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Rollup merge of #132214 - fmease:mv-impl-trait-val-paths, r=compiler-errors

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Cleanup: Move an impl-Trait check from AST validation to AST lowering

Namely the one that rejects `impl Trait` in qself types and non-final path segments.
There's no good reason to perform this during AST validation.
We have better infrastructure in place in the AST lowerer (`ImplTraitContext`).
This shaves off a lot of code.
We now lower `impl Trait` in bad positions to `{type error}` which allows us to
remove a special case from HIR ty lowering.

Coincidentally fixes #126725. Well, it only *masks* it by passing `{type error}` to HIR analysis instead of a "bad" opaque. I was able to find a new reproducer for it. See the issue.
This commit is contained in:
Matthias Krüger
2024-10-27 19:49:07 +01:00
committed by GitHub
parent 60beb5979b 442f39582d
commit 574a8ba6af
13 changed files with 78 additions and 153 deletions
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46
compiler/rustc_ast_passes/src/ast_validation.rs
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@@ -80,10 +80,6 @@ struct AstValidator<'a> {
disallow_tilde_const: Option<TildeConstReason>,
/// Used to ban `impl Trait` in path projections like `<impl Iterator>::Item`
/// or `Foo::Bar<impl Trait>`
is_impl_trait_banned: bool,
/// Used to ban explicit safety on foreign items when the extern block is not marked as unsafe.
extern_mod_safety: Option<Safety>,
@@ -123,12 +119,6 @@ impl<'a> AstValidator<'a> {
self.extern_mod_safety = old;
}
fn with_banned_impl_trait(&mut self, f: impl FnOnce(&mut Self)) {
let old = mem::replace(&mut self.is_impl_trait_banned, true);
f(self);
self.is_impl_trait_banned = old;
}
fn with_tilde_const(
&mut self,
disallowed: Option<TildeConstReason>,
@@ -213,37 +203,6 @@ impl<'a> AstValidator<'a> {
.with_tilde_const(Some(TildeConstReason::TraitObject), |this| {
visit::walk_ty(this, t)
}),
TyKind::Path(qself, path) => {
// We allow these:
// - `Option<impl Trait>`
// - `option::Option<impl Trait>`
// - `option::Option<T>::Foo<impl Trait>`
//
// But not these:
// - `<impl Trait>::Foo`
// - `option::Option<impl Trait>::Foo`.
//
// To implement this, we disallow `impl Trait` from `qself`
// (for cases like `<impl Trait>::Foo>`)
// but we allow `impl Trait` in `GenericArgs`
// iff there are no more PathSegments.
if let Some(qself) = qself {
// `impl Trait` in `qself` is always illegal
self.with_banned_impl_trait(|this| this.visit_ty(&qself.ty));
}
// Note that there should be a call to visit_path here,
// so if any logic is added to process `Path`s a call to it should be
// added both in visit_path and here. This code mirrors visit::walk_path.
for (i, segment) in path.segments.iter().enumerate() {
// Allow `impl Trait` iff we're on the final path segment
if i == path.segments.len() - 1 {
self.visit_path_segment(segment);
} else {
self.with_banned_impl_trait(|this| this.visit_path_segment(segment));
}
}
}
_ => visit::walk_ty(self, t),
}
}
@@ -737,10 +696,6 @@ impl<'a> AstValidator<'a> {
}
}
TyKind::ImplTrait(_, bounds) => {
if self.is_impl_trait_banned {
self.dcx().emit_err(errors::ImplTraitPath { span: ty.span });
}
if let Some(outer_impl_trait_sp) = self.outer_impl_trait {
self.dcx().emit_err(errors::NestedImplTrait {
span: ty.span,
@@ -1729,7 +1684,6 @@ pub fn check_crate(
has_proc_macro_decls: false,
outer_impl_trait: None,
disallow_tilde_const: Some(TildeConstReason::Item),
is_impl_trait_banned: false,
extern_mod_safety: None,
lint_buffer: lints,
};