Follow up to #51508, make parse_block public instead parse_block_expr
This is an follow up to #51508
I mistakenly made parse_block_expr public instead of parse_block.
This fixes this.
refactor: create multiple HIR items for imports
When lowering `use` statements into HIR, they get a `Def` of the thing they're pointing at. This is great for things that need to know what was just pulled into scope. However, this is a bit misleading, because a `use` statement can pull things from multiple namespaces if their names collide. This is a problem for rustdoc, because if there are a module and a function with the same name (for example) then it will only document the module import, because that's that the lowered `use` statement points to.
The current version of this PR does the following:
* Whenever the resolver comes across a `use` statement, it loads the definitions into a new `import_map` instead of the existing `def_map`. This keeps the resolutions per-namespace so that all the target definitions are available.
* When lowering `use` statements, it looks up the resolutions in the `import_map` and creates multiple `Item`s if there is more than one resolution.
* To ensure the `NodeId`s are properly tracked in the lowered module, they need to be created in the AST, and pulled out as needed if multiple resolutions are available.
Fixes https://github.com/rust-lang/rust/issues/34843
Make parse_seq_to_end and parse_path public
(see SergioBenitez/Rocket#660, rust-lang/rust#51265)
Rocket currently uses `parse_seq_to_end` and `parse_path` in its codegen macros. Assuming I tested correctly, this is the minimal set of methods that are currently necessary to build Rocket again. I would be happy to add documentation of this and Rocket's other usages, if desired.
Fix for $crate var normalization in proc macro for externally defined macros
Fixes#51331, a bug that has existed in at least *some* form for a year and a half.
The PR includes the addition of a `fold_qpath` method to `syntax::fold::Folder`. Overriding this method is useful for folds that modify paths in a way that invalidates indices (insertion or removal of a component), as it provides the opportunity to update `qself.position` in `<A as B>::C` paths. I added it because the bugfix is messy without it.
(unfortunately, grepping around the codebase, I did not see anything else that could use it.)
Make span_fatal and parse_block public
span_fatal and parse_block were made private in #51265. These methods are used in stainless.
Related #51498#51504
parser: Split `+=` into `+` and `=` where `+` is explicitly requested (such as generics)
Added functions in tokens to check whether a token leads with `+`. Used them when parsing to allow for token splitting of `+=` into `+` and `=`.
Fixes https://github.com/rust-lang/rust/issues/47856
