[ADT] Fix accidental pointer comparison in test

Author: sam-mccall

llvm/unittests/ADT/FunctionRefTest.cpp

@@ -49,9 +49,9 @@ TEST(FunctionRefTest, BadCopy) {
 }
 
 // Test that overloads on function_refs are resolved as expected.
-const char *returns(StringRef) { return "not a function"; }
-const char *returns(function_ref<double()> F) { return "number"; }
-const char *returns(function_ref<StringRef()> F) { return "string"; }
+std::string returns(StringRef) { return "not a function"; }
+std::string returns(function_ref<double()> F) { return "number"; }
+std::string returns(function_ref<StringRef()> F) { return "string"; }
 
 TEST(FunctionRefTest, SFINAE) {
   EXPECT_EQ("not a function", returns("boo!"));