[ASTMatchers]: fix crash in hasReturnValue

[mgehre]

Summary

The crash was reproduced by the included test case. It was initially
found through a crash of clang-tidy's misc-misplaced-widening-cast
check.

[alexfh]

LG.

This should also fix http://llvm.org/PR27298

[alexfh]

include/clang/ASTMatchers/ASTMatchers.h

5018 ↗

(On Diff #53311)

nit: might be a bit clearer, if you reverse the condition:

if (const auto *RetValue = Node.getRetValue())
  return InnerMatcher.matches(*RetValue, Finder, Builder);
return false;

cfe/trunk/include/clang/ASTMatchers/ASTMatchers.h

 /// Given
 /// \code
 ///   return a + b;
 /// \endcode
 /// hasReturnValue(binaryOperator())
 ///   matches 'return a + b'
 /// with binaryOperator()
 ///   matching 'a + b'
-AST_MATCHER_P(ReturnStmt, hasReturnValue, internal::Matcher<Expr>, 
+AST_MATCHER_P(ReturnStmt, hasReturnValue, internal::Matcher<Expr>,
               InnerMatcher) {
-  return InnerMatcher.matches(*Node.getRetValue(), Finder, Builder);
+  if (const auto *RetValue = Node.getRetValue())
+    return InnerMatcher.matches(*RetValue, Finder, Builder);
+  return false;
 }
 
 
 /// \brief Matches CUDA kernel call expression.
 ///
 /// Example matches,
 /// \code
 ///   kernel<<<i,j>>>();

cfe/trunk/unittests/ASTMatchers/ASTMatchersTest.cpp

TEST(NullPointerConstants, Basic) {
   EXPECT_TRUE(matches("int *ip = 0;", expr(nullPointerConstant())));
   EXPECT_TRUE(notMatches("int i = 0;", expr(nullPointerConstant())));
 }
 
 TEST(StatementMatcher, HasReturnValue) {
   StatementMatcher RetVal = returnStmt(hasReturnValue(binaryOperator()));
   EXPECT_TRUE(matches("int F() { int a, b; return a + b; }", RetVal));
   EXPECT_FALSE(matches("int F() { int a; return a; }", RetVal));
+  EXPECT_FALSE(matches("void F() { return; }", RetVal));
 }
 
 } // end namespace ast_matchers
 } // end namespace clang