Support multi-character punct tokens in MBE
Fixes#11497
In the context of MBE, consecutive puncts are parsed as multi-character punct tokens whenever possible. For example, `:::` is parsed as ``[Punct(`::`), Punct(`:`)]`` and shouldn't get matched to patterns like `: : :` or `: ::`.
We have implemented this behavior only for when we match puncts against `tt` fragments, but not when we match puncts literally. This PR extracts the multi-character punct handling procedure into a separate method and extends its support for literal matching.
For good measure, this PR adds support for `<-` token, which is still [considered as one token in rustc](e396186407/compiler/rustc_ast/src/token.rs (L249)) despite the placement syntax having been removed.
fix: prefix prelude items whose name collides in current scope
Fixes#13873
When we assemble path for prelude items whose name collides with other item in scope, we should always prefix it with module paths.
fix: merge multiple intersecting ranges
Fixes#13791
In `check_intersection_and_push()`, there may exist two ranges we should merge with the new one. We've been assuming there should be only one range that intersects, which lead to [this assertion](da15d92a32/crates/text-edit/src/lib.rs (L192)) to fail under specific circumstances.
Use `rustc_safe_intrinsic` attribute to check for intrinsic safety
Instead of maintaining a list that is poorly kept in sync we can just use the attribute.
This will make new RA versions unusable with old toolchains that don't have the attribute yet. Should we keep maintaining the list as a fallback or just don't care?
derive 'Hash'
clippy doesn't like that `PartialEq` is derived, and `Hash` is manually implemented. This PR resolves that by deriving the `Hash` implementation.
Moar linting: needless_borrow, let_unit_value, ...
* There are a few needless borrows that don't seem to be needed. I even did a quick assembly comparison and posted a q to stackoveflow on it. See [here](https://stackoverflow.com/questions/74910196/advantages-of-pass-by-ref-val-with-impl-intoiteratoritem-impl-asrefstr)
* removed several `let _ = ...` when they don't look necessary (even a few ones that were not suggested by clippy (?))
* some unneeded assignment+return - keep the code a bit leaner
* a few `writeln!` instead of `write!`, or even consolidate write!
* a nice optimization to use `ch.is_ascii_digit` instead of `ch.is_digit(10)`
