyn Error + 'static&gt;&gt;,
+#         _occurrence: Option&lt;(u32, &amp;'static str)&gt;,
+#     ) -&gt; Self {
+#         Self { kind, error_cause }
+#     }
+# 
+#     pub fn root_cause(&amp;self) -&gt; Option&lt;&amp;(dyn Error + 'static)&gt; {
+#         let mut cause = self as &amp;(dyn Error + 'static);
+#         while let Some(c) = cause.source() {
+#             cause = c;
+#         }
+#         Some(cause)
+#     }
+# 
+#     pub fn find_cause&lt;U: Error + 'static&gt;(&amp;self) -&gt; Option&lt;&amp;U&gt; {
+#         let mut cause = self as &amp;(dyn Error + 'static);
+#         loop {
+#             if cause.is::&lt;U&gt;() {
+#                 return cause.downcast_ref::&lt;U&gt;();
+#             }
+# 
+#             match cause.source() {
+#                 Some(c) =&gt; cause = c,
+#                 None =&gt; return None,
+#             }
+#         }
+#     }
+# 
+#     pub fn find_chain_cause&lt;U: Error + 'static&gt;(&amp;self) -&gt; Option&lt;&amp;ChainError&lt;U&gt;&gt; {
+#         let mut cause = self as &amp;(dyn Error + 'static);
+#         loop {
+#             if cause.is::&lt;ChainError&lt;U&gt;&gt;() {
+#                 return cause.downcast_ref::&lt;ChainError&lt;U&gt;&gt;();
+#             }
+# 
+#             match cause.source() {
+#                 Some(c) =&gt; cause = c,
+#                 None =&gt; return None,
+#             }
+#         }
+#     }
+# 
+#     pub fn kind&lt;'a&gt;(&amp;'a self) -&gt; &amp;'a T {
+#         &amp;self.kind
+#     }
+# }
+# 
+# pub trait ChainErrorDown {
+#     fn is_chain&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; bool;
+#     fn downcast_chain_ref&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; Option&lt;&amp;ChainError&lt;T&gt;&gt;;
+#     fn downcast_chain_mut&lt;T: 'static + Display + Debug&gt;(&amp;mut self) -&gt; Option&lt;&amp;mut ChainError&lt;T&gt;&gt;;
+# }
+# 
+# use std::any::TypeId;
+# 
+# impl&lt;U: 'static + Display + Debug&gt; ChainErrorDown for ChainError&lt;U&gt; {
+#     fn is_chain&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; bool {
+#         TypeId::of::&lt;T&gt;() == TypeId::of::&lt;U&gt;()
+#     }
+# 
+#     fn downcast_chain_ref&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; Option&lt;&amp;ChainError&lt;T&gt;&gt; {
+#         if self.is_chain::&lt;T&gt;() {
+#             unsafe { Some(&amp;*(self as *const dyn Error as *const &amp;ChainError&lt;T&gt;)) }
+#         } else {
+#             None
+#         }
+#     }
+# 
+#     fn downcast_chain_mut&lt;T: 'static + Display + Debug&gt;(&amp;mut self) -&gt; Option&lt;&amp;mut ChainError&lt;T&gt;&gt; {
+#         if self.is_chain::&lt;T&gt;() {
+#             unsafe { Some(&amp;mut *(self as *mut dyn Error as *mut &amp;mut ChainError&lt;T&gt;)) }
+#         } else {
+#             None
+#         }
+#     }
+# }
+# 
+# impl ChainErrorDown for dyn Error + 'static {
+#     fn is_chain&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; bool {
+#         self.is::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# 
+#     fn downcast_chain_ref&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; Option&lt;&amp;ChainError&lt;T&gt;&gt; {
+#         self.downcast_ref::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# 
+#     fn downcast_chain_mut&lt;T: 'static + Display + Debug&gt;(&amp;mut self) -&gt; Option&lt;&amp;mut ChainError&lt;T&gt;&gt; {
+#         self.downcast_mut::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# }
+# 
+# impl ChainErrorDown for dyn Error + 'static + Send {
+#     fn is_chain&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; bool {
+#         self.is::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# 
+#     fn downcast_chain_ref&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; Option&lt;&amp;ChainError&lt;T&gt;&gt; {
+#         self.downcast_ref::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# 
+#     fn downcast_chain_mut&lt;T: 'static + Display + Debug&gt;(&amp;mut self) -&gt; Option&lt;&amp;mut ChainError&lt;T&gt;&gt; {
+#         self.downcast_mut::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# }
+# 
+# impl ChainErrorDown for dyn Error + 'static + Send + Sync {
+#     fn is_chain&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; bool {
+#         self.is::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# 
+#     fn downcast_chain_ref&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; Option&lt;&amp;ChainError&lt;T&gt;&gt; {
+#         self.downcast_ref::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# 
+#     fn downcast_chain_mut&lt;T: 'static + Display + Debug&gt;(&amp;mut self) -&gt; Option&lt;&amp;mut ChainError&lt;T&gt;&gt; {
+#         self.downcast_mut::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# }
+# 
+# impl&lt;T: 'static + Display + Debug&gt; Error for ChainError&lt;T&gt; {
+#     fn source(&amp;self) -&gt; Option&lt;&amp;(dyn Error + 'static)&gt; {
+#         if let Some(ref e) = self.error_cause {
+#             Some(e.as_ref())
+#         } else {
+#             None
+#         }
+#     }
+# }
+# 
+# impl&lt;T: 'static + Display + Debug&gt; Error for &amp;ChainError&lt;T&gt; {
+#     fn source(&amp;self) -&gt; Option&lt;&amp;(dyn Error + 'static)&gt; {
+#         if let Some(ref e) = self.error_cause {
+#             Some(e.as_ref())
+#         } else {
+#             None
+#         }
+#     }
+# }
+# 
+# impl&lt;T: 'static + Display + Debug&gt; Error for &amp;mut ChainError&lt;T&gt; {
+#     fn source(&amp;self) -&gt; Option&lt;&amp;(dyn Error + 'static)&gt; {
+#         if let Some(ref e) = self.error_cause {
+#             Some(e.as_ref())
+#         } else {
+#             None
+#         }
+#     }
+# }
+# 
+# impl&lt;T: 'static + Display + Debug&gt; Display for ChainError&lt;T&gt; {
+#     fn fmt(&amp;self, f: &amp;mut Formatter) -&gt; Result {
+#         write!(f, &quot;{}&quot;, self.kind)?;
+# 
+#         #[cfg(feature = &quot;display-cause&quot;)]
+#         {
+#             if let Some(e) = self.source() {
+#                 writeln!(f, &quot;\nCaused by:&quot;)?;
+#                 Display::fmt(&amp;e, f)?;
+#             }
+#         }
+#         Ok(())
+#     }
+# }
+# 
+# impl&lt;T: 'static + Display + Debug&gt; Debug for ChainError&lt;T&gt; {
+#     fn fmt(&amp;self, f: &amp;mut Formatter) -&gt; Result {
+#         #[cfg(not(feature = &quot;no-fileline&quot;))]
+#         {
+#             if let Some(o) = self.occurrence {
+#                 write!(f, &quot;{}:{}: &quot;, o.1, o.0)?;
+#             }
+#         }
+# 
+#         Debug::fmt(&amp;self.kind, f)?;
+# 
+#         #[cfg(not(feature = &quot;no-debug-cause&quot;))]
+#         {
+#             if let Some(e) = self.source() {
+#                 writeln!(f, &quot;\nCaused by:&quot;)?;
+#                 Debug::fmt(&amp;e, f)?;
+#             }
+#         }
+#         Ok(())
+#     }
+# }
+# 
+# #[macro_export]
+# macro_rules! cherr {
+#     ( $k:expr ) =&gt; {
+#         ChainError::&lt;_&gt;::new($k, None, Some((line!(), file!())))
+#     };
+#     ( $e:expr, $k:expr ) =&gt; {
+#         ChainError::&lt;_&gt;::new($k, Some(Box::from($e)), Some((line!(), file!())))
+#     };
+# }
+# 
+# #[macro_export]
+# macro_rules! mstrerr {
+#     ( $t:ident, $v:expr $(, $more:expr)* ) =&gt; {
+#         |e| cherr!(e, $t (format!($v, $( $more , )* )))
+#     };
+#     ( $t:path, $v:expr $(, $more:expr)* ) =&gt; {
+#         |e| cherr!(e, $t (format!($v, $( $more , )* )))
+#     };
+#     ( $v:expr $(, $more:expr)* ) =&gt; {
+#         |e| cherr!(e, format!($v, $( $more , )* ))
+#     };
+# }
+# 
+# #[macro_export]
+# macro_rules! derive_str_cherr {
+#     ($e:ident) =&gt; {
+#         struct $e(String);
+#         impl ::std::fmt::Display for $e {
+#             fn fmt(&amp;self, f: &amp;mut ::std::fmt::Formatter) -&gt; ::std::fmt::Result {
+#                 write!(f, &quot;{}&quot;, self.0)
+#             }
+#         }
+#         impl ::std::fmt::Debug for $e {
+#             fn fmt(&amp;self, f: &amp;mut ::std::fmt::Formatter) -&gt; ::std::fmt::Result {
+#                 write!(f, &quot;{}({})&quot;, stringify!($e), self.0)
+#             }
+#         }
+#         impl ::std::error::Error for $e {}
+#     };
+# }
+# 
+# #[macro_export]
+# macro_rules! try_cherr_ref {
+#     ( $e:expr, $t:ident ) =&gt; {
+#         $e.downcast_ref::&lt;ChainError&lt;$t&gt;&gt;()
+#     };
+#     ( $e:expr, $t:path ) =&gt; {
+#         $e.downcast_ref::&lt;ChainError&lt;$t&gt;&gt;()
+#     };
+# }
+# 
+# #[macro_export]
+# macro_rules! try_cherr_mut {
+#     ( $e:expr, $t:ident ) =&gt; {
+#         $e.downcast_mut::&lt;ChainError&lt;$t&gt;&gt;()
+#     };
+#     ( $e:expr, $t:path ) =&gt; {
+#         $e.downcast_mut::&lt;ChainError&lt;$t&gt;&gt;()
+#     };
+# }
+# }
+</code></pre></pre>
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+                        <h1 class="menu-title">chainerror</h1> 
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+                    <main>
+                        <pre><pre class="playpen"><code class="language-rust">use crate::chainerror::*;
+use std::error::Error;
+use std::io;
+use std::result::Result;
+
+fn do_some_io() -&gt; Result&lt;(), Box&lt;Error&gt;&gt; {
+    Err(io::Error::from(io::ErrorKind::NotFound))?;
+    Ok(())
+}
+
+fn func2() -&gt; Result&lt;(), Box&lt;Error&gt;&gt; {
+    let filename = &quot;foo.txt&quot;;
+    do_some_io().map_err(mstrerr!(&quot;Error reading '{}'&quot;, filename))?;
+    Ok(())
+}
+
+fn func1() -&gt; Result&lt;(), Box&lt;Error&gt;&gt; {
+    func2().map_err(mstrerr!(&quot;func1 error&quot;))?;
+    Ok(())
+}
+
+fn main() -&gt; Result&lt;(), Box&lt;Error&gt;&gt; {
+    if let Err(e) = func1() {
+        eprintln!(&quot;Error: {}&quot;, e);
+        let mut s = e.as_ref();
+        while let Some(c) = s.source() {
+            if let Some(ioerror) = c.downcast_ref::&lt;io::Error&gt;() {
+                eprintln!(&quot;caused by: std::io::Error: {}&quot;, ioerror);
+                match ioerror.kind() {
+                    io::ErrorKind::NotFound =&gt; eprintln!(&quot;of kind: std::io::ErrorKind::NotFound&quot;),
+                    _ =&gt; {}
+                }
+            } else {
+                eprintln!(&quot;caused by: {}&quot;, c);
+            }
+            s = c;
+        }
+    }
+    Ok(())
+}
+# #[allow(dead_code)]
+# mod chainerror {
+# use std::error::Error;
+# use std::fmt::{Debug, Display, Formatter, Result};
+# use std::result::Result as StdResult;
+# 
+# pub struct ChainError&lt;T&gt; {
+#     #[cfg(not(feature = &quot;no-fileline&quot;))]
+#     occurrence: Option&lt;(u32, &amp;'static str)&gt;,
+#     kind: T,
+#     error_cause: Option&lt;Box&lt;dyn Error + 'static&gt;&gt;,
+# }
+# 
+# pub type ChainResult&lt;O, E&gt; = StdResult&lt;O, ChainError&lt;E&gt;&gt;;
+# 
+# impl&lt;T: 'static + Display + Debug&gt; ChainError&lt;T&gt; {
+#     #[cfg(not(feature = &quot;no-fileline&quot;))]
+#     pub fn new(
+#         kind: T,
+#         error_cause: Option&lt;Box&lt;dyn Error + 'static&gt;&gt;,
+#         occurrence: Option&lt;(u32, &amp;'static str)&gt;,
+#     ) -&gt; Self {
+#         Self {
+#             occurrence,
+#             kind,
+#             error_cause,
+#         }
+#     }
+# 
+#     #[cfg(feature = &quot;no-fileline&quot;)]
+#     pub fn new(
+#         kind: T,
+#         error_cause: Option&lt;Box&lt;dyn Error + 'static&gt;&gt;,
+#         _occurrence: Option&lt;(u32, &amp;'static str)&gt;,
+#     ) -&gt; Self {
+#         Self { kind, error_cause }
+#     }
+# 
+#     pub fn root_cause(&amp;self) -&gt; Option&lt;&amp;(dyn Error + 'static)&gt; {
+#         let mut cause = self as &amp;(dyn Error + 'static);
+#         while let Some(c) = cause.source() {
+#             cause = c;
+#         }
+#         Some(cause)
+#     }
+# 
+#     pub fn find_cause&lt;U: Error + 'static&gt;(&amp;self) -&gt; Option&lt;&amp;U&gt; {
+#         let mut cause = self as &amp;(dyn Error + 'static);
+#         loop {
+#             if cause.is::&lt;U&gt;() {
+#                 return cause.downcast_ref::&lt;U&gt;();
+#             }
+# 
+#             match cause.source() {
+#                 Some(c) =&gt; cause = c,
+#                 None =&gt; return None,
+#             }
+#         }
+#     }
+# 
+#     pub fn find_chain_cause&lt;U: Error + 'static&gt;(&amp;self) -&gt; Option&lt;&amp;ChainError&lt;U&gt;&gt; {
+#         let mut cause = self as &amp;(dyn Error + 'static);
+#         loop {
+#             if cause.is::&lt;ChainError&lt;U&gt;&gt;() {
+#                 return cause.downcast_ref::&lt;ChainError&lt;U&gt;&gt;();
+#             }
+# 
+#             match cause.source() {
+#                 Some(c) =&gt; cause = c,
+#                 None =&gt; return None,
+#             }
+#         }
+#     }
+# 
+#     pub fn kind&lt;'a&gt;(&amp;'a self) -&gt; &amp;'a T {
+#         &amp;self.kind
+#     }
+# }
+# 
+# pub trait ChainErrorDown {
+#     fn is_chain&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; bool;
+#     fn downcast_chain_ref&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; Option&lt;&amp;ChainError&lt;T&gt;&gt;;
+#     fn downcast_chain_mut&lt;T: 'static + Display + Debug&gt;(&amp;mut self) -&gt; Option&lt;&amp;mut ChainError&lt;T&gt;&gt;;
+# }
+# 
+# use std::any::TypeId;
+# 
+# impl&lt;U: 'static + Display + Debug&gt; ChainErrorDown for ChainError&lt;U&gt; {
+#     fn is_chain&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; bool {
+#         TypeId::of::&lt;T&gt;() == TypeId::of::&lt;U&gt;()
+#     }
+# 
+#     fn downcast_chain_ref&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; Option&lt;&amp;ChainError&lt;T&gt;&gt; {
+#         if self.is_chain::&lt;T&gt;() {
+#             unsafe { Some(&amp;*(self as *const dyn Error as *const &amp;ChainError&lt;T&gt;)) }
+#         } else {
+#             None
+#         }
+#     }
+# 
+#     fn downcast_chain_mut&lt;T: 'static + Display + Debug&gt;(&amp;mut self) -&gt; Option&lt;&amp;mut ChainError&lt;T&gt;&gt; {
+#         if self.is_chain::&lt;T&gt;() {
+#             unsafe { Some(&amp;mut *(self as *mut dyn Error as *mut &amp;mut ChainError&lt;T&gt;)) }
+#         } else {
+#             None
+#         }
+#     }
+# }
+# 
+# impl ChainErrorDown for dyn Error + 'static {
+#     fn is_chain&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; bool {
+#         self.is::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# 
+#     fn downcast_chain_ref&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; Option&lt;&amp;ChainError&lt;T&gt;&gt; {
+#         self.downcast_ref::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# 
+#     fn downcast_chain_mut&lt;T: 'static + Display + Debug&gt;(&amp;mut self) -&gt; Option&lt;&amp;mut ChainError&lt;T&gt;&gt; {
+#         self.downcast_mut::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# }
+# 
+# impl ChainErrorDown for dyn Error + 'static + Send {
+#     fn is_chain&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; bool {
+#         self.is::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# 
+#     fn downcast_chain_ref&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; Option&lt;&amp;ChainError&lt;T&gt;&gt; {
+#         self.downcast_ref::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# 
+#     fn downcast_chain_mut&lt;T: 'static + Display + Debug&gt;(&amp;mut self) -&gt; Option&lt;&amp;mut ChainError&lt;T&gt;&gt; {
+#         self.downcast_mut::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# }
+# 
+# impl ChainErrorDown for dyn Error + 'static + Send + Sync {
+#     fn is_chain&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; bool {
+#         self.is::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# 
+#     fn downcast_chain_ref&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; Option&lt;&amp;ChainError&lt;T&gt;&gt; {
+#         self.downcast_ref::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# 
+#     fn downcast_chain_mut&lt;T: 'static + Display + Debug&gt;(&amp;mut self) -&gt; Option&lt;&amp;mut ChainError&lt;T&gt;&gt; {
+#         self.downcast_mut::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# }
+# 
+# impl&lt;T: 'static + Display + Debug&gt; Error for ChainError&lt;T&gt; {
+#     fn source(&amp;self) -&gt; Option&lt;&amp;(dyn Error + 'static)&gt; {
+#         if let Some(ref e) = self.error_cause {
+#             Some(e.as_ref())
+#         } else {
+#             None
+#         }
+#     }
+# }
+# 
+# impl&lt;T: 'static + Display + Debug&gt; Error for &amp;ChainError&lt;T&gt; {
+#     fn source(&amp;self) -&gt; Option&lt;&amp;(dyn Error + 'static)&gt; {
+#         if let Some(ref e) = self.error_cause {
+#             Some(e.as_ref())
+#         } else {
+#             None
+#         }
+#     }
+# }
+# 
+# impl&lt;T: 'static + Display + Debug&gt; Error for &amp;mut ChainError&lt;T&gt; {
+#     fn source(&amp;self) -&gt; Option&lt;&amp;(dyn Error + 'static)&gt; {
+#         if let Some(ref e) = self.error_cause {
+#             Some(e.as_ref())
+#         } else {
+#             None
+#         }
+#     }
+# }
+# 
+# impl&lt;T: 'static + Display + Debug&gt; Display for ChainError&lt;T&gt; {
+#     fn fmt(&amp;self, f: &amp;mut Formatter) -&gt; Result {
+#         write!(f, &quot;{}&quot;, self.kind)?;
+# 
+#         #[cfg(feature = &quot;display-cause&quot;)]
+#         {
+#             if let Some(e) = self.source() {
+#                 writeln!(f, &quot;\nCaused by:&quot;)?;
+#                 Display::fmt(&amp;e, f)?;
+#             }
+#         }
+#         Ok(())
+#     }
+# }
+# 
+# impl&lt;T: 'static + Display + Debug&gt; Debug for ChainError&lt;T&gt; {
+#     fn fmt(&amp;self, f: &amp;mut Formatter) -&gt; Result {
+#         #[cfg(not(feature = &quot;no-fileline&quot;))]
+#         {
+#             if let Some(o) = self.occurrence {
+#                 write!(f, &quot;{}:{}: &quot;, o.1, o.0)?;
+#             }
+#         }
+# 
+#         Debug::fmt(&amp;self.kind, f)?;
+# 
+#         #[cfg(not(feature = &quot;no-debug-cause&quot;))]
+#         {
+#             if let Some(e) = self.source() {
+#                 writeln!(f, &quot;\nCaused by:&quot;)?;
+#                 Debug::fmt(&amp;e, f)?;
+#             }
+#         }
+#         Ok(())
+#     }
+# }
+# 
+# #[macro_export]
+# macro_rules! cherr {
+#     ( $k:expr ) =&gt; {
+#         ChainError::&lt;_&gt;::new($k, None, Some((line!(), file!())))
+#     };
+#     ( $e:expr, $k:expr ) =&gt; {
+#         ChainError::&lt;_&gt;::new($k, Some(Box::from($e)), Some((line!(), file!())))
+#     };
+# }
+# 
+# #[macro_export]
+# macro_rules! mstrerr {
+#     ( $t:ident, $v:expr $(, $more:expr)* ) =&gt; {
+#         |e| cherr!(e, $t (format!($v, $( $more , )* )))
+#     };
+#     ( $t:path, $v:expr $(, $more:expr)* ) =&gt; {
+#         |e| cherr!(e, $t (format!($v, $( $more , )* )))
+#     };
+#     ( $v:expr $(, $more:expr)* ) =&gt; {
+#         |e| cherr!(e, format!($v, $( $more , )* ))
+#     };
+# }
+# 
+# #[macro_export]
+# macro_rules! derive_str_cherr {
+#     ($e:ident) =&gt; {
+#         struct $e(String);
+#         impl ::std::fmt::Display for $e {
+#             fn fmt(&amp;self, f: &amp;mut ::std::fmt::Formatter) -&gt; ::std::fmt::Result {
+#                 write!(f, &quot;{}&quot;, self.0)
+#             }
+#         }
+#         impl ::std::fmt::Debug for $e {
+#             fn fmt(&amp;self, f: &amp;mut ::std::fmt::Formatter) -&gt; ::std::fmt::Result {
+#                 write!(f, &quot;{}({})&quot;, stringify!($e), self.0)
+#             }
+#         }
+#         impl ::std::error::Error for $e {}
+#     };
+# }
+# 
+# #[macro_export]
+# macro_rules! try_cherr_ref {
+#     ( $e:expr, $t:ident ) =&gt; {
+#         $e.downcast_ref::&lt;ChainError&lt;$t&gt;&gt;()
+#     };
+#     ( $e:expr, $t:path ) =&gt; {
+#         $e.downcast_ref::&lt;ChainError&lt;$t&gt;&gt;()
+#     };
+# }
+# 
+# #[macro_export]
+# macro_rules! try_cherr_mut {
+#     ( $e:expr, $t:ident ) =&gt; {
+#         $e.downcast_mut::&lt;ChainError&lt;$t&gt;&gt;()
+#     };
+#     ( $e:expr, $t:path ) =&gt; {
+#         $e.downcast_mut::&lt;ChainError&lt;$t&gt;&gt;()
+#     };
+# }
+# }
+</code></pre></pre>
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+                        <h1 class="menu-title">chainerror</h1> 
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+                    <main>
+                        <pre><pre class="playpen"><code class="language-rust">use crate::chainerror::*;
+use std::error::Error;
+use std::io;
+use std::result::Result;
+
+fn do_some_io() -&gt; Result&lt;(), Box&lt;Error&gt;&gt; {
+    Err(io::Error::from(io::ErrorKind::NotFound))?;
+    Ok(())
+}
+
+fn func2() -&gt; Result&lt;(), Box&lt;Error&gt;&gt; {
+    let filename = &quot;foo.txt&quot;;
+    do_some_io().map_err(mstrerr!(&quot;Error reading '{}'&quot;, filename))?;
+    Ok(())
+}
+
+fn func1() -&gt; Result&lt;(), Box&lt;Error&gt;&gt; {
+    func2().map_err(mstrerr!(&quot;func1 error&quot;))?;
+    Ok(())
+}
+
+fn main() -&gt; Result&lt;(), Box&lt;Error&gt;&gt; {
+    if let Err(e) = func1() {
+        eprintln!(&quot;Error: {}&quot;, e);
+        if let Some(s) = e.downcast_chain_ref::&lt;String&gt;() {
+            if let Some(ioerror) = s.find_cause::&lt;io::Error&gt;() {
+                eprintln!(&quot;caused by: std::io::Error: {}&quot;, ioerror);
+                match ioerror.kind() {
+                    io::ErrorKind::NotFound =&gt; eprintln!(&quot;of kind: std::io::ErrorKind::NotFound&quot;),
+                    _ =&gt; {}
+                }
+            }
+
+            if let Some(e) = s.root_cause() {
+                let ioerror = e.downcast_ref::&lt;io::Error&gt;().unwrap();
+                eprintln!(&quot;The root cause was: std::io::Error: {:#?}&quot;, ioerror);
+            }
+        }
+    }
+    Ok(())
+}
+# #[allow(dead_code)]
+# mod chainerror {
+# use std::error::Error;
+# use std::fmt::{Debug, Display, Formatter, Result};
+# use std::result::Result as StdResult;
+# 
+# pub struct ChainError&lt;T&gt; {
+#     #[cfg(not(feature = &quot;no-fileline&quot;))]
+#     occurrence: Option&lt;(u32, &amp;'static str)&gt;,
+#     kind: T,
+#     error_cause: Option&lt;Box&lt;dyn Error + 'static&gt;&gt;,
+# }
+# 
+# pub type ChainResult&lt;O, E&gt; = StdResult&lt;O, ChainError&lt;E&gt;&gt;;
+# 
+# impl&lt;T: 'static + Display + Debug&gt; ChainError&lt;T&gt; {
+#     #[cfg(not(feature = &quot;no-fileline&quot;))]
+#     pub fn new(
+#         kind: T,
+#         error_cause: Option&lt;Box&lt;dyn Error + 'static&gt;&gt;,
+#         occurrence: Option&lt;(u32, &amp;'static str)&gt;,
+#     ) -&gt; Self {
+#         Self {
+#             occurrence,
+#             kind,
+#             error_cause,
+#         }
+#     }
+# 
+#     #[cfg(feature = &quot;no-fileline&quot;)]
+#     pub fn new(
+#         kind: T,
+#         error_cause: Option&lt;Box&lt;dyn Error + 'static&gt;&gt;,
+#         _occurrence: Option&lt;(u32, &amp;'static str)&gt;,
+#     ) -&gt; Self {
+#         Self { kind, error_cause }
+#     }
+# 
+#     pub fn root_cause(&amp;self) -&gt; Option&lt;&amp;(dyn Error + 'static)&gt; {
+#         let mut cause = self as &amp;(dyn Error + 'static);
+#         while let Some(c) = cause.source() {
+#             cause = c;
+#         }
+#         Some(cause)
+#     }
+# 
+#     pub fn find_cause&lt;U: Error + 'static&gt;(&amp;self) -&gt; Option&lt;&amp;U&gt; {
+#         let mut cause = self as &amp;(dyn Error + 'static);
+#         loop {
+#             if cause.is::&lt;U&gt;() {
+#                 return cause.downcast_ref::&lt;U&gt;();
+#             }
+# 
+#             match cause.source() {
+#                 Some(c) =&gt; cause = c,
+#                 None =&gt; return None,
+#             }
+#         }
+#     }
+# 
+#     pub fn find_chain_cause&lt;U: Error + 'static&gt;(&amp;self) -&gt; Option&lt;&amp;ChainError&lt;U&gt;&gt; {
+#         let mut cause = self as &amp;(dyn Error + 'static);
+#         loop {
+#             if cause.is::&lt;ChainError&lt;U&gt;&gt;() {
+#                 return cause.downcast_ref::&lt;ChainError&lt;U&gt;&gt;();
+#             }
+# 
+#             match cause.source() {
+#                 Some(c) =&gt; cause = c,
+#                 None =&gt; return None,
+#             }
+#         }
+#     }
+# 
+#     pub fn kind&lt;'a&gt;(&amp;'a self) -&gt; &amp;'a T {
+#         &amp;self.kind
+#     }
+# }
+# 
+# pub trait ChainErrorDown {
+#     fn is_chain&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; bool;
+#     fn downcast_chain_ref&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; Option&lt;&amp;ChainError&lt;T&gt;&gt;;
+#     fn downcast_chain_mut&lt;T: 'static + Display + Debug&gt;(&amp;mut self) -&gt; Option&lt;&amp;mut ChainError&lt;T&gt;&gt;;
+# }
+# 
+# use std::any::TypeId;
+# 
+# impl&lt;U: 'static + Display + Debug&gt; ChainErrorDown for ChainError&lt;U&gt; {
+#     fn is_chain&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; bool {
+#         TypeId::of::&lt;T&gt;() == TypeId::of::&lt;U&gt;()
+#     }
+# 
+#     fn downcast_chain_ref&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; Option&lt;&amp;ChainError&lt;T&gt;&gt; {
+#         if self.is_chain::&lt;T&gt;() {
+#             unsafe { Some(&amp;*(self as *const dyn Error as *const &amp;ChainError&lt;T&gt;)) }
+#         } else {
+#             None
+#         }
+#     }
+# 
+#     fn downcast_chain_mut&lt;T: 'static + Display + Debug&gt;(&amp;mut self) -&gt; Option&lt;&amp;mut ChainError&lt;T&gt;&gt; {
+#         if self.is_chain::&lt;T&gt;() {
+#             unsafe { Some(&amp;mut *(self as *mut dyn Error as *mut &amp;mut ChainError&lt;T&gt;)) }
+#         } else {
+#             None
+#         }
+#     }
+# }
+# 
+# impl ChainErrorDown for dyn Error + 'static {
+#     fn is_chain&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; bool {
+#         self.is::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# 
+#     fn downcast_chain_ref&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; Option&lt;&amp;ChainError&lt;T&gt;&gt; {
+#         self.downcast_ref::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# 
+#     fn downcast_chain_mut&lt;T: 'static + Display + Debug&gt;(&amp;mut self) -&gt; Option&lt;&amp;mut ChainError&lt;T&gt;&gt; {
+#         self.downcast_mut::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# }
+# 
+# impl ChainErrorDown for dyn Error + 'static + Send {
+#     fn is_chain&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; bool {
+#         self.is::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# 
+#     fn downcast_chain_ref&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; Option&lt;&amp;ChainError&lt;T&gt;&gt; {
+#         self.downcast_ref::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# 
+#     fn downcast_chain_mut&lt;T: 'static + Display + Debug&gt;(&amp;mut self) -&gt; Option&lt;&amp;mut ChainError&lt;T&gt;&gt; {
+#         self.downcast_mut::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# }
+# 
+# impl ChainErrorDown for dyn Error + 'static + Send + Sync {
+#     fn is_chain&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; bool {
+#         self.is::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# 
+#     fn downcast_chain_ref&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; Option&lt;&amp;ChainError&lt;T&gt;&gt; {
+#         self.downcast_ref::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# 
+#     fn downcast_chain_mut&lt;T: 'static + Display + Debug&gt;(&amp;mut self) -&gt; Option&lt;&amp;mut ChainError&lt;T&gt;&gt; {
+#         self.downcast_mut::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# }
+# 
+# impl&lt;T: 'static + Display + Debug&gt; Error for ChainError&lt;T&gt; {
+#     fn source(&amp;self) -&gt; Option&lt;&amp;(dyn Error + 'static)&gt; {
+#         if let Some(ref e) = self.error_cause {
+#             Some(e.as_ref())
+#         } else {
+#             None
+#         }
+#     }
+# }
+# 
+# impl&lt;T: 'static + Display + Debug&gt; Error for &amp;ChainError&lt;T&gt; {
+#     fn source(&amp;self) -&gt; Option&lt;&amp;(dyn Error + 'static)&gt; {
+#         if let Some(ref e) = self.error_cause {
+#             Some(e.as_ref())
+#         } else {
+#             None
+#         }
+#     }
+# }
+# 
+# impl&lt;T: 'static + Display + Debug&gt; Error for &amp;mut ChainError&lt;T&gt; {
+#     fn source(&amp;self) -&gt; Option&lt;&amp;(dyn Error + 'static)&gt; {
+#         if let Some(ref e) = self.error_cause {
+#             Some(e.as_ref())
+#         } else {
+#             None
+#         }
+#     }
+# }
+# 
+# impl&lt;T: 'static + Display + Debug&gt; Display for ChainError&lt;T&gt; {
+#     fn fmt(&amp;self, f: &amp;mut Formatter) -&gt; Result {
+#         write!(f, &quot;{}&quot;, self.kind)?;
+# 
+#         #[cfg(feature = &quot;display-cause&quot;)]
+#         {
+#             if let Some(e) = self.source() {
+#                 writeln!(f, &quot;\nCaused by:&quot;)?;
+#                 Display::fmt(&amp;e, f)?;
+#             }
+#         }
+#         Ok(())
+#     }
+# }
+# 
+# impl&lt;T: 'static + Display + Debug&gt; Debug for ChainError&lt;T&gt; {
+#     fn fmt(&amp;self, f: &amp;mut Formatter) -&gt; Result {
+#         #[cfg(not(feature = &quot;no-fileline&quot;))]
+#         {
+#             if let Some(o) = self.occurrence {
+#                 write!(f, &quot;{}:{}: &quot;, o.1, o.0)?;
+#             }
+#         }
+# 
+#         Debug::fmt(&amp;self.kind, f)?;
+# 
+#         #[cfg(not(feature = &quot;no-debug-cause&quot;))]
+#         {
+#             if let Some(e) = self.source() {
+#                 writeln!(f, &quot;\nCaused by:&quot;)?;
+#                 Debug::fmt(&amp;e, f)?;
+#             }
+#         }
+#         Ok(())
+#     }
+# }
+# 
+# #[macro_export]
+# macro_rules! cherr {
+#     ( $k:expr ) =&gt; {
+#         ChainError::&lt;_&gt;::new($k, None, Some((line!(), file!())))
+#     };
+#     ( $e:expr, $k:expr ) =&gt; {
+#         ChainError::&lt;_&gt;::new($k, Some(Box::from($e)), Some((line!(), file!())))
+#     };
+# }
+# 
+# #[macro_export]
+# macro_rules! mstrerr {
+#     ( $t:ident, $v:expr $(, $more:expr)* ) =&gt; {
+#         |e| cherr!(e, $t (format!($v, $( $more , )* )))
+#     };
+#     ( $t:path, $v:expr $(, $more:expr)* ) =&gt; {
+#         |e| cherr!(e, $t (format!($v, $( $more , )* )))
+#     };
+#     ( $v:expr $(, $more:expr)* ) =&gt; {
+#         |e| cherr!(e, format!($v, $( $more , )* ))
+#     };
+# }
+# 
+# #[macro_export]
+# macro_rules! derive_str_cherr {
+#     ($e:ident) =&gt; {
+#         struct $e(String);
+#         impl ::std::fmt::Display for $e {
+#             fn fmt(&amp;self, f: &amp;mut ::std::fmt::Formatter) -&gt; ::std::fmt::Result {
+#                 write!(f, &quot;{}&quot;, self.0)
+#             }
+#         }
+#         impl ::std::fmt::Debug for $e {
+#             fn fmt(&amp;self, f: &amp;mut ::std::fmt::Formatter) -&gt; ::std::fmt::Result {
+#                 write!(f, &quot;{}({})&quot;, stringify!($e), self.0)
+#             }
+#         }
+#         impl ::std::error::Error for $e {}
+#     };
+# }
+# 
+# #[macro_export]
+# macro_rules! try_cherr_ref {
+#     ( $e:expr, $t:ident ) =&gt; {
+#         $e.downcast_ref::&lt;ChainError&lt;$t&gt;&gt;()
+#     };
+#     ( $e:expr, $t:path ) =&gt; {
+#         $e.downcast_ref::&lt;ChainError&lt;$t&gt;&gt;()
+#     };
+# }
+# 
+# #[macro_export]
+# macro_rules! try_cherr_mut {
+#     ( $e:expr, $t:ident ) =&gt; {
+#         $e.downcast_mut::&lt;ChainError&lt;$t&gt;&gt;()
+#     };
+#     ( $e:expr, $t:path ) =&gt; {
+#         $e.downcast_mut::&lt;ChainError&lt;$t&gt;&gt;()
+#     };
+# }
+# }
+</code></pre></pre>
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+                        <h1 class="menu-title">chainerror</h1> 
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+                        <pre><pre class="playpen"><code class="language-rust">use crate::chainerror::*;
+use std::error::Error;
+use std::io;
+use std::result::Result;
+
+fn do_some_io() -&gt; Result&lt;(), Box&lt;Error&gt;&gt; {
+    Err(io::Error::from(io::ErrorKind::NotFound))?;
+    Ok(())
+}
+
+derive_str_cherr!(Func2Error);
+
+fn func2() -&gt; Result&lt;(), Box&lt;Error&gt;&gt; {
+    let filename = &quot;foo.txt&quot;;
+    do_some_io().map_err(mstrerr!(Func2Error, &quot;Error reading '{}'&quot;, filename))?;
+    Ok(())
+}
+
+derive_str_cherr!(Func1Error);
+
+fn func1() -&gt; Result&lt;(), Box&lt;Error&gt;&gt; {
+    func2().map_err(mstrerr!(Func1Error, &quot;func1 error&quot;))?;
+    Ok(())
+}
+
+fn main() -&gt; Result&lt;(), Box&lt;Error&gt;&gt; {
+    if let Err(e) = func1() {
+        if let Some(f1err) = e.downcast_chain_ref::&lt;Func1Error&gt;() {
+            eprintln!(&quot;Func1Error: {}&quot;, f1err);
+
+            if let Some(f2err) = f1err.find_cause::&lt;ChainError&lt;Func2Error&gt;&gt;() {
+                eprintln!(&quot;Func2Error: {}&quot;, f2err);
+            }
+
+            if let Some(f2err) = f1err.find_chain_cause::&lt;Func2Error&gt;() {
+                eprintln!(&quot;Debug Func2Error:\n{:?}&quot;, f2err);
+            }
+        }
+    }
+    Ok(())
+}
+# #[allow(dead_code)]
+# mod chainerror {
+# use std::error::Error;
+# use std::fmt::{Debug, Display, Formatter, Result};
+# use std::result::Result as StdResult;
+# 
+# pub struct ChainError&lt;T&gt; {
+#     #[cfg(not(feature = &quot;no-fileline&quot;))]
+#     occurrence: Option&lt;(u32, &amp;'static str)&gt;,
+#     kind: T,
+#     error_cause: Option&lt;Box&lt;dyn Error + 'static&gt;&gt;,
+# }
+# 
+# pub type ChainResult&lt;O, E&gt; = StdResult&lt;O, ChainError&lt;E&gt;&gt;;
+# 
+# impl&lt;T: 'static + Display + Debug&gt; ChainError&lt;T&gt; {
+#     #[cfg(not(feature = &quot;no-fileline&quot;))]
+#     pub fn new(
+#         kind: T,
+#         error_cause: Option&lt;Box&lt;dyn Error + 'static&gt;&gt;,
+#         occurrence: Option&lt;(u32, &amp;'static str)&gt;,
+#     ) -&gt; Self {
+#         Self {
+#             occurrence,
+#             kind,
+#             error_cause,
+#         }
+#     }
+# 
+#     #[cfg(feature = &quot;no-fileline&quot;)]
+#     pub fn new(
+#         kind: T,
+#         error_cause: Option&lt;Box&lt;dyn Error + 'static&gt;&gt;,
+#         _occurrence: Option&lt;(u32, &amp;'static str)&gt;,
+#     ) -&gt; Self {
+#         Self { kind, error_cause }
+#     }
+# 
+#     pub fn root_cause(&amp;self) -&gt; Option&lt;&amp;(dyn Error + 'static)&gt; {
+#         let mut cause = self as &amp;(dyn Error + 'static);
+#         while let Some(c) = cause.source() {
+#             cause = c;
+#         }
+#         Some(cause)
+#     }
+# 
+#     pub fn find_cause&lt;U: Error + 'static&gt;(&amp;self) -&gt; Option&lt;&amp;U&gt; {
+#         let mut cause = self as &amp;(dyn Error + 'static);
+#         loop {
+#             if cause.is::&lt;U&gt;() {
+#                 return cause.downcast_ref::&lt;U&gt;();
+#             }
+# 
+#             match cause.source() {
+#                 Some(c) =&gt; cause = c,
+#                 None =&gt; return None,
+#             }
+#         }
+#     }
+# 
+#     pub fn find_chain_cause&lt;U: Error + 'static&gt;(&amp;self) -&gt; Option&lt;&amp;ChainError&lt;U&gt;&gt; {
+#         let mut cause = self as &amp;(dyn Error + 'static);
+#         loop {
+#             if cause.is::&lt;ChainError&lt;U&gt;&gt;() {
+#                 return cause.downcast_ref::&lt;ChainError&lt;U&gt;&gt;();
+#             }
+# 
+#             match cause.source() {
+#                 Some(c) =&gt; cause = c,
+#                 None =&gt; return None,
+#             }
+#         }
+#     }
+# 
+#     pub fn kind&lt;'a&gt;(&amp;'a self) -&gt; &amp;'a T {
+#         &amp;self.kind
+#     }
+# }
+# 
+# pub trait ChainErrorDown {
+#     fn is_chain&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; bool;
+#     fn downcast_chain_ref&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; Option&lt;&amp;ChainError&lt;T&gt;&gt;;
+#     fn downcast_chain_mut&lt;T: 'static + Display + Debug&gt;(&amp;mut self) -&gt; Option&lt;&amp;mut ChainError&lt;T&gt;&gt;;
+# }
+# 
+# use std::any::TypeId;
+# 
+# impl&lt;U: 'static + Display + Debug&gt; ChainErrorDown for ChainError&lt;U&gt; {
+#     fn is_chain&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; bool {
+#         TypeId::of::&lt;T&gt;() == TypeId::of::&lt;U&gt;()
+#     }
+# 
+#     fn downcast_chain_ref&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; Option&lt;&amp;ChainError&lt;T&gt;&gt; {
+#         if self.is_chain::&lt;T&gt;() {
+#             unsafe { Some(&amp;*(self as *const dyn Error as *const &amp;ChainError&lt;T&gt;)) }
+#         } else {
+#             None
+#         }
+#     }
+# 
+#     fn downcast_chain_mut&lt;T: 'static + Display + Debug&gt;(&amp;mut self) -&gt; Option&lt;&amp;mut ChainError&lt;T&gt;&gt; {
+#         if self.is_chain::&lt;T&gt;() {
+#             unsafe { Some(&amp;mut *(self as *mut dyn Error as *mut &amp;mut ChainError&lt;T&gt;)) }
+#         } else {
+#             None
+#         }
+#     }
+# }
+# 
+# impl ChainErrorDown for dyn Error + 'static {
+#     fn is_chain&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; bool {
+#         self.is::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# 
+#     fn downcast_chain_ref&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; Option&lt;&amp;ChainError&lt;T&gt;&gt; {
+#         self.downcast_ref::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# 
+#     fn downcast_chain_mut&lt;T: 'static + Display + Debug&gt;(&amp;mut self) -&gt; Option&lt;&amp;mut ChainError&lt;T&gt;&gt; {
+#         self.downcast_mut::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# }
+# 
+# impl ChainErrorDown for dyn Error + 'static + Send {
+#     fn is_chain&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; bool {
+#         self.is::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# 
+#     fn downcast_chain_ref&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; Option&lt;&amp;ChainError&lt;T&gt;&gt; {
+#         self.downcast_ref::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# 
+#     fn downcast_chain_mut&lt;T: 'static + Display + Debug&gt;(&amp;mut self) -&gt; Option&lt;&amp;mut ChainError&lt;T&gt;&gt; {
+#         self.downcast_mut::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# }
+# 
+# impl ChainErrorDown for dyn Error + 'static + Send + Sync {
+#     fn is_chain&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; bool {
+#         self.is::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# 
+#     fn downcast_chain_ref&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; Option&lt;&amp;ChainError&lt;T&gt;&gt; {
+#         self.downcast_ref::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# 
+#     fn downcast_chain_mut&lt;T: 'static + Display + Debug&gt;(&amp;mut self) -&gt; Option&lt;&amp;mut ChainError&lt;T&gt;&gt; {
+#         self.downcast_mut::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# }
+# 
+# impl&lt;T: 'static + Display + Debug&gt; Error for ChainError&lt;T&gt; {
+#     fn source(&amp;self) -&gt; Option&lt;&amp;(dyn Error + 'static)&gt; {
+#         if let Some(ref e) = self.error_cause {
+#             Some(e.as_ref())
+#         } else {
+#             None
+#         }
+#     }
+# }
+# 
+# impl&lt;T: 'static + Display + Debug&gt; Error for &amp;ChainError&lt;T&gt; {
+#     fn source(&amp;self) -&gt; Option&lt;&amp;(dyn Error + 'static)&gt; {
+#         if let Some(ref e) = self.error_cause {
+#             Some(e.as_ref())
+#         } else {
+#             None
+#         }
+#     }
+# }
+# 
+# impl&lt;T: 'static + Display + Debug&gt; Error for &amp;mut ChainError&lt;T&gt; {
+#     fn source(&amp;self) -&gt; Option&lt;&amp;(dyn Error + 'static)&gt; {
+#         if let Some(ref e) = self.error_cause {
+#             Some(e.as_ref())
+#         } else {
+#             None
+#         }
+#     }
+# }
+# 
+# impl&lt;T: 'static + Display + Debug&gt; Display for ChainError&lt;T&gt; {
+#     fn fmt(&amp;self, f: &amp;mut Formatter) -&gt; Result {
+#         write!(f, &quot;{}&quot;, self.kind)?;
+# 
+#         #[cfg(feature = &quot;display-cause&quot;)]
+#         {
+#             if let Some(e) = self.source() {
+#                 writeln!(f, &quot;\nCaused by:&quot;)?;
+#                 Display::fmt(&amp;e, f)?;
+#             }
+#         }
+#         Ok(())
+#     }
+# }
+# 
+# impl&lt;T: 'static + Display + Debug&gt; Debug for ChainError&lt;T&gt; {
+#     fn fmt(&amp;self, f: &amp;mut Formatter) -&gt; Result {
+#         #[cfg(not(feature = &quot;no-fileline&quot;))]
+#         {
+#             if let Some(o) = self.occurrence {
+#                 write!(f, &quot;{}:{}: &quot;, o.1, o.0)?;
+#             }
+#         }
+# 
+#         Debug::fmt(&amp;self.kind, f)?;
+# 
+#         #[cfg(not(feature = &quot;no-debug-cause&quot;))]
+#         {
+#             if let Some(e) = self.source() {
+#                 writeln!(f, &quot;\nCaused by:&quot;)?;
+#                 Debug::fmt(&amp;e, f)?;
+#             }
+#         }
+#         Ok(())
+#     }
+# }
+# 
+# #[macro_export]
+# macro_rules! cherr {
+#     ( $k:expr ) =&gt; {
+#         ChainError::&lt;_&gt;::new($k, None, Some((line!(), file!())))
+#     };
+#     ( $e:expr, $k:expr ) =&gt; {
+#         ChainError::&lt;_&gt;::new($k, Some(Box::from($e)), Some((line!(), file!())))
+#     };
+# }
+# 
+# #[macro_export]
+# macro_rules! mstrerr {
+#     ( $t:ident, $v:expr $(, $more:expr)* ) =&gt; {
+#         |e| cherr!(e, $t (format!($v, $( $more , )* )))
+#     };
+#     ( $t:path, $v:expr $(, $more:expr)* ) =&gt; {
+#         |e| cherr!(e, $t (format!($v, $( $more , )* )))
+#     };
+#     ( $v:expr $(, $more:expr)* ) =&gt; {
+#         |e| cherr!(e, format!($v, $( $more , )* ))
+#     };
+# }
+# 
+# #[macro_export]
+# macro_rules! derive_str_cherr {
+#     ($e:ident) =&gt; {
+#         struct $e(String);
+#         impl ::std::fmt::Display for $e {
+#             fn fmt(&amp;self, f: &amp;mut ::std::fmt::Formatter) -&gt; ::std::fmt::Result {
+#                 write!(f, &quot;{}&quot;, self.0)
+#             }
+#         }
+#         impl ::std::fmt::Debug for $e {
+#             fn fmt(&amp;self, f: &amp;mut ::std::fmt::Formatter) -&gt; ::std::fmt::Result {
+#                 write!(f, &quot;{}({})&quot;, stringify!($e), self.0)
+#             }
+#         }
+#         impl ::std::error::Error for $e {}
+#     };
+# }
+# 
+# #[macro_export]
+# macro_rules! try_cherr_ref {
+#     ( $e:expr, $t:ident ) =&gt; {
+#         $e.downcast_ref::&lt;ChainError&lt;$t&gt;&gt;()
+#     };
+#     ( $e:expr, $t:path ) =&gt; {
+#         $e.downcast_ref::&lt;ChainError&lt;$t&gt;&gt;()
+#     };
+# }
+# 
+# #[macro_export]
+# macro_rules! try_cherr_mut {
+#     ( $e:expr, $t:ident ) =&gt; {
+#         $e.downcast_mut::&lt;ChainError&lt;$t&gt;&gt;()
+#     };
+#     ( $e:expr, $t:path ) =&gt; {
+#         $e.downcast_mut::&lt;ChainError&lt;$t&gt;&gt;()
+#     };
+# }
+# }
+</code></pre></pre>
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+                        <h1 class="menu-title">chainerror</h1> 
+
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+                    <main>
+                        <pre><pre class="playpen"><code class="language-rust">use crate::chainerror::*;
+use std::error::Error;
+use std::io;
+use std::result::Result;
+
+fn do_some_io() -&gt; Result&lt;(), Box&lt;Error&gt;&gt; {
+    Err(io::Error::from(io::ErrorKind::NotFound))?;
+    Ok(())
+}
+
+derive_str_cherr!(Func2Error);
+
+fn func2() -&gt; Result&lt;(), Box&lt;Error&gt;&gt; {
+    let filename = &quot;foo.txt&quot;;
+    do_some_io().map_err(mstrerr!(Func2Error, &quot;Error reading '{}'&quot;, filename))?;
+    Ok(())
+}
+
+derive_str_cherr!(Func1ErrorFunc2);
+derive_str_cherr!(Func1ErrorIO);
+
+fn func1() -&gt; Result&lt;(), Box&lt;Error&gt;&gt; {
+    func2().map_err(mstrerr!(Func1ErrorFunc2, &quot;func1 error calling func2&quot;))?;
+    let filename = &quot;bar.txt&quot;;
+    do_some_io().map_err(mstrerr!(Func1ErrorIO, &quot;Error reading '{}'&quot;, filename))?;
+    Ok(())
+}
+
+fn main() -&gt; Result&lt;(), Box&lt;Error&gt;&gt; {
+    if let Err(e) = func1() {
+        if let Some(s) = e.downcast_ref::&lt;ChainError&lt;Func1ErrorIO&gt;&gt;() {
+            eprintln!(&quot;Func1ErrorIO:\n{:?}&quot;, s);
+        }
+
+        if let Some(s) = try_cherr_ref!(e, Func1ErrorFunc2) {
+            eprintln!(&quot;Func1ErrorFunc2:\n{:?}&quot;, s);
+        }
+    }
+    Ok(())
+}
+# #[allow(dead_code)]
+# mod chainerror {
+# use std::error::Error;
+# use std::fmt::{Debug, Display, Formatter, Result};
+# use std::result::Result as StdResult;
+# 
+# pub struct ChainError&lt;T&gt; {
+#     #[cfg(not(feature = &quot;no-fileline&quot;))]
+#     occurrence: Option&lt;(u32, &amp;'static str)&gt;,
+#     kind: T,
+#     error_cause: Option&lt;Box&lt;dyn Error + 'static&gt;&gt;,
+# }
+# 
+# pub type ChainResult&lt;O, E&gt; = StdResult&lt;O, ChainError&lt;E&gt;&gt;;
+# 
+# impl&lt;T: 'static + Display + Debug&gt; ChainError&lt;T&gt; {
+#     #[cfg(not(feature = &quot;no-fileline&quot;))]
+#     pub fn new(
+#         kind: T,
+#         error_cause: Option&lt;Box&lt;dyn Error + 'static&gt;&gt;,
+#         occurrence: Option&lt;(u32, &amp;'static str)&gt;,
+#     ) -&gt; Self {
+#         Self {
+#             occurrence,
+#             kind,
+#             error_cause,
+#         }
+#     }
+# 
+#     #[cfg(feature = &quot;no-fileline&quot;)]
+#     pub fn new(
+#         kind: T,
+#         error_cause: Option&lt;Box&lt;dyn Error + 'static&gt;&gt;,
+#         _occurrence: Option&lt;(u32, &amp;'static str)&gt;,
+#     ) -&gt; Self {
+#         Self { kind, error_cause }
+#     }
+# 
+#     pub fn root_cause(&amp;self) -&gt; Option&lt;&amp;(dyn Error + 'static)&gt; {
+#         let mut cause = self as &amp;(dyn Error + 'static);
+#         while let Some(c) = cause.source() {
+#             cause = c;
+#         }
+#         Some(cause)
+#     }
+# 
+#     pub fn find_cause&lt;U: Error + 'static&gt;(&amp;self) -&gt; Option&lt;&amp;U&gt; {
+#         let mut cause = self as &amp;(dyn Error + 'static);
+#         loop {
+#             if cause.is::&lt;U&gt;() {
+#                 return cause.downcast_ref::&lt;U&gt;();
+#             }
+# 
+#             match cause.source() {
+#                 Some(c) =&gt; cause = c,
+#                 None =&gt; return None,
+#             }
+#         }
+#     }
+# 
+#     pub fn find_chain_cause&lt;U: Error + 'static&gt;(&amp;self) -&gt; Option&lt;&amp;ChainError&lt;U&gt;&gt; {
+#         let mut cause = self as &amp;(dyn Error + 'static);
+#         loop {
+#             if cause.is::&lt;ChainError&lt;U&gt;&gt;() {
+#                 return cause.downcast_ref::&lt;ChainError&lt;U&gt;&gt;();
+#             }
+# 
+#             match cause.source() {
+#                 Some(c) =&gt; cause = c,
+#                 None =&gt; return None,
+#             }
+#         }
+#     }
+# 
+#     pub fn kind&lt;'a&gt;(&amp;'a self) -&gt; &amp;'a T {
+#         &amp;self.kind
+#     }
+# }
+# 
+# pub trait ChainErrorDown {
+#     fn is_chain&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; bool;
+#     fn downcast_chain_ref&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; Option&lt;&amp;ChainError&lt;T&gt;&gt;;
+#     fn downcast_chain_mut&lt;T: 'static + Display + Debug&gt;(&amp;mut self) -&gt; Option&lt;&amp;mut ChainError&lt;T&gt;&gt;;
+# }
+# 
+# use std::any::TypeId;
+# 
+# impl&lt;U: 'static + Display + Debug&gt; ChainErrorDown for ChainError&lt;U&gt; {
+#     fn is_chain&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; bool {
+#         TypeId::of::&lt;T&gt;() == TypeId::of::&lt;U&gt;()
+#     }
+# 
+#     fn downcast_chain_ref&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; Option&lt;&amp;ChainError&lt;T&gt;&gt; {
+#         if self.is_chain::&lt;T&gt;() {
+#             unsafe { Some(&amp;*(self as *const dyn Error as *const &amp;ChainError&lt;T&gt;)) }
+#         } else {
+#             None
+#         }
+#     }
+# 
+#     fn downcast_chain_mut&lt;T: 'static + Display + Debug&gt;(&amp;mut self) -&gt; Option&lt;&amp;mut ChainError&lt;T&gt;&gt; {
+#         if self.is_chain::&lt;T&gt;() {
+#             unsafe { Some(&amp;mut *(self as *mut dyn Error as *mut &amp;mut ChainError&lt;T&gt;)) }
+#         } else {
+#             None
+#         }
+#     }
+# }
+# 
+# impl ChainErrorDown for dyn Error + 'static {
+#     fn is_chain&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; bool {
+#         self.is::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# 
+#     fn downcast_chain_ref&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; Option&lt;&amp;ChainError&lt;T&gt;&gt; {
+#         self.downcast_ref::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# 
+#     fn downcast_chain_mut&lt;T: 'static + Display + Debug&gt;(&amp;mut self) -&gt; Option&lt;&amp;mut ChainError&lt;T&gt;&gt; {
+#         self.downcast_mut::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# }
+# 
+# impl ChainErrorDown for dyn Error + 'static + Send {
+#     fn is_chain&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; bool {
+#         self.is::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# 
+#     fn downcast_chain_ref&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; Option&lt;&amp;ChainError&lt;T&gt;&gt; {
+#         self.downcast_ref::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# 
+#     fn downcast_chain_mut&lt;T: 'static + Display + Debug&gt;(&amp;mut self) -&gt; Option&lt;&amp;mut ChainError&lt;T&gt;&gt; {
+#         self.downcast_mut::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# }
+# 
+# impl ChainErrorDown for dyn Error + 'static + Send + Sync {
+#     fn is_chain&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; bool {
+#         self.is::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# 
+#     fn downcast_chain_ref&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; Option&lt;&amp;ChainError&lt;T&gt;&gt; {
+#         self.downcast_ref::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# 
+#     fn downcast_chain_mut&lt;T: 'static + Display + Debug&gt;(&amp;mut self) -&gt; Option&lt;&amp;mut ChainError&lt;T&gt;&gt; {
+#         self.downcast_mut::&lt;ChainError&lt;T&gt;&gt;()
+#     }
+# }
+# 
+# impl&lt;T: 'static + Display + Debug&gt; Error for ChainError&lt;T&gt; {
+#     fn source(&amp;self) -&gt; Option&lt;&amp;(dyn Error + 'static)&gt; {
+#         if let Some(ref e) = self.error_cause {
+#             Some(e.as_ref())
+#         } else {
+#             None
+#         }
+#     }
+# }
+# 
+# impl&lt;T: 'static + Display + Debug&gt; Error for &amp;ChainError&lt;T&gt; {
+#     fn source(&amp;self) -&gt; Option&lt;&amp;(dyn Error + 'static)&gt; {
+#         if let Some(ref e) = self.error_cause {
+#             Some(e.as_ref())
+#         } else {
+#             None
+#         }
+#     }
+# }
+# 
+# impl&lt;T: 'static + Display + Debug&gt; Error for &amp;mut ChainError&lt;T&gt; {
+#     fn source(&amp;self) -&gt; Option&lt;&amp;(dyn Error + 'static)&gt; {
+#         if let Some(ref e) = self.error_cause {
+#             Some(e.as_ref())
+#         } else {
+#             None
+#         }
+#     }
+# }
+# 
+# impl&lt;T: 'static + Display + Debug&gt; Display for ChainError&lt;T&gt; {
+#     fn fmt(&amp;self, f: &amp;mut Formatter) -&gt; Result {
+#         write!(f, &quot;{}&quot;, self.kind)?;
+# 
+#         #[cfg(feature = &quot;display-cause&quot;)]
+#         {
+#             if let Some(e) = self.source() {
+#                 writeln!(f, &quot;\nCaused by:&quot;)?;
+#                 Display::fmt(&amp;e, f)?;
+#             }
+#         }
+#         Ok(())
+#     }
+# }
+# 
+# impl&lt;T: 'static + Display + Debug&gt; Debug for ChainError&lt;T&gt; {
+#     fn fmt(&amp;self, f: &amp;mut Formatter) -&gt; Result {
+#         #[cfg(not(feature = &quot;no-fileline&quot;))]
+#         {
+#             if let Some(o) = self.occurrence {
+#                 write!(f, &quot;{}:{}: &quot;, o.1, o.0)?;
+#             }
+#         }
+# 
+#         Debug::fmt(&amp;self.kind, f)?;
+# 
+#         #[cfg(not(feature = &quot;no-debug-cause&quot;))]
+#         {
+#             if let Some(e) = self.source() {
+#                 writeln!(f, &quot;\nCaused by:&quot;)?;
+#                 Debug::fmt(&amp;e, f)?;
+#             }
+#         }
+#         Ok(())
+#     }
+# }
+# 
+# #[macro_export]
+# macro_rules! cherr {
+#     ( $k:expr ) =&gt; {
+#         ChainError::&lt;_&gt;::new($k, None, Some((line!(), file!())))
+#     };
+#     ( $e:expr, $k:expr ) =&gt; {
+#         ChainError::&lt;_&gt;::new($k, Some(Box::from($e)), Some((line!(), file!())))
+#     };
+# }
+# 
+# #[macro_export]
+# macro_rules! mstrerr {
+#     ( $t:ident, $v:expr $(, $more:expr)* ) =&gt; {
+#         |e| cherr!(e, $t (format!($v, $( $more , )* )))
+#     };
+#     ( $t:path, $v:expr $(, $more:expr)* ) =&gt; {
+#         |e| cherr!(e, $t (format!($v, $( $more , )* )))
+#     };
+#     ( $v:expr $(, $more:expr)* ) =&gt; {
+#         |e| cherr!(e, format!($v, $( $more , )* ))
+#     };
+# }
+# 
+# #[macro_export]
+# macro_rules! derive_str_cherr {
+#     ($e:ident) =&gt; {
+#         struct $e(String);
+#         impl ::std::fmt::Display for $e {
+#             fn fmt(&amp;self, f: &amp;mut ::std::fmt::Formatter) -&gt; ::std::fmt::Result {
+#                 write!(f, &quot;{}&quot;, self.0)
+#             }
+#         }
+#         impl ::std::fmt::Debug for $e {
+#             fn fmt(&amp;self, f: &amp;mut ::std::fmt::Formatter) -&gt; ::std::fmt::Result {
+#                 write!(f, &quot;{}({})&quot;, stringify!($e), self.0)
+#             }
+#         }
+#         impl ::std::error::Error for $e {}
+#     };
+# }
+# 
+# #[macro_export]
+# macro_rules! try_cherr_ref {
+#     ( $e:expr, $t:ident ) =&gt; {
+#         $e.downcast_ref::&lt;ChainError&lt;$t&gt;&gt;()
+#     };
+#     ( $e:expr, $t:path ) =&gt; {
+#         $e.downcast_ref::&lt;ChainError&lt;$t&gt;&gt;()
+#     };
+# }
+# 
+# #[macro_export]
+# macro_rules! try_cherr_mut {
+#     ( $e:expr, $t:ident ) =&gt; {
+#         $e.downcast_mut::&lt;ChainError&lt;$t&gt;&gt;()
+#     };
+#     ( $e:expr, $t:path ) =&gt; {
+#         $e.downcast_mut::&lt;ChainError&lt;$t&gt;&gt;()
+#     };
+# }
+# }
+</code></pre></pre>
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