[issue42123] Run parser twice; enable invalid_* rules only on the second run

[Lysandros Nikolaou]

Lysandros Nikolaou <lisandrosnik at gmail.com> added the comment:

We do not have a big corpus of SyntaxErrors to test against, but some manual testing of running a file with a SyntaxError after a long complex line 1000 times shows no slowdown.

We keep the token stream for the second run, so we don't need to run the tokenizer all over again and the parsing is done much more quickly.

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue42123>
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