jinja2.Environment().filters[name] have unexpected type instead of Any

[Tatsh]

Summary

I see really strange output for just a single line for code like this (used in testing):

env = jinja2.Environment(extensions=[...])
func = env.filters['func']
result = func('something')  # this line

func should just be treated as Any here, which is what mypy and Pyright do, unless you want to add support for Jinja2 semantics and find what func should be.

error[missing-argument]: No argument provided for required parameter `linecount`
   --> tests/test_extensions.py:146:14
    |
144 |     env = jinja2.Environment(extensions=[ShellExtension], autoescape=True)
145 |     indent = env.filters['shell_indent']
146 |     result = indent('echo hello\necho world')
    |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
147 |     assert result == '    echo hello\n    echo world'
    |
info: Union variant `[V](value: Iterable[V], linecount: int, fill_with: V | None = None) -> Iterator[list[V]]` is incompatible with this call site
info: Attempted to call union type `Unknown | ([_T](x: SupportsAbs[_T], /) -> _T) | ((environment: Environment, obj: Any, name: str) -> Undefined | Any) | ... omitted 29 union elements`
info: rule `missing-argument` is enabled by default

And there's way more for just this 1 line:

Details

error[missing-argument]: No argument provided for required parameter `seq`
   --> tests/test_extensions.py:146:14
    |
144 |     env = jinja2.Environment(extensions=[ShellExtension], autoescape=True)
145 |     indent = env.filters['shell_indent']
146 |     result = indent('echo hello\necho world')
    |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
147 |     assert result == '    echo hello\n    echo world'
    |
info: Union variant `[V](environment: Environment, seq: Reversible[V]) -> V | Undefined` is incompatible with this call site
info: Attempted to call union type `Unknown | ([_T](x: SupportsAbs[_T], /) -> _T) | ((environment: Environment, obj: Any, name: str) -> Undefined | Any) | ... omitted 29 union elements`
info: rule `missing-argument` is enabled by default

error[missing-argument]: No argument provided for required parameter `value`
   --> tests/test_extensions.py:146:14
    |
144 |     env = jinja2.Environment(extensions=[ShellExtension], autoescape=True)
145 |     indent = env.filters['shell_indent']
146 |     result = indent('echo hello\necho world')
    |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
147 |     assert result == '    echo hello\n    echo world'
    |
info: Union variant `[V](environment: Environment, value: Iterable[V], case_sensitive: bool = False, attribute: str | int | None = None) -> V | Undefined` is incompatible with this call site
info: Attempted to call union type `Unknown | ([_T](x: SupportsAbs[_T], /) -> _T) | ((environment: Environment, obj: Any, name: str) -> Undefined | Any) | ... omitted 29 union elements`
info: rule `missing-argument` is enabled by default

error[missing-argument]: No argument provided for required parameter `value`
   --> tests/test_extensions.py:146:14
    |
144 |     env = jinja2.Environment(extensions=[ShellExtension], autoescape=True)
145 |     indent = env.filters['shell_indent']
146 |     result = indent('echo hello\necho world')
    |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
147 |     assert result == '    echo hello\n    echo world'
    |
info: Union variant `[V](environment: Environment, value: Iterable[V], reverse: bool = False, case_sensitive: bool = False, attribute: str | int | None = None) -> list[V]` is incompatible with this call site
info: Attempted to call union type `Unknown | ([_T](x: SupportsAbs[_T], /) -> _T) | ((environment: Environment, obj: Any, name: str) -> Undefined | Any) | ... omitted 29 union elements`
info: rule `missing-argument` is enabled by default

error[missing-argument]: No argument provided for required parameter `seq`
   --> tests/test_extensions.py:146:14
    |
144 |     env = jinja2.Environment(extensions=[ShellExtension], autoescape=True)
145 |     indent = env.filters['shell_indent']
146 |     result = indent('echo hello\necho world')
    |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
147 |     assert result == '    echo hello\n    echo world'
    |
info: Union variant `[V](context: Context, seq: Sequence[V]) -> V | Undefined` is incompatible with this call site
info: Attempted to call union type `Unknown | ([_T](x: SupportsAbs[_T], /) -> _T) | ((environment: Environment, obj: Any, name: str) -> Undefined | Any) | ... omitted 29 union elements`
info: rule `missing-argument` is enabled by default

error[missing-argument]: No arguments provided for required parameters `s`, `old`, `new`
   --> tests/test_extensions.py:146:14
    |
144 |     env = jinja2.Environment(extensions=[ShellExtension], autoescape=True)
145 |     indent = env.filters['shell_indent']
146 |     result = indent('echo hello\necho world')
    |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
147 |     assert result == '    echo hello\n    echo world'
    |
info: Union variant `(eval_ctx: EvalContext, s: str, old: str, new: str, count: int | None = None) -> str` is incompatible with this call site
info: Attempted to call union type `Unknown | ([_T](x: SupportsAbs[_T], /) -> _T) | ((environment: Environment, obj: Any, name: str) -> Undefined | Any) | ... omitted 29 union elements`
info: rule `missing-argument` is enabled by default

error[missing-argument]: No argument provided for required parameter `s`
   --> tests/test_extensions.py:146:14
    |
144 |     env = jinja2.Environment(extensions=[ShellExtension], autoescape=True)
145 |     indent = env.filters['shell_indent']
146 |     result = indent('echo hello\necho world')
    |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
147 |     assert result == '    echo hello\n    echo world'
    |
info: Union variant `(env: Environment, s: str, length: int = 255, killwords: bool = False, end: str = "...", leeway: int | None = None) -> str` is incompatible with this call site
info: Attempted to call union type `Unknown | ([_T](x: SupportsAbs[_T], /) -> _T) | ((environment: Environment, obj: Any, name: str) -> Undefined | Any) | ... omitted 29 union elements`
info: rule `missing-argument` is enabled by default

error[missing-argument]: No argument provided for required parameter `value`
   --> tests/test_extensions.py:146:14
    |
144 |     env = jinja2.Environment(extensions=[ShellExtension], autoescape=True)
145 |     indent = env.filters['shell_indent']
146 |     result = indent('echo hello\necho world')
    |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
147 |     assert result == '    echo hello\n    echo world'
    |
info: Union variant `(eval_ctx: EvalContext, value: str, trim_url_limit: int | None = None, nofollow: bool = False, target: str | None = None, rel: str | None = None, extra_schemes: Iterable[str] | None = None) -> str` is incompatible with this call site
info: Attempted to call union type `Unknown | ([_T](x: SupportsAbs[_T], /) -> _T) | ((environment: Environment, obj: Any, name: str) -> Undefined | Any) | ... omitted 29 union elements`
info: rule `missing-argument` is enabled by default

error[missing-argument]: No argument provided for required parameter `s`
   --> tests/test_extensions.py:146:14
    |
144 |     env = jinja2.Environment(extensions=[ShellExtension], autoescape=True)
145 |     indent = env.filters['shell_indent']
146 |     result = indent('echo hello\necho world')
    |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
147 |     assert result == '    echo hello\n    echo world'
    |
info: Union variant `(environment: Environment, s: str, width: int = 79, break_long_words: bool = True, wrapstring: str | None = None, break_on_hyphens: bool = True) -> str` is incompatible with this call site
info: Attempted to call union type `Unknown | ([_T](x: SupportsAbs[_T], /) -> _T) | ((environment: Environment, obj: Any, name: str) -> Undefined | Any) | ... omitted 29 union elements`
info: rule `missing-argument` is enabled by default

error[missing-argument]: No argument provided for required parameter `d`
   --> tests/test_extensions.py:146:14
    |
144 |     env = jinja2.Environment(extensions=[ShellExtension], autoescape=True)
145 |     indent = env.filters['shell_indent']
146 |     result = indent('echo hello\necho world')
    |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
147 |     assert result == '    echo hello\n    echo world'
    |
info: Union variant `(eval_ctx: EvalContext, d: Mapping[str, Any], autospace: bool = True) -> str` is incompatible with this call site
info: Attempted to call union type `Unknown | ([_T](x: SupportsAbs[_T], /) -> _T) | ((environment: Environment, obj: Any, name: str) -> Undefined | Any) | ... omitted 29 union elements`
info: rule `missing-argument` is enabled by default

error[missing-argument]: No argument provided for required parameter `value`
   --> tests/test_extensions.py:146:14
    |
144 |     env = jinja2.Environment(extensions=[ShellExtension], autoescape=True)
145 |     indent = env.filters['shell_indent']
146 |     result = indent('echo hello\necho world')
    |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
147 |     assert result == '    echo hello\n    echo world'
    |
info: Union variant `(eval_ctx: EvalContext, value: Any, indent: int | None = None) -> Markup` is incompatible with this call site
info: Attempted to call union type `Unknown | ([_T](x: SupportsAbs[_T], /) -> _T) | ((environment: Environment, obj: Any, name: str) -> Undefined | Any) | ... omitted 29 union elements`
info: rule `missing-argument` is enabled by default

error[missing-argument]: No arguments provided for required parameters `obj`, `name`
   --> tests/test_extensions.py:146:14
    |
144 |     env = jinja2.Environment(extensions=[ShellExtension], autoescape=True)
145 |     indent = env.filters['shell_indent']
146 |     result = indent('echo hello\necho world')
    |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
147 |     assert result == '    echo hello\n    echo world'
    |
info: Union variant `(environment: Environment, obj: Any, name: str) -> Undefined | Any` is incompatible with this call site
info: Attempted to call union type `Unknown | ([_T](x: SupportsAbs[_T], /) -> _T) | ((environment: Environment, obj: Any, name: str) -> Undefined | Any) | ... omitted 29 union elements`
info: rule `missing-argument` is enabled by default

error[invalid-argument-type]: Argument is incorrect
   --> tests/test_extensions.py:146:21
    |
144 |     env = jinja2.Environment(extensions=[ShellExtension], autoescape=True)
145 |     indent = env.filters['shell_indent']
146 |     result = indent('echo hello\necho world')
    |                     ^^^^^^^^^^^^^^^^^^^^^^^^ Expected `Environment`, found `Literal["echo hello\necho world"]`
147 |     assert result == '    echo hello\n    echo world'
    |
info: Union variant `(environment: Environment, obj: Any, name: str) -> Undefined | Any` is incompatible with this call site
info: Attempted to call union type `Unknown | ([_T](x: SupportsAbs[_T], /) -> _T) | ((environment: Environment, obj: Any, name: str) -> Undefined | Any) | ... omitted 29 union elements`
info: rule `invalid-argument-type` is enabled by default

error[invalid-argument-type]: Argument is incorrect
   --> tests/test_extensions.py:146:21
    |
144 |     env = jinja2.Environment(extensions=[ShellExtension], autoescape=True)
145 |     indent = env.filters['shell_indent']
146 |     result = indent('echo hello\necho world')
    |                     ^^^^^^^^^^^^^^^^^^^^^^^^ Expected `Mapping[Unknown, Unknown]`, found `Literal["echo hello\necho world"]`
147 |     assert result == '    echo hello\n    echo world'
    |
info: Union variant `[K, V](value: Mapping[K, V], case_sensitive: bool = False, by: Literal["key", "value"] = "key", reverse: bool = False) -> list[tuple[K, V]]` is incompatible with this call site
info: Attempted to call union type `Unknown | ([_T](x: SupportsAbs[_T], /) -> _T) | ((environment: Environment, obj: Any, name: str) -> Undefined | Any) | ... omitted 29 union elements`
info: rule `invalid-argument-type` is enabled by default

error[invalid-argument-type]: Argument is incorrect
   --> tests/test_extensions.py:146:21
    |
144 |     env = jinja2.Environment(extensions=[ShellExtension], autoescape=True)
145 |     indent = env.filters['shell_indent']
146 |     result = indent('echo hello\necho world')
    |                     ^^^^^^^^^^^^^^^^^^^^^^^^ Expected `Environment`, found `Literal["echo hello\necho world"]`
147 |     assert result == '    echo hello\n    echo world'
    |
info: Union variant `[V](environment: Environment, seq: Reversible[V]) -> V | Undefined` is incompatible with this call site
info: Attempted to call union type `Unknown | ([_T](x: SupportsAbs[_T], /) -> _T) | ((environment: Environment, obj: Any, name: str) -> Undefined | Any) | ... omitted 29 union elements`
info: rule `invalid-argument-type` is enabled by default

error[invalid-argument-type]: Argument is incorrect
   --> tests/test_extensions.py:146:21
    |
144 |     env = jinja2.Environment(extensions=[ShellExtension], autoescape=True)
145 |     indent = env.filters['shell_indent']
146 |     result = indent('echo hello\necho world')
    |                     ^^^^^^^^^^^^^^^^^^^^^^^^ Expected `Mapping[Unknown, Unknown] | Undefined`, found `Literal["echo hello\necho world"]`
147 |     assert result == '    echo hello\n    echo world'
    |
info: Union variant `[K, V](value: Mapping[K, V] | Undefined) -> Iterator[tuple[K, V]]` is incompatible with this call site
info: Attempted to call union type `Unknown | ([_T](x: SupportsAbs[_T], /) -> _T) | ((environment: Environment, obj: Any, name: str) -> Undefined | Any) | ... omitted 29 union elements`
info: rule `invalid-argument-type` is enabled by default

error[invalid-argument-type]: Argument is incorrect
   --> tests/test_extensions.py:146:21
    |
144 |     env = jinja2.Environment(extensions=[ShellExtension], autoescape=True)
145 |     indent = env.filters['shell_indent']
146 |     result = indent('echo hello\necho world')
    |                     ^^^^^^^^^^^^^^^^^^^^^^^^ Expected `Environment`, found `Literal["echo hello\necho world"]`
147 |     assert result == '    echo hello\n    echo world'
    |
info: Union variant `[V](environment: Environment, value: Iterable[V], case_sensitive: bool = False, attribute: str | int | None = None) -> V | Undefined` is incompatible with this call site
info: Attempted to call union type `Unknown | ([_T](x: SupportsAbs[_T], /) -> _T) | ((environment: Environment, obj: Any, name: str) -> Undefined | Any) | ... omitted 29 union elements`
info: rule `invalid-argument-type` is enabled by default

error[invalid-argument-type]: Argument is incorrect
   --> tests/test_extensions.py:146:21
    |
144 |     env = jinja2.Environment(extensions=[ShellExtension], autoescape=True)
145 |     indent = env.filters['shell_indent']
146 |     result = indent('echo hello\necho world')
    |                     ^^^^^^^^^^^^^^^^^^^^^^^^ Expected `Environment`, found `Literal["echo hello\necho world"]`
147 |     assert result == '    echo hello\n    echo world'
    |
info: Union variant `[V](environment: Environment, value: Iterable[V], reverse: bool = False, case_sensitive: bool = False, attribute: str | int | None = None) -> list[V]` is incompatible with this call site
info: Attempted to call union type `Unknown | ([_T](x: SupportsAbs[_T], /) -> _T) | ((environment: Environment, obj: Any, name: str) -> Undefined | Any) | ... omitted 29 union elements`
info: rule `invalid-argument-type` is enabled by default

error[invalid-argument-type]: Argument is incorrect
   --> tests/test_extensions.py:146:21
    |
144 |     env = jinja2.Environment(extensions=[ShellExtension], autoescape=True)
145 |     indent = env.filters['shell_indent']
146 |     result = indent('echo hello\necho world')
    |                     ^^^^^^^^^^^^^^^^^^^^^^^^ Expected `Context`, found `Literal["echo hello\necho world"]`
147 |     assert result == '    echo hello\n    echo world'
    |
info: Union variant `[V](context: Context, seq: Sequence[V]) -> V | Undefined` is incompatible with this call site
info: Attempted to call union type `Unknown | ([_T](x: SupportsAbs[_T], /) -> _T) | ((environment: Environment, obj: Any, name: str) -> Undefined | Any) | ... omitted 29 union elements`
info: rule `invalid-argument-type` is enabled by default

error[invalid-argument-type]: Argument is incorrect
   --> tests/test_extensions.py:146:21
    |
144 |     env = jinja2.Environment(extensions=[ShellExtension], autoescape=True)
145 |     indent = env.filters['shell_indent']
146 |     result = indent('echo hello\necho world')
    |                     ^^^^^^^^^^^^^^^^^^^^^^^^ Expected `EvalContext`, found `Literal["echo hello\necho world"]`
147 |     assert result == '    echo hello\n    echo world'
    |
info: Union variant `(eval_ctx: EvalContext, s: str, old: str, new: str, count: int | None = None) -> str` is incompatible with this call site
info: Attempted to call union type `Unknown | ([_T](x: SupportsAbs[_T], /) -> _T) | ((environment: Environment, obj: Any, name: str) -> Undefined | Any) | ... omitted 29 union elements`
info: rule `invalid-argument-type` is enabled by default

error[invalid-argument-type]: Argument is incorrect
   --> tests/test_extensions.py:146:21
    |
144 |     env = jinja2.Environment(extensions=[ShellExtension], autoescape=True)
145 |     indent = env.filters['shell_indent']
146 |     result = indent('echo hello\necho world')
    |                     ^^^^^^^^^^^^^^^^^^^^^^^^ Expected `int | float`, found `Literal["echo hello\necho world"]`
147 |     assert result == '    echo hello\n    echo world'
    |
info: Union variant `(value: int | float, precision: int = 0, method: Literal["common", "ceil", "floor"] = "common") -> int | float` is incompatible with this call site
info: Attempted to call union type `Unknown | ([_T](x: SupportsAbs[_T], /) -> _T) | ((environment: Environment, obj: Any, name: str) -> Undefined | Any) | ... omitted 29 union elements`
info: rule `invalid-argument-type` is enabled by default

error[invalid-argument-type]: Argument is incorrect
   --> tests/test_extensions.py:146:21
    |
144 |     env = jinja2.Environment(extensions=[ShellExtension], autoescape=True)
145 |     indent = env.filters['shell_indent']
146 |     result = indent('echo hello\necho world')
    |                     ^^^^^^^^^^^^^^^^^^^^^^^^ Expected `Environment`, found `Literal["echo hello\necho world"]`
147 |     assert result == '    echo hello\n    echo world'
    |
info: Union variant `(env: Environment, s: str, length: int = 255, killwords: bool = False, end: str = "...", leeway: int | None = None) -> str` is incompatible with this call site
info: Attempted to call union type `Unknown | ([_T](x: SupportsAbs[_T], /) -> _T) | ((environment: Environment, obj: Any, name: str) -> Undefined | Any) | ... omitted 29 union elements`
info: rule `invalid-argument-type` is enabled by default

error[invalid-argument-type]: Argument is incorrect
   --> tests/test_extensions.py:146:21
    |
144 |     env = jinja2.Environment(extensions=[ShellExtension], autoescape=True)
145 |     indent = env.filters['shell_indent']
146 |     result = indent('echo hello\necho world')
    |                     ^^^^^^^^^^^^^^^^^^^^^^^^ Expected `EvalContext`, found `Literal["echo hello\necho world"]`
147 |     assert result == '    echo hello\n    echo world'
    |
info: Union variant `(eval_ctx: EvalContext, value: str, trim_url_limit: int | None = None, nofollow: bool = False, target: str | None = None, rel: str | None = None, extra_schemes: Iterable[str] | None = None) -> str` is incompatible with this call site
info: Attempted to call union type `Unknown | ([_T](x: SupportsAbs[_T], /) -> _T) | ((environment: Environment, obj: Any, name: str) -> Undefined | Any) | ... omitted 29 union elements`
info: rule `invalid-argument-type` is enabled by default

error[invalid-argument-type]: Argument is incorrect
   --> tests/test_extensions.py:146:21
    |
144 |     env = jinja2.Environment(extensions=[ShellExtension], autoescape=True)
145 |     indent = env.filters['shell_indent']
146 |     result = indent('echo hello\necho world')
    |                     ^^^^^^^^^^^^^^^^^^^^^^^^ Expected `Environment`, found `Literal["echo hello\necho world"]`
147 |     assert result == '    echo hello\n    echo world'
    |
info: Union variant `(environment: Environment, s: str, width: int = 79, break_long_words: bool = True, wrapstring: str | None = None, break_on_hyphens: bool = True) -> str` is incompatible with this call site
info: Attempted to call union type `Unknown | ([_T](x: SupportsAbs[_T], /) -> _T) | ((environment: Environment, obj: Any, name: str) -> Undefined | Any) | ... omitted 29 union elements`
info: rule `invalid-argument-type` is enabled by default

error[invalid-argument-type]: Argument is incorrect
   --> tests/test_extensions.py:146:21
    |
144 |     env = jinja2.Environment(extensions=[ShellExtension], autoescape=True)
145 |     indent = env.filters['shell_indent']
146 |     result = indent('echo hello\necho world')
    |                     ^^^^^^^^^^^^^^^^^^^^^^^^ Expected `EvalContext`, found `Literal["echo hello\necho world"]`
147 |     assert result == '    echo hello\n    echo world'
    |
info: Union variant `(eval_ctx: EvalContext, d: Mapping[str, Any], autospace: bool = True) -> str` is incompatible with this call site
info: Attempted to call union type `Unknown | ([_T](x: SupportsAbs[_T], /) -> _T) | ((environment: Environment, obj: Any, name: str) -> Undefined | Any) | ... omitted 29 union elements`
info: rule `invalid-argument-type` is enabled by default

error[invalid-argument-type]: Argument is incorrect
   --> tests/test_extensions.py:146:21
    |
144 |     env = jinja2.Environment(extensions=[ShellExtension], autoescape=True)
145 |     indent = env.filters['shell_indent']
146 |     result = indent('echo hello\necho world')
    |                     ^^^^^^^^^^^^^^^^^^^^^^^^ Expected `EvalContext`, found `Literal["echo hello\necho world"]`
147 |     assert result == '    echo hello\n    echo world'
    |
info: Union variant `(eval_ctx: EvalContext, value: Any, indent: int | None = None) -> Markup` is incompatible with this call site
info: Attempted to call union type `Unknown | ([_T](x: SupportsAbs[_T], /) -> _T) | ((environment: Environment, obj: Any, name: str) -> Undefined | Any) | ... omitted 29 union elements`
info: rule `invalid-argument-type` is enabled by default

error[invalid-argument-type]: Argument is incorrect
   --> tests/test_extensions.py:146:21
    |
144 |     env = jinja2.Environment(extensions=[ShellExtension], autoescape=True)
145 |     indent = env.filters['shell_indent']
146 |     result = indent('echo hello\necho world')
    |                     ^^^^^^^^^^^^^^^^^^^^^^^^ Expected `SupportsAbs[Unknown]`, found `Literal["echo hello\necho world"]`
147 |     assert result == '    echo hello\n    echo world'
    |
info: Union variant `[_T](x: SupportsAbs[_T], /) -> _T` is incompatible with this call site
info: Attempted to call union type `Unknown | ([_T](x: SupportsAbs[_T], /) -> _T) | ((environment: Environment, obj: Any, name: str) -> Undefined | Any) | ... omitted 29 union elements`
info: rule `invalid-argument-type` is enabled by default

Version

ty 0.0.29

[sharkdp]

Thank you for reporting this.

Environment.filters is defined as DEFAULT_FILTERS.copy() here, and DEFAULT_FILTERS eventually refers to this large dict definition:

https://github.com/pallets/jinja/blob/5ef70112a1ff19c05324ff889dd30405b1002044/src/jinja2/filters.py#L1812-L1867

This is why ty infers env.filters as Unknown | dict[str, <large union of precise callable types>] for env.filters. This is not wrong, but obviously not very helpful either.

I'm not sure how to best solve this though. Ideally, jinja's Environment.filters would be annotated with something like dict[str, Callable].

I guess we could consider collapsing large unions like this to a common supertype, if they are used as the argument of an invariant generic type parameter, but I'm not sure if that's feasible. I'm not sure why mypy and pyright fall back to dict[str, Any] / dict[str, Unknown] for jinja2.filters.FILTERS.

At the very least, we should probably make sure that we do not emit 27 diagnostics on the same function call, that is ridiculous.

FWIW, pyrefly does the same as ty here (except that it emits 33 diagnostics. I have not investigated more closely what the difference is, though 😄).

[Tatsh]

I think mypy just assumes dictionaries are always homogeneous when they don't have a hint like in the case of Jinja2. It deduces Any instead of trying to build out a union, probably for performance reasons at least. This makes ty and pyrefly a lot more advanced than Mypy for this.