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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
commit 574a8ba6af
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13 changed files with 78 additions and 153 deletions
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19
compiler/rustc_ast_lowering/src/path.rs
View File

@ -34,7 +34,10 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
modifiers: Option<ast::TraitBoundModifiers>,
) -> hir::QPath<'hir> {
let qself_position = qself.as_ref().map(|q| q.position);
let qself = qself.as_ref().map(|q| self.lower_ty(&q.ty, itctx));
let qself = qself
.as_ref()
// Reject cases like `<impl Trait>::Assoc` and `<impl Trait as Trait>::Assoc`.
.map(|q| self.lower_ty(&q.ty, ImplTraitContext::Disallowed(ImplTraitPosition::Path)));
let partial_res =
self.resolver.get_partial_res(id).unwrap_or_else(|| PartialRes::new(Res::Err));
@ -75,6 +78,16 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
None
};
// Only permit `impl Trait` in the final segment. E.g., we permit `Option<impl Trait>`,
// `option::Option<T>::Xyz<impl Trait>` and reject `option::Option<impl Trait>::Xyz`.
let itctx = |i| {
if i + 1 == p.segments.len() {
itctx
} else {
ImplTraitContext::Disallowed(ImplTraitPosition::Path)
}
};
let path_span_lo = p.span.shrink_to_lo();
let proj_start = p.segments.len() - unresolved_segments;
let path = self.arena.alloc(hir::Path {
@ -121,7 +134,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
segment,
param_mode,
generic_args_mode,
itctx,
itctx(i),
bound_modifier_allowed_features.clone(),
)
},
@ -185,7 +198,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
segment,
param_mode,
generic_args_mode,
itctx,
itctx(i),
None,
));
let qpath = hir::QPath::TypeRelative(ty, hir_segment);

2
compiler/rustc_ast_passes/messages.ftl
View File

@ -146,8 +146,6 @@ ast_passes_generic_before_constraints = generic arguments must come before the f
ast_passes_generic_default_trailing = generic parameters with a default must be trailing
ast_passes_impl_trait_path = `impl Trait` is not allowed in path parameters
ast_passes_incompatible_features = `{$f1}` and `{$f2}` are incompatible, using them at the same time is not allowed
.help = remove one of these features

46
compiler/rustc_ast_passes/src/ast_validation.rs
View File

@ -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,
};

7
compiler/rustc_ast_passes/src/errors.rs
View File

@ -418,13 +418,6 @@ pub(crate) struct TraitObjectBound {
pub span: Span,
}
#[derive(Diagnostic)]
#[diag(ast_passes_impl_trait_path, code = E0667)]
pub(crate) struct ImplTraitPath {
#[primary_span]
pub span: Span,
}
#[derive(Diagnostic)]
#[diag(ast_passes_nested_impl_trait, code = E0666)]
pub(crate) struct NestedImplTrait {

6
compiler/rustc_error_codes/src/error_codes/E0667.md
View File

@ -1,8 +1,10 @@
#### Note: this error code is no longer emitted by the compiler.
`impl Trait` is not allowed in path parameters.
Erroneous code example:
```compile_fail,E0667
```ignore (removed error code)
fn some_fn(mut x: impl Iterator) -> <impl Iterator>::Item { // error!
x.next().unwrap()
}
@ -11,7 +13,7 @@ fn some_fn(mut x: impl Iterator) -> <impl Iterator>::Item { // error!
You cannot use `impl Trait` in path parameters. If you want something
equivalent, you can do this instead:
```
```ignore (removed error code)
fn some_fn<T: Iterator>(mut x: T) -> T::Item { // ok!
x.next().unwrap()
}

9
compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs
View File

@ -1203,15 +1203,6 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
err.emit()
} else if let Err(reported) = qself_ty.error_reported() {
reported
} else if let ty::Alias(ty::Opaque, alias_ty) = qself_ty.kind() {
// `<impl Trait as OtherTrait>::Assoc` makes no sense.
struct_span_code_err!(
self.dcx(),
tcx.def_span(alias_ty.def_id),
E0667,
"`impl Trait` is not allowed in path parameters"
)
.emit() // Already reported in an earlier stage.
} else {
self.maybe_report_similar_assoc_fn(span, qself_ty, qself)?;

20
tests/crashes/126725.rs
View File

@ -1,20 +0,0 @@
//@ known-bug: rust-lang/rust#126725
trait Foo {
fn foo<'a>(&'a self) -> <&'a impl Sized as Bar>::Output;
}
trait Bar {
type Output;
}
struct X(i32);
impl<'a> Bar for &'a X {
type Output = &'a i32;
}
impl Foo for X {
fn foo<'a>(&'a self) -> <&'a Self as Bar>::Output {
&self.0
}
}

11
tests/ui/impl-trait/impl_trait_projections.rs
View File

@ -10,30 +10,27 @@ fn path_parametrized_type_is_allowed() -> option::Option<impl Debug> {
}
fn projection_is_disallowed(x: impl Iterator) -> <impl Iterator>::Item {
//~^ ERROR `impl Trait` is not allowed in path parameters
//~| ERROR `impl Trait` is not allowed in path parameters
//~^ ERROR `impl Trait` is not allowed in paths
x.next().unwrap()
}
fn projection_with_named_trait_is_disallowed(mut x: impl Iterator)
-> <impl Iterator as Iterator>::Item
//~^ ERROR `impl Trait` is not allowed in path parameters
//~^ ERROR `impl Trait` is not allowed in paths
{
x.next().unwrap()
}
fn projection_with_named_trait_inside_path_is_disallowed()
-> <::std::ops::Range<impl Debug> as Iterator>::Item
//~^ ERROR `impl Trait` is not allowed in path parameters
//~| ERROR `impl Debug: Step` is not satisfied
//~^ ERROR `impl Trait` is not allowed in paths
{
//~^ ERROR `impl Debug: Step` is not satisfied
(1i32..100).next().unwrap()
}
fn projection_from_impl_trait_inside_dyn_trait_is_disallowed()
-> <dyn Iterator<Item = impl Debug> as Iterator>::Item
//~^ ERROR `impl Trait` is not allowed in path parameters
//~^ ERROR `impl Trait` is not allowed in paths
{
panic!()
}

70
tests/ui/impl-trait/impl_trait_projections.stderr
View File

@ -1,73 +1,35 @@
error[E0667]: `impl Trait` is not allowed in path parameters
error[E0562]: `impl Trait` is not allowed in paths
--> $DIR/impl_trait_projections.rs:12:51
|
LL | fn projection_is_disallowed(x: impl Iterator) -> <impl Iterator>::Item {
| ^^^^^^^^^^^^^
|
= note: `impl Trait` is only allowed in arguments and return types of functions and methods
error[E0667]: `impl Trait` is not allowed in path parameters
--> $DIR/impl_trait_projections.rs:19:9
error[E0562]: `impl Trait` is not allowed in paths
--> $DIR/impl_trait_projections.rs:18:9
|
LL | -> <impl Iterator as Iterator>::Item
| ^^^^^^^^^^^^^
|
= note: `impl Trait` is only allowed in arguments and return types of functions and methods
error[E0667]: `impl Trait` is not allowed in path parameters
--> $DIR/impl_trait_projections.rs:26:27
error[E0562]: `impl Trait` is not allowed in paths
--> $DIR/impl_trait_projections.rs:25:27
|
LL | -> <::std::ops::Range<impl Debug> as Iterator>::Item
| ^^^^^^^^^^
|
= note: `impl Trait` is only allowed in arguments and return types of functions and methods
error[E0667]: `impl Trait` is not allowed in path parameters
--> $DIR/impl_trait_projections.rs:35:29
error[E0562]: `impl Trait` is not allowed in paths
--> $DIR/impl_trait_projections.rs:32:29
|
LL | -> <dyn Iterator<Item = impl Debug> as Iterator>::Item
| ^^^^^^^^^^
error[E0667]: `impl Trait` is not allowed in path parameters
--> $DIR/impl_trait_projections.rs:12:51
|
LL | fn projection_is_disallowed(x: impl Iterator) -> <impl Iterator>::Item {
| ^^^^^^^^^^^^^
= note: `impl Trait` is only allowed in arguments and return types of functions and methods
error[E0277]: the trait bound `impl Debug: Step` is not satisfied
--> $DIR/impl_trait_projections.rs:26:8
|
LL | -> <::std::ops::Range<impl Debug> as Iterator>::Item
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `Step` is not implemented for `impl Debug`, which is required by `std::ops::Range<impl Debug>: Iterator`
|
= help: the following other types implement trait `Step`:
Char
Ipv4Addr
Ipv6Addr
char
i128
i16
i32
i64
and 8 others
= note: required for `std::ops::Range<impl Debug>` to implement `Iterator`
error: aborting due to 4 previous errors
error[E0277]: the trait bound `impl Debug: Step` is not satisfied
--> $DIR/impl_trait_projections.rs:29:1
|
LL | / {
LL | |
LL | | (1i32..100).next().unwrap()
LL | | }
| |_^ the trait `Step` is not implemented for `impl Debug`, which is required by `std::ops::Range<impl Debug>: Iterator`
|
= help: the following other types implement trait `Step`:
Char
Ipv4Addr
Ipv6Addr
char
i128
i16
i32
i64
and 8 others
= note: required for `std::ops::Range<impl Debug>` to implement `Iterator`
error: aborting due to 7 previous errors
Some errors have detailed explanations: E0277, E0667.
For more information about an error, try `rustc --explain E0277`.
For more information about this error, try `rustc --explain E0562`.

22
tests/ui/impl-trait/in-trait/bad-projection-from-opaque.rs Normal file
View File

@ -0,0 +1,22 @@
// issue: rust-lang/rust#126725
trait Foo {
fn foo<'a>() -> <&'a impl Sized as Bar>::Output;
//~^ ERROR `impl Trait` is not allowed in paths
}
trait Bar {
type Output;
}
impl<'a> Bar for &'a () {
type Output = &'a i32;
}
impl Foo for () {
fn foo<'a>() -> <&'a Self as Bar>::Output {
&0
}
}
fn main() {}

11
tests/ui/impl-trait/in-trait/bad-projection-from-opaque.stderr Normal file
View File

@ -0,0 +1,11 @@
error[E0562]: `impl Trait` is not allowed in paths
--> $DIR/bad-projection-from-opaque.rs:4:26
|
LL | fn foo<'a>() -> <&'a impl Sized as Bar>::Output;
| ^^^^^^^^^^
|
= note: `impl Trait` is only allowed in arguments and return types of functions and methods
error: aborting due to 1 previous error
For more information about this error, try `rustc --explain E0562`.

2
tests/ui/impl-trait/issues/issue-57979-impl-trait-in-path.rs
View File

@ -6,7 +6,7 @@
pub trait Bar { }
pub trait Quux<T> { type Assoc; }
pub fn demo(_: impl Quux<(), Assoc=<() as Quux<impl Bar>>::Assoc>) { }
//~^ ERROR `impl Trait` is not allowed in path parameters
//~^ ERROR `impl Trait` is not allowed in paths
impl<T> Quux<T> for () { type Assoc = u32; }
fn main() { }

6
tests/ui/impl-trait/issues/issue-57979-impl-trait-in-path.stderr
View File

@ -1,9 +1,11 @@
error[E0667]: `impl Trait` is not allowed in path parameters
error[E0562]: `impl Trait` is not allowed in paths
--> $DIR/issue-57979-impl-trait-in-path.rs:8:48
|
LL | pub fn demo(_: impl Quux<(), Assoc=<() as Quux<impl Bar>>::Assoc>) { }
| ^^^^^^^^
|
= note: `impl Trait` is only allowed in arguments and return types of functions and methods
error: aborting due to 1 previous error
For more information about this error, try `rustc --explain E0667`.
For more information about this error, try `rustc --explain E0562`.