Add regression test to close #42790

Author: AnthonyLatsis

test/expr/closure/inference.swift

@@ -77,3 +77,11 @@ cc(1) // Ok
 func SR12955() {
   let f: @convention(c) (T) -> Void // expected-error {{cannot find type 'T' in scope}}
 }
+
+do {
+  func SR168<T>(c: () -> ()) -> T.Type { T.self } // expected-note {{in call to function 'SR168(c:)'}}
+
+  let x = SR168 { // expected-error {{generic parameter 'T' could not be inferred}}
+    print("")
+  }
+}