ast: IdentifierReference's reference_flag is always empty

[Dunqing]

SemanticBuilder's already resolved reference usage but never doesn't set reference_flag for IdentifierReference.

Although we can get reference_flag by reference_id, would be great if we could directly reference_flag.

[Dunqing]

SemanticBuilder's already resolved reference usage but never doesn't set reference_flag for IdentifierReference.

I know the reason now. We can only get the immutable IdentifierReference from AstKind, so we can't change the reference_flag. In this way, we need to change reference_flag: ReferenceFlag to reference_flag: Cell<ReferenceFlag>

[overlookmotel]

Agreed, if we are keeping that field, it should be Cell<ReferenceFlag>. But should we remove it entirely from IdentifierReference? Or remove it from Reference? It doesn't really need to be in 2 places does it? Will make transformer/minifier more complex to have to update in 2 places when flags get changed.

[Dunqing]

make transformer/minifier more complex to have to update in 2 places when flags get changed.

Yes! It is better to remove reference_flag from IdentifierReference

[overlookmotel]

Yes! It is better to remove reference_flag from IdentifierReference

I agree that's the better one to remove. It makes more sense for that info to be stored in Reference.

Annoyingly, removing reference_flag from IdentifierReference doesn't save any bytes in AST, as that type has excess padding anyway. Whereas removing it from Reference would reduce size of Reference by 4 bytes.

But still, in my view it's more important that our data structures make logical sense, than that we've optimized every last drop out of them.

[overlookmotel]

Closed in #5077.