This commit resolves all outstanding duplicate label
and duplicate citation warnings.
I have not yet addressed unreferenced footnote warnings.
I took the general strategy of replacing a target above a section heading
with references directly to that section heading,
or where impractical, disambiguting the target with ``PEP NNN``.
I also converted all the citations in PEP 482 to links,
as they were causing duplicate citation warnings.
The new language is more precise, and leaves the door open for more implementation options, by not seeming to require that the pattern implementation must import collections.abc.
The new language allows only using sys.modules if has already been imported (e.g. by peeking in sys.modules).
Also, for internal use of CPython, two new flags, `Py_TPFLAGS_SEQUENCE` and `Py_TPFLAGS_MAPPING` are introduced, which support recognizing built-in sequence and mapping types without importing collections.abc.
Clean up PEP 634 (the new PEP 622).
Renamed Constant Value Pattern to Value Pattern. Renamed a few other grammar rules as well.
Leave open for the SC to decide: whether to change `name := pattern` to `pattern as name`.
Note that the companion PEP 635 (motivation and rationale) and PEP 636 (tutorial) are not yet ready.
Adam Turner
Hugo van Kemenade
Dimitri Papadopoulos Orfanos
Brandt Bucher
Brandt Bucher
Mark Shannon
Guido van Rossum
Ken Jin
Daniel F Moisset