…er discussion rust-lang#50264

rust-lang#50264

Functions with uninhabited return values are already marked `noreturn`,
but we were still generating return instructions for this. When running
with `-C passes=lint`, LLVM prints:

    Unusual: Return statement in function with noreturn attribute

The LLVM manual makes a stronger statement about `noreturn` though:

> This produces undefined behavior at runtime if the function ever does
dynamically return.

We now emit an `abort` anywhere that would have tried to return an
uninhabited value.

…dtolnay

Document std::fs::File close behavior ignoring errors

Resolves rust-lang#52685

update miri

r? @oli-obk

Fixes rust-lang#59477

update stdsimd

Cc @gnzlbg

`as_deref()` and `as_deref_mut()` impls

addresses rust-lang#50264
renamed `deref()` -> `as_deref()`
added `deref_mut()` impls + tests
fixed breaking changes

Never return uninhabited values at all

Functions with uninhabited return values are already marked `noreturn`,
but we were still generating return instructions for this. When running
with `-C passes=lint`, LLVM prints:

    Unusual: Return statement in function with noreturn attribute

The LLVM manual makes a stronger statement about `noreturn` though:

> This produces undefined behavior at runtime if the function ever does
dynamically return.

We now emit an `abort` anywhere that would have tried to return an
uninhabited value.

Fixes rust-lang#48227
cc rust-lang#7463 rust-lang#48229

r? @eddyb

Add description for -Os and -Oz in rustc.1

… r=luqmana

Temporarily disable stack probing for gnux32.