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[ty] Treat lambda functions as instances of types.FunctionType (#18431)

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lipefree 2025-06-02 17:46:26 +02:00 • committed by GitHub
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19
crates/ty_python_semantic/resources/mdtest/expression/lambda.md
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@ -115,3 +115,22 @@ a5: Callable[[], None] = lambda x: None
# error: [invalid-assignment] # error: [invalid-assignment]
a6: Callable[[int], None] = lambda: None a6: Callable[[int], None] = lambda: None
``` ```
## Function-like behavior of lambdas
All `lambda` functions are instances of `types.FunctionType` and should have access to the same set
of attributes.
```py
x = lambda y: y
reveal_type(x.__code__) # revealed: CodeType
reveal_type(x.__name__) # revealed: str
reveal_type(x.__defaults__) # revealed: tuple[Any, ...] | None
reveal_type(x.__annotations__) # revealed: dict[str, @Todo(Support for `typing.TypeAlias`)]
reveal_type(x.__dict__) # revealed: dict[str, Any]
reveal_type(x.__doc__) # revealed: str | None
reveal_type(x.__kwdefaults__) # revealed: dict[str, Any] | None
reveal_type(x.__module__) # revealed: str
reveal_type(x.__qualname__) # revealed: str
```

2
crates/ty_python_semantic/src/types/infer.rs
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@ -4956,7 +4956,7 @@ impl<'db> TypeInferenceBuilder<'db> {
// TODO: Useful inference of a lambda's return type will require a different approach, // TODO: Useful inference of a lambda's return type will require a different approach,
// which does the inference of the body expression based on arguments at each call site, // which does the inference of the body expression based on arguments at each call site,
// rather than eagerly computing a return type without knowing the argument types. // rather than eagerly computing a return type without knowing the argument types.
CallableType::single(self.db(), Signature::new(parameters, Some(Type::unknown()))) CallableType::function_like(self.db(), Signature::new(parameters, Some(Type::unknown())))
} }
/// Returns the type of the first parameter if the given scope is function-like (i.e. function or lambda). /// Returns the type of the first parameter if the given scope is function-like (i.e. function or lambda).