…les.

This reduces the number of `associated_item` queries done here.

Quickly skip impls that do not define any items with the same name

…=sfackler

Derive Clone + Eq for std::string::FromUtf8Error

Implement `Clone` and `Eq` for `std::string::FromUtf8Error`.

Both the inner `Vec<u8>` and `std::str::Utf8Error` are also `Clone + Eq`, so I don't see why we shouldn't derive them on `FromUtf8Error` as well.

(impl are insta-stable, requiring FCP from T-libs.)

implement AsMut<str> for String

Closes #68741.

rustc_codegen_llvm: always set AlwaysPreserve on all debuginfo variables

Making this depend on the optimization level appears to have been a copy-paste mistake (other LLVM functions called in this module also take a `bool` argument, but there it means something unrelated).
Also see #8855 (comment).

I don't believe we have any reason to let LLVM omit user variables from DWARF, and we were already setting this to `true` when LLVM *could* optimize them away, so this PR should have no effect anyway.

r? @michaelwoerister or @nagisa cc @hanna-kruppe @nikomatsakis

…nkov

Speed up the inherent impl overlap check

This gives a ~7% improvement in compile times for the stm32f0(x2) crate.

Also addresses @eddyb's comment in #68837 (comment).

Pretty-print generic params and where clauses on associated types

closes #67509