Fix invalid tag closing when leaving expansion "original code"

[GuillaumeGomez]

Fixes #148184.

Problem was that in case an element inside the expansion's "original" element was not closed, this element would get its pending_exit field set to true, removing it when the next non-mergeable item gets pushed instead of being put inside it, and then next exit_elem would try to exit an empty class queue.

r? @notriddle

[rustbot]

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  • 8442380

[fmease]

(Currently reading through PR #146992 commit by commit to catch up.)

Quick side note: ElementStack ClassStack is not actually a stack, it's a tree!

Reading through this for the first time that's a bit confusing (moreso the resulting method names like enter_stack don't help me form an intuition (granted, it's 2AM for me rn and I'm only skimming the code) (was renamed in a later commit)).

[GuillaumeGomez]

Nah, it used to be a tree, it's now a stack (always one child). :3