From 18cf44b61b2bb5387fcf3011bce0cd63cd41d51f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Esteban=20K=C3=BCber?= <esteban@kuber.com.ar>
Date: Tue, 6 Apr 2021 18:17:50 -0700
Subject: [PATCH] Do not ICE when closure is involved in TAIT

Fix #83613.
---
 .../src/traits/coherence.rs                   |  7 +++++-
 src/test/ui/traits/alias/issue-83613.rs       | 13 +++++++++++
 src/test/ui/traits/alias/issue-83613.stderr   | 23 +++++++++++++++++++
 3 files changed, 42 insertions(+), 1 deletion(-)
 create mode 100644 src/test/ui/traits/alias/issue-83613.rs
 create mode 100644 src/test/ui/traits/alias/issue-83613.stderr

diff --git a/compiler/rustc_trait_selection/src/traits/coherence.rs b/compiler/rustc_trait_selection/src/traits/coherence.rs
index 38cb4ee66ca..9bb4af16a8f 100644
--- a/compiler/rustc_trait_selection/src/traits/coherence.rs
+++ b/compiler/rustc_trait_selection/src/traits/coherence.rs
@@ -586,6 +586,11 @@ fn ty_is_local_constructor(ty: Ty<'_>, in_crate: InCrate) -> bool {
             false
         }
 
+        ty::Closure(..) => {
+            // Similar to the `Opaque` case (#83613).
+            false
+        }
+
         ty::Dynamic(ref tt, ..) => {
             if let Some(principal) = tt.principal() {
                 def_id_is_local(principal.def_id(), in_crate)
@@ -596,7 +601,7 @@ fn ty_is_local_constructor(ty: Ty<'_>, in_crate: InCrate) -> bool {
 
         ty::Error(_) => true,
 
-        ty::Closure(..) | ty::Generator(..) | ty::GeneratorWitness(..) => {
+        ty::Generator(..) | ty::GeneratorWitness(..) => {
             bug!("ty_is_local invoked on unexpected type: {:?}", ty)
         }
     }
diff --git a/src/test/ui/traits/alias/issue-83613.rs b/src/test/ui/traits/alias/issue-83613.rs
new file mode 100644
index 00000000000..146920ac685
--- /dev/null
+++ b/src/test/ui/traits/alias/issue-83613.rs
@@ -0,0 +1,13 @@
+#![feature(min_type_alias_impl_trait)]
+trait OpaqueTrait {}
+impl<T> OpaqueTrait for T {}
+type OpaqueType = impl OpaqueTrait;
+fn mk_opaque() -> OpaqueType {
+    || 0
+}
+trait AnotherTrait {}
+impl<T: Send> AnotherTrait for T {}
+impl AnotherTrait for OpaqueType {}
+//~^ ERROR conflicting implementations of trait `AnotherTrait` for type `impl OpaqueTrait`
+//~| ERROR cannot implement trait on type alias impl trait
+fn main() {}
diff --git a/src/test/ui/traits/alias/issue-83613.stderr b/src/test/ui/traits/alias/issue-83613.stderr
new file mode 100644
index 00000000000..0ab39ae6672
--- /dev/null
+++ b/src/test/ui/traits/alias/issue-83613.stderr
@@ -0,0 +1,23 @@
+error[E0119]: conflicting implementations of trait `AnotherTrait` for type `impl OpaqueTrait`
+  --> $DIR/issue-83613.rs:10:1
+   |
+LL | impl<T: Send> AnotherTrait for T {}
+   | -------------------------------- first implementation here
+LL | impl AnotherTrait for OpaqueType {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `impl OpaqueTrait`
+
+error: cannot implement trait on type alias impl trait
+  --> $DIR/issue-83613.rs:10:1
+   |
+LL | impl AnotherTrait for OpaqueType {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+note: type alias impl trait defined here
+  --> $DIR/issue-83613.rs:4:19
+   |
+LL | type OpaqueType = impl OpaqueTrait;
+   |                   ^^^^^^^^^^^^^^^^
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0119`.