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no unnormalized types for implied bounds
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lcnr committed Aug 25, 2022
1 parent 7e3e8a8 commit ef7bda3
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13 changes: 12 additions & 1 deletion compiler/rustc_trait_selection/src/traits/engine.rs
Original file line number Diff line number Diff line change
Expand Up @@ -124,7 +124,18 @@ impl<'a, 'tcx> ObligationCtxt<'a, 'tcx> {
let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
let cause = ObligationCause::misc(span, hir_id);
for ty in assumed_wf_types {
implied_bounds.insert(ty);
// FIXME(@lcnr): rustc currently does not check wf for types
// pre-normalization, meaning that implied bounds are sometimes
// incorrect. See #100910 for more details.
//
// Not adding the unnormalized types here mostly fixes that, except
// that there are projections which are still ambiguous in the item definition
// but do normalize successfully when using the item, see #98543.
//
// Anyways, I will hopefully soon change implied bounds to make all of this
// sound and then uncomment this line again.

// implied_bounds.insert(ty);
let normalized = self.normalize(cause.clone(), param_env, ty);
implied_bounds.insert(normalized);
}
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28 changes: 28 additions & 0 deletions src/test/ui/implied-bounds/impl-header-unnormalized-types.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,28 @@
struct Foo<T>(T);

trait GoodBye {
type Forget;
}
impl<T> GoodBye for T {
type Forget = ();
}

trait NeedsWf<'a, 'b> {
type Assoc;
}

impl<'a, 'b> NeedsWf<'a, 'b> for Foo<<&'a &'b () as GoodBye>::Forget> {
type Assoc = &'a &'b ();
//~^ ERROR in type `&'a &'b ()`, reference has a longer lifetime than the data it references
}

fn needs_wf<'a, 'b, T: NeedsWf<'a, 'b>>() {}

fn foo<'a: 'a, 'b: 'b>(_: &'b String) {
needs_wf::<'a, 'b, Foo<()>>();
}

fn main() {
let x = String::from("hello");
foo::<'static, '_>(&x);
}
20 changes: 20 additions & 0 deletions src/test/ui/implied-bounds/impl-header-unnormalized-types.stderr
Original file line number Diff line number Diff line change
@@ -0,0 +1,20 @@
error[E0491]: in type `&'a &'b ()`, reference has a longer lifetime than the data it references
--> $DIR/impl-header-unnormalized-types.rs:15:18
|
LL | type Assoc = &'a &'b ();
| ^^^^^^^^^^
|
note: the pointer is valid for the lifetime `'a` as defined here
--> $DIR/impl-header-unnormalized-types.rs:14:6
|
LL | impl<'a, 'b> NeedsWf<'a, 'b> for Foo<<&'a &'b () as GoodBye>::Forget> {
| ^^
note: but the referenced data is only valid for the lifetime `'b` as defined here
--> $DIR/impl-header-unnormalized-types.rs:14:10
|
LL | impl<'a, 'b> NeedsWf<'a, 'b> for Foo<<&'a &'b () as GoodBye>::Forget> {
| ^^

error: aborting due to previous error

For more information about this error, try `rustc --explain E0491`.

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