Fix #12619 FP unusedPrivateFunction with trailing return type and override (#6299)

Author: chrchr-github

lib/symboldatabase.cpp

@@ -1959,7 +1959,9 @@ bool SymbolDatabase::isFunction(const Token *tok, const Scope* outerScope, const
         }
 
         // skip over trailing return type
+        bool hasTrailingRet = false;
         if (tok2 && tok2->str() == ".") {
+            hasTrailingRet = true;
             for (tok2 = tok2->next(); tok2; tok2 = tok2->next()) {
                 if (Token::Match(tok2, ";|{|=|override|final"))
                     break;
@@ -2030,7 +2032,8 @@ bool SymbolDatabase::isFunction(const Token *tok, const Scope* outerScope, const
              (tok2->isUpperCaseName() && Token::Match(tok2, "%name% (") && tok2->next()->link()->strAt(1) == "{") ||
              Token::Match(tok2, ": ::| %name% (|::|<|{") ||
              Token::Match(tok2, "&|&&| ;|{") ||
-             Token::Match(tok2, "= delete|default ;"))) {
+             Token::Match(tok2, "= delete|default ;") ||
+             (hasTrailingRet && Token::Match(tok2, "final|override")))) {
             funcStart = tok;
             argStart = tok->next();
             declEnd = Token::findmatch(tok2, "{|;");

test/testunusedprivfunc.cpp

@@ -83,6 +83,7 @@ class TestUnusedPrivateFunction : public TestFixture {
 
         TEST_CASE(templateSimplification); //ticket #6183
         TEST_CASE(maybeUnused);
+        TEST_CASE(trailingReturn);
     }
 
 #define check(...) check_(__FILE__, __LINE__, __VA_ARGS__)
@@ -863,6 +864,18 @@ class TestUnusedPrivateFunction : public TestFixture {
               "};");
         ASSERT_EQUALS("", errout_str());
     }
+
+    void trailingReturn() {
+        check("struct B { virtual void f(); };\n"
+              "struct D : B {\n"
+              "    auto f() -> void override;\n"
+              "private:\n"
+              "    auto g() -> void;\n"
+              "};\n"
+              "auto D::f() -> void { g(); }\n"
+              "auto D::g() -> void {}\n");
+        ASSERT_EQUALS("", errout_str());
+    }
 };
 
 REGISTER_TEST(TestUnusedPrivateFunction)