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ruff/crates/ty_python_semantic/resources/mdtest/expression/attribute.md
Alex Waygood 1f8297cfe6
[ty] Improve error messages for unresolved attribute diagnostics (#20963) 
## Summary

- Type checkers (and type-checker authors) think in terms of types, but
I think most Python users think in terms of values. Rather than saying
that a _type_ `X` "has no attribute `foo`" (which I think sounds strange
to many users), say that "an object of type `X` has no attribute `foo`"
- Special-case certain types so that the diagnostic messages read more
like normal English: rather than saying "Type `<class 'Foo'>` has no
attribute `bar`" or "Object of type `<class 'Foo'>` has no attribute
`bar`", just say "Class `Foo` has no attribute `bar`"

## Test Plan

Mdtests and snapshots updated
2025-10-19 10:58:25 +01:00

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Attribute access

Boundness

def _(flag: bool):
    class A:
        always_bound: int = 1

        if flag:
            union = 1
        else:
            union = "abc"

        if flag:
            union_declared: int = 1
        else:
            union_declared: str = "abc"

        if flag:
            possibly_unbound: str = "abc"

    reveal_type(A.always_bound)  # revealed: int

    reveal_type(A.union)  # revealed: Unknown | Literal[1, "abc"]

    reveal_type(A.union_declared)  # revealed: int | str

    # error: [possibly-missing-attribute] "Attribute `possibly_unbound` may be missing on class `A`"
    reveal_type(A.possibly_unbound)  # revealed: str

    # error: [unresolved-attribute] "Class `A` has no attribute `non_existent`"
    reveal_type(A.non_existent)  # revealed: Unknown