make ChainError Send + Sync

booksrc/tutorial10.md

@@ -8,7 +8,7 @@ a `std::error::Error`.
 Not using `String` errors anymore, the `cherr!()` macro seen in the beginning of
 the tutorial has to be used again.
 
-Only returning `Func1ErrorKind` in `func1()` now let us get rid of `Result<(), Box<Error>>` and we can
+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.

booksrc/tutorial2.md

@@ -24,7 +24,7 @@ along with the filename (`file!()`) and line number (`line!()`)
 and returns `newerror`.
 
 `Err()?` then returns the inner error applying `.into()`, so that we
-again have a `Err(Box<Error>)` as a result.
+again have a `Err(Box<Error + Send + Sync>)` as a result.
 
 The `Debug` implementation of `ChainError<T>` (which is returned by `cherr!()`)
 prints the `Debug` of `T` prefixed with the stored filename and line number.

booksrc/tutorial9.md

@@ -7,7 +7,7 @@ In this example `func1()` can return either `Func1ErrorFunc2` or `Func1ErrorIO`.
 We might want to `match` on `func1()` with something like:
 
 ~~~rust,ignore
-fn main() -> Result<(), Box<Error>> {
+fn main() -> Result<(), Box<Error + Send + Sync>> {
     match func1() {
         Err(e) if let Some(s) = e.downcast_chain_ref::<Func1ErrorIO>() =>
         eprintln!("Func1ErrorIO:\n{:?}", s),