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Rollup merge of #132832 - compiler-errors:late-ty, r=cjgillot

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Deny capturing late-bound ty/const params in nested opaques

First, this reverts a7f609504c. I can't exactly remember why I approved this specific bit of https://github.com/rust-lang/rust/pull/132466; specifically, I don't know that the purpose of that commit is, and afaict we will never have an opaque that captures late-bound params through a const because opaques can't be used inside of anon consts. Am I missing something `@cjgillot?` Since I can't see a case where this matters, and no tests seem to fail.

The second commit adds a `deny_late_regions: bool` to distinguish `Scope::LateBoundary` which should deny *any* late-bound params or just ty/consts. Then, when resolving opaques we wrap ourselves in a `Scope::LateBoundary { deny_late_regions: false }` so that we deny late-bound ty/const, which fixes a bunch of ICEs that all vaguely look like `impl for<T> Trait<Assoc = impl OtherTrait<T>>`.

I guess this could be achieved other ways; for example, with a different scope kind, or maybe we could just reuse `Scope::Opaque`. But this seems a bit more verbose. I'm open to feedback anyways.

Fixes #131535
Fixes #131637
Fixes #132530

I opted to remove those crashes tests ^ without adding them as regular tests, since they're basically triggering uninteresting late-bound ICEs far off in the trait solver, and the reason that existing tests such as `tests/ui/type-alias-impl-trait/non-lifetime-binder-in-constraint.rs` don't ICE are kinda just coincidental (i.e. due to a missing impl block). I don't really feel motivated to add random permutations to tests just to exercise non-lifetime binders.

r? cjgillot
This commit is contained in:
Matthias Krüger 2024-11-16 21:05:46 +01:00 committed by GitHub
commit a1c98ca160
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8 changed files with 50 additions and 47 deletions
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45
compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs
View File

@ -177,6 +177,7 @@ enum Scope<'a> {
LateBoundary {
s: ScopeRef<'a>,
what: &'static str,
deny_late_regions: bool,
},
Root {
@ -234,9 +235,11 @@ impl<'a> fmt::Debug for TruncatedScopeDebug<'a> {
.field("s", &"..")
.finish(),
Scope::TraitRefBoundary { s: _ } => f.debug_struct("TraitRefBoundary").finish(),
Scope::LateBoundary { s: _, what } => {
f.debug_struct("LateBoundary").field("what", what).finish()
}
Scope::LateBoundary { s: _, what, deny_late_regions } => f
.debug_struct("LateBoundary")
.field("what", what)
.field("deny_late_regions", deny_late_regions)
.finish(),
Scope::Root { opt_parent_item } => {
f.debug_struct("Root").field("opt_parent_item", &opt_parent_item).finish()
}
@ -573,17 +576,11 @@ impl<'a, 'tcx> Visitor<'tcx> for BoundVarContext<'a, 'tcx> {
// give, we will reverse the IndexMap after early captures.
let mut late_depth = 0;
let mut scope = self.scope;
let mut crossed_late_boundary = None;
let mut opaque_capture_scopes = vec![(opaque.def_id, &captures)];
loop {
match *scope {
Scope::Binder { ref bound_vars, scope_type, s, .. } => {
for (&original_lifetime, &def) in bound_vars.iter().rev() {
if let ResolvedArg::LateBound(..) = def
&& crossed_late_boundary.is_some()
{
continue;
}
if let DefKind::LifetimeParam = self.tcx.def_kind(original_lifetime) {
let def = def.shifted(late_depth);
let ident = lifetime_ident(original_lifetime);
@ -624,12 +621,8 @@ impl<'a, 'tcx> Visitor<'tcx> for BoundVarContext<'a, 'tcx> {
Scope::ObjectLifetimeDefault { s, .. }
| Scope::Supertrait { s, .. }
| Scope::TraitRefBoundary { s, .. } => {
scope = s;
}
Scope::LateBoundary { s, what, .. } => {
crossed_late_boundary = Some(what);
| Scope::TraitRefBoundary { s, .. }
| Scope::LateBoundary { s, .. } => {
scope = s;
}
}
@ -640,7 +633,16 @@ impl<'a, 'tcx> Visitor<'tcx> for BoundVarContext<'a, 'tcx> {
let scope = Scope::Opaque { captures: &captures, def_id: opaque.def_id, s: self.scope };
self.with(scope, |this| {
let scope = Scope::TraitRefBoundary { s: this.scope };
this.with(scope, |this| {
let scope = Scope::LateBoundary {
s: this.scope,
what: "nested `impl Trait`",
// We can capture late-bound regions; we just don't duplicate
// lifetime or const params, so we can't allow those.
deny_late_regions: false,
};
this.with(scope, |this| intravisit::walk_opaque_ty(this, opaque))
})
});
let captures = captures.into_inner().into_iter().collect();
@ -997,9 +999,12 @@ impl<'a, 'tcx> Visitor<'tcx> for BoundVarContext<'a, 'tcx> {
}
fn visit_anon_const(&mut self, c: &'tcx hir::AnonConst) {
self.with(Scope::LateBoundary { s: self.scope, what: "constant" }, |this| {
self.with(
Scope::LateBoundary { s: self.scope, what: "constant", deny_late_regions: true },
|this| {
intravisit::walk_anon_const(this, c);
});
},
);
}
fn visit_generic_param(&mut self, p: &'tcx GenericParam<'tcx>) {
@ -1291,8 +1296,10 @@ impl<'a, 'tcx> BoundVarContext<'a, 'tcx> {
scope = s;
}
Scope::LateBoundary { s, what } => {
Scope::LateBoundary { s, what, deny_late_regions } => {
if deny_late_regions {
crossed_late_boundary = Some(what);
}
scope = s;
}
}
@ -1508,7 +1515,7 @@ impl<'a, 'tcx> BoundVarContext<'a, 'tcx> {
scope = s;
}
Scope::LateBoundary { s, what } => {
Scope::LateBoundary { s, what, deny_late_regions: _ } => {
crossed_late_boundary = Some(what);
scope = s;
}

4
tests/crashes/131535.rs
View File

@ -1,4 +0,0 @@
//@ known-bug: #131535
#![feature(non_lifetime_binders)]
trait v0<> {}
fn kind :(v0<'_, > impl for<v4> v0<'_, v2 = impl v0<v4> + '_>) {}

7
tests/crashes/131637.rs
View File

@ -1,7 +0,0 @@
//@ known-bug: #121637
#![feature(non_lifetime_binders)]
trait Trait<Type> {
type Type;
fn method(&self) -> impl for<T> Trait<impl Trait<T>>;
}

9
tests/crashes/132530.rs
View File

@ -1,9 +0,0 @@
//@ known-bug: #132530
#![feature(non_lifetime_binders)]
trait Trait<'a, A> {
type Assoc<'a> = i32;
}
fn a() -> impl for<T> Trait<Assoc = impl Trait<T>> {}

1
tests/ui/type-alias-impl-trait/non-lifetime-binder-in-constraint.rs
View File

@ -7,6 +7,7 @@ fn produce() -> impl for<T> Trait<(), Assoc = impl Trait<T>> {
//~^ ERROR associated type `Assoc` not found for `Trait`
//~| ERROR associated type `Assoc` not found for `Trait`
//~| the trait bound `{integer}: Trait<()>` is not satisfied
//~| ERROR cannot capture late-bound type parameter in nested `impl Trait`
16
}

8
tests/ui/type-alias-impl-trait/non-lifetime-binder-in-constraint.stderr
View File

@ -1,3 +1,9 @@
error: cannot capture late-bound type parameter in nested `impl Trait`
--> $DIR/non-lifetime-binder-in-constraint.rs:6:58
|
LL | fn produce() -> impl for<T> Trait<(), Assoc = impl Trait<T>> {
| - parameter defined here ^
error[E0220]: associated type `Assoc` not found for `Trait`
--> $DIR/non-lifetime-binder-in-constraint.rs:6:39
|
@ -27,7 +33,7 @@ help: this trait has no implementations, consider adding one
LL | trait Trait<T: ?Sized> {}
| ^^^^^^^^^^^^^^^^^^^^^^
error: aborting due to 3 previous errors
error: aborting due to 4 previous errors
Some errors have detailed explanations: E0220, E0277.
For more information about an error, try `rustc --explain E0220`.

3
tests/ui/type-alias-impl-trait/non-lifetime-binder.rs
View File

@ -5,6 +5,7 @@ trait Trait<T> {}
fn f() -> impl for<T> Trait<impl Trait<T>> {}
//~^ ERROR nested `impl Trait` is not allowed
//~| ERROR the trait bound `(): Trait<impl Trait<T>>` is not satisfied
//~| ERROR the trait bound `(): Trait<impl Trait<{type error}>>` is not satisfied
//~| ERROR cannot capture late-bound type parameter in nested `impl Trait`
fn main() {}

14
tests/ui/type-alias-impl-trait/non-lifetime-binder.stderr
View File

@ -7,11 +7,19 @@ LL | fn f() -> impl for<T> Trait<impl Trait<T>> {}
| | nested `impl Trait` here
| outer `impl Trait`
error[E0277]: the trait bound `(): Trait<impl Trait<T>>` is not satisfied
error: cannot capture late-bound type parameter in nested `impl Trait`
--> $DIR/non-lifetime-binder.rs:6:40
|
LL | fn f() -> impl for<T> Trait<impl Trait<T>> {}
| - ^
| |
| parameter defined here
error[E0277]: the trait bound `(): Trait<impl Trait<{type error}>>` is not satisfied
--> $DIR/non-lifetime-binder.rs:6:11
|
LL | fn f() -> impl for<T> Trait<impl Trait<T>> {}
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `Trait<impl Trait<T>>` is not implemented for `()`
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `Trait<impl Trait<{type error}>>` is not implemented for `()`
|
help: this trait has no implementations, consider adding one
--> $DIR/non-lifetime-binder.rs:4:1
@ -19,7 +27,7 @@ help: this trait has no implementations, consider adding one
LL | trait Trait<T> {}
| ^^^^^^^^^^^^^^
error: aborting due to 2 previous errors
error: aborting due to 3 previous errors
Some errors have detailed explanations: E0277, E0666.
For more information about an error, try `rustc --explain E0277`.