report unused-value warning also for warn_unused types

llvm-svn: 186793

2 files changed, 30 insertions, 1 deletions

diff --git a/clang/lib/AST/Expr.cpp b/clang/lib/AST/Expr.cpp
index 8473c096afe..5c1a27da365 100644
--- a/clang/lib/AST/Expr.cpp
+++ b/clang/lib/AST/Expr.cpp
@@ -2075,8 +2075,17 @@ bool Expr::isUnusedResultAWarning(const Expr *&WarnE, SourceLocation &Loc,
     return false;
 
   case CXXTemporaryObjectExprClass:
-  case CXXConstructExprClass:
+  case CXXConstructExprClass: {
+    if (const CXXRecordDecl *Type = getType()->getAsCXXRecordDecl()) {
+      if (Type->hasAttr<WarnUnusedAttr>()) {
+        WarnE = this;
+        Loc = getLocStart();
+        R1 = getSourceRange();
+        return true;
+      }
+    }
     return false;
+  }
 
   case ObjCMessageExprClass: {
     const ObjCMessageExpr *ME = cast<ObjCMessageExpr>(this);
diff --git a/clang/test/SemaCXX/warn-unused-value.cpp b/clang/test/SemaCXX/warn-unused-value.cpp
index 072ee60f1f3..5e43d3ec042 100644
--- a/clang/test/SemaCXX/warn-unused-value.cpp
+++ b/clang/test/SemaCXX/warn-unused-value.cpp
@@ -49,3 +49,23 @@ namespace test2 {
   }
 }
 
+namespace test3 {
+struct Used {
+  Used();
+  Used(int);
+  Used(int, int);
+};
+struct __attribute__((warn_unused)) Unused {
+  Unused();
+  Unused(int);
+  Unused(int, int);
+};
+void f() {
+  Used();
+  Used(1);
+  Used(1, 1);
+  Unused();     // expected-warning {{expression result unused}}
+  Unused(1);    // expected-warning {{expression result unused}}
+  Unused(1, 1); // expected-warning {{expression result unused}}
+}
+}