Fix an ICE that I just made worse

2 files changed, 28 insertions, 0 deletions

diff --git a/src/test/ui/pattern/usefulness/const-partial_eq-fallback-ice.rs b/src/test/ui/pattern/usefulness/const-partial_eq-fallback-ice.rs
new file mode 100644
index 00000000000..daa432d9ae5
--- /dev/null
+++ b/src/test/ui/pattern/usefulness/const-partial_eq-fallback-ice.rs
@@ -0,0 +1,20 @@
+#![allow(warnings)]
+
+struct MyType;
+
+impl PartialEq<usize> for MyType {
+    fn eq(&self, y: &usize) -> bool {
+        true
+    }
+}
+
+const CONSTANT: &&MyType = &&MyType;
+
+fn main() {
+    if let CONSTANT = &&MyType {
+        //~^ ERROR must be annotated with `#[derive(PartialEq, Eq)]`
+        println!("semantic!");
+    } else {
+        println!("structural!");
+    }
+}
diff --git a/src/test/ui/pattern/usefulness/const-partial_eq-fallback-ice.stderr b/src/test/ui/pattern/usefulness/const-partial_eq-fallback-ice.stderr
new file mode 100644
index 00000000000..358421cd6d2
--- /dev/null
+++ b/src/test/ui/pattern/usefulness/const-partial_eq-fallback-ice.stderr
@@ -0,0 +1,8 @@
+error: to use a constant of type `MyType` in a pattern, `MyType` must be annotated with `#[derive(PartialEq, Eq)]`
+  --> $DIR/const-partial_eq-fallback-ice.rs:14:12
+   |
+LL |     if let CONSTANT = &&MyType {
+   |            ^^^^^^^^
+
+error: aborting due to previous error
+