Fix #12894 FP redundantAssignment with call to operator= (danmar#7012)

Author: chrchr-github

lib/astutils.cpp

@@ -1117,19 +1117,23 @@ bool exprDependsOnThis(const Token* expr, bool onVar, nonneg int depth)
     ++depth;
 
     // calling nonstatic method?
-    if (Token::Match(expr, "%name% (") && expr->function() && expr->function()->nestedIn && expr->function()->nestedIn->isClassOrStruct() && !expr->function()->isStatic()) {
-        // is it a method of this?
-        const Scope* fScope = expr->scope();
-        while (!fScope->functionOf && fScope->nestedIn)
-            fScope = fScope->nestedIn;
-
-        const Scope* classScope = fScope->functionOf;
-        if (classScope && classScope->function)
-            classScope = classScope->function->token->scope();
-
-        if (classScope && classScope->isClassOrStruct())
-            return contains(classScope->findAssociatedScopes(), expr->function()->nestedIn);
-        return false;
+    if (Token::Match(expr, "%name% (")) {
+        if (expr->function() && expr->function()->nestedIn && expr->function()->nestedIn->isClassOrStruct() && !expr->function()->isStatic()) {
+            // is it a method of this?
+            const Scope* fScope = expr->scope();
+            while (!fScope->functionOf && fScope->nestedIn)
+                fScope = fScope->nestedIn;
+
+            const Scope* classScope = fScope->functionOf;
+            if (classScope && classScope->function)
+                classScope = classScope->function->token->scope();
+
+            if (classScope && classScope->isClassOrStruct())
+                return contains(classScope->findAssociatedScopes(), expr->function()->nestedIn);
+            return false;
+        }
+        if (expr->isOperatorKeyword() && !Token::simpleMatch(expr->next()->astParent(), "."))
+            return true;
     }
     if (onVar && expr->variable()) {
         const Variable* var = expr->variable();
@@ -3014,7 +3018,7 @@ bool isThisChanged(const Token* tok, int indirect, const Settings& settings)
         if (tok->previous()->function()) {
             return (!tok->previous()->function()->isConst() && !tok->previous()->function()->isStatic());
         }
-        if (!tok->previous()->isKeyword()) {
+        if (!tok->previous()->isKeyword() || tok->previous()->isOperatorKeyword()) {
             return true;
         }
     }

test/testother.cpp

@@ -10534,6 +10534,23 @@ class TestOther : public TestFixture {
               "    return j;\n"
               "}\n");
         ASSERT_EQUALS("", errout_str());
+
+        check("struct S {\n" // #12894
+              "    std::string a;\n"
+              "    void f(const S& s);\n"
+              "    void g(const S& s);\n"
+              "};\n"
+              "void S::f(const S& s) {\n"
+              "    std::string x = a;\n"
+              "    this->operator=(s);\n"
+              "    a = x;\n"
+              "}\n"
+              "void S::g(const S& s) {\n"
+              "    std::string x = a;\n"
+              "    operator=(s);\n"
+              "    a = x;\n"
+              "}\n");
+        ASSERT_EQUALS("", errout_str());
     }
 
     void varFuncNullUB() { // #4482