diff --git a/src/librustc_typeck/check/writeback.rs b/src/librustc_typeck/check/writeback.rs index ecb8e09ec2461..13baf667808f8 100644 --- a/src/librustc_typeck/check/writeback.rs +++ b/src/librustc_typeck/check/writeback.rs @@ -466,6 +466,8 @@ impl<'cx, 'gcx, 'tcx> WritebackCx<'cx, 'gcx, 'tcx> { let hir_id = self.tcx().hir().as_local_hir_id(def_id).unwrap(); let instantiated_ty = self.resolve(&opaque_defn.concrete_ty, &hir_id); + debug_assert!(!instantiated_ty.has_escaping_bound_vars()); + let generics = self.tcx().generics_of(def_id); let definition_ty = if generics.parent.is_some() { @@ -524,8 +526,9 @@ impl<'cx, 'gcx, 'tcx> WritebackCx<'cx, 'gcx, 'tcx> { }, lt_op: |region| { match region { - // ignore static regions - ty::ReStatic => region, + // Skip static and bound regions: they don't + // require substitution. + ty::ReStatic | ty::ReLateBound(..) => region, _ => { trace!("checking {:?}", region); for (subst, p) in opaque_defn.substs.iter().zip(&generics.params) { diff --git a/src/test/ui/existential_types/issue-60655-latebound-regions.rs b/src/test/ui/existential_types/issue-60655-latebound-regions.rs new file mode 100644 index 0000000000000..a4fe86501299f --- /dev/null +++ b/src/test/ui/existential_types/issue-60655-latebound-regions.rs @@ -0,0 +1,30 @@ +// Test that existential types are allowed to contain late-bound regions. + +// compile-pass +// edition:2018 + +#![feature(async_await, existential_type)] + +use std::future::Future; + +pub existential type Func: Sized; + +// Late bound region should be allowed to escape the function, since it's bound +// in the type. +fn null_function_ptr() -> Func { + None:: fn(&'a ())> +} + +async fn async_nop(_: &u8) {} + +pub existential type ServeFut: Future; + +// Late bound regions occur in the generator witness type here. +fn serve() -> ServeFut { + async move { + let x = 5; + async_nop(&x).await + } +} + +fn main() {}