Fix issue 9317: False positive returnDanglingLifetime when using reference to constant inside if statement (#2241)

lib/symboldatabase.h

@@ -1145,19 +1145,6 @@ public:
           container(nullptr),
           containerTypeToken(nullptr)
     {}
-    ValueType(const ValueType& vt)
-        : sign(vt.sign),
-          type(vt.type),
-          bits(vt.bits),
-          pointer(vt.pointer),
-          constness(vt.constness),
-          typeScope(vt.typeScope),
-          smartPointerType(vt.smartPointerType),
-          smartPointerTypeToken(vt.smartPointerTypeToken),
-          container(vt.container),
-          containerTypeToken(vt.containerTypeToken),
-          originalTypeName(vt.originalTypeName)
-    {}
     ValueType(enum Sign s, enum Type t, nonneg int p)
         : sign(s),
           type(t),
@@ -1195,8 +1182,6 @@ public:
           containerTypeToken(nullptr),
           originalTypeName(otn)
     {}
-    ValueType &operator=(const ValueType &other) = delete;
-
     static ValueType parseDecl(const Token *type, const Settings *settings);
 
     static Type typeFromString(const std::string &typestr, bool longType);

lib/valueflow.cpp

@@ -676,6 +676,8 @@ static void setTokenValue(Token* tok, const ValueFlow::Value &value, const Setti
     }
 
     if (value.isLifetimeValue()) {
+        if (!isLifetimeBorrowed(parent, settings))
+            return;
         if (value.lifetimeKind == ValueFlow::Value::LifetimeKind::Iterator && astIsIterator(parent)) {
             setTokenValue(parent,value,settings);
         } else if (astIsPointer(tok) && astIsPointer(parent) &&
@@ -3497,6 +3499,17 @@ bool isLifetimeBorrowed(const Token *tok, const Settings *settings)
         if (!Token::simpleMatch(tok, "{")) {
             const ValueType *vt = tok->valueType();
             const ValueType *vtParent = tok->astParent()->valueType();
+            ValueType svt;
+            // TODO: Move logic to ValueType
+            if (!vtParent && Token::simpleMatch(tok->astParent(), "return")) {
+                const Scope* fscope = tok->scope();
+                while(fscope && !fscope->function)
+                    fscope = fscope->nestedIn;
+                if (fscope && fscope->function && fscope->function->retDef) {
+                    svt = ValueType::parseDecl(fscope->function->retDef, settings);
+                    vtParent = &svt;
+                }
+            }
             if (isLifetimeBorrowed(vt, vtParent))
                 return true;
             if (isLifetimeOwned(vt, vtParent))

test/testautovariables.cpp

@@ -2156,6 +2156,22 @@ private:
               "   return v;\n"
               "}\n");
         ASSERT_EQUALS("", errout.str());
+
+        check("std::string f(const std::string& x) {\n"
+              "  const char c[] = \"\";\n"
+              "  if (!x.empty())\n"
+              "    return x + c;\n"
+              "  return \"\";\n"
+              "}\n");
+        ASSERT_EQUALS("", errout.str());
+
+        check("std::string f(const std::string& x) {\n"
+              "  const char c[] = \"123\";\n"
+              "  if (!x.empty())\n"
+              "    return c + 1;\n"
+              "  return \"\";\n"
+              "}\n");
+        ASSERT_EQUALS("", errout.str());
     }
 
     void invalidLifetime() {