Add test for 113326

tests/ui/type-alias-impl-trait/recursive-fn-tait.rs

@@ -0,0 +1,17 @@
+// test for #113326
+#![feature(type_alias_impl_trait)]
+
+pub type Diff = impl Fn(usize) -> usize;
+
+pub fn lift() -> Diff {
+    |_: usize |loop {}
+}
+
+pub fn add(
+    n: Diff,
+    m: Diff,
+) -> Diff {
+    move |x: usize| m(n(x)) //~ ERROR: concrete type differs
+}
+
+fn main() {}

tests/ui/type-alias-impl-trait/recursive-fn-tait.stderr

@@ -0,0 +1,14 @@
+error: concrete type differs from previous defining opaque type use
+  --> $DIR/recursive-fn-tait.rs:14:5
+   |
+LL |     move |x: usize| m(n(x))
+   |     ^^^^^^^^^^^^^^^^^^^^^^^ expected `{closure@$DIR/recursive-fn-tait.rs:7:5: 7:16}`, got `{closure@$DIR/recursive-fn-tait.rs:14:5: 14:20}`
+   |
+note: previous use here
+  --> $DIR/recursive-fn-tait.rs:7:5
+   |
+LL |     |_: usize |loop {}
+   |     ^^^^^^^^^^^^^^^^^^
+
+error: aborting due to previous error
+