… of Deref

… errors

Fixes rust-lang#130413

…y` lint

This code can sometimes witness malformed coverage attributes in builds that
are going to fail, so use `span_delayed_bug` to avoid an inappropriate ICE in
that case.

…bank

Don't give method suggestions when method probe fails due to bad implementation of `Deref`

If we have a bad `Deref` impl, we used to bail with `MethodError::NoMatch`, which makes the error reporting code think that there was no applicable method (and thus try to suggest importing something, even if it's in scope).

Suppress this error, which fixes rust-lang#131003.

TransmuteFrom: Gracefully handle unnormalized types and normalization errors

~~Refactor to share code between `TransmuteFrom`'s trait selection and error reporting code paths. Additionally normalizes the source and destination types, and gracefully handles normalization errors.~~

Fixes rust-lang#130413

r​? `@compiler-errors`

.gitignore files for nix

This adds support for direnv and nix flakes / nix shell. I'm not sure if we should have a working nix configuration though.

r? ``@noratrieb``

…r=estebank

Refactoring to `OpaqueTyOrigin`

Pulled out of a larger PR that uses these changes to do cross-crate encoding of opaque origin, so we can use them for edition 2024 migrations. These changes should be self-explanatory on their own, tho 😄

Avoid ICE in coverage builds with bad `#[coverage(..)]` attributes

This code can sometimes witness malformed coverage attributes in builds that are going to fail, so use `span_delayed_bug` to avoid an inappropriate ICE in that case.

Fixes rust-lang#127880.

…y-instability-lint-for-rustc-query-impl, r=compiler-errors

Handle `rustc_query_impl` cases of `rustc::potential_query_instability` lint

This PR removes `#![allow(rustc::potential_query_instability)]` line from [`compiler/rustc_query_impl/src/lib.rs`](https://github.com/rust-lang/rust/blob/master/compiler/rustc_query_impl/src/lib.rs#L5) <s>and converts `FxHash{Map,Set}` types into `FxIndex{Map,Set}` to suppress lint errors</s> (was not necessary for this PR).

A somewhat tracking issue: rust-lang#84447

r? ``@compiler-errors``

…ekmut-pop, r=Amanieu

Avoid emptiness check in `PeekMut::pop`

This PR avoids an unnecessary emptiness check in `PeekMut::pop` by replacing `Option::unwrap` with `Option::unwrap_unchecked`.