refactor: simplify downcasting logic with std::mem::transmute (#20)

Simplified the downcasting implementations by replacing pointer casting
logic with `std::mem::transmute`, ensuring type safety after matching.
Added tests to validate various downcasting behaviors for both owned and
trait-object error scenarios, improving overall reliability and test
coverage.

.github/workflows/coverage.yml

@@ -13,31 +13,26 @@ on:
     types:
       - created
 
+
 jobs:
-  test:
-    name: coverage
+  coverage:
     runs-on: ubuntu-latest
+    env:
+      CARGO_TERM_COLOR: always
     steps:
-      - uses: actions/checkout@v1
+      - uses: actions/checkout@v4
       - uses: dtolnay/rust-toolchain@master
         with:
           target: x86_64-unknown-linux-gnu
           toolchain: nightly
           components: llvm-tools-preview
-
       - name: Install cargo-llvm-cov
-        run: >
-          curl -LsSf 'https://github.com/taiki-e/cargo-llvm-cov/releases/download/v0.5.23/cargo-llvm-cov-x86_64-unknown-linux-musl.tar.gz'
-          | tar xzf -
-          && mv cargo-llvm-cov $HOME/.cargo/bin
-
-      - name: Run cargo-llvm-cov
-        run: cargo llvm-cov --doctests --all --all-features --lcov --output-path lcov.info
-
+        uses: taiki-e/install-action@cargo-llvm-cov
+      - name: Generate code coverage
+        run: cargo +nightly llvm-cov --all-features --workspace --codecov --doctests --output-path codecov.json
       - name: Upload coverage to Codecov
         uses: codecov/codecov-action@v3
         with:
-          directory: ./
-          fail_ci_if_error: false
-          files: ./lcov.info
-          verbose: true
+          token: ${{ secrets.CODECOV_TOKEN }} # not required for public repos
+          files: codecov.json
+          fail_ci_if_error: true

.github/workflows/gh-pages.yml

@@ -7,7 +7,7 @@ on:
 
 jobs:
   deploy:
-    runs-on: ubuntu-18.04
+    runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v2
 

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "chainerror"
-version = "0.8.0"
+version = "1.0.0"
 authors = ["Harald Hoyer <harald@redhat.com>"]
 edition = "2018"
 license = "MIT OR Apache-2.0"
@@ -21,3 +21,6 @@ github = { repository = "haraldh/chainerror", workflow = "Rust" }
 maintenance = { status = "actively-developed" }
 is-it-maintained-issue-resolution = { repository = "haraldh/chainerror" }
 is-it-maintained-open-issues = { repository = "haraldh/chainerror" }
+
+[package.metadata.docs.rs]
+cargo-args = ["-Zunstable-options", "-Zrustdoc-scrape-examples"]

README.md

@@ -46,7 +46,7 @@ and you have no idea where it comes from.
 With `chainerror`, you can supply a context and get a nice error backtrace:
 
 ```rust
-use chainerror::prelude::v1::*;
+use chainerror::Context as _;
 use std::path::PathBuf;
 
 type BoxedError = Box<dyn std::error::Error + Send + Sync>;
@@ -84,12 +84,87 @@ Os { code: 2, kind: NotFound, message: "No such file or directory" }
 `chainerror` uses `.source()` of `std::error::Error` along with `#[track_caller]` and `Location` to provide a nice debug error backtrace.
 It encapsulates all types, which have `Display + Debug` and can store the error cause internally.
 
-Along with the `ChainError<T>` struct, `chainerror` comes with some useful helper macros to save a lot of typing.
+Along with the `Error<T>` struct, `chainerror` comes with some useful helper macros to save a lot of typing.
 
 `chainerror` has no dependencies!
 
 Debug information is worth it!
 
+## Multiple Output Formats
+
+`chainerror` supports multiple output formats, which can be selected with the different format specifiers:
+
+* `{}`: Display
+```console
+func1 error calling func2
+```
+
+* `{:#}`: Alternative Display
+```console
+func1 error calling func2
+Caused by:
+  func2 error: calling func3
+Caused by:
+  (passed error)
+Caused by:
+  Error reading 'foo.txt'
+Caused by:
+  entity not found
+```
+
+* `{:?}`: Debug
+```console
+examples/example.rs:50:13: func1 error calling func2
+Caused by:
+examples/example.rs:25:13: Func2Error(func2 error: calling func3)
+Caused by:
+examples/example.rs:18:13: (passed error)
+Caused by:
+examples/example.rs:13:18: Error reading 'foo.txt'
+Caused by:
+Kind(NotFound)
+
+```
+
+* `{:#?}`: Alternative Debug
+```console
+Error<example::Func1Error> {
+    occurrence: Some(
+        "examples/example.rs:50:13",
+    ),
+    kind: func1 error calling func2,
+    source: Some(
+        Error<example::Func2Error> {
+            occurrence: Some(
+                "examples/example.rs:25:13",
+            ),
+            kind: Func2Error(func2 error: calling func3),
+            source: Some(
+                Error<chainerror::AnnotatedError> {
+                    occurrence: Some(
+                        "examples/example.rs:18:13",
+                    ),
+                    kind: (passed error),
+                    source: Some(
+                        Error<alloc::string::String> {
+                            occurrence: Some(
+                                "examples/example.rs:13:18",
+                            ),
+                            kind: "Error reading 'foo.txt'",
+                            source: Some(
+                                Kind(
+                                    NotFound,
+                                ),
+                            ),
+                        },
+                    ),
+                },
+            ),
+        },
+    ),
+}
+```
+
 ## Tutorial
 
 Read the [Tutorial](https://haraldh.github.io/chainerror/tutorial1.html)
@@ -98,8 +173,8 @@ Read the [Tutorial](https://haraldh.github.io/chainerror/tutorial1.html)
 
 Licensed under either of
 
-* Apache License, Version 2.0, ([LICENSE-APACHE](LICENSE-APACHE) or https://www.apache.org/licenses/LICENSE-2.0)
-* MIT license ([LICENSE-MIT](LICENSE-MIT) or https://opensource.org/licenses/MIT)
+* Apache License, Version 2.0, ([LICENSE-APACHE](LICENSE-APACHE) or <https://www.apache.org/licenses/LICENSE-2.0>)
+* MIT license ([LICENSE-MIT](LICENSE-MIT) or <https://opensource.org/licenses/MIT>)
 
 at your option.
 

README.tpl

@@ -1,24 +0,0 @@
-[![Crate](https://img.shields.io/crates/v/chainerror.svg)](https://crates.io/crates/chainerror)
-[![Rust Documentation](https://img.shields.io/badge/api-rustdoc-blue.svg)](https://docs.rs/chainerror/)
-[![Coverage Status](https://coveralls.io/repos/github/haraldh/chainerror/badge.svg?branch=master)](https://coveralls.io/github/haraldh/chainerror?branch=master)
-{{badges}}
-
-# {{crate}}
-
-{{readme}}
-
-## License
-
-Licensed under either of
-
-* Apache License, Version 2.0, ([LICENSE-APACHE](LICENSE-APACHE) or https://www.apache.org/licenses/LICENSE-2.0)
-* MIT license ([LICENSE-MIT](LICENSE-MIT) or https://opensource.org/licenses/MIT)
-
-at your option.
-
-### Contribution
-
-Unless you explicitly state otherwise, any contribution intentionally
-submitted for inclusion in the work by you, as defined in the Apache-2.0
-license, shall be dual licensed as above, without any additional terms or
-conditions.

booksrc/LICENSE-APACHE

@@ -0,0 +1 @@
+../LICENSE-APACHE

booksrc/LICENSE-MIT

@@ -0,0 +1 @@
+../LICENSE-MIT

booksrc/tutorial10.md

@@ -1,6 +1,6 @@
 # ErrorKind to the rescue
 
-To cope with different kind of errors, we introduce the kind of an error `Func1ErrorKind` with an enum.
+To cope with different kind of errors, we introduce the `kind` of an error `Func1ErrorKind` with an enum.
 
 Because we derive `Debug` and implement `Display` our `Func1ErrorKind` enum, this enum can be used as
 a `std::error::Error`.
@@ -8,10 +8,9 @@ a `std::error::Error`.
 Only returning `Func1ErrorKind` in `func1()` now let us get rid of `Result<(), Box<Error + Send + Sync>>` and we can
 use `ChainResult<(), Func1ErrorKind>`.
 
-In `main` we can now directly use the methods of `ChainError<T>` without downcasting the error first.
+In `main` we can now directly use the methods of `chainerror::Error<T>` without downcasting the error first.
 
-Also a nice `match` on `ChainError<T>.kind()` is now possible, which returns `&T`, meaning 
-`&Func1ErrorKind` here.
+Also, a nice `match` on `chainerror::Error<T>.kind()` is now possible, which returns `&T`, meaning `&Func1ErrorKind` here.
 
 ~~~rust
 {{#include ../examples/tutorial10.rs}}

booksrc/tutorial11.md

@@ -21,7 +21,7 @@ which gives us a lot more detail.
 
 To create your own Errors, you might find [crates](https://crates.io) which create enum `Display+Debug` via derive macros.
 
-Also noteworthy is [custom_error](https://crates.io/crates/custom_error) to define your custom errors,
+Also, noteworthy is [custom_error](https://crates.io/crates/custom_error) to define your custom errors,
 which can then be used with `chainerror`.
 
 ~~~rust

booksrc/tutorial12.md

@@ -1,6 +1,6 @@
 # Deref for the ErrorKind
 
-Because ChainError<T> implements Deref to &T, we can also match on `*e` instead of `e.kind()`
+Because chainerror::Error<T> implements Deref to &T, we can also match on `*e` instead of `e.kind()`
 or call a function with `&e`
 ~~~rust
 {{#include ../examples/tutorial12.rs}}

booksrc/tutorial13.md

@@ -1,6 +1,6 @@
 # Writing a library
 
-I would advise to only expose an `mycrate::ErrorKind` and type alias `mycrate::Error` to `ChainError<mycrate::ErrorKind>`
+I would advise to only expose an `mycrate::ErrorKind` and type alias `mycrate::Error` to `chainerror::Error<mycrate::ErrorKind>`
 so you can tell your library users to use the `.kind()` method as `std::io::Error` does.
 
 If you later decide to make your own `Error` implementation, your library users don't

booksrc/tutorial2.md

@@ -25,7 +25,7 @@ along with the `Location` of the `context()` call and returns `Err(newerror)`.
 `?` then returns the inner error applying `.into()`, so that we
 again have a `Err(Box<Error + Send + Sync>)` as a result.
 
-The `Debug` implementation of `ChainError<T>` (which is returned by `context()`)
+The `Debug` implementation of `chainerror::Error<T>` (which is returned by `context()`)
 prints the `Debug` of `T` prefixed with the stored filename and line number.
 
-`ChainError<T>` in our case is `ChainError<&str>`.
+`chainerror::Error<T>` in our case is `chainerror::Error<&str>`.

booksrc/tutorial3.md

@@ -14,13 +14,13 @@ If you compare the output to the previous example, you will see,
 that:
 
 ~~~
-Error: src/main.rs:19: "func1 error"
+Error: examples/tutorial2.rs:20:16: func1 error
 ~~~
 
 changed to just:
 
 ~~~
-src/main.rs:16: "func1 error"
+examples/tutorial3.rs:17:13: func1 error
 ~~~
 
 This is, because we caught the error of `func1()` in `main()` and print it out ourselves.

booksrc/tutorial5.md

@@ -14,5 +14,4 @@ Sometimes you want to inspect the `source()` of an `Error`.
 Note, that because we changed the output of the error in `main()` from 
 `Debug` to `Display`, we don't see the error backtrace with filename and line number.
 
-To enable the `Display` backtrace, you have to enable the feature `display-cause` for `chainerror`.
- 
+To use the `Display` backtrace, you have to use the alternative display format output `{:#}`.

booksrc/tutorial7.md

@@ -4,15 +4,15 @@
 
 ~~~rust,ignore
 fn is_chain<T: 'static + Display + Debug>(&self) -> bool
-fn downcast_chain_ref<T: 'static + Display + Debug>(&self) -> Option<&ChainError<T>>
-fn downcast_chain_mut<T: 'static + Display + Debug>(&mut self) -> Option<&mut ChainError<T>>
+fn downcast_chain_ref<T: 'static + Display + Debug>(&self) -> Option<&chainerror::Error<T>>
+fn downcast_chain_mut<T: 'static + Display + Debug>(&mut self) -> Option<&mut chainerror::Error<T>>
 fn root_cause(&self) -> Option<&(dyn Error + 'static)>
 fn find_cause<U: Error + 'static>(&self) -> Option<&U>
-fn find_chain_cause<U: Error + 'static>(&self) -> Option<&ChainError<U>>
+fn find_chain_cause<U: Error + 'static>(&self) -> Option<&chainerror::Error<U>>
 fn kind<'a>(&'a self) -> &'a T
 ~~~
 
-Using `downcast_chain_ref::<String>()` gives a `ChainError<String>`, which can be used
+Using `downcast_chain_ref::<String>()` gives a `chainerror::Error<String>`, which can be used
 to call `.find_cause::<io::Error>()`. 
 
 ~~~rust,ignore

booksrc/tutorial8.md

@@ -1,14 +1,14 @@
 # Finding an Error cause
 
-To distinguish the errors occuring in various places, we can define named string errors with the
+To distinguish the errors occurring in various places, we can define named string errors with the
 "new type" pattern.
 
 ~~~rust,ignore
-derive_str_context!(Func2Error);
-derive_str_context!(Func1Error);
+chainerror::str_context!(Func2Error);
+chainerror::str_context!(Func1Error);
 ~~~
 
-Instead of `ChainError<String>` we now have `struct Func1Error(String)` and `ChainError<Func1Error>`.
+Instead of `chainerror::Error<String>` we now have `struct Func1Error(String)` and `chainerror::Error<Func1Error>`.
 
 In the `main` function you can see, how we can match the different errors.
 
@@ -18,9 +18,9 @@ Also see:
 ~~~
 as a shortcut to
 ~~~rust,ignore
-            if let Some(f2err) = f1err.find_cause::<ChainError<Func2Error>>() {
+            if let Some(f2err) = f1err.find_cause::<chainerror::Error<Func2Error>>() {
 ~~~
-hiding the `ChainError<T>` implementation detail.
+hiding the `chainerror::Error<T>` implementation detail.
 
 ~~~rust
 {{#include ../examples/tutorial8.rs}}

examples/example.rs

@@ -1,24 +1,28 @@
+use chainerror::Context as _;
 use std::error::Error;
+use std::fmt;
 use std::io;
-use std::result::Result;
-
-use chainerror::prelude::v1::*;
 
 fn do_some_io() -> Result<(), Box<dyn Error + Send + Sync>> {
     Err(io::Error::from(io::ErrorKind::NotFound))?;
     Ok(())
 }
 
-fn func3() -> Result<(), Box<dyn Error + Send + Sync>> {
+fn func4() -> Result<(), Box<dyn Error + Send + Sync>> {
     let filename = "foo.txt";
     do_some_io().context(format!("Error reading '{}'", filename))?;
     Ok(())
 }
 
-derive_str_context!(Func2Error);
+fn func3() -> Result<(), Box<dyn Error + Send + Sync>> {
+    func4().annotate()?;
+    Ok(())
+}
 
-fn func2() -> ChainResult<(), Func2Error> {
-    func3().context(Func2Error("func2 error: calling func3".to_string()))?;
+chainerror::str_context!(Func2Error);
+
+fn func2() -> chainerror::Result<(), Func2Error> {
+    func3().context(Func2Error::new("func2 error: calling func3"))?;
     Ok(())
 }
 
@@ -27,8 +31,8 @@ enum Func1Error {
     IO(String),
 }
 
-impl ::std::fmt::Display for Func1Error {
-    fn fmt(&self, f: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
+impl fmt::Display for Func1Error {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         match self {
             Func1Error::Func2 => write!(f, "func1 error calling func2"),
             Func1Error::IO(filename) => write!(f, "Error reading '{}'", filename),
@@ -36,13 +40,13 @@ impl ::std::fmt::Display for Func1Error {
     }
 }
 
-impl ::std::fmt::Debug for Func1Error {
-    fn fmt(&self, f: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
+impl fmt::Debug for Func1Error {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         write!(f, "{}", self)
     }
 }
 
-fn func1() -> ChainResult<(), Func1Error> {
+fn func1() -> chainerror::Result<(), Func1Error> {
     func2().context(Func1Error::Func2)?;
     let filename = String::from("bar.txt");
     do_some_io().context(Func1Error::IO(filename))?;

examples/tutorial1.rs

@@ -3,7 +3,6 @@
 
 use std::error::Error;
 use std::io;
-use std::result::Result;
 
 fn do_some_io() -> Result<(), Box<dyn Error + Send + Sync>> {
     Err(io::Error::from(io::ErrorKind::NotFound))?;

examples/tutorial10.rs

@@ -1,14 +1,14 @@
-use chainerror::prelude::v1::*;
+use chainerror::Context as _;
+
 use std::error::Error;
 use std::io;
-use std::result::Result;
 
 fn do_some_io() -> Result<(), Box<dyn Error + Send + Sync>> {
     Err(io::Error::from(io::ErrorKind::NotFound))?;
     Ok(())
 }
 
-derive_str_context!(Func2Error);
+chainerror::str_context!(Func2Error);
 
 fn func2() -> Result<(), Box<dyn Error + Send + Sync>> {
     let filename = "foo.txt";
@@ -32,7 +32,7 @@ impl ::std::fmt::Display for Func1ErrorKind {
 }
 impl ::std::error::Error for Func1ErrorKind {}
 
-fn func1() -> ChainResult<(), Func1ErrorKind> {
+fn func1() -> chainerror::Result<(), Func1ErrorKind> {
     func2().context(Func1ErrorKind::Func2)?;
     let filename = String::from("bar.txt");
     do_some_io().context(Func1ErrorKind::IO(filename))?;

examples/tutorial11.rs

@@ -1,14 +1,14 @@
-use chainerror::prelude::v1::*;
+use chainerror::Context as _;
+
 use std::error::Error;
 use std::io;
-use std::result::Result;
 
 fn do_some_io() -> Result<(), Box<dyn Error + Send + Sync>> {
     Err(io::Error::from(io::ErrorKind::NotFound))?;
     Ok(())
 }
 
-derive_str_context!(Func2Error);
+chainerror::str_context!(Func2Error);
 
 fn func2() -> Result<(), Box<dyn Error + Send + Sync>> {
     let filename = "foo.txt";
@@ -38,7 +38,7 @@ impl ::std::fmt::Debug for Func1ErrorKind {
 
 impl ::std::error::Error for Func1ErrorKind {}
 
-fn func1() -> ChainResult<(), Func1ErrorKind> {
+fn func1() -> chainerror::Result<(), Func1ErrorKind> {
     func2().context(Func1ErrorKind::Func2)?;
     let filename = String::from("bar.txt");
     do_some_io().context(Func1ErrorKind::IO(filename))?;

examples/tutorial12.rs

@@ -1,14 +1,14 @@
-use chainerror::prelude::v1::*;
+use chainerror::Context as _;
+
 use std::error::Error;
 use std::io;
-use std::result::Result;
 
 fn do_some_io() -> Result<(), Box<dyn Error + Send + Sync>> {
     Err(io::Error::from(io::ErrorKind::NotFound))?;
     Ok(())
 }
 
-derive_str_context!(Func2Error);
+chainerror::str_context!(Func2Error);
 
 fn func2() -> Result<(), Box<dyn Error + Send + Sync>> {
     let filename = "foo.txt";
@@ -38,7 +38,7 @@ impl ::std::fmt::Debug for Func1ErrorKind {
 
 impl ::std::error::Error for Func1ErrorKind {}
 
-fn func1() -> ChainResult<(), Func1ErrorKind> {
+fn func1() -> chainerror::Result<(), Func1ErrorKind> {
     func2().context(Func1ErrorKind::Func2)?;
     let filename = String::from("bar.txt");
     do_some_io().context(Func1ErrorKind::IO(filename))?;

examples/tutorial13.rs

@@ -2,7 +2,8 @@
 #![allow(clippy::redundant_pattern_matching)]
 
 pub mod mycrate {
-    use chainerror::prelude::v1::*;
+    use chainerror::Context as _;
+
     use std::io;
 
     fn do_some_io() -> std::result::Result<(), Box<dyn std::error::Error + Send + Sync>> {
@@ -10,7 +11,7 @@ pub mod mycrate {
         Ok(())
     }
 
-    derive_str_context!(Func2Error);
+    chainerror::str_context!(Func2Error);
 
     fn func2() -> std::result::Result<(), Box<dyn std::error::Error + Send + Sync>> {
         let filename = "foo.txt";
@@ -24,7 +25,7 @@ pub mod mycrate {
         IO(String),
     }
 
-    derive_err_kind!(Error, ErrorKind);
+    chainerror::err_kind!(Error, ErrorKind);
 
     pub type Result<T> = std::result::Result<T, Error>;
 

examples/tutorial15.rs

@@ -2,7 +2,8 @@
 #![allow(clippy::redundant_pattern_matching)]
 
 pub mod mycrate {
-    use chainerror::prelude::v1::*;
+    use chainerror::{Context as _, ErrorDown as _};
+
     use std::io;
 
     fn do_some_io(_f: &str) -> std::result::Result<(), io::Error> {
@@ -10,7 +11,7 @@ pub mod mycrate {
         Ok(())
     }
 
-    derive_str_context!(Func2Error);
+    chainerror::str_context!(Func2Error);
 
     fn func2() -> std::result::Result<(), Box<dyn std::error::Error + Send + Sync>> {
         let filename = "foo.txt";
@@ -26,7 +27,7 @@ pub mod mycrate {
         Unknown,
     }
 
-    derive_err_kind!(Error, ErrorKind);
+    chainerror::err_kind!(Error, ErrorKind);
     pub type Result<T> = std::result::Result<T, Error>;
 
     impl std::fmt::Display for ErrorKind {

examples/tutorial2.rs

@@ -1,8 +1,7 @@
-use chainerror::prelude::v1::*;
+use chainerror::Context as _;
 
 use std::error::Error;
 use std::io;
-use std::result::Result;
 
 fn do_some_io() -> Result<(), Box<dyn Error + Send + Sync>> {
     Err(io::Error::from(io::ErrorKind::NotFound))?;

examples/tutorial3.rs

@@ -1,8 +1,7 @@
-use chainerror::prelude::v1::*;
+use chainerror::Context as _;
 
 use std::error::Error;
 use std::io;
-use std::result::Result;
 
 fn do_some_io() -> Result<(), Box<dyn Error + Send + Sync>> {
     Err(io::Error::from(io::ErrorKind::NotFound))?;

examples/tutorial4.rs

@@ -1,7 +1,7 @@
-use chainerror::prelude::v1::*;
+use chainerror::Context as _;
+
 use std::error::Error;
 use std::io;
-use std::result::Result;
 
 fn do_some_io() -> Result<(), Box<dyn Error + Send + Sync>> {
     Err(io::Error::from(io::ErrorKind::NotFound))?;

examples/tutorial5.rs

@@ -1,7 +1,7 @@
-use chainerror::prelude::v1::*;
+use chainerror::Context as _;
+
 use std::error::Error;
 use std::io;
-use std::result::Result;
 
 fn do_some_io() -> Result<(), Box<dyn Error + Send + Sync>> {
     Err(io::Error::from(io::ErrorKind::NotFound))?;

examples/tutorial6.rs

@@ -1,10 +1,10 @@
 #![allow(clippy::single_match)]
 #![allow(clippy::redundant_pattern_matching)]
 
-use chainerror::prelude::v1::*;
+use chainerror::Context as _;
+
 use std::error::Error;
 use std::io;
-use std::result::Result;
 
 fn do_some_io() -> Result<(), Box<dyn Error + Send + Sync>> {
     Err(io::Error::from(io::ErrorKind::NotFound))?;

examples/tutorial7.rs

@@ -1,10 +1,10 @@
 #![allow(clippy::single_match)]
 #![allow(clippy::redundant_pattern_matching)]
 
-use chainerror::prelude::v1::*;
+use chainerror::{Context as _, ErrorDown as _};
+
 use std::error::Error;
 use std::io;
-use std::result::Result;
 
 fn do_some_io() -> Result<(), Box<dyn Error + Send + Sync>> {
     Err(io::Error::from(io::ErrorKind::NotFound))?;

examples/tutorial8.rs

@@ -1,14 +1,14 @@
-use chainerror::prelude::v1::*;
+use chainerror::{Context as _, ErrorDown as _};
+
 use std::error::Error;
 use std::io;
-use std::result::Result;
 
 fn do_some_io() -> Result<(), Box<dyn Error + Send + Sync>> {
     Err(io::Error::from(io::ErrorKind::NotFound))?;
     Ok(())
 }
 
-derive_str_context!(Func2Error);
+chainerror::str_context!(Func2Error);
 
 fn func2() -> Result<(), Box<dyn Error + Send + Sync>> {
     let filename = "foo.txt";
@@ -16,10 +16,10 @@ fn func2() -> Result<(), Box<dyn Error + Send + Sync>> {
     Ok(())
 }
 
-derive_str_context!(Func1Error);
+chainerror::str_context!(Func1Error);
 
 fn func1() -> Result<(), Box<dyn Error + Send + Sync>> {
-    func2().context(Func1Error("func1 error".to_string()))?;
+    func2().context(Func1Error::new("func1 error"))?;
     Ok(())
 }
 
@@ -28,7 +28,7 @@ fn main() -> Result<(), Box<dyn Error + Send + Sync>> {
         if let Some(f1err) = e.downcast_chain_ref::<Func1Error>() {
             eprintln!("Func1Error: {}", f1err);
 
-            if let Some(f2err) = f1err.find_cause::<ChainError<Func2Error>>() {
+            if let Some(f2err) = f1err.find_cause::<chainerror::Error<Func2Error>>() {
                 eprintln!("Func2Error: {}", f2err);
             }
 

examples/tutorial9.rs

@@ -1,14 +1,14 @@
-use chainerror::prelude::v1::*;
+use chainerror::{Context as _, ErrorDown};
+
 use std::error::Error;
 use std::io;
-use std::result::Result;
 
 fn do_some_io() -> Result<(), Box<dyn Error + Send + Sync>> {
     Err(io::Error::from(io::ErrorKind::NotFound))?;
     Ok(())
 }
 
-derive_str_context!(Func2Error);
+chainerror::str_context!(Func2Error);
 
 fn func2() -> Result<(), Box<dyn Error + Send + Sync>> {
     let filename = "foo.txt";
@@ -16,11 +16,11 @@ fn func2() -> Result<(), Box<dyn Error + Send + Sync>> {
     Ok(())
 }
 
-derive_str_context!(Func1ErrorFunc2);
-derive_str_context!(Func1ErrorIO);
+chainerror::str_context!(Func1ErrorFunc2);
+chainerror::str_context!(Func1ErrorIO);
 
 fn func1() -> Result<(), Box<dyn Error + Send + Sync>> {
-    func2().context(Func1ErrorFunc2("func1 error calling func2".to_string()))?;
+    func2().context(Func1ErrorFunc2::new("func1 error calling func2"))?;
     let filename = "bar.txt";
     do_some_io().context(Func1ErrorIO(format!("Error reading '{}'", filename)))?;
     Ok(())
@@ -28,7 +28,7 @@ fn func1() -> Result<(), Box<dyn Error + Send + Sync>> {
 
 fn main() -> Result<(), Box<dyn Error + Send + Sync>> {
     if let Err(e) = func1() {
-        if let Some(s) = e.downcast_ref::<ChainError<Func1ErrorIO>>() {
+        if let Some(s) = e.downcast_ref::<chainerror::Error<Func1ErrorIO>>() {
             eprintln!("Func1ErrorIO:\n{:?}", s);
         }
 

src/lib.rs

@@ -8,18 +8,6 @@ use std::error::Error as StdError;
 use std::fmt::{Debug, Display, Formatter};
 use std::panic::Location;
 
-pub mod prelude {
-    //! convenience prelude
-    pub mod v1 {
-        //! convenience prelude
-        pub use super::super::ChainErrorDown as _;
-        pub use super::super::Error as ChainError;
-        pub use super::super::Result as ChainResult;
-        pub use super::super::ResultTrait as _;
-        pub use crate::{derive_err_kind, derive_str_context};
-    }
-}
-
 /// chains an inner error kind `T` with a causing error
 pub struct Error<T> {
     occurrence: Option<String>,
@@ -55,7 +43,8 @@ impl<T: 'static + Display + Debug> Error<T> {
     /// # Examples
     ///
     /// ```rust
-    /// use chainerror::prelude::v1::*;
+    /// use chainerror::Context as _;
+    /// use chainerror::ErrorDown as _;
     /// use std::error::Error;
     /// use std::io;
     ///
@@ -64,7 +53,7 @@ impl<T: 'static + Display + Debug> Error<T> {
     ///     Ok(())
     /// }
     ///
-    /// derive_str_context!(Func2Error);
+    /// chainerror::str_context!(Func2Error);
     ///
     /// fn func2() -> Result<(), Box<dyn Error + Send + Sync>> {
     ///     let filename = "foo.txt";
@@ -72,10 +61,10 @@ impl<T: 'static + Display + Debug> Error<T> {
     ///     Ok(())
     /// }
     ///
-    /// derive_str_context!(Func1Error);
+    /// chainerror::str_context!(Func1Error);
     ///
     /// fn func1() -> Result<(), Box<dyn Error + Send + Sync>> {
-    ///     func2().context(Func1Error("func1 error".into()))?;
+    ///     func2().context(Func1Error::new("func1 error"))?;
     ///     Ok(())
     /// }
     ///
@@ -100,20 +89,19 @@ impl<T: 'static + Display + Debug> Error<T> {
             .next()
     }
 
-    /// Find the first error cause of type `ChainError<U>`, if any exists
+    /// Find the first error cause of type [`Error<U>`](Error), if any exists
     ///
-    /// Same as `find_cause`, but hides the `ChainError<U>` implementation internals
+    /// Same as `find_cause`, but hides the [`Error<U>`](Error) implementation internals
     ///
     /// # Examples
     ///
     /// ```rust
-    /// # use chainerror::prelude::v1::*;
-    /// # derive_str_context!(FooError);
-    /// # let err = ChainError::new(String::new(), None, None);
+    /// # chainerror::str_context!(FooError);
+    /// # let err = chainerror::Error::new(String::new(), None, None);
     /// // Instead of writing
-    /// err.find_cause::<ChainError<FooError>>();
+    /// err.find_cause::<chainerror::Error<FooError>>();
     ///
-    /// // leave out the ChainError<FooError> implementation detail
+    /// // leave out the chainerror::Error<FooError> implementation detail
     /// err.find_chain_cause::<FooError>();
     /// ```
     #[inline]
@@ -123,24 +111,23 @@ impl<T: 'static + Display + Debug> Error<T> {
             .next()
     }
 
-    /// Find the first error cause of type `ChainError<U>` or `U`, if any exists and return `U`
+    /// Find the first error cause of type [`Error<U>`](Error) or `U`, if any exists and return `U`
     ///
-    /// Same as `find_cause` and `find_chain_cause`, but hides the `ChainError<U>` implementation internals
+    /// Same as `find_cause` and `find_chain_cause`, but hides the [`Error<U>`](Error) implementation internals
     ///
     /// # Examples
     ///
     /// ```rust
-    /// # use chainerror::prelude::v1::*;
-    /// # derive_str_context!(FooErrorKind);
-    /// # let err = ChainError::new(String::new(), None, None);
+    /// # chainerror::str_context!(FooErrorKind);
+    /// # let err = chainerror::Error::new(String::new(), None, None);
     /// // Instead of writing
-    /// err.find_cause::<ChainError<FooErrorKind>>();
+    /// err.find_cause::<chainerror::Error<FooErrorKind>>();
     /// // and/or
     /// err.find_chain_cause::<FooErrorKind>();
     /// // and/or
     /// err.find_cause::<FooErrorKind>();
     ///
-    /// // leave out the ChainError<FooErrorKind> implementation detail
+    /// // leave out the chainerror::Error<FooErrorKind> implementation detail
     /// err.find_kind_or_cause::<FooErrorKind>();
     /// ```
     #[inline]
@@ -154,12 +141,12 @@ impl<T: 'static + Display + Debug> Error<T> {
             .next()
     }
 
-    /// Return a reference to T of `ChainError<T>`
+    /// Return a reference to T of [`Error<T>`](Error)
     ///
     /// # Examples
     ///
     /// ```rust
-    /// use chainerror::prelude::v1::*;
+    /// use chainerror::Context as _;
     /// use std::error::Error;
     /// use std::io;
     ///
@@ -168,7 +155,7 @@ impl<T: 'static + Display + Debug> Error<T> {
     ///     Ok(())
     /// }
     ///
-    /// derive_str_context!(Func2Error);
+    /// chainerror::str_context!(Func2Error);
     ///
     /// fn func2() -> Result<(), Box<dyn Error + Send + Sync>> {
     ///     let filename = "foo.txt";
@@ -192,7 +179,7 @@ impl<T: 'static + Display + Debug> Error<T> {
     /// #     }
     /// # }
     ///
-    /// fn func1() -> ChainResult<(), Func1ErrorKind> {
+    /// fn func1() -> chainerror::Result<(), Func1ErrorKind> {
     ///     func2().context(Func1ErrorKind::Func2)?;
     ///     do_some_io().context(Func1ErrorKind::IO("bar.txt".into()))?;
     ///     Ok(())
@@ -224,11 +211,14 @@ impl<T: 'static + Display + Debug> Error<T> {
     }
 }
 
-/// Convenience methods for `Result<>` to turn the error into a decorated ChainError
-pub trait ResultTrait<O, E: Into<Box<dyn StdError + 'static + Send + Sync>>> {
+/// Convenience methods for `Result<>` to turn the error into a decorated [`Error`](Error)
+pub trait Context<O, E: Into<Box<dyn StdError + 'static + Send + Sync>>> {
     /// Decorate the error with a `kind` of type `T` and the source `Location`
     fn context<T: 'static + Display + Debug>(self, kind: T) -> std::result::Result<O, Error<T>>;
 
+    /// Decorate the error just with the source `Location`
+    fn annotate(self) -> std::result::Result<O, Error<AnnotatedError>>;
+
     /// Decorate the `error` with a `kind` of type `T` produced with a `FnOnce(&error)` and the source `Location`
     fn map_context<T: 'static + Display + Debug, F: FnOnce(&E) -> T>(
         self,
@@ -236,7 +226,22 @@ pub trait ResultTrait<O, E: Into<Box<dyn StdError + 'static + Send + Sync>>> {
     ) -> std::result::Result<O, Error<T>>;
 }
 
-impl<O, E: Into<Box<dyn StdError + 'static + Send + Sync>>> ResultTrait<O, E>
+/// Convenience type to just decorate the error with the source `Location`
+pub struct AnnotatedError(());
+
+impl Display for AnnotatedError {
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+        write!(f, "(passed error)")
+    }
+}
+
+impl Debug for AnnotatedError {
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+        write!(f, "(passed error)")
+    }
+}
+
+impl<O, E: Into<Box<dyn StdError + 'static + Send + Sync>>> Context<O, E>
     for std::result::Result<O, E>
 {
     #[track_caller]
@@ -252,6 +257,19 @@ impl<O, E: Into<Box<dyn StdError + 'static + Send + Sync>>> ResultTrait<O, E>
         }
     }
 
+    #[track_caller]
+    #[inline]
+    fn annotate(self) -> std::result::Result<O, Error<AnnotatedError>> {
+        match self {
+            Ok(t) => Ok(t),
+            Err(error_cause) => Err(Error::new(
+                AnnotatedError(()),
+                Some(error_cause.into()),
+                Some(Location::caller().to_string()),
+            )),
+        }
+    }
+
     #[track_caller]
     #[inline]
     fn map_context<T: 'static + Display + Debug, F: FnOnce(&E) -> T>(
@@ -297,21 +315,21 @@ impl<T: 'static + Display + Debug> std::ops::Deref for Error<T> {
     }
 }
 
-/// Convenience trait to hide the `ChainError<T>` implementation internals
-pub trait ChainErrorDown {
-    /// Test if of type `ChainError<T>`
+/// Convenience trait to hide the [`Error<T>`](Error) implementation internals
+pub trait ErrorDown {
+    /// Test if of type `Error<T>`
     fn is_chain<T: 'static + Display + Debug>(&self) -> bool;
-    /// Downcast to a reference of `ChainError<T>`
+    /// Downcast to a reference of `Error<T>`
     fn downcast_chain_ref<T: 'static + Display + Debug>(&self) -> Option<&Error<T>>;
-    /// Downcast to a mutable reference of `ChainError<T>`
+    /// Downcast to a mutable reference of `Error<T>`
     fn downcast_chain_mut<T: 'static + Display + Debug>(&mut self) -> Option<&mut Error<T>>;
-    /// Downcast to T of `ChainError<T>`
+    /// Downcast to T of `Error<T>`
     fn downcast_inner_ref<T: 'static + StdError>(&self) -> Option<&T>;
-    /// Downcast to T mutable reference of `ChainError<T>`
+    /// Downcast to T mutable reference of `Error<T>`
     fn downcast_inner_mut<T: 'static + StdError>(&mut self) -> Option<&mut T>;
 }
 
-impl<U: 'static + Display + Debug> ChainErrorDown for Error<U> {
+impl<U: 'static + Display + Debug> ErrorDown for Error<U> {
     #[inline]
     fn is_chain<T: 'static + Display + Debug>(&self) -> bool {
         TypeId::of::<T>() == TypeId::of::<U>()
@@ -320,11 +338,8 @@ impl<U: 'static + Display + Debug> ChainErrorDown for Error<U> {
     #[inline]
     fn downcast_chain_ref<T: 'static + Display + Debug>(&self) -> Option<&Error<T>> {
         if self.is_chain::<T>() {
-            #[allow(clippy::cast_ptr_alignment)]
-            unsafe {
-                #[allow(trivial_casts)]
-                Some(*(self as *const dyn StdError as *const &Error<T>))
-            }
+            // Use transmute when we've verified the types match
+            unsafe { Some(std::mem::transmute::<&Error<U>, &Error<T>>(self)) }
         } else {
             None
         }
@@ -333,11 +348,8 @@ impl<U: 'static + Display + Debug> ChainErrorDown for Error<U> {
     #[inline]
     fn downcast_chain_mut<T: 'static + Display + Debug>(&mut self) -> Option<&mut Error<T>> {
         if self.is_chain::<T>() {
-            #[allow(clippy::cast_ptr_alignment)]
-            unsafe {
-                #[allow(trivial_casts)]
-                Some(&mut *(self as *mut dyn StdError as *mut &mut Error<T>))
-            }
+            // Use transmute when we've verified the types match
+            unsafe { Some(std::mem::transmute::<&mut Error<U>, &mut Error<T>>(self)) }
         } else {
             None
         }
@@ -345,11 +357,8 @@ impl<U: 'static + Display + Debug> ChainErrorDown for Error<U> {
     #[inline]
     fn downcast_inner_ref<T: 'static + StdError>(&self) -> Option<&T> {
         if self.is_chain::<T>() {
-            #[allow(clippy::cast_ptr_alignment)]
-            unsafe {
-                #[allow(trivial_casts)]
-                Some(&(*(self as *const dyn StdError as *const &Error<T>)).kind)
-            }
+            // Use transmute when we've verified the types match
+            unsafe { Some(std::mem::transmute::<&U, &T>(&self.kind)) }
         } else {
             None
         }
@@ -358,18 +367,15 @@ impl<U: 'static + Display + Debug> ChainErrorDown for Error<U> {
     #[inline]
     fn downcast_inner_mut<T: 'static + StdError>(&mut self) -> Option<&mut T> {
         if self.is_chain::<T>() {
-            #[allow(clippy::cast_ptr_alignment)]
-            unsafe {
-                #[allow(trivial_casts)]
-                Some(&mut (*(self as *mut dyn StdError as *mut &mut Error<T>)).kind)
-            }
+            // Use transmute when we've verified the types match
+            unsafe { Some(std::mem::transmute::<&mut U, &mut T>(&mut self.kind)) }
         } else {
             None
         }
     }
 }
 
-impl ChainErrorDown for dyn StdError + 'static {
+impl ErrorDown for dyn StdError + 'static {
     #[inline]
     fn is_chain<T: 'static + Display + Debug>(&self) -> bool {
         self.is::<Error<T>>()
@@ -402,7 +408,7 @@ impl ChainErrorDown for dyn StdError + 'static {
     }
 }
 
-impl ChainErrorDown for dyn StdError + 'static + Send {
+impl ErrorDown for dyn StdError + 'static + Send {
     #[inline]
     fn is_chain<T: 'static + Display + Debug>(&self) -> bool {
         self.is::<Error<T>>()
@@ -435,7 +441,7 @@ impl ChainErrorDown for dyn StdError + 'static + Send {
     }
 }
 
-impl ChainErrorDown for dyn StdError + 'static + Send + Sync {
+impl ErrorDown for dyn StdError + 'static + Send + Sync {
     #[inline]
     fn is_chain<T: 'static + Display + Debug>(&self) -> bool {
         self.is::<Error<T>>()
@@ -505,7 +511,7 @@ impl<T: 'static + Display + Debug> Debug for Error<T> {
     #[inline]
     fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
         if f.alternate() {
-            let mut f = f.debug_struct(&format!("ChainError<{}>", std::any::type_name::<T>()));
+            let mut f = f.debug_struct(&format!("Error<{}>", std::any::type_name::<T>()));
 
             let f = f
                 .field("occurrence", &self.occurrence)
@@ -549,7 +555,8 @@ where
 /// # Examples
 ///
 /// ```rust
-/// # use chainerror::prelude::v1::*;
+/// # use chainerror::Context as _;
+/// # use chainerror::ErrorDown as _;
 /// # use std::error::Error;
 /// # use std::io;
 /// # use std::result::Result;
@@ -557,23 +564,23 @@ where
 /// #     Err(io::Error::from(io::ErrorKind::NotFound))?;
 /// #     Ok(())
 /// # }
-/// derive_str_context!(Func2Error);
+/// chainerror::str_context!(Func2Error);
 ///
-/// fn func2() -> ChainResult<(), Func2Error> {
+/// fn func2() -> chainerror::Result<(), Func2Error> {
 ///     let filename = "foo.txt";
 ///     do_some_io().context(Func2Error(format!("Error reading '{}'", filename)))?;
 ///     Ok(())
 /// }
 ///
-/// derive_str_context!(Func1Error);
+/// chainerror::str_context!(Func1Error);
 ///
 /// fn func1() -> Result<(), Box<dyn Error>> {
-///     func2().context(Func1Error("func1 error".into()))?;
+///     func2().context(Func1Error::new("func1 error"))?;
 ///     Ok(())
 /// }
 /// #     if let Err(e) = func1() {
 /// #         if let Some(f1err) = e.downcast_chain_ref::<Func1Error>() {
-/// #             assert!(f1err.find_cause::<ChainError<Func2Error>>().is_some());
+/// #             assert!(f1err.find_cause::<chainerror::Error<Func2Error>>().is_some());
 /// #             assert!(f1err.find_chain_cause::<Func2Error>().is_some());
 /// #         } else {
 /// #             panic!();
@@ -583,10 +590,16 @@ where
 /// #     }
 /// ```
 #[macro_export]
-macro_rules! derive_str_context {
+macro_rules! str_context {
     ($e:ident) => {
         #[derive(Clone)]
         pub struct $e(pub String);
+        impl $e {
+            #[allow(dead_code)]
+            pub fn new<S: Into<String>>(s: S) -> Self {
+                $e(s.into())
+            }
+        }
         impl ::std::fmt::Display for $e {
             fn fmt(&self, f: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
                 write!(f, "{}", self.0)
@@ -601,9 +614,9 @@ macro_rules! derive_str_context {
     };
 }
 
-/// Derive an Error for an ErrorKind, which wraps a `ChainError` and implements a `kind()` method
+/// Derive an Error for an ErrorKind, which wraps a [`Error`](Error) and implements a `kind()` method
 ///
-/// It basically hides `ChainError` to the outside and only exposes the `kind()`
+/// It basically hides [`Error`](Error) to the outside and only exposes the [`kind()`](Error::kind)
 /// method.
 ///
 /// Error::kind() returns the ErrorKind
@@ -612,7 +625,7 @@ macro_rules! derive_str_context {
 /// # Examples
 ///
 /// ```rust
-/// use chainerror::prelude::v1::*;
+/// use chainerror::Context as _;
 /// use std::io;
 ///
 /// fn do_some_io(_f: &str) -> std::result::Result<(), io::Error> {
@@ -626,7 +639,7 @@ macro_rules! derive_str_context {
 ///     Unknown,
 /// }
 ///
-/// derive_err_kind!(Error, ErrorKind);
+/// chainerror::err_kind!(Error, ErrorKind);
 ///
 /// impl std::fmt::Display for ErrorKind {
 ///     fn fmt(&self, f: &mut ::std::fmt::Formatter) -> std::fmt::Result {
@@ -664,9 +677,15 @@ macro_rules! derive_str_context {
 ///     do_some_io(filename).map_context(|e| ErrorKind::from(e))?;
 ///     Ok(())
 /// }
+///
+/// # fn main() {
+/// #   if let Err(e) = func1() {
+/// #       eprintln!("Error:\n{:?}", e);
+/// #   }
+/// # }
 /// ```
 #[macro_export]
-macro_rules! derive_err_kind {
+macro_rules! err_kind {
     ($e:ident, $k:ident) => {
         pub struct $e($crate::Error<$k>);
 
@@ -682,7 +701,7 @@ macro_rules! derive_err_kind {
             }
         }
 
-        impl From<ChainError<$k>> for $e {
+        impl From<$crate::Error<$k>> for $e {
             fn from(e: $crate::Error<$k>) -> Self {
                 $e(e)
             }
@@ -716,3 +735,291 @@ macro_rules! derive_err_kind {
         }
     };
 }
+
+#[cfg(test)]
+mod tests {
+    use super::Context as _;
+    use super::*;
+    use std::io;
+
+    #[test]
+    fn test_error_chain_with_multiple_causes() {
+        // Create a chain of errors
+        let io_error = io::Error::new(io::ErrorKind::NotFound, "file not found");
+
+        str_context!(Level3Error);
+        str_context!(Level2Error);
+        str_context!(Level1Error);
+
+        let err = Result::<(), _>::Err(io_error.into())
+            .context(Level3Error("level 3".into()))
+            .context(Level2Error("level 2".into()))
+            .context(Level1Error("level 1".into()))
+            .unwrap_err();
+
+        // Test the error chain
+        assert!(err.is_chain::<Level1Error>());
+        assert!(err.find_chain_cause::<Level2Error>().is_some());
+        assert!(err.find_chain_cause::<Level3Error>().is_some());
+        assert!(err.find_chain_cause::<io::Error>().is_some());
+    }
+
+    #[test]
+    fn test_error_root_cause() {
+        let io_error = io::Error::new(io::ErrorKind::NotFound, "file not found");
+
+        str_context!(WrapperError);
+        let err = Result::<(), _>::Err(io_error.into())
+            .context(WrapperError("wrapper".into()))
+            .unwrap_err();
+
+        let root = err.root_cause().unwrap();
+        assert!(root.is_chain::<io::Error>());
+    }
+
+    #[test]
+    fn test_error_display_and_debug() {
+        str_context!(CustomError);
+        let err = Error::new(
+            CustomError("test error".into()),
+            None,
+            Some("src/lib.rs:100".into()),
+        );
+
+        // Test Display formatting
+        assert_eq!(format!("{}", err), "test error");
+
+        // Test alternate Display formatting
+        assert_eq!(format!("{:#}", err), "test error");
+
+        // Test Debug formatting
+        let debug_output = format!("{:?}", err);
+        assert!(debug_output.contains("test error"));
+        assert!(debug_output.contains("src/lib.rs:100"));
+    }
+
+    #[test]
+    fn test_error_annotation() {
+        let io_error = io::Error::new(io::ErrorKind::NotFound, "file not found");
+        let err = Result::<(), _>::Err(io_error.into())
+            .annotate()
+            .unwrap_err();
+
+        assert!(err.source().is_some());
+        err.source()
+            .unwrap()
+            .downcast_inner_ref::<io::Error>()
+            .unwrap();
+    }
+
+    #[test]
+    fn test_map_context() {
+        let io_error = io::Error::new(io::ErrorKind::NotFound, "file not found");
+
+        str_context!(MappedError);
+        let err = Result::<(), _>::Err(io_error.into())
+            .map_context(|e| MappedError(format!("Mapped: {}", e)))
+            .unwrap_err();
+
+        assert!(err.is_chain::<MappedError>());
+        assert!(err.find_chain_cause::<io::Error>().is_some());
+    }
+
+    #[test]
+    fn test_error_downcasting() {
+        str_context!(OriginalError);
+        let original = Error::new(OriginalError("test".into()), None, None);
+
+        let error: Box<dyn StdError + Send + Sync> = Box::new(original);
+
+        // Test downcast_chain_ref
+        assert!(error.is_chain::<OriginalError>());
+        assert!(error.downcast_chain_ref::<OriginalError>().is_some());
+
+        // Test downcast_inner_ref
+        let inner = error.downcast_inner_ref::<OriginalError>();
+        assert!(inner.is_some());
+    }
+
+    #[derive(Debug, Clone)]
+    enum TestErrorKind {
+        Basic(String),
+        Complex { message: String },
+    }
+
+    impl Display for TestErrorKind {
+        fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+            match self {
+                TestErrorKind::Basic(msg) => write!(f, "Basic error: {}", msg),
+                TestErrorKind::Complex { message } => write!(f, "Complex error: {}", message),
+            }
+        }
+    }
+
+    #[test]
+    fn test_err_kind_macro() {
+        err_kind!(TestError, TestErrorKind);
+
+        let err = TestError::from(TestErrorKind::Basic("test".into()));
+        assert!(matches!(err.kind(), TestErrorKind::Basic(_)));
+        // The annotated error should display "(passed error)" even in a chain
+        assert_eq!(format!("{}", err), "Basic error: test");
+        assert_eq!(format!("{:?}", err), "Basic(\"test\")");
+
+        let complex_err = TestError::from(TestErrorKind::Complex {
+            message: "test".into(),
+        });
+        assert!(matches!(complex_err.kind(), TestErrorKind::Complex { .. }));
+        // The annotated error should display "(passed error)" even in a chain
+        assert_eq!(format!("{}", complex_err), "Complex error: test");
+        assert_eq!(
+            format!("{:?}", complex_err),
+            "Complex { message: \"test\" }"
+        );
+    }
+    #[test]
+    fn test_annotated_error_display_and_debug() {
+        let annotated = AnnotatedError(());
+
+        // Test Display formatting
+        assert_eq!(format!("{}", annotated), "(passed error)");
+
+        // Test Debug formatting
+        assert_eq!(format!("{:?}", annotated), "(passed error)");
+
+        // Test with error chain
+        let io_error = io::Error::new(io::ErrorKind::NotFound, "file not found");
+        let err = Result::<(), _>::Err(io_error.into())
+            .annotate()
+            .unwrap_err();
+
+        // The annotated error should display "(passed error)" even in a chain
+        assert_eq!(format!("{}", err), "(passed error)");
+        assert!(format!("{:?}", err).contains("(passed error)"));
+
+        // Verify the error chain is preserved
+        assert!(err.source().is_some());
+        assert!(err.source().unwrap().is_chain::<io::Error>());
+    }
+
+    // Helper error types for testing
+    #[derive(Debug)]
+    struct TestError(String);
+
+    impl std::fmt::Display for TestError {
+        fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+            write!(f, "{}", self.0)
+        }
+    }
+
+    impl std::error::Error for TestError {}
+
+    #[test]
+    fn test_downcast_chain_operations() {
+        // Create a test error chain
+        let original_error = Error::new(
+            TestError("test message".to_string()),
+            None,
+            Some("test location".to_string()),
+        );
+
+        // Test is_chain
+        assert!(original_error.is_chain::<TestError>());
+        assert!(!original_error.is_chain::<io::Error>());
+
+        // Test downcast_chain_ref
+        let downcast_ref = original_error.downcast_chain_ref::<TestError>();
+        assert!(downcast_ref.is_some());
+        let downcast_kind = downcast_ref.unwrap().kind();
+        assert_eq!(format!("{}", downcast_kind), "test message");
+        assert_eq!(
+            format!("{:?}", downcast_kind),
+            "TestError(\"test message\")"
+        );
+
+        // Test invalid downcast_chain_ref
+        let invalid_downcast = original_error.downcast_chain_ref::<io::Error>();
+        assert!(invalid_downcast.is_none());
+
+        // Test downcast_chain_mut
+        let mut mutable_error = original_error;
+        let downcast_mut = mutable_error.downcast_chain_mut::<TestError>();
+        assert!(downcast_mut.is_some());
+        assert_eq!(downcast_mut.unwrap().kind().0, "test message");
+
+        // Test invalid downcast_chain_mut
+        let invalid_downcast_mut = mutable_error.downcast_chain_mut::<io::Error>();
+        assert!(invalid_downcast_mut.is_none());
+    }
+
+    #[test]
+    fn test_downcast_inner_operations() {
+        // Create a test error
+        let mut error = Error::new(
+            TestError("inner test".to_string()),
+            None,
+            Some("test location".to_string()),
+        );
+
+        // Test downcast_inner_ref
+        let inner_ref = error.downcast_inner_ref::<TestError>();
+        assert!(inner_ref.is_some());
+        assert_eq!(inner_ref.unwrap().0, "inner test");
+        // Test invalid downcast_inner_ref
+        let invalid_inner = error.downcast_inner_ref::<io::Error>();
+        assert!(invalid_inner.is_none());
+
+        // Test downcast_inner_mut
+        let inner_mut = error.downcast_inner_mut::<TestError>();
+        assert!(inner_mut.is_some());
+        assert_eq!(inner_mut.unwrap().0, "inner test");
+
+        // Test invalid downcast_inner_mut
+        let invalid_inner_mut = error.downcast_inner_mut::<io::Error>();
+        assert!(invalid_inner_mut.is_none());
+    }
+
+    #[test]
+    fn test_error_down_for_dyn_error() {
+        // Create a boxed error
+        let error: Box<dyn std::error::Error + 'static> = Box::new(Error::new(
+            TestError("dyn test".to_string()),
+            None,
+            Some("test location".to_string()),
+        ));
+
+        // Test is_chain through trait object
+        assert!(error.is_chain::<TestError>());
+        assert!(!error.is_chain::<io::Error>());
+
+        // Test downcast_chain_ref through trait object
+        let chain_ref = error.downcast_chain_ref::<TestError>();
+        assert!(chain_ref.is_some());
+        assert_eq!(chain_ref.unwrap().kind().0, "dyn test");
+
+        // Test downcast_inner_ref through trait object
+        let inner_ref = error.downcast_inner_ref::<TestError>();
+        assert!(inner_ref.is_some());
+        assert_eq!(inner_ref.unwrap().0, "dyn test");
+    }
+
+    #[test]
+    fn test_error_down_with_sync_send() {
+        // Create a boxed error with Send + Sync
+        let error: Box<dyn std::error::Error + Send + Sync> = Box::new(Error::new(
+            TestError("sync test".to_string()),
+            None,
+            Some("test location".to_string()),
+        ));
+
+        // Test operations on Send + Sync error
+        assert!(error.is_chain::<TestError>());
+        assert!(error.downcast_chain_ref::<TestError>().is_some());
+        assert!(error.downcast_inner_ref::<TestError>().is_some());
+
+        // Test invalid downcasts
+        assert!(!error.is_chain::<io::Error>());
+        assert!(error.downcast_chain_ref::<io::Error>().is_none());
+        assert!(error.downcast_inner_ref::<io::Error>().is_none());
+    }
+}

tests/test_basic.rs

@@ -0,0 +1,33 @@
+use chainerror::Context;
+
+#[test]
+fn test_basic() {
+    use std::path::PathBuf;
+    type BoxedError = Box<dyn std::error::Error + Send + Sync>;
+    fn read_config_file(path: PathBuf) -> Result<(), BoxedError> {
+        // do stuff, return other errors
+        let _buf = std::fs::read_to_string(&path).context(format!("Reading file: {:?}", &path))?;
+        // do stuff, return other errors
+        Ok(())
+    }
+    fn process_config_file() -> Result<(), BoxedError> {
+        // do stuff, return other errors
+        read_config_file("_non_existent.txt".into()).context("read the config file")?;
+        // do stuff, return other errors
+        Ok(())
+    }
+
+    if let Err(e) = process_config_file() {
+        let os_notfound_error = std::io::Error::from_raw_os_error(2);
+        let s = format!("{:?}", e);
+        let lines = s.lines().collect::<Vec<_>>();
+        assert_eq!(lines.len(), 5);
+        assert!(lines[0].starts_with("tests/test_basic.rs:"));
+        assert_eq!(lines[1], "Caused by:");
+        assert!(lines[2].starts_with("tests/test_basic.rs:"));
+        assert_eq!(lines[3], "Caused by:");
+        assert_eq!(lines[4], format!("{:?}", os_notfound_error));
+    } else {
+        panic!();
+    }
+}

tests/test_iter.rs

@@ -1,4 +1,4 @@
-use chainerror::prelude::v1::*;
+use chainerror::Context;
 use std::error::Error;
 use std::io;