This drops the parking_lot dependency; the ReentrantMutex type appeared
to be unused (at least, no compilation failures occurred).
This is technically a possible change in behavior of its users, as
lock() would wait on other threads releasing their guards, but since we
didn't actually remove any threading or such in this code, it appears
that we never used that behavior (the behavior change is only noticeable
if the type previously was used in two threads, in a single thread
ReentrantMutex is useless).
Refactor and categorize lowering wrt. items / exprs
Split lowering into more files along the lines of "expression related" and "item related".
Also refactor huge methods into smaller ones.
A next step might be to introduce "type related" and merge patterns and statements combined with expressions into "value related". There's still more work to do but the PR was getting too big :)
r? @oli-obk
diagnostics: Describe crate root modules in `DefKind::Mod` as "crate"
Or we can use "extern crate" like resolve previously did sometimes, not sure.
r? @davidtwco
A program like the following one:
```rust
enum E { A, B, C }
fn f(x: E) -> bool {
match x {
A | B => false,
C => true
}
}
```
is rejected by the compiler due to `E` variant paths not being in scope.
In this case `A`, `B` are resolved as pattern bindings and consequently
the pattern is considered invalid as the inner or-patterns do not bind
to the same set of identifiers.
This is expected but the compiler errors that follow could be surprising
or confusing to some users. This commit adds a help note explaining that
if the user desired to match against variants or consts, they should use
a qualified path. The note is restricted to cases where the identifier
starts with an upper-case sequence so as to reduce the false negatives.
Since this happens during resolution, there's no clean way to check what
the patterns match against. The syntactic criterium, however, is in line
with the convention that's assumed by the `non-camel-case-types` lint.
