This might spare someone else a little time searching the stdlib for unicode/grapheme support.

s/for reads and writes/for both ...

Added missing condition:
`dst` must be readable

For all methods which read a value of type T, `read`, `read_unaligned`,
`read_volatile` and `replace`, added missing
constraint:
The value they point to must be properly initialized

Added missing conditions:
- Valid for writes
- Valid for destructing

Updating str.chars docs to mention crates.io.

This might spare someone else a little time searching the stdlib for unicode/grapheme support.

Improve #Safety of various methods in core::ptr

For `read`, `read_unaligned`,`read_volatile`, `replace`, and `drop_in_place`:

- The value they point to must be properly initialized

For `replace`, additionally:

- The pointer must be readable

macOS: avoid calling pthread_self() twice

Rename `FunctionRetTy` to `FnRetTy`

As per FIXME comment

r? @Centril

[tiny] parser: `macro_rules` is a weak keyword

r? @Centril

…lan-DPC

Clean up E0309 explanation

r? @Dylan-DPC

…acrum

debug_assert a few more raw pointer methods

Fixes rust-lang#53871