Auto merge of #34200 - sanxiyn:rollup, r=sanxiyn

Rollup of 12 pull requests

- Successful merges: #34088, #34129, #34136, #34145, #34146, #34148, #34159, #34160, #34165, #34175, #34184, #34185
- Failed merges:

README.md

@@ -75,13 +75,13 @@ build.
    $ pacman -Sy pacman-mirrors
    ```
 
-Download [MinGW from
-here](http://mingw-w64.org/doku.php/download/mingw-builds), and choose the
-`version=4.9.x,threads=win32,exceptions=dwarf/seh` flavor when installing. Also, make sure to install to a path without spaces in it. After installing,
-add its `bin` directory to your `PATH`. This is due to [#28260](https://github.com/rust-lang/rust/issues/28260), in the future,
-installing from pacman should be just fine.
+   Download [MinGW from
+   here](http://mingw-w64.org/doku.php/download/mingw-builds), and choose the
+   `version=4.9.x,threads=win32,exceptions=dwarf/seh` flavor when installing. Also, make sure to install to a path without spaces in it. After installing,
+   add its `bin` directory to your `PATH`. This is due to [#28260](https://github.com/rust-lang/rust/issues/28260), in the future,
+   installing from pacman should be just fine.
 
-   ```
+   ```sh
    # Make git available in MSYS2 (if not already available on path)
    $ pacman -S git
 
@@ -90,6 +90,8 @@ installing from pacman should be just fine.
 
 3. Run `mingw32_shell.bat` or `mingw64_shell.bat` from wherever you installed
    MSYS2 (i.e. `C:\msys`), depending on whether you want 32-bit or 64-bit Rust.
+   (As of the latest version of MSYS2 you have to run `msys2_shell.cmd -mingw32`
+   or `msys2_shell.cmd -mingw64` from the command line instead)
 
 4. Navigate to Rust's source code, configure and build it:
 

src/doc/book/error-handling.md

@@ -1829,7 +1829,7 @@ use std::error::Error;
 
 fn search<P: AsRef<Path>>
          (file_path: P, city: &str)
-         -> Result<Vec<PopulationCount>, Box<Error+Send+Sync>> {
+         -> Result<Vec<PopulationCount>, Box<Error>> {
     let mut found = vec![];
     let file = try!(File::open(file_path));
     let mut rdr = csv::Reader::from_reader(file);
@@ -1858,20 +1858,17 @@ Instead of `x.unwrap()`, we now have `try!(x)`. Since our function returns a
 `Result<T, E>`, the `try!` macro will return early from the function if an
 error occurs.
 
-There is one big gotcha in this code: we used `Box<Error + Send + Sync>`
-instead of `Box<Error>`. We did this so we could convert a plain string to an
-error type. We need these extra bounds so that we can use the
-[corresponding `From`
-impls](../std/convert/trait.From.html):
+At the end of `search` we also convert a plain string to an error type 
+by using the [corresponding `From` impls](../std/convert/trait.From.html):
 
 ```rust,ignore
 // We are making use of this impl in the code above, since we call `From::from`
 // on a `&'static str`.
-impl<'a, 'b> From<&'b str> for Box<Error + Send + Sync + 'a>
+impl<'a> From<&'a str> for Box<Error>
 
 // But this is also useful when you need to allocate a new string for an
 // error message, usually with `format!`.
-impl From<String> for Box<Error + Send + Sync>
+impl From<String> for Box<Error>
 ```
 
 Since `search` now returns a `Result<T, E>`, `main` should use case analysis
@@ -1964,7 +1961,7 @@ use std::io;
 
 fn search<P: AsRef<Path>>
          (file_path: &Option<P>, city: &str)
-         -> Result<Vec<PopulationCount>, Box<Error+Send+Sync>> {
+         -> Result<Vec<PopulationCount>, Box<Error>> {
     let mut found = vec![];
     let input: Box<io::Read> = match *file_path {
         None => Box::new(io::stdin()),
@@ -2175,9 +2172,8 @@ heuristics!
   `unwrap`. Be warned: if it winds up in someone else's hands, don't be
   surprised if they are agitated by poor error messages!
 * If you're writing a quick 'n' dirty program and feel ashamed about panicking
-  anyway, then use either a `String` or a `Box<Error + Send + Sync>` for your
-  error type (the `Box<Error + Send + Sync>` type is because of the
-  [available `From` impls](../std/convert/trait.From.html)).
+  anyway, then use either a `String` or a `Box<Error>` for your
+  error type.
 * Otherwise, in a program, define your own error types with appropriate
   [`From`](../std/convert/trait.From.html)
   and