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carljm merged 6 commits into from
Feb 20, 2026
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Conformance suite: Minor tweaks to several assertions for better compatibility with ty #2178

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11875d9
Conformance suite: Minor tweaks to several assertions for better comp…
AlexWaygood Feb 16, 2026
652dde5
update results for other type checkers
AlexWaygood Feb 16, 2026
7b6a5d2
revert some questionable changes to tests around type-parameter defaults
AlexWaygood Feb 16, 2026
88bf117
Apply suggestion from @rchen152
AlexWaygood Feb 16, 2026
9955ae1
Mark Zuban as partially conformant with `generics_scoping.toml`
AlexWaygood Feb 16, 2026
d59f132
rename tag
AlexWaygood Feb 16, 2026
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48 changes: 26 additions & 22 deletions conformance/results/mypy/generics_scoping.toml
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@@ -1,26 +1,30 @@
output = """
generics_scoping.py:29: error: Argument 1 to "meth_2" of "MyClass" has incompatible type "str"; expected "int" [arg-type]
generics_scoping.py:50: error: Type variable "generics_scoping.S" is unbound [valid-type]
generics_scoping.py:50: note: (Hint: Use "Generic[S]" or "Protocol[S]" base class to bind "S" inside a class)
generics_scoping.py:50: note: (Hint: Use "S" in function signature to bind "S" inside a function)
generics_scoping.py:54: error: Type variable "generics_scoping.S" is unbound [valid-type]
generics_scoping.py:54: note: (Hint: Use "Generic[S]" or "Protocol[S]" base class to bind "S" inside a class)
generics_scoping.py:54: note: (Hint: Use "S" in function signature to bind "S" inside a function)
generics_scoping.py:65: error: Free type variable expected in Generic[...] [misc]
generics_scoping.py:75: error: Type variable "T" is bound by an outer class [valid-type]
generics_scoping.py:78: error: Type variable "generics_scoping.T" is unbound [valid-type]
generics_scoping.py:78: note: (Hint: Use "Generic[T]" or "Protocol[T]" base class to bind "T" inside a class)
generics_scoping.py:78: note: (Hint: Use "T" in function signature to bind "T" inside a function)
generics_scoping.py:87: error: Can't use bound type variable "T" to define generic alias [valid-type]
generics_scoping.py:94: error: Type variable "generics_scoping.T" is unbound [valid-type]
generics_scoping.py:94: note: (Hint: Use "Generic[T]" or "Protocol[T]" base class to bind "T" inside a class)
generics_scoping.py:94: note: (Hint: Use "T" in function signature to bind "T" inside a function)
generics_scoping.py:95: error: Type variable "generics_scoping.T" is unbound [valid-type]
generics_scoping.py:95: note: (Hint: Use "Generic[T]" or "Protocol[T]" base class to bind "T" inside a class)
generics_scoping.py:95: note: (Hint: Use "T" in function signature to bind "T" inside a function)
generics_scoping.py:96: error: Type variable "generics_scoping.T" is unbound [valid-type]
generics_scoping.py:96: note: (Hint: Use "Generic[T]" or "Protocol[T]" base class to bind "T" inside a class)
generics_scoping.py:96: note: (Hint: Use "T" in function signature to bind "T" inside a function)
generics_scoping.py:16: error: Expression is of type "int", not "Literal[1]" [assert-type]
generics_scoping.py:20: error: Expression is of type "str", not "Literal['a']" [assert-type]
generics_scoping.py:34: error: Argument 1 to "meth_2" of "MyClass" has incompatible type "str"; expected "int" [arg-type]
generics_scoping.py:50: error: Expression is of type "str", not "Literal['abc']" [assert-type]
generics_scoping.py:54: error: Expression is of type "bytes", not "Literal[b'abc']" [assert-type]
generics_scoping.py:61: error: Type variable "generics_scoping.S" is unbound [valid-type]
generics_scoping.py:61: note: (Hint: Use "Generic[S]" or "Protocol[S]" base class to bind "S" inside a class)
generics_scoping.py:61: note: (Hint: Use "S" in function signature to bind "S" inside a function)
generics_scoping.py:65: error: Type variable "generics_scoping.S" is unbound [valid-type]
generics_scoping.py:65: note: (Hint: Use "Generic[S]" or "Protocol[S]" base class to bind "S" inside a class)
generics_scoping.py:65: note: (Hint: Use "S" in function signature to bind "S" inside a function)
generics_scoping.py:76: error: Free type variable expected in Generic[...] [misc]
generics_scoping.py:86: error: Type variable "T" is bound by an outer class [valid-type]
generics_scoping.py:89: error: Type variable "generics_scoping.T" is unbound [valid-type]
generics_scoping.py:89: note: (Hint: Use "Generic[T]" or "Protocol[T]" base class to bind "T" inside a class)
generics_scoping.py:89: note: (Hint: Use "T" in function signature to bind "T" inside a function)
generics_scoping.py:98: error: Can't use bound type variable "T" to define generic alias [valid-type]
generics_scoping.py:105: error: Type variable "generics_scoping.T" is unbound [valid-type]
generics_scoping.py:105: note: (Hint: Use "Generic[T]" or "Protocol[T]" base class to bind "T" inside a class)
generics_scoping.py:105: note: (Hint: Use "T" in function signature to bind "T" inside a function)
generics_scoping.py:106: error: Type variable "generics_scoping.T" is unbound [valid-type]
generics_scoping.py:106: note: (Hint: Use "Generic[T]" or "Protocol[T]" base class to bind "T" inside a class)
generics_scoping.py:106: note: (Hint: Use "T" in function signature to bind "T" inside a function)
generics_scoping.py:107: error: Type variable "generics_scoping.T" is unbound [valid-type]
generics_scoping.py:107: note: (Hint: Use "Generic[T]" or "Protocol[T]" base class to bind "T" inside a class)
generics_scoping.py:107: note: (Hint: Use "T" in function signature to bind "T" inside a function)
"""
conformance_automated = "Pass"
errors_diff = """
Expand Down
18 changes: 9 additions & 9 deletions conformance/results/mypy/generics_syntax_scoping.toml
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Expand Up @@ -19,18 +19,18 @@ generics_syntax_scoping.py:95: error: "T" already defined as a type parameter [
generics_syntax_scoping.py:98: error: "T" already defined as a type parameter [misc]
generics_syntax_scoping.py:98: error: Variable "generics_syntax_scoping.ClassE.T" is not valid as a type [valid-type]
generics_syntax_scoping.py:98: note: See https://mypy.readthedocs.io/en/stable/common_issues.html#variables-vs-type-aliases
generics_syntax_scoping.py:116: error: Expression is of type "Any", not "TypeVar" [assert-type]
generics_syntax_scoping.py:116: note: "assert_type" expects everything to be "Any" in unchecked functions
generics_syntax_scoping.py:121: error: Expression is of type "Any", not "complex" [assert-type]
generics_syntax_scoping.py:121: note: "assert_type" expects everything to be "Any" in unchecked functions
generics_syntax_scoping.py:124: error: Expression is of type "Any", not "complex" [assert-type]
generics_syntax_scoping.py:124: note: "assert_type" expects everything to be "Any" in unchecked functions
generics_syntax_scoping.py:117: error: Expression is of type "Any", not "TypeVar" [assert-type]
generics_syntax_scoping.py:117: note: "assert_type" expects everything to be "Any" in unchecked functions
generics_syntax_scoping.py:122: error: Expression is of type "Any", not "complex" [assert-type]
generics_syntax_scoping.py:122: note: "assert_type" expects everything to be "Any" in unchecked functions
generics_syntax_scoping.py:125: error: Expression is of type "Any", not "complex" [assert-type]
generics_syntax_scoping.py:125: note: "assert_type" expects everything to be "Any" in unchecked functions
"""
conformance_automated = "Fail"
errors_diff = """
Line 62: Unexpected errors ['generics_syntax_scoping.py:62: error: Expression is of type "Any", not "str" [assert-type]']
Line 67: Unexpected errors ['generics_syntax_scoping.py:67: error: Expression is of type "Any", not "int" [assert-type]']
Line 116: Unexpected errors ['generics_syntax_scoping.py:116: error: Expression is of type "Any", not "TypeVar" [assert-type]']
Line 121: Unexpected errors ['generics_syntax_scoping.py:121: error: Expression is of type "Any", not "complex" [assert-type]']
Line 124: Unexpected errors ['generics_syntax_scoping.py:124: error: Expression is of type "Any", not "complex" [assert-type]']
Line 117: Unexpected errors ['generics_syntax_scoping.py:117: error: Expression is of type "Any", not "TypeVar" [assert-type]']
Line 122: Unexpected errors ['generics_syntax_scoping.py:122: error: Expression is of type "Any", not "complex" [assert-type]']
Line 125: Unexpected errors ['generics_syntax_scoping.py:125: error: Expression is of type "Any", not "complex" [assert-type]']
"""
24 changes: 14 additions & 10 deletions conformance/results/pyrefly/generics_scoping.toml
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Expand Up @@ -4,16 +4,20 @@ Does not implement several scoping checks/restrictions for generics
"""
conformance_automated = "Fail"
errors_diff = """
Line 50: Expected 1 errors
Line 54: Expected 1 errors
Line 75: Expected 1 errors
Line 78: Expected 1 errors
Line 87: Expected 1 errors
Line 94: Expected 1 errors
Line 95: Expected 1 errors
Line 96: Expected 1 errors
Line 61: Expected 1 errors
Line 65: Expected 1 errors
Line 86: Expected 1 errors
Line 89: Expected 1 errors
Line 98: Expected 1 errors
Line 105: Expected 1 errors
Line 106: Expected 1 errors
Line 107: Expected 1 errors
"""
output = """
ERROR generics_scoping.py:29:10-13: Argument `Literal['a']` is not assignable to parameter `x` with type `int` in function `MyClass.meth_2` [bad-argument-type]
ERROR generics_scoping.py:65:11-20: Redundant type parameter declaration [invalid-type-var]
ERROR generics_scoping.py:16:12-34: assert_type(int, Literal[1]) failed [assert-type]
ERROR generics_scoping.py:20:12-38: assert_type(str, Literal['a']) failed [assert-type]
ERROR generics_scoping.py:34:10-13: Argument `Literal['a']` is not assignable to parameter `x` with type `int` in function `MyClass.meth_2` [bad-argument-type]
ERROR generics_scoping.py:50:12-48: assert_type(str, Literal['abc']) failed [assert-type]
ERROR generics_scoping.py:54:12-50: assert_type(bytes, Literal[b'abc']) failed [assert-type]
ERROR generics_scoping.py:76:11-20: Redundant type parameter declaration [invalid-type-var]
"""
24 changes: 14 additions & 10 deletions conformance/results/pyright/generics_scoping.toml
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@@ -1,16 +1,20 @@
conformant = "Pass"
output = """
generics_scoping.py:29:10 - error: Argument of type "Literal['a']" cannot be assigned to parameter "x" of type "int" in function "meth_2"
generics_scoping.py:16:13 - error: "assert_type" mismatch: expected "Literal[1]" but received "int" (reportAssertTypeFailure)
generics_scoping.py:20:13 - error: "assert_type" mismatch: expected "Literal['a']" but received "str" (reportAssertTypeFailure)
generics_scoping.py:34:10 - error: Argument of type "Literal['a']" cannot be assigned to parameter "x" of type "int" in function "meth_2"
  "Literal['a']" is not assignable to "int" (reportArgumentType)
generics_scoping.py:50:13 - error: Type variable "S" has no meaning in this context (reportGeneralTypeIssues)
generics_scoping.py:54:19 - error: Type variable "S" has no meaning in this context (reportGeneralTypeIssues)
generics_scoping.py:65:29 - error: TypeVar "T" is already in use by an outer scope (reportGeneralTypeIssues)
generics_scoping.py:75:24 - error: TypeVar "T" is already in use by an outer scope (reportGeneralTypeIssues)
generics_scoping.py:78:17 - error: Type variable "T" has no meaning in this context (reportGeneralTypeIssues)
generics_scoping.py:87:5 - error: Generic type alias within class cannot use bound type variables T (reportInvalidTypeForm)
generics_scoping.py:94:14 - error: Type variable "T" has no meaning in this context (reportGeneralTypeIssues)
generics_scoping.py:95:19 - error: Type variable "T" has no meaning in this context (reportGeneralTypeIssues)
generics_scoping.py:96:6 - error: Type variable "T" has no meaning in this context (reportGeneralTypeIssues)
generics_scoping.py:50:13 - error: "assert_type" mismatch: expected "Literal['abc']" but received "str" (reportAssertTypeFailure)
generics_scoping.py:54:13 - error: "assert_type" mismatch: expected "Literal[b"abc"]" but received "bytes" (reportAssertTypeFailure)
generics_scoping.py:61:13 - error: Type variable "S" has no meaning in this context (reportGeneralTypeIssues)
generics_scoping.py:65:19 - error: Type variable "S" has no meaning in this context (reportGeneralTypeIssues)
generics_scoping.py:76:29 - error: TypeVar "T" is already in use by an outer scope (reportGeneralTypeIssues)
generics_scoping.py:86:24 - error: TypeVar "T" is already in use by an outer scope (reportGeneralTypeIssues)
generics_scoping.py:89:17 - error: Type variable "T" has no meaning in this context (reportGeneralTypeIssues)
generics_scoping.py:98:5 - error: Generic type alias within class cannot use bound type variables T (reportInvalidTypeForm)
generics_scoping.py:105:14 - error: Type variable "T" has no meaning in this context (reportGeneralTypeIssues)
generics_scoping.py:106:19 - error: Type variable "T" has no meaning in this context (reportGeneralTypeIssues)
generics_scoping.py:107:6 - error: Type variable "T" has no meaning in this context (reportGeneralTypeIssues)
"""
conformance_automated = "Pass"
errors_diff = """
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2 changes: 1 addition & 1 deletion conformance/results/results.html
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Expand Up @@ -307,7 +307,7 @@ <h3>Python Type System Conformance Test Results</h3>
<tr><th class="column col1">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;generics_scoping</th>
<th class="column col2 conformant">Pass</th>
<th class="column col2 conformant">Pass</th>
<th class="column col2 conformant">Pass</th>
<th class="column col2 not-conformant">Unknown</th>
<th class="column col2 partially-conformant"><div class="hover-text">Partial<span class="tooltip-text" id="bottom"><p>Does not implement several scoping checks/restrictions for generics</p></span></div></th>
</tr>
<tr><th class="column col1">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;generics_self_advanced</th>
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48 changes: 26 additions & 22 deletions conformance/results/zuban/generics_scoping.toml
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@@ -1,26 +1,30 @@
conformance_automated = "Pass"
conformance_automated = "Fail"
errors_diff = """
Lines 15, 16: Expected error (tag 'fun1-int')
Lines 19, 20: Expected error (tag 'fun1-str')
Lines 49, 50: Expected error (tag 'method-str')
Lines 53, 54: Expected error (tag 'method-bytes')
"""
output = """
generics_scoping.py:29: error: Argument 1 to "meth_2" of "MyClass" has incompatible type "str"; expected "int" [arg-type]
generics_scoping.py:50: error: Type variable "generics_scoping.S" is unbound [misc]
generics_scoping.py:50: note: (Hint: Use "Generic[S]" or "Protocol[S]" base class to bind "S" inside a class)
generics_scoping.py:50: note: (Hint: Use "S" in function signature to bind "S" inside a function)
generics_scoping.py:54: error: Type variable "generics_scoping.S" is unbound [misc]
generics_scoping.py:54: note: (Hint: Use "Generic[S]" or "Protocol[S]" base class to bind "S" inside a class)
generics_scoping.py:54: note: (Hint: Use "S" in function signature to bind "S" inside a function)
generics_scoping.py:65: error: Free type variable expected in Generic[...] [misc]
generics_scoping.py:75: error: Type variable "T" is bound by an outer class [misc]
generics_scoping.py:78: error: Type variable "T" is bound by an outer class [misc]
generics_scoping.py:80: error: Type variable "T" is bound by an outer class [misc]
generics_scoping.py:87: error: Can't use bound type variable "T" to define generic alias [misc]
generics_scoping.py:94: error: Type variable "generics_scoping.T" is unbound [misc]
generics_scoping.py:94: note: (Hint: Use "Generic[T]" or "Protocol[T]" base class to bind "T" inside a class)
generics_scoping.py:94: note: (Hint: Use "T" in function signature to bind "T" inside a function)
generics_scoping.py:95: error: Type variable "generics_scoping.T" is unbound [misc]
generics_scoping.py:95: note: (Hint: Use "Generic[T]" or "Protocol[T]" base class to bind "T" inside a class)
generics_scoping.py:95: note: (Hint: Use "T" in function signature to bind "T" inside a function)
generics_scoping.py:96: error: Type variable "generics_scoping.T" is unbound [misc]
generics_scoping.py:96: note: (Hint: Use "Generic[T]" or "Protocol[T]" base class to bind "T" inside a class)
generics_scoping.py:96: note: (Hint: Use "T" in function signature to bind "T" inside a function)
generics_scoping.py:34: error: Argument 1 to "meth_2" of "MyClass" has incompatible type "str"; expected "int" [arg-type]
generics_scoping.py:61: error: Type variable "generics_scoping.S" is unbound [misc]
generics_scoping.py:61: note: (Hint: Use "Generic[S]" or "Protocol[S]" base class to bind "S" inside a class)
generics_scoping.py:61: note: (Hint: Use "S" in function signature to bind "S" inside a function)
generics_scoping.py:65: error: Type variable "generics_scoping.S" is unbound [misc]
generics_scoping.py:65: note: (Hint: Use "Generic[S]" or "Protocol[S]" base class to bind "S" inside a class)
generics_scoping.py:65: note: (Hint: Use "S" in function signature to bind "S" inside a function)
generics_scoping.py:76: error: Free type variable expected in Generic[...] [misc]
generics_scoping.py:86: error: Type variable "T" is bound by an outer class [misc]
generics_scoping.py:89: error: Type variable "T" is bound by an outer class [misc]
generics_scoping.py:91: error: Type variable "T" is bound by an outer class [misc]
generics_scoping.py:98: error: Can't use bound type variable "T" to define generic alias [misc]
generics_scoping.py:105: error: Type variable "generics_scoping.T" is unbound [misc]
generics_scoping.py:105: note: (Hint: Use "Generic[T]" or "Protocol[T]" base class to bind "T" inside a class)
generics_scoping.py:105: note: (Hint: Use "T" in function signature to bind "T" inside a function)
generics_scoping.py:106: error: Type variable "generics_scoping.T" is unbound [misc]
generics_scoping.py:106: note: (Hint: Use "Generic[T]" or "Protocol[T]" base class to bind "T" inside a class)
generics_scoping.py:106: note: (Hint: Use "T" in function signature to bind "T" inside a function)
generics_scoping.py:107: error: Type variable "generics_scoping.T" is unbound [misc]
generics_scoping.py:107: note: (Hint: Use "Generic[T]" or "Protocol[T]" base class to bind "T" inside a class)
generics_scoping.py:107: note: (Hint: Use "T" in function signature to bind "T" inside a function)
"""
4 changes: 3 additions & 1 deletion conformance/tests/annotations_generators.py
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Expand Up @@ -190,4 +190,6 @@ async def generator30() -> AsyncIterator[int]:
yield


assert_type(generator30, Callable[[], AsyncIterator[int]])
async def uses_generator30() -> None:
async for x in generator30():
assert_type(x, int)
Comment on lines -193 to +195
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@AlexWaygood AlexWaygood Feb 16, 2026 •
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ty infers a "function-literal" type for generator30, not a Callable type. A function-literal type is more precise than a Callable type: it retains, for example, the information that generator30 is an instance of types.FunctionType, which is not true for all arbitrary Callable types.

I don't believe the spec states anywhere that type checkers must infer a Callable type for function objects (only that functions must be considered to inhabit Callable types), so I think this change is appropriate.

I tried doing just assert_type(generator30(), AsyncIterator[int]), but then zuban (reasonably) complained that the result of generator30() was never awaited, which wasn't relevant to what the test was trying to assert.

21 changes: 16 additions & 5 deletions conformance/tests/generics_scoping.py
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@@ -1,6 +1,6 @@
# Specification: https://typing.readthedocs.io/en/latest/spec/generics.html#scoping-rules-for-type-variables

from typing import TypeVar, Generic, Iterable, TypeAlias, assert_type
from typing import TypeVar, Generic, Iterable, TypeAlias, assert_type, Literal

# > A type variable used in a generic function could be inferred to represent
# > different types in the same code block.
Expand All @@ -11,8 +11,13 @@ def fun_1(x: T) -> T: # T here
def fun_2(x: T) -> T: # and here could be different
return x

assert_type(fun_1(1), int)
assert_type(fun_2('a'), str)
# One of these two should pass; either is acceptable:
assert_type(fun_1(1), int) # E[fun1-int]
assert_type(fun_1(1), Literal[1]) # E[fun1-int]
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@carljm carljm Feb 16, 2026

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How does the conformance checker handle it if there's an error on both of these lines? It's the intent of the test that that should be considered non-conforming.

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@AlexWaygood AlexWaygood Feb 16, 2026

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I believe a tagged error like this is still non-optional: an error must be emitted on at least one of these lines. This seems to be reflected by the fact that zuban is no longer considered conformant on this PR branch, if you look at the changes to the reported results -- it apparently doesn't emit an error on either of these lines. (That seems like a bug in zuban to me -- int and Literal[1] are not equivalent types, so fun_1(1) cannot be equivalent to both int and Literal[1].)

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@AlexWaygood AlexWaygood Feb 16, 2026

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yes, as per https://github.com/python/typing/tree/main/conformance#test-case-syntax:

# E[tag], where tag is an arbitrary string: must appear multiple times in a file with the same tag. Exactly one line with this tag must raise an error.

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@rchen152 rchen152 Feb 16, 2026

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cc @davidhalter - FYI this conformance change turned up what looks like a bug in zuban.

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@davidhalter davidhalter Feb 20, 2026

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@rchen152 Thanks, it looks like something about the nesting causes issues. Will investigate.

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@davidhalter davidhalter Feb 23, 2026

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I quickly fixed this (on master branch). Zuban inferred essentially an intersection type of int & Literal[1], which is relevant for some type inference details. Now it's still inferred this way, but the assert_type will only assert the type of Literal[1] and not int.

I don't think this was necessarily a bug in Zuban, but it's probably easier to work with the conformance tests if I implement it this way.

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@erictraut erictraut Feb 23, 2026

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int & Literal[1] is equivalent to Literal[1], and the spec says that assert_type verifies type equivalency.


# One of these two should pass; either is acceptable:
assert_type(fun_1("a"), str) # E[fun1-str]
assert_type(fun_1("a"), Literal["a"]) # E[fun1-str]

# > A type variable used in a method of a generic class that coincides
# > with one of the variables that parameterize this class is always bound
Expand All @@ -39,8 +44,14 @@ def method(self, x: T, y: S) -> S:
return y

x: Foo[int] = Foo()
assert_type(x.method(0, "abc"), str)
assert_type(x.method(0, b"abc"), bytes)

# Either of these is acceptable; one of the two should pass:
assert_type(x.method(0, "abc"), str) # E[method-str]
assert_type(x.method(0, "abc"), Literal["abc"]) # E[method-str]

# Either of these is acceptable; one of the two should pass:
assert_type(x.method(0, b"abc"), bytes) # E[method-bytes]
assert_type(x.method(0, b"abc"), Literal[b"abc"]) # E[method-bytes]

# > Unbound type variables should not appear in the bodies of generic functions,
# > or in the class bodies apart from method definitions.
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27 changes: 14 additions & 13 deletions conformance/tests/generics_syntax_scoping.py
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Expand Up @@ -102,23 +102,24 @@ def method3[T](self, x: T): # E
T = int(0)


class Outer2[T]:
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@AlexWaygood AlexWaygood Feb 16, 2026

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the assertions in this test ran into issues because ty inferred T as having type Literal[""] where T = str("").

ty also rejected the assert_type(T, complex) call lower down after the T = 3j assignment, because we view complex in a type expression as immediately expanding to the union int | float | complex, and the second argument to assert_type takes a type expression -- but complex (the type inferred for T) is not equivalent to int | float | complex.

T = int(1)

assert_type(T, int)
def f(a: int, b: str, c: complex):
class Outer2[T]:
T = a

class Inner1:
T = str("")
assert_type(T, int)

assert_type(T, str)
class Inner1:
T = b

def inner_method(self):
assert_type(T, TypeVar)
assert_type(T, str)

def outer_method(self):
T = 3j
def inner_method(self):
assert_type(T, TypeVar)

assert_type(T, complex)
def outer_method(self):
T = c

def inner_func():
assert_type(T, complex)

def inner_func():
assert_type(T, complex)