Bug 3917 – opEquals for Ojbect could be more efficient

The implementation of opEquals in object_.d has an unnecessary recursive call. The complete implementation is this: bool opEquals(Object lhs, Object rhs) { // If aliased to the same object or both null => equal if (lhs is rhs) return true; // If either is null => non-equal if (lhs is null || rhs is null) return false; // If same exact type => one call to method opEquals if (typeid(lhs) == typeid(rhs)) return lhs.opEquals(rhs); // General case => symmetric calls to method opEquals return lhs.opEquals(rhs) && rhs.opEquals(lhs); } bool opEquals(TypeInfo lhs, TypeInfo rhs) { // If aliased to the same object or both null => equal if (lhs is rhs) return true; // If either is null => non-equal if (lhs is null || rhs is null) return false; // If same exact type => one call to method opEquals if (typeid(lhs) == typeid(rhs)) return lhs.opEquals(rhs); // Factor out top level const // (This still isn't right, should follow same rules as compiler does for type equality.) TypeInfo_Const c = cast(TypeInfo_Const) lhs; if (c) lhs = c.base; c = cast(TypeInfo_Const) rhs; if (c) rhs = c.base; // General case => symmetric calls to method opEquals return lhs.opEquals(rhs) && rhs.opEquals(lhs); } The third if statement that compares two typeids recurses into opEquals for typeinfos. In the typeinfo comparison, the typeinfos should never be null, and the typeinfos of the typeinfo will always be identical (TypeInfo_Class). In addition, the stuff at the end dealing with const will never come into play because the dynamic typeinfo (the classinfo) never deals with const. I'd propose to rewrite the opEquals as follows: bool opEquals(Object lhs, Object rhs) { // If aliased to the same object or both null => equal if (lhs is rhs) return true; // If either is null => non-equal if (lhs is null || rhs is null) return false; // If same exact type => one call to method opEquals if (typeid(lhs) is typeid(rhs) || typeid(lhs).opEquals(typeid(rhs))) return lhs.opEquals(rhs); // General case => symmetric calls to method opEquals return lhs.opEquals(rhs) && rhs.opEquals(lhs); } I don't know what else the opEquals that compares typeinfos is for, because it's not a public function, so it could potentially be removed.

Fixed DMD 2.048.

Commit pushed to master at https://github.com/D-Programming-Language/druntime https://github.com/D-Programming-Language/druntime/commit/87051cc25c5e69889a2084e1bf562fa798cbee93 Remove unused object.opEquals(TypeInfo, TypeInfo) It seems that just had been forgotten to remove it when bug 3917 was fixed.