1 files changed, 19 insertions, 0 deletions
diff --git a/tests/ui/closures/issue-78720.rs b/tests/ui/closures/issue-78720.rs
new file mode 100644
index 000000000..4cdb9f491
--- /dev/null
+++ b/tests/ui/closures/issue-78720.rs
@@ -0,0 +1,19 @@
+fn server() -> impl {
+//~^ ERROR at least one trait must be specified
+    ().map2(|| "")
+}
+
+trait FilterBase2 {
+    fn map2<F>(self, f: F) -> Map2<F> {}
+    //~^ ERROR mismatched types
+    //~^^ ERROR the size for values of type `Self` cannot be known at compilation time
+}
+
+struct Map2<Segment2> {
+    _func: F,
+    //~^ ERROR cannot find type `F` in this scope
+}
+
+impl<F> FilterBase2 for F {}
+
+fn main() {}