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Fail gracefully when encountering an HRTB in APIT.

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This commit is contained in:
Camille GILLOT 2022-05-27 11:02:11 +02:00
parent 7e9b92cb43
commit bacd8adeda
4 changed files with 87 additions and 8 deletions
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2
compiler/rustc_hir/src/hir.rs
View File

@ -734,7 +734,7 @@ pub fn bounds(&self) -> GenericBounds<'hir> {
}
}
#[derive(Debug, HashStable_Generic, PartialEq, Eq)]
#[derive(Copy, Clone, Debug, HashStable_Generic, PartialEq, Eq)]
pub enum PredicateOrigin {
WhereClause,
GenericParam,

71
compiler/rustc_resolve/src/late/lifetimes.rs
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@ -207,6 +207,13 @@ enum Scope<'a> {
/// In some cases not allowing late bounds allows us to avoid ICEs.
/// This is almost ways set to true.
allow_late_bound: bool,
/// If this binder comes from a where clause, specify how it was created.
/// This is used to diagnose inaccessible lifetimes in APIT:
/// ```ignore (illustrative)
/// fn foo(x: impl for<'a> Trait<'a, Assoc = impl Copy + 'a>) {}
/// ```
where_bound_origin: Option<hir::PredicateOrigin>,
},
/// Lifetimes introduced by a fn are scoped to the call-site for that fn,
@ -277,8 +284,9 @@ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
opaque_type_parent,
scope_type,
hir_id,
s: _,
allow_late_bound,
where_bound_origin,
s: _,
} => f
.debug_struct("Binder")
.field("lifetimes", lifetimes)
@ -286,8 +294,9 @@ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
.field("opaque_type_parent", opaque_type_parent)
.field("scope_type", scope_type)
.field("hir_id", hir_id)
.field("s", &"..")
.field("allow_late_bound", allow_late_bound)
.field("where_bound_origin", where_bound_origin)
.field("s", &"..")
.finish(),
Scope::Body { id, s: _ } => {
f.debug_struct("Body").field("id", id).field("s", &"..").finish()
@ -638,6 +647,7 @@ fn visit_fn(
opaque_type_parent: false,
scope_type: BinderScopeType::Normal,
allow_late_bound: true,
where_bound_origin: None,
};
self.with(scope, move |this| intravisit::walk_fn(this, fk, fd, b, s, hir_id));
}
@ -753,6 +763,7 @@ fn visit_item(&mut self, item: &'tcx hir::Item<'tcx>) {
scope_type: BinderScopeType::Normal,
s: ROOT_SCOPE,
allow_late_bound: false,
where_bound_origin: None,
};
self.with(scope, |this| {
let scope = Scope::TraitRefBoundary { s: this.scope };
@ -818,6 +829,7 @@ fn visit_ty(&mut self, ty: &'tcx hir::Ty<'tcx>) {
opaque_type_parent: false,
scope_type: BinderScopeType::Normal,
allow_late_bound: true,
where_bound_origin: None,
};
self.with(scope, |this| {
// a bare fn has no bounds, so everything
@ -1006,6 +1018,7 @@ fn visit_ty(&mut self, ty: &'tcx hir::Ty<'tcx>) {
opaque_type_parent: false,
scope_type: BinderScopeType::Normal,
allow_late_bound: false,
where_bound_origin: None,
};
this.with(scope, |this| {
this.visit_generics(generics);
@ -1026,6 +1039,7 @@ fn visit_ty(&mut self, ty: &'tcx hir::Ty<'tcx>) {
opaque_type_parent: false,
scope_type: BinderScopeType::Normal,
allow_late_bound: false,
where_bound_origin: None,
};
self.with(scope, |this| {
let scope = Scope::TraitRefBoundary { s: this.scope };
@ -1084,6 +1098,7 @@ fn visit_trait_item(&mut self, trait_item: &'tcx hir::TraitItem<'tcx>) {
opaque_type_parent: true,
scope_type: BinderScopeType::Normal,
allow_late_bound: false,
where_bound_origin: None,
};
self.with(scope, |this| {
let scope = Scope::TraitRefBoundary { s: this.scope };
@ -1151,6 +1166,7 @@ fn visit_impl_item(&mut self, impl_item: &'tcx hir::ImplItem<'tcx>) {
opaque_type_parent: true,
scope_type: BinderScopeType::Normal,
allow_late_bound: true,
where_bound_origin: None,
};
self.with(scope, |this| {
let scope = Scope::TraitRefBoundary { s: this.scope };
@ -1266,6 +1282,7 @@ fn visit_generics(&mut self, generics: &'tcx hir::Generics<'tcx>) {
ref bounded_ty,
bounds,
ref bound_generic_params,
origin,
..
}) => {
let (lifetimes, binders): (FxIndexMap<LocalDefId, Region>, Vec<_>) =
@ -1296,6 +1313,7 @@ fn visit_generics(&mut self, generics: &'tcx hir::Generics<'tcx>) {
opaque_type_parent: false,
scope_type: BinderScopeType::Normal,
allow_late_bound: true,
where_bound_origin: Some(origin),
};
this.with(scope, |this| {
this.visit_ty(&bounded_ty);
@ -1368,6 +1386,7 @@ fn visit_param_bound(&mut self, bound: &'tcx hir::GenericBound<'tcx>) {
opaque_type_parent: false,
scope_type,
allow_late_bound: true,
where_bound_origin: None,
};
self.with(scope, |this| {
intravisit::walk_param_bound(this, bound);
@ -1420,6 +1439,7 @@ fn visit_poly_trait_ref(
opaque_type_parent: false,
scope_type,
allow_late_bound: true,
where_bound_origin: None,
};
self.with(scope, |this| {
walk_list!(this, visit_generic_param, trait_ref.bound_generic_params);
@ -1680,6 +1700,7 @@ fn visit_early_late<F>(
opaque_type_parent: true,
scope_type: BinderScopeType::Normal,
allow_late_bound: true,
where_bound_origin: None,
};
self.with(scope, walk);
}
@ -1783,12 +1804,48 @@ fn resolve_lifetime_ref(
}
self.insert_lifetime(lifetime_ref, def);
} else {
self.tcx.sess.delay_span_bug(
lifetime_ref.span,
&format!("Could not resolve {:?} in scope {:#?}", lifetime_ref, self.scope,),
);
return;
}
// We may fail to resolve higher-ranked lifetimes that are mentionned by APIT.
// AST-based resolution does not care for impl-trait desugaring, which are the
// responibility of lowering. This may create a mismatch between the resolution
// AST found (`region_def_id`) which points to HRTB, and what HIR allows.
// ```
// fn foo(x: impl for<'a> Trait<'a, Assoc = impl Copy + 'a>) {}
// ```
//
// In such case, walk back the binders to diagnose it properly.
let mut scope = self.scope;
loop {
match *scope {
Scope::Binder {
where_bound_origin: Some(hir::PredicateOrigin::ImplTrait), ..
} => {
let mut err = self.tcx.sess.struct_span_err(
lifetime_ref.span,
"`impl Trait` can only mention lifetimes bound at the fn or impl level",
);
err.span_note(self.tcx.def_span(region_def_id), "lifetime declared here");
err.emit();
return;
}
Scope::Root => break,
Scope::Binder { s, .. }
| Scope::Body { s, .. }
| Scope::Elision { s, .. }
| Scope::ObjectLifetimeDefault { s, .. }
| Scope::Supertrait { s, .. }
| Scope::TraitRefBoundary { s, .. } => {
scope = s;
}
}
}
self.tcx.sess.delay_span_bug(
lifetime_ref.span,
&format!("Could not resolve {:?} in scope {:#?}", lifetime_ref, self.scope,),
);
}
fn visit_segment_args(

8
src/test/ui/impl-trait/universal_wrong_hrtb.rs Normal file
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@ -0,0 +1,8 @@
trait Trait<'a> {
type Assoc;
}
fn test_argument_position(x: impl for<'a> Trait<'a, Assoc = impl Copy + 'a>) {}
//~^ ERROR `impl Trait` can only mention lifetimes bound at the fn or impl level
fn main() {}

14
src/test/ui/impl-trait/universal_wrong_hrtb.stderr Normal file
View File

@ -0,0 +1,14 @@
error: `impl Trait` can only mention lifetimes bound at the fn or impl level
--> $DIR/universal_wrong_hrtb.rs:5:73
|
LL | fn test_argument_position(x: impl for<'a> Trait<'a, Assoc = impl Copy + 'a>) {}
| ^^
|
note: lifetime declared here
--> $DIR/universal_wrong_hrtb.rs:5:39
|
LL | fn test_argument_position(x: impl for<'a> Trait<'a, Assoc = impl Copy + 'a>) {}
| ^^
error: aborting due to previous error