Specialize `match` syntax error for star pattern outside sequence pattern
Open
@johnslavik is already working on this.
Since Mar 3, 2026.
interpreter-core
topic-parser
type-feature
- Dominant language
- Python
- Stars
- 77.2k
- Forks
- 35.9k
- PR merge metrics
- PR metrics pending
Description
Feature or enhancement
Proposal:
Consider a specialized syntax error for these cases:
# Star pattern is only allowed inside a sequence pattern
match subject:
case *_:
pass
case *_ as x:
pass
case *foo:
pass
case *foo | 1:
pass
case 1 | *foo:
pass
case Foo(*_):
pass
case Foo(x=*_):
pass
case {*_}:
pass
This was taken from https://github.com/astral-sh/ruff/blob/6ff4da454c448f01eb0b71728f3941870c811bfc/crates/ruff_python_parser/resources/invalid/statements/match/star_pattern_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 *_:
- ^
-SyntaxError: invalid syntax
+ ^
+SyntaxError: star pattern is only allowed inside a sequence pattern
The code doesn't look obviously incorrect syntactically, which is why I think it's a good idea to add a more specific message.
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
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Assessment
This issue has not been assessed yet.