Fixes rust-lang#86781

It can be found from ExternalCrate.

…nsm in multiple-definitions test

found while looking through some clippy lint warnings

Add a regression test for issue-63355

Closes rust-lang#63355
r? ``@nikomatsakis``

…bank

Recover from a misplaced inner doc comment

Fixes rust-lang#86781

Check that const parameters of trait methods have compatible types

This PR fixes rust-lang#86820. The problem is that this currently passes the type checker:
```rust
trait Tr {
    fn foo<const N: u8>(self) -> u8;
}

impl Tr for f32 {
    fn foo<const N: bool>(self) -> u8 { 42 }
}
```
i.e. the type checker fails to check whether const parameters in `impl` methods have the same type as the corresponding declaration in the trait. With my changes, I get, for the above code:
```
error[E0053]: method `foo` has an incompatible const parameter type for trait
 --> test.rs:6:18
  |
6 |     fn foo<const N: bool>(self) -> u8 { 42 }
  |                  ^
  |
note: the const parameter `N` has type `bool`, but the declaration in trait `Tr::foo` has type `u8`
 --> test.rs:2:18
  |
2 |     fn foo<const N: u8>(self) -> u8;
  |                  ^

error: aborting due to previous error
```
This fixes rust-lang#86820, where an ICE happens later on because the trait method is declared with a const parameter of type `u8`, but the `impl` uses one of type `usize`:
> `expected int of size 8, but got size 1`

rustdoc: Cleanup ExternalCrate

- Remove unnecessary CrateNum from Cache.externs
- Remove trival impl Clean for CrateNum

…nitions, r=petrochenkov

Remove nondeterminism in multiple-definitions test

Compare all fields in `DllImport` when sorting to avoid nondeterminism in the error for multiple inconsistent definitions of an extern function.  Restore the multiple-definitions test.

Resolves rust-lang#87084.

…-items, r=Manishearth,oli-obk

Add diagnostic items for Clippy

This adds a bunch of diagnostic items to `std`/`core`/`alloc` functions, structs and traits used in Clippy. The actual refactorings in Clippy to use these items will be done in a different PR in Clippy after the next sync.

This PR doesn't include all paths Clippy uses, I've only gone through the first 85 lines of Clippy's [`paths.rs`](https://github.com/rust-lang/rust-clippy/blob/ecf85f4bdc319f9d9d853d1fff68a8a25e64c7a8/clippy_utils/src/paths.rs) (after rust-lang/rust-clippy#7466) to get some feedback early on. I've also decided against adding diagnostic items to methods, as it would be nicer and more scalable to access them in a nicer fashion, like adding a `is_diagnostic_assoc_item(did, sym::Iterator, sym::map)` function or something similar (Suggested by `@camsteffen` [on Zulip](https://rust-lang.zulipchat.com/#narrow/stream/147480-t-compiler.2Fwg-diagnostics/topic/Diagnostic.20Item.20Naming.20Convention.3F/near/225024603))

There seems to be some different naming conventions when it comes to diagnostic items, some use UpperCamelCase (`BinaryHeap`) and some snake_case (`hashmap_type`). This PR uses UpperCamelCase for structs and traits and snake_case with the module name as a prefix for functions. Any feedback on is this welcome.

cc: rust-lang/rust-clippy#5393

r? `@Manishearth`

fix typo in compile_fail doctest

Fixes a typo introduced by rust-lang#86211. For some reason this typo makes Miri go all crazy when running libcore doctests (rust-lang/miri#1852). Kudos to ``@hyd-dev`` for noticing the typo.

Cc ``@tlyu`` ``@joshtriplett``

rustc_middle: remove redundant clone

found while looking through some clippy lint warnings