Improve c/v handling

Author: web-flow

lib/valueflow.cpp

@@ -1948,10 +1948,12 @@ static bool isLifetimeBorrowed(const ValueType *vt, const ValueType *vtParent)
             return true;
         if (vtParent->pointer < vt->pointer && vtParent->isIntegral())
             return true;
-        std::string vtParentStr = vtParent->str();
-        if (startsWith(vtParentStr, "const ")) // HACK: assignment to const
-            vtParentStr.erase(0, 6);
-        if (vtParentStr == vt->str())
+        ValueType temp = *vtParent;
+        if ((temp.constness & 1) && !(vt->constness & 1)) // allow assignment to const/volatile
+            temp.constness &= ~1;
+        if ((temp.volatileness & 1) && !(vt->volatileness & 1))
+            temp.volatileness &= ~1;
+        if (temp.str() == vt->str())
             return true;
     }