From d63f82e1efbfbe2344ffa3a47602faaee6429d04 Mon Sep 17 00:00:00 2001
From: Oli Scherer <git-spam-no-reply9815368754983@oli-obk.de>
Date: Tue, 10 May 2022 14:50:31 +0000
Subject: [PATCH] Use lifetimes on type-alias-impl-trait used in function
 signatures to infer output type lifetimes

---
 compiler/rustc_middle/src/ty/fold.rs            |  2 +-
 .../type-alias-impl-trait/constrain_inputs.rs   | 17 +++++++++++++++++
 2 files changed, 18 insertions(+), 1 deletion(-)
 create mode 100644 src/test/ui/type-alias-impl-trait/constrain_inputs.rs

diff --git a/compiler/rustc_middle/src/ty/fold.rs b/compiler/rustc_middle/src/ty/fold.rs
index 896a8280551d2..a2a450d76f18a 100644
--- a/compiler/rustc_middle/src/ty/fold.rs
+++ b/compiler/rustc_middle/src/ty/fold.rs
@@ -1349,7 +1349,7 @@ impl<'tcx> TypeVisitor<'tcx> for LateBoundRegionsCollector {
         // ignore the inputs to a projection, as they may not appear
         // in the normalized form
         if self.just_constrained {
-            if let ty::Projection(..) | ty::Opaque(..) = t.kind() {
+            if let ty::Projection(..) = t.kind() {
                 return ControlFlow::CONTINUE;
             }
         }
diff --git a/src/test/ui/type-alias-impl-trait/constrain_inputs.rs b/src/test/ui/type-alias-impl-trait/constrain_inputs.rs
new file mode 100644
index 0000000000000..c32174288ee68
--- /dev/null
+++ b/src/test/ui/type-alias-impl-trait/constrain_inputs.rs
@@ -0,0 +1,17 @@
+// check-pass
+
+#![feature(type_alias_impl_trait)]
+
+mod foo {
+    type Ty<'a> = impl Sized;
+    fn defining(s: &str) -> Ty<'_> { s }
+    fn execute(ty: Ty<'_>) -> &str { todo!() }
+}
+
+mod bar {
+    type Ty<'a> = impl FnOnce() -> &'a str;
+    fn defining(s: &str) -> Ty<'_> { move || s }
+    fn execute(ty: Ty<'_>) -> &str { ty() }
+}
+
+fn main() {}