internal: Record import origins in ItemScope and PerNS
This records the import items definitions come from in the module scope (as well as what an import resolves to in an ItemScope). It does ignore glob imports as thats a lot more work for little to no gain, glob imports act as if the importing items are "inlined" into the scope which suffices for almost all use cases I believe (to my knowledge, attributes on them have little effect).
There is still a lot of work needed to make this available to the IDE layer, but this lays out the ground work for havin IDE layer support.
cc https://github.com/rust-lang/rust-analyzer/issues/14079
the "add missing members" assists: implemented substitution of default values of const params
To achieve this, I've made `hir::ConstParamData` store the default values
Fix signature help of methods from macros
Currently the receiver type is copied from AST instead re-formatting through `HirDisplay`. Macro generated functions seem to have no spaces and their signature help are rendered like `fn foo(&'amutself)` instead of `fn foo(&'a mut self)`.
internal: use `Cast::cast()` instead of explicit interning
I firmly believe that we should generally use `cast()` instead of interning `GenericArgData` to construct `GenericArg` because it's less verbose and more readable.
Report `incorrect-ident-case` for inner items
Fixes#15319
Although we have been collecting the diagnostics for inner items within function bodies, we were discarding them and never reported to the users. This PR makes sure that they are all reported and additionally collects the diagnostics for inner items within const bodies, static bodies, and enum variant bodies.
Map our diagnostics to rustc and clippy's ones
And control their severity by lint attributes `#[allow]`, `#[deny]` and ... .
It doesn't work with proc macros and I would like to fix that before merge but I don't know how to do it.
