r208824 - When an overloaded comparison operator returns a reference, do not consider

[Richard Trieu]

Author: rtrieu
Date: Wed May 14 18:22:10 2014
New Revision: 208824

URL: http://llvm.org/viewvc/llvm-project?rev=208824&view=rev
Log:
When an overloaded comparison operator returns a reference, do not consider
it for -Wunused-comparion warnings.  This fixes PR19724.

Modified:
    cfe/trunk/lib/AST/Expr.cpp
    cfe/trunk/test/SemaCXX/warn-unused-comparison.cpp

Modified: cfe/trunk/lib/AST/Expr.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/AST/Expr.cpp?rev=208824&r1=208823&r2=208824&view=diff
==============================================================================
--- cfe/trunk/lib/AST/Expr.cpp (original)
+++ cfe/trunk/lib/AST/Expr.cpp Wed May 14 18:22:10 2014
@@ -2094,6 +2094,8 @@ bool Expr::isUnusedResultAWarning(const
     case OO_Greater:
     case OO_GreaterEqual:
     case OO_LessEqual:
+      if (Op->getCallReturnType()->isReferenceType())
+        break;
       WarnE = this;
       Loc = Op->getOperatorLoc();
       R1 = Op->getSourceRange();

Modified: cfe/trunk/test/SemaCXX/warn-unused-comparison.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaCXX/warn-unused-comparison.cpp?rev=208824&r1=208823&r2=208824&view=diff
==============================================================================
--- cfe/trunk/test/SemaCXX/warn-unused-comparison.cpp (original)
+++ cfe/trunk/test/SemaCXX/warn-unused-comparison.cpp Wed May 14 18:22:10 2014
@@ -106,3 +106,16 @@ namespace PR10291 {
 
   X<int> x;
 }
+
+namespace PR19724 {
+class stream {
+} cout, cin;
+
+stream &operator<(stream &s, int);
+bool operator<(stream &s, stream &s2);
+
+void test() {
+  cout < 5;    // no waring, operator returns a reference
+  cout < cin;  // expected-warning {{relational comparison result unused}}
+}
+}