Feature or enhancement

Proposal:

Consider a specialized syntax error for these cases:

# Unary addition isn't allowed but we parse it for better error recovery.matchsubject:case+1:passcase1|+2|-3:passcase [1,+2,-3]:passcaseFoo(x=+1,y=-2):passcase {True:+1,False:-2}:pass

This was taken fromhttps://github.com/astral-sh/ruff/blob/6ff4da454c448f01eb0b71728f3941870c811bfc/crates/ruff_python_parser/resources/invalid/statements/match/unary_add_usage.py. 2+ years in Ruff's parser.

Current vs proposed:

❯ ./python.exe t.py  File "/Users/bartosz.slawecki/Python/cpython/t.py", line 2    case +1:         ^-SyntaxError: invalid syntax+SyntaxError: cannot use unary addition in a literal pattern

The code doesn't look incorrect syntactically, which is why I think it's a good idea to add a more specific message (although it is not extremely unclear as-is assuming a pointer^ is shown).

Has this already been discussed elsewhere?

This is a minor feature, which does not need previous discussion elsewhere

Links to previous discussion of this feature:

No response

Linked PRs

• gh-145239: Specialize match syntax error for unary addition in pattern #145658