support the warn_unused_result in C++ class methods

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@92095 91177308-0d34-0410-b5e6-96231b3b80d8

lib/AST/Expr.cpp

@@ -402,6 +402,8 @@ Decl *CallExpr::getCalleeDecl() {
   Expr *CEE = getCallee()->IgnoreParenCasts();
   if (DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(CEE))
     return DRE->getDecl();
+  if (MemberExpr *ME = dyn_cast<MemberExpr>(CEE))
+    return ME->getMemberDecl();
 
   return 0;
 }

test/SemaCXX/warn-unused-variables.cpp

@@ -32,3 +32,14 @@ namespace PR5531 {
     C();
   }
 }
+
+
+struct X {
+ int foo() __attribute__((warn_unused_result));
+};
+
+void bah() {
+  X x, *x2;
+  x.foo(); // expected-warning {{ignoring return value of function declared with warn_unused_result attribute}}
+  x2->foo(); // expected-warning {{ignoring return value of function declared with warn_unused_result attribute}}
+}