Merge pull request swiftlang#60386 from theblixguy/discardable-result-look-through-func-conv-5.7

[5.7] [Sema] Look through FunctionConversionExpr when finding @discardableResult callee

Author: tkremenek

lib/Sema/TypeCheckStmt.cpp

@@ -1412,6 +1412,8 @@ void TypeChecker::checkIgnoredExpr(Expr *E) {
         fn = FVE->getSubExpr();
       } else if (auto dotSyntaxRef = dyn_cast<DotSyntaxBaseIgnoredExpr>(fn)) {
         fn = dotSyntaxRef->getRHS();
+      } else if (auto fnConvExpr = dyn_cast<FunctionConversionExpr>(fn)) {
+        fn = fnConvExpr->getSubExpr();
       } else {
         break;
       }

test/Concurrency/attr_discardableResult_async_await.swift

@@ -0,0 +1,11 @@
+// RUN: %target-typecheck-verify-swift  -disable-availability-checking
+// REQUIRES: concurrency
+
+// https://github.com/apple/swift/issues/60276
+
+@discardableResult @MainActor
+func mainActorAsyncDiscardable() async -> Int { 0 }
+
+func consumesMainActorAsyncDiscardable() async {
+  await mainActorAsyncDiscardable() // ok
+}