Fix false positive 9167 (#1904)

Skip returns from local class/struct definition in FwdAnalysis.

lib/astutils.cpp

@@ -1146,7 +1146,7 @@ static bool hasFunctionCall(const Token *tok)
     return hasFunctionCall(tok->astOperand1()) || hasFunctionCall(tok->astOperand2());
 }
 
-struct FwdAnalysis::Result FwdAnalysis::checkRecursive(const Token *expr, const Token *startToken, const Token *endToken, const std::set<unsigned int> &exprVarIds, bool local)
+struct FwdAnalysis::Result FwdAnalysis::checkRecursive(const Token *expr, const Token *startToken, const Token *endToken, const std::set<unsigned int> &exprVarIds, bool local, bool inInnerClass)
 {
     // Parse the given tokens
     for (const Token *tok = startToken; tok != endToken; tok = tok->next()) {
@@ -1162,13 +1162,21 @@ struct FwdAnalysis::Result FwdAnalysis::checkRecursive(const Token *expr, const
         if (Token::simpleMatch(tok, "goto"))
             return Result(Result::Type::BAILOUT);
 
+        if (!inInnerClass && tok->str() == "{" && tok->scope()->isClassOrStruct()) {
+            // skip returns from local class definition
+            FwdAnalysis::Result result = checkRecursive(expr, tok, tok->link(), exprVarIds, local, true);
+            if (result.type != Result::Type::NONE)
+                return result;
+            tok=tok->link();
+        }
+
         if (tok->str() == "continue")
             // TODO
             return Result(Result::Type::BAILOUT);
 
         if (const Token *lambdaEndToken = findLambdaEndToken(tok)) {
             tok = lambdaEndToken;
-            const Result lambdaResult = checkRecursive(expr, lambdaEndToken->link()->next(), lambdaEndToken, exprVarIds, local);
+            const Result lambdaResult = checkRecursive(expr, lambdaEndToken->link()->next(), lambdaEndToken, exprVarIds, local, inInnerClass);
             if (lambdaResult.type == Result::Type::READ || lambdaResult.type == Result::Type::BAILOUT)
                 return lambdaResult;
         }
@@ -1184,10 +1192,13 @@ struct FwdAnalysis::Result FwdAnalysis::checkRecursive(const Token *expr, const
                     return Result(Result::Type::READ);
             }
 
-            if (!local && mWhat == What::Reassign)
+            // #9167: if the return is inside an inner class, it does not tell us anything
-                return Result(Result::Type::BAILOUT);
+            if (!inInnerClass) {
+                if (!local && mWhat == What::Reassign)
+                    return Result(Result::Type::BAILOUT);
 
-            return Result(Result::Type::RETURN);
+                return Result(Result::Type::RETURN);
+            }
         }
 
         if (tok->str() == "}") {
@@ -1218,7 +1229,7 @@ struct FwdAnalysis::Result FwdAnalysis::checkRecursive(const Token *expr, const
                 }
 
                 // check loop body again..
-                const struct FwdAnalysis::Result &result = checkRecursive(expr, tok->link(), tok, exprVarIds, local);
+                const struct FwdAnalysis::Result &result = checkRecursive(expr, tok->link(), tok, exprVarIds, local, inInnerClass);
                 if (result.type == Result::Type::BAILOUT || result.type == Result::Type::READ)
                     return result;
             }
@@ -1297,14 +1308,14 @@ struct FwdAnalysis::Result FwdAnalysis::checkRecursive(const Token *expr, const
             if (Token::simpleMatch(tok->link()->previous(), "switch ("))
                 // TODO: parse switch
                 return Result(Result::Type::BAILOUT);
-            const Result &result1 = checkRecursive(expr, tok->tokAt(2), tok->linkAt(1), exprVarIds, local);
+            const Result &result1 = checkRecursive(expr, tok->tokAt(2), tok->linkAt(1), exprVarIds, local, inInnerClass);
             if (result1.type == Result::Type::READ || result1.type == Result::Type::BAILOUT)
                 return result1;
             if (mWhat == What::ValueFlow && result1.type == Result::Type::WRITE)
                 mValueFlowKnown = false;
             if (Token::simpleMatch(tok->linkAt(1), "} else {")) {
                 const Token *elseStart = tok->linkAt(1)->tokAt(2);
-                const Result &result2 = checkRecursive(expr, elseStart, elseStart->link(), exprVarIds, local);
+                const Result &result2 = checkRecursive(expr, elseStart, elseStart->link(), exprVarIds, local, inInnerClass);
                 if (mWhat == What::ValueFlow && result2.type == Result::Type::WRITE)
                     mValueFlowKnown = false;
                 if (result2.type == Result::Type::READ || result2.type == Result::Type::BAILOUT)
@@ -1426,7 +1437,7 @@ FwdAnalysis::Result FwdAnalysis::check(const Token *expr, const Token *startToke
     if (mWhat == What::UnusedValue && isGlobalData(expr))
         return Result(FwdAnalysis::Result::Type::BAILOUT);
 
-    Result result = checkRecursive(expr, startToken, endToken, exprVarIds, local);
+    Result result = checkRecursive(expr, startToken, endToken, exprVarIds, local, false);
 
     // Break => continue checking in outer scope
     while (mWhat!=What::ValueFlow && result.type == FwdAnalysis::Result::Type::BREAK) {
@@ -1435,7 +1446,7 @@ FwdAnalysis::Result FwdAnalysis::check(const Token *expr, const Token *startToke
             s = s->nestedIn;
         if (s->type != Scope::eSwitch && s->type != Scope::eWhile && s->type != Scope::eFor)
             break;
-        result = checkRecursive(expr, s->bodyEnd->next(), endToken, exprVarIds, local);
+        result = checkRecursive(expr, s->bodyEnd->next(), endToken, exprVarIds, local, false);
     }
 
     return result;

lib/astutils.h

@@ -219,7 +219,7 @@ private:
     };
 
     struct Result check(const Token *expr, const Token *startToken, const Token *endToken);
-    struct Result checkRecursive(const Token *expr, const Token *startToken, const Token *endToken, const std::set<unsigned int> &exprVarIds, bool local);
+    struct Result checkRecursive(const Token *expr, const Token *startToken, const Token *endToken, const std::set<unsigned int> &exprVarIds, bool local, bool inInnerClass);
 
     // Is expression a l-value global data?
     bool isGlobalData(const Token *expr) const;

test/testunusedvar.cpp

@@ -144,6 +144,7 @@ private:
         TEST_CASE(localvarstring2); // ticket #2929
         TEST_CASE(localvarconst1);
         TEST_CASE(localvarconst2);
+        TEST_CASE(localvarreturn); // ticket #9167
 
         TEST_CASE(localvarthrow); // ticket #3687
 
@@ -4086,6 +4087,21 @@ private:
         ASSERT_EQUALS("", errout.str());
     }
 
+    void localvarreturn() { // ticket #9167
+        functionVariableUsage("void foo() {\n"
+                              "    const int MyInt = 1;\n"
+                              "    class bar {\n"
+                              "      public:\n"       
+                              "        bool operator()(const int &uIndexA, const int &uIndexB) const {\n"
+                              "            return true;\n"    
+                              "        }\n"           
+                              "        bar() {}\n"
+                              "    };\n"
+                              "    return MyInt;\n"
+                              "}");
+        ASSERT_EQUALS("", errout.str());
+    }
+
     void localvarthrow() { // ticket #3687
         functionVariableUsage("void foo() {\n"
                               "    try {}"