[PATCH] D68845: Don't emit unwanted constructor calls in co_return statements

[Aaron Puchert via Phabricator via cfe-commits]

aaronpuchert updated this revision to Diff 224513.
aaronpuchert added a comment.

Also remove FIXME comment.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D68845/new/

https://reviews.llvm.org/D68845

Files:
  clang/lib/Sema/SemaCoroutine.cpp
  clang/test/SemaCXX/coroutine-rvo.cpp


Index: clang/test/SemaCXX/coroutine-rvo.cpp
===================================================================
--- clang/test/SemaCXX/coroutine-rvo.cpp
+++ clang/test/SemaCXX/coroutine-rvo.cpp
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -triple x86_64-apple-darwin9 %s -stdlib=libc++ -std=c++1z -fcoroutines-ts -fsyntax-only
+// RUN: %clang_cc1 -verify -std=c++17 -fcoroutines-ts -fsyntax-only %s
 
 namespace std::experimental {
 template <class Promise = void> struct coroutine_handle {
@@ -38,11 +38,17 @@
   void await_resume() noexcept;
 };
 
+struct Default {};
+
 struct MoveOnly {
-  MoveOnly() {};
+  MoveOnly() = default;
   MoveOnly(const MoveOnly&) = delete;
-  MoveOnly(MoveOnly&&) noexcept {};
-  ~MoveOnly() {};
+  MoveOnly(MoveOnly&&) = default;
+};
+
+struct NoCopyNoMove {
+  NoCopyNoMove() = default;
+  NoCopyNoMove(const NoCopyNoMove&) = delete;
 };
 
 template <typename T>
@@ -52,18 +58,31 @@
     auto final_suspend() { return suspend_never{}; }
     auto get_return_object() { return task{}; }
     static void unhandled_exception() {}
-    void return_value(T&& value) {}
+    void return_value(T&& value) {} // expected-note 2{{passing argument}}
   };
 };
 
-task<MoveOnly> f() {
-  MoveOnly value;
+task<NoCopyNoMove> local2val() {
+  NoCopyNoMove value;
   co_return value;
 }
 
-int main() {
-  f();
-  return 0;
+task<MoveOnly> param2val(MoveOnly value) {
+  co_return value;
 }
 
-// expected-no-diagnostics
+task<Default> lvalue2val(Default& value) {
+  co_return value; // expected-error{{rvalue reference to type 'Default' cannot bind to lvalue of type 'Default'}}
+}
+
+task<NoCopyNoMove> rvalue2val(NoCopyNoMove&& value) {
+  co_return value;
+}
+
+task<NoCopyNoMove&> lvalue2ref(NoCopyNoMove& value) {
+  co_return value;
+}
+
+task<Default&> rvalue2ref(Default&& value) {
+  co_return value; // expected-error{{non-const lvalue reference to type 'Default' cannot bind to a temporary of type 'Default'}}
+}
Index: clang/lib/Sema/SemaCoroutine.cpp
===================================================================
--- clang/lib/Sema/SemaCoroutine.cpp
+++ clang/lib/Sema/SemaCoroutine.cpp
@@ -866,20 +866,13 @@
 
   // Move the return value if we can
   if (E) {
-    auto NRVOCandidate = this->getCopyElisionCandidate(E->getType(), E, CES_AsIfByStdMove);
-    if (NRVOCandidate) {
-      InitializedEntity Entity =
-          InitializedEntity::InitializeResult(Loc, E->getType(), NRVOCandidate);
-      ExprResult MoveResult = this->PerformMoveOrCopyInitialization(
-          Entity, NRVOCandidate, E->getType(), E);
-      if (MoveResult.get())
-        E = MoveResult.get();
-    }
+    VarDecl *NRVOCandidate =
+        getCopyElisionCandidate(E->getType(), E, CES_Default);
+    if (NRVOCandidate && !NRVOCandidate->getType()->isLValueReferenceType())
+      E = ImplicitCastExpr::Create(Context, E->getType(), CK_NoOp, E, {},
+                                   VK_XValue);
   }
 
-  // FIXME: If the operand is a reference to a variable that's about to go out
-  // of scope, we should treat the operand as an xvalue for this overload
-  // resolution.
   VarDecl *Promise = FSI->CoroutinePromise;
   ExprResult PC;
   if (E && (isa<InitListExpr>(E) || !E->getType()->isVoidType())) {


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