This commit simplifies async/await tokenization in tokenizer.c,
tokenize.py & lib2to3/tokenize.py. Previous solution was to keep
a stack of async-def & def blocks, whereas the new approach is just
to remember position of the outermost async-def block.
This change won't bring any parsing performance improvements, but
it makes the code much easier to read and validate.
This commit fixes how one-line async-defs and defs are tracked
by tokenizer. It allows to correctly parse invalid code such
as:
>>> async def f():
... def g(): pass
... async = 10
and valid code such as:
>>> async def f():
... async def g(): pass
... await z
As a consequence, is is now possible to have one-line
'async def foo(): await ..' functions:
>>> async def foo(): return await bar()
The new parser does not rely on Spark (which is now removed from our repo),
uses modern 3.x idioms and is significantly smaller and simpler.
It generates exactly the same AST files (.h and .c), so in practice no builds
should be affected.
