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Update error message for Type application #20928

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Update error message for Type application #20928

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73480b2
Update error message for type application support
hyperkai Feb 28, 2026
a96eda4
Clarify error messages for type applications
hyperkai Feb 28, 2026
27ff5a6
Fix type application error in check-typevar-tuple test
hyperkai Feb 28, 2026
7d799ce
Clarify error message for type application
hyperkai Feb 28, 2026
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2 changes: 1 addition & 1 deletion mypy/message_registry.py
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Original file line number Diff line number Diff line change
Expand Up @@ -121,7 +121,7 @@ def with_additional_msg(self, info: str) -> ErrorMessage:
"Function is missing a type annotation", codes.NO_UNTYPED_DEF
)
ONLY_CLASS_APPLICATION: Final = ErrorMessage(
"Type application is only supported for generic classes"
"Type application is only supported for generic classes and type aliases"
)
RETURN_TYPE_EXPECTED: Final = ErrorMessage(
"Function is missing a return type annotation", codes.NO_UNTYPED_DEF
Expand Down
10 changes: 5 additions & 5 deletions test-data/unit/check-generics.test
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Expand Up @@ -426,7 +426,7 @@ from typing import TypeVar
T = TypeVar('T')
def f(x: T) -> T: pass

y = f[int] # E: Type application is only supported for generic classes
y = f[int] # E: Type application is only supported for generic classes and type aliases
[out]


Expand Down Expand Up @@ -1004,7 +1004,7 @@ reveal_type(y) # N: Revealed type is "builtins.int"

U[int] # E: Type application targets a non-generic function or class
O[int] # E: Bad number of arguments for type alias, expected 0, given 1 \
# E: Type application is only supported for generic classes
# E: Type application is only supported for generic classes and type aliases

[case testAliasesInClassBodyNormalVsSubscripted]

Expand Down Expand Up @@ -1072,9 +1072,9 @@ reveal_type(ts) # N: Revealed type is "Any"
us = UA.x # E: "<typing special form>" has no attribute "x"
reveal_type(us) # N: Revealed type is "Any"

xx = CA[str] + 1 # E: Type application is only supported for generic classes
yy = TA[str]() # E: Type application is only supported for generic classes
zz = UA[str].x # E: Type application is only supported for generic classes
xx = CA[str] + 1 # E: Type application is only supported for generic classes and type aliases
yy = TA[str]() # E: Type application is only supported for generic classes and type aliases
zz = UA[str].x # E: Type application is only supported for generic classes and type aliases
[builtins fixtures/tuple.pyi]
[typing fixtures/typing-medium.pyi]
[out]
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2 changes: 1 addition & 1 deletion test-data/unit/check-parameter-specification.test
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Expand Up @@ -92,7 +92,7 @@ class B(Generic[P]): ...
Other = B[P]

T = TypeVar('T', bound=Alias[..., Any])
Alias[..., Any] # E: Type application is only supported for generic classes
Alias[..., Any] # E: Type application is only supported for generic classes and type aliases
B[...]
Other[...]
[builtins fixtures/paramspec.pyi]
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2 changes: 1 addition & 1 deletion test-data/unit/check-typevar-tuple.test
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Expand Up @@ -2763,6 +2763,6 @@ T = TypeVar('T')

def func(d: Callable[[Unpack[Ts]], T]) -> T: ...

y = func[1, int] # E: Type application is only supported for generic classes \
y = func[1, int] # E: Type application is only supported for generic classes and type aliases \
# E: Invalid type: try using Literal[1] instead?
[builtins fixtures/tuple.pyi]
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