This refactors how we deal with items in hir-def lowering.
- It now lowers all of them through an "ExpressionStore" (kind of a misnomer as this point) as their so called *Signatures.
- We now uniformly lower type AST into TypeRefs before type inference.
- Likewise, this moves macro expansion out of type inference, resulting in a single place where we do non-defmap macro expansion.
- Finally, this PR removes a lot of information from ItemTree, making the DefMap a lot less likely to be recomputed and have it only depend on actual early name resolution related information (not 100% true, we still have ADT fields in there but thats a follow up removal).
This is required to format evaluated consts, because we need trait env, and it needs the crate (currently it uses the last crate in topological order, which is wrong, the next commit will fix that).
Also fix the `needs_drop()` intrinsic.
Unions also need this information (to err if they have a drop-needing field), but this will come in a follow-up PR.
This PR touches a lot of parts. But the main changes are changing
`hir_expand::Name` to be raw edition-dependently and only when necessary
(unrelated to how the user originally wrote the identifier),
and changing `is_keyword()` and `is_raw_identifier()` to be edition-aware
(this was done in #17896, but the FIXMEs were fixed here).
It is possible that I missed some cases, but most IDE parts should properly
escape (or not escape) identifiers now.
The rules of thumb are:
- If we show the identifier to the user, its rawness should be determined
by the edition of the edited crate. This is nice for IDE features,
but really important for changes we insert to the source code.
- For tests, I chose `Edition::CURRENT` (so we only have to (maybe) update
tests when an edition becomes stable, to avoid churn).
- For debugging tools (helper methods and logs), I used `Edition::LATEST`.
Instead of using `core::fmt::format` to format panic messages, which may in turn
panic too and cause recursive panics and other messy things, redirect
`panic_fmt` to `const_panic_fmt` like CTFE, which in turn goes to
`panic_display` and does the things normally. See the tests for the full
call stack.
fixes#117448
For example unnecessary imports in std::prelude that can be eliminated:
```rust
use std::option::Option::Some;//~ WARNING the item `Some` is imported redundantly
use std::option::Option::None; //~ WARNING the item `None` is imported redundantly
```
