Fix PythonRstNode.__contains__ returning a match index instead of a bool

[pjljvandelaar]

Problem

__contains__ returned the raw result of find_in_list, which is an index, not a boolean:

return find_in_list(self.children, item)

find_in_list returns the end index of the match, or a negative sentinel when there is none. Python coerces whatever __contains__ returns with bool(), so the in operator was inverted at both ends of the range:

situation	find_in_list	item in node	correct
no match	-2	True	False
match ending at index 0	0	False	True
match ending at index >= 1	n	True	True

So x in node answered "yes" for everything that is not there, and "no" for a match on the first child.

How it surfaced

Adding the missing -> bool return annotation (ANN204) made pyright report:

src/renaissance/integrations/python/ast/rst_node.py:292
  Type "Unknown | Literal[-2]" is not assignable to return type "bool"  (reportReturnType)

The magic -2

find_in_list had a bare -2 as its "not found" value, while the module already defines sentinels on lines 14-15:

MIS_MATCH = -12
INCOMPLETE_MATCH = -11

-2 is not one of them and carried no meaning — every caller only tests the sign (found_position >= 0 in match_pattern, less_than(0) in test_match_tree). It is replaced by MIS_MATCH, which is what the function means and is already the sentinel find_variants uses internally for a rejected variant. No caller or test depends on the literal -2 (verified by search).

Test correction

test_is_match_all_stmt passed only because of the bug: find_in_list returned -2, and -2 is truthy.

match_all = self.pattern_factory.create("$$pa")
assert_that(match_all.node, is_in(atu))

Two things were wrong. create() wraps the pattern in a module, so .node was the Module translation unit (pattern.py), not a statement — it could never match a statement in atu. And pattern_kind is resolved on the PythonPattern wrapper, not on the inner .node, so even create_statement(...).node is not recognised as MATCH_ALL:

expression	parser_kind	pattern_kind	find_in_list
create("$$pa")	Module	None	-2
create("$$pa").node	Module	None	-2
create_statement("$$pa").node	Expr	None	-2
create_statement("$$pa")	Expr	match_all	3

The test now uses the form that actually expresses its intent, and passes for the right reason — a $$pa wildcard matches the whole 4-statement module, end index 3.

Changes

• src/renaissance/integrations/python/ast/rst_node.py — return find_in_list(self.children, item) >= 0
• src/renaissance/syntax_tree/match_finder.py — return -2 → return MIS_MATCH, docstring updated
• test/python/ast/test_patternic_style.py — assert on the pattern, not on its .node

Verification

• Full suite before and after: 143 failed / 2209 passed / 91 skipped / 31 xfailed — identical failing set (the failures are pre-existing clang issues)
• ruff check clean, ruff format --check clean
• lint_budget --check green; removes the reportReturnType regression