Change 'Example' to 'Examples' throughout collections' rustdocs.
Delete the outdated source layout README
Add a doctest for the std::string::as_string method.

Change Example to Examples.

Add a doctest that better demonstrates the utility of as_string.

Update the doctest example to use String instead of &String.
typeck: Make the supplied parameters to be a tuple

When a type error occurs, check_method_argument_types() tries to provide
arguments filled with ty::mk_err(). However, if a function takes the
parameters as a tuple, the arguments should be converted to a tuple
before being passed to check_argument_types().

Fixes #19521.
auto merge of #19648 : mquandalle/rust/patch-1, r=alexcrichton
auto merge of #19628 : jbranchaud/rust/add-string-as-string-doctest, r=steveklabnik
auto merge of #19638 : barosl/rust/typeck-tupled-arguments-ice, r=jakub

When a type error occurs, `check_method_argument_types()` tries to provide arguments filled with `ty::mk_err()`. However, if a function takes the parameters as a tuple, the arguments should be converted to a tuple before passing it to `check_argument_types()`.

Fixes #19521.
auto merge of #19655 : jbranchaud/rust/change-example-to-examples, r=steveklabnik

@steveklabnik I got a start on this.
Merge remote-tracking branch 'upstream/master'