Rustdoc markdown handling is currently split between:

- html::markdown, which contains all the meaty login
- markdown, which is only used for when rustdoc renders a standalone
  markdown file

Adds module-level doc-comment to markdown, and rename the function so
it's clear that it's doing IO (instead of just rendering to a string).

These are all standard dictionary words and don't require hyphenation.

…, r=GuillaumeGomez

rustdoc: Document `markdown` module.

Rustdoc markdown handling is currently split between:

- html::markdown, which contains all the meaty login
- markdown, which is only used for when rustdoc renders a standalone markdown file

Adds module-level doc-comment to markdown, and rename the function so it's clear that it's doing IO (instead of just rendering to a string).

…l, r=fmease

Minor tweaks to `compare_impl_item.rs`

1. Stop using the `InstantiatedPredicates` struct for `hybrid_preds` in `compare_impl_item.rs`, since we never actually push anything into the `spans` part of it.
2. Remove redundant impl args and don't do useless identity substitution, prefer calling `instantiate_identity`.

Add a test case for rust-lang#131164

The upstream has already been fixed, but it won't be backported to LLVM 19.

r? jieyouxu or compiler

try-job: x86_64-gnu-stable

…r=jieyouxu

"innermost", "outermost", "leftmost", and "rightmost" don't need hyphens

These are all standard dictionary words and don't require hyphenation.

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Encountered an instance of this in error messages and it bugged me, so I
figured I'd fix it across the entire codebase.

Fix a typo in documentation of `pointer::sub_ptr()`

Just a typo in docs.