Move const folding to the peephole optimizer

Feature or enhancement

Proposal:

For additional context see https://github.com/python/cpython/pull/126830#issuecomment-2476525196.

Flow graph optimizer has more information and can do better job.

The problem is that we need to convert from UNARY_OP(-, CONST(1)) to CONST(-1), still before the code generation phase, because this leads to a few problems, one of which is shown below.

x = 1

match x:
    case -0:
        y = 0

eclips4@nixos ~/p/p/cpython (remove-ast-optimizer)> ./python example.py
  File "/home/eclips4/programming/programming-languages/cpython/example.py", line 4
    case -0:
         ^^
SyntaxError: patterns may only match literals and attribute lookups

cc @markshannon

Has this already been discussed elsewhere?

No response given

Links to previous discussion of this feature:

No response

Linked PRs

• gh-128802
• gh-129426
• gh-129550
• gh-129568
• gh-129634
• gh-129703
• gh-129963
• gh-130016
• gh-130032
• gh-130109
• gh-130769
• gh-131054
• gh-131826
• gh-131830
• gh-146631
• gh-147187