Author: ericwf
Date: Mon Mar 26 17:58:16 2018
New Revision: 328602
URL: http://llvm.org/viewvc/llvm-project?rev=328602&view=rev
Log:
Fix unused expression warning in co_await.
Previously, anytime the result of the resume expression in
operator co_await was unused, a warning was generated. This
patch fixes the issue by only generating the unused result warning
if calling `await_resume()` would also generate a warning.
Modified:
cfe/trunk/lib/AST/Expr.cpp
cfe/trunk/test/SemaCXX/coroutines.cpp
Modified: cfe/trunk/lib/AST/Expr.cpp
URL:
http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/AST/Expr.cpp?rev=328602&r1=328601&r2=328602&view=diff
==============================================================================
--- cfe/trunk/lib/AST/Expr.cpp (original)
+++ cfe/trunk/lib/AST/Expr.cpp Mon Mar 26 17:58:16 2018
@@ -2049,6 +2049,9 @@ bool Expr::isUnusedResultAWarning(const
case GenericSelectionExprClass:
return cast<GenericSelectionExpr>(this)->getResultExpr()->
isUnusedResultAWarning(WarnE, Loc, R1, R2, Ctx);
+ case CoawaitExprClass:
+ return cast<CoawaitExpr>(this)->getResumeExpr()->
+ isUnusedResultAWarning(WarnE, Loc, R1, R2, Ctx);
case ChooseExprClass:
return cast<ChooseExpr>(this)->getChosenSubExpr()->
isUnusedResultAWarning(WarnE, Loc, R1, R2, Ctx);
Modified: cfe/trunk/test/SemaCXX/coroutines.cpp
URL:
http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaCXX/coroutines.cpp?rev=328602&r1=328601&r2=328602&view=diff
==============================================================================
--- cfe/trunk/test/SemaCXX/coroutines.cpp (original)
+++ cfe/trunk/test/SemaCXX/coroutines.cpp Mon Mar 26 17:58:16 2018
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -std=c++14 -fcoroutines-ts -verify %s -fcxx-exceptions
-fexceptions
+// RUN: %clang_cc1 -std=c++14 -fcoroutines-ts -verify %s -fcxx-exceptions
-fexceptions -Wunused-result
void no_coroutine_traits_bad_arg_await() {
co_await a; // expected-error {{include <experimental/coroutine>}}
@@ -1337,3 +1337,27 @@ bad_coroutine_calls_with_no_matching_con
}
} // namespace CoroHandleMemberFunctionTest
+
+
+class awaitable_no_unused_warn {
+public:
+ using handle_type = std::experimental::coroutine_handle<>;
+ constexpr bool await_ready() { return false; }
+ void await_suspend(handle_type) noexcept {}
+ int await_resume() { return 1; }
+};
+
+
+class awaitable_unused_warn {
+public:
+ using handle_type = std::experimental::coroutine_handle<>;
+ constexpr bool await_ready() { return false; }
+ void await_suspend(handle_type) noexcept {}
+ [[nodiscard]]
+ int await_resume() { return 1; }
+};
+
+void test_unused_warning() {
+ co_await awaitable_no_unused_warn();
+ co_await awaitable_unused_warn(); // expected-warning {{ignoring return
value of function declared with 'nodiscard' attribute}}
+}
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