Fix #12615 FP syntaxError with operator= (#6295)

Author: chrchr-github

lib/tokenize.cpp

@@ -8636,7 +8636,7 @@ void Tokenizer::findGarbageCode() const
             syntaxError(tok);
         if (Token::Match(tok, "%assign% typename|class %assign%"))
             syntaxError(tok);
-        if (Token::Match(tok, "%assign% [;)}]") && (!isCPP() || !Token::Match(tok->previous(), "operator %assign% ;")))
+        if (Token::Match(tok, "%assign% [;)}]") && (!isCPP() || !Token::simpleMatch(tok->previous(), "operator")))
             syntaxError(tok);
         if (Token::Match(tok, "%cop%|=|,|[ %or%|%oror%|/|%"))
             syntaxError(tok);

test/testgarbage.cpp

@@ -252,6 +252,7 @@ class TestGarbage : public TestFixture {
         TEST_CASE(garbageCode224);
         TEST_CASE(garbageCode225);
         TEST_CASE(garbageCode226);
+        TEST_CASE(garbageCode227);
 
         TEST_CASE(garbageCodeFuzzerClientMode1); // test cases created with the fuzzer client, mode 1
 
@@ -1753,6 +1754,9 @@ class TestGarbage : public TestFixture {
         ASSERT_THROW_INTERNAL(checkCode("int a() { (b((c)\\)) } {}"), SYNTAX);
         ASSERT_THROW_INTERNAL(checkCode("int a() { (b((c)@)) } {}"), SYNTAX);
     }
+    void garbageCode227() { // #12615
+        ASSERT_NO_THROW(checkCode("f(&S::operator=);"));
+    }
 
     void syntaxErrorFirstToken() {
         ASSERT_THROW_INTERNAL(checkCode("&operator(){[]};"), SYNTAX); // #7818