Feature or enhancement

Proposal:

For additional context see #126830 (comment).

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-126835: Disable tuple folding in the AST optimizer #128802
• gh-126835: Move optimization of constant sequence creation from codegen to CFG #129426
• gh-126835: Move constant unaryop & binop folding to CFG #129550
• gh-126835: Move constant subscript folding to CFG #129568
• gh-126835: Fix optimize_if_const_subscr refleaks #129634
• gh-126835: make CFG optimizer skip over NOP's when looking for const sequence construction #129703
• gh-126835: Fold unary & binary complex constant expressions during code generation. #129963
• gh-126835: Remove unused docstring const #130016
• gh-126835: Move const list & set folding in for_iter & contains from ast_opt.c to flowgraph.c #130032
• gh-126835: Set location for noped out instructions after constant folding in CFG. #130109
• gh-126835: Move constant tuple folding to CFG #130769
• gh-126835: Avoid creating unnecessary tuple when looking for constant sequence during constant folding #131054
• gh-126835: Refine constant folding tests in test_peepholer.py::TestTranforms #131826
• gh-126835: Rename AST optimization related stuff after moving const folding to the peephole optimizier #131830