pub fn snapshot_top_frame_meaning_keys() -> Vec<SymStr> ⓘExpand description
Snapshot of the keys currently bound at the topmost (calling) undo frame
for the Meaning table. Used by Perl-style autoload triggers that need to
promote everything a package’s load just installed at this scope to
GLOBAL — without that promotion, sibling autoload triggers fired AFTER
a group pop would re-fire on a now-undefined sibling CS (the canonical
case is \begin{subequations} triggering amsmath autoload at depth=N,
then a later \begin{align} at depth=0 finding \align undefined
because amsmath’s depth=N install was popped on \end{subequations}).