Feature gating *declarations* => new crate `rustc_feature`
This PR moves the data-oriented parts of feature gating into its own crate, `rustc_feature`.
The parts consist of some data types as well as `accepted`, `active`, `removed`, and `builtin_attrs`.
Feature gate checking itself remains in `syntax::feature_gate::check`. The parts which define how to emit feature gate errors could probably be moved to `rustc_errors` or to the new `rustc_session` crate introduced in #66878. The visitor itself could probably be moved as a pass in `rustc_passes` depending on how the dependency edges work out.
The PR also contains some drive-by cleanup of feature gate checking. As such, the PR probably best read commit-by-commit.
r? @oli-obk
cc @petrochenkov
cc @Mark-Simulacrum
Store pointer width as u32 on Config
This removes the dependency on IntTy, UintTy from Session.
It's not obviously a win, but it seems a bit odd to store the AST IntTy/UintTy in Session, rather we store the pointer width as an integer and add normalization methods to IntTy and UintTy.
Use proc-macro to derive HashStable everywhere
Hello,
A second proc-macro is added to derive HashStable for crates librustc depends on.
This proc-macro `HashStable_Generic` (to bikeshed) allows to decouple code and strip much of librustc's boilerplate.
Still, two implementations `Span` and `TokenKind` require to be placed in librustc.
The latter only depends on the `bug` macro. Advise welcome on how to sever that link.
A trait `StableHasingContextLike` has been introduced at each crate root,
in order to handle those implementations which require librustc's very `StableHashingContext`.
This overall effort allowed to remove the `impl_stable_hash_for` macro.
Each commit passes the `x.py check`.
I still have to double check there was no change in the implementation.
Ast address-of
This is the parts of #64588 that don't affect MIR. If an address-of expression makes it to MIR lowering we error and lower to the best currently expressible approximation to limit further errors.
r? @Centril
Enable `if` and `match` in constants behind a feature flag
This PR is an initial implementation of #49146. It introduces a `const_if_match` feature flag and does the following if it is enabled:
- Allows `Downcast` projections, `SwitchInt` terminators and `FakeRead`s for matched places through the MIR const-checker.
- Allows `if` and `match` expressions through the HIR const-checker.
- Stops converting `&&` to `&` and `||` to `|` in `const` and `static` items.
As a result, the following operations are now allowed in a const context behind the feature flag:
- `if` and `match`
- short circuiting logic operators (`&&` and `||`)
- the `assert` and `debug_assert` macros (if the `const_panic` feature flag is also enabled)
However, the following operations remain forbidden:
- `while`, `loop` and `for` (see #52000)
- the `?` operator (calls `From::from` on its error variant)
- the `assert_eq` and `assert_ne` macros, along with their `debug` variants (calls `fmt::Debug`)
This PR is possible now that we use dataflow for const qualification (see #64470 and #66385).
r? @oli-obk
cc @rust-lang/wg-const-eval @eddyb
Mazdak Farrokhzad