We want to avoid implementing GetAddress for &T because it's error-prone. But often in transformer you only have a &T not a &Box<T> and want to get it's address (e.g. in a visitor like exit_function).
This is legitimate because the &mut T passed into visitor function is always a reference to value in the arena.
We could achieve this by:
Pushing Ancestor to the stack of ancestors before calling enter_* and pop it after calling exit_*.
TraverseAncestry::parent return not stack.last() but 1 ancestor before it.
TraverseAncestry::ancestor return the item at index last_index - level - 1 (not last_index - level).
TraverseAncestry::ancestors skip the last item on stack.
Always push to ancestors stack in all walk_* functions (I think we skip that for leaf nodes at present).
Then existing APIs behave as they do now, but TraverseAncestry::current_address can get the address of the current node with stack.last().address().
Problem: What about visitors for enums e.g. Expression? current_address would return the address of parent node, because enums don't get an Ancestor. Either:
Live with it. or
Move pushing to ancestor stack up into the walk_* functions for enums (a bit tricky, because some nodes don't always live within an enum).
See: https://github.com/oxc-project/oxc/pull/6881#discussion_r1816560516
We want to avoid implementing
GetAddressfor&Tbecause it's error-prone. But often in transformer you only have a&Tnot a&Box<T>and want to get it's address (e.g. in a visitor likeexit_function).This is legitimate because the
&mut Tpassed into visitor function is always a reference to value in the arena.We could achieve this by:
Ancestorto the stack of ancestors before callingenter_*and pop it after callingexit_*.TraverseAncestry::parentreturn notstack.last()but 1 ancestor before it.TraverseAncestry::ancestorreturn the item at indexlast_index - level - 1(notlast_index - level).TraverseAncestry::ancestorsskip the last item on stack.walk_*functions (I think we skip that for leaf nodes at present).Then existing APIs behave as they do now, but
TraverseAncestry::current_addresscan get the address of the current node withstack.last().address().Problem: What about visitors for enums e.g.
Expression?current_addresswould return the address of parent node, because enums don't get anAncestor. Either:walk_*functions for enums (a bit tricky, because some nodes don't always live within an enum).