Python parsing of subscripts that unpack a string or parenthesised expression produces ERROR nodes #367

Observed. test/python/ast/test_python_lst_node.py::TestPythonLstNode::test_from_cst_returns_statement failed in CI on PR #318 (run 40916710765), with the Hypothesis input for 0J[*''] in ...: pass. The first child of the created node has SemanticKind.NODE instead of loop.

Cause. tree-sitter-python 0.25.0 does not parse a starred expression in a subscript (PEP 646, Python 3.11+) when the operand is a string or a parenthesised expression:

The parse is (module (ERROR (identifier) (slice (list_splat (ERROR (string (string_start) (string_end))) (identifier)))) (pass_statement)). CPython 3.14 accepts the code: ast.parse gives Subscript(value=Constant(0j), slice=Tuple([Starred(Constant(''))]), ctx=Store()).

Reproduce. PythonFactory(LSTNode).create_from_text("x[*'a']\n").children[0].semantic_kind, or add @reproduce_failure('6.169.4', b'AEEBQQEAQQNBDkEAgTAAgUoBQQBBBIBBAkEAQQAAQQk=') to the test.

Not a regression. The PR changes no parser code and no parser or Hypothesis dependency. The test draws random examples, and this input is rare.

Options. Report it upstream to tree-sitter-python; until then, record the case as an explicit xfail example, or have the test skip inputs that tree-sitter cannot parse.