Fix crash on invalid type variable with ParamSpec (#15953)
Fixes https://github.com/python/mypy/issues/15948
The fix is straightforward: invalid type variable resulted in applying
type arguments packing/simplification when we shouldn't. Making the
latter more strict fixes the issue.
---------
Co-authored-by: Jelle Zijlstra <jelle.zijlstra@gmail.com>
diff --git a/mypy/typeanal.py b/mypy/typeanal.py
index 806b996..e29cca0 100644
--- a/mypy/typeanal.py
+++ b/mypy/typeanal.py
@@ -458,11 +458,30 @@
# These do not support mypy_extensions VarArgs, etc. as they were already analyzed
# TODO: should these be re-analyzed to get rid of this inconsistency?
count = len(an_args)
- if count > 0:
- first_arg = get_proper_type(an_args[0])
- if not (count == 1 and isinstance(first_arg, (Parameters, ParamSpecType, AnyType))):
- return [Parameters(an_args, [ARG_POS] * count, [None] * count)]
- return list(an_args)
+ if count == 0:
+ return []
+ if count == 1 and isinstance(get_proper_type(an_args[0]), AnyType):
+ # Single Any is interpreted as ..., rather that a single argument with Any type.
+ # I didn't find this in the PEP, but it sounds reasonable.
+ return list(an_args)
+ if any(isinstance(a, (Parameters, ParamSpecType)) for a in an_args):
+ if len(an_args) > 1:
+ first_wrong = next(
+ arg for arg in an_args if isinstance(arg, (Parameters, ParamSpecType))
+ )
+ self.fail(
+ "Nested parameter specifications are not allowed",
+ first_wrong,
+ code=codes.VALID_TYPE,
+ )
+ return [AnyType(TypeOfAny.from_error)]
+ return list(an_args)
+ first = an_args[0]
+ return [
+ Parameters(
+ an_args, [ARG_POS] * count, [None] * count, line=first.line, column=first.column
+ )
+ ]
def cannot_resolve_type(self, t: UnboundType) -> None:
# TODO: Move error message generation to messages.py. We'd first
@@ -503,7 +522,11 @@
names: list[str | None] = [None] * len(args)
pre = Parameters(
- args + pre.arg_types, [ARG_POS] * len(args) + pre.arg_kinds, names + pre.arg_names
+ args + pre.arg_types,
+ [ARG_POS] * len(args) + pre.arg_kinds,
+ names + pre.arg_names,
+ line=t.line,
+ column=t.column,
)
return ps.copy_modified(prefix=pre) if isinstance(ps, ParamSpecType) else pre
@@ -913,7 +936,7 @@
if params:
ts, kinds, names = params
# bind these types
- return Parameters(self.anal_array(ts), kinds, names)
+ return Parameters(self.anal_array(ts), kinds, names, line=t.line, column=t.column)
else:
return AnyType(TypeOfAny.from_error)
else:
diff --git a/test-data/unit/check-parameter-specification.test b/test-data/unit/check-parameter-specification.test
index dba7397..257fb92 100644
--- a/test-data/unit/check-parameter-specification.test
+++ b/test-data/unit/check-parameter-specification.test
@@ -1741,3 +1741,26 @@
reveal_type(bar) # N: Revealed type is "Overload(def (x: builtins.int) -> builtins.float, def (x: builtins.str) -> builtins.str)"
[builtins fixtures/paramspec.pyi]
+
+[case testParamSpecDecoratorOverloadNoCrashOnInvalidTypeVar]
+from typing import Any, Callable, List
+from typing_extensions import ParamSpec
+
+P = ParamSpec("P")
+T = 1
+
+Alias = Callable[P, List[T]] # type: ignore
+def dec(fn: Callable[P, T]) -> Alias[P, T]: ... # type: ignore
+f: Any
+dec(f) # No crash
+[builtins fixtures/paramspec.pyi]
+
+[case testParamSpecErrorNestedParams]
+from typing import Generic
+from typing_extensions import ParamSpec
+
+P = ParamSpec("P")
+class C(Generic[P]): ...
+c: C[int, [int, str], str] # E: Nested parameter specifications are not allowed
+reveal_type(c) # N: Revealed type is "__main__.C[Any]"
+[builtins fixtures/paramspec.pyi]
