[test] Add more opaque return tests

Author: angela-laar

lib/AST/Decl.cpp

@@ -3088,9 +3088,7 @@ TypeRepr *ValueDecl::getResultTypeRepr() const {
 }
 
 TypeRepr *ValueDecl::getOpaqueResultTypeRepr() const {
-  TypeRepr *returnRepr = nullptr;
-
-  returnRepr = this->getResultTypeRepr();
+  auto *returnRepr = this->getResultTypeRepr();
 
   auto *dc = getDeclContext();
   auto &ctx = dc->getASTContext();

test/type/implicit_some/opaque_return.swift

@@ -115,3 +115,13 @@ struct S: P {
 
   var asExistential: any P { self }
 }
+
+enum E {
+    func f() -> Int {
+        1
+    }
+}
+
+protocol Q {
+    func f() -> Int
+}