Why this function just decides to not call another function and do its thing instead?

Ali Çehreli acehreli at yahoo.com
Sat Sep 17 19:40:17 UTC 2022

On 9/17/22 10:14, frame wrote:
> On Saturday, 17 September 2022 at 15:04:48 UTC, solidstate1991 wrote:
>> And then instead just decides that the `localName` and `namespaceURI` 
>> pairs are not equal, and in those cases the Visual Studio debugger 
>> doesn't detect any entering into any of the `DOMString.equals` 
>> overrides, all while the debugger shows those strings are equal.
> `opEquals` probably was not called if an operand was null. It seems that 
> `Attr.localName` can return null.

Indeed. Copying from my /usr/include/dlang/dmd/object.d:

     Implementation for class opEquals override. Calls the class-defined 
methods after a null check.
     Please note this is not nogc right now, even if your implementation 
is, because of
     the typeinfo name string compare. This is because of dmd's dll 
implementation. However,
     it can infer to @safe if your class' opEquals is.
bool opEquals(LHS, RHS)(LHS lhs, RHS rhs) if (is(LHS : const Object) && 
is(RHS : const Object))
     static if (__traits(compiles, lhs.opEquals(rhs)) && 
__traits(compiles, rhs.opEquals(lhs)))
         // 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 (!lhs.opEquals(rhs)) return false;

         // If same exact type => one call to method opEquals
         if (typeid(lhs) is typeid(rhs) ||
             !__ctfe && typeid(lhs).opEquals(typeid(rhs)))
                 /* CTFE doesn't like typeid much. 'is' works, but 
opEquals doesn't
                 (issue 7147). But CTFE also guarantees that equal 
TypeInfos are
                 always identical. So, no opEquals needed during CTFE. */
             return true;

         // General case => symmetric calls to method opEquals
         return rhs.opEquals(lhs);
         // this is a compatibility hack for the old const cast behavior
         // if none of the new overloads compile, we'll go back plain 
         // including casting away const. It does this through the pointer
         // to bypass any opCast that may be present on the original class.
         return .opEquals!(Object, Object)(*cast(Object*) &lhs, 
*cast(Object*) &rhs);



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