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[red-knot] Instance attributes: type inference clarifications (#15512)

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## Summary

Some clarifications in the instance-attributes tests, mostly regarding
type inference behavior following this discussion:

https://github.com/astral-sh/ruff/pull/15474#discussion_r1917044566
This commit is contained in:
David Peter
2025-01-15 21:17:55 +01:00
committed by GitHub
parent 49557a9129
commit c034e280a9
1 changed files with 25 additions and 16 deletions
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41
crates/red_knot_python_semantic/resources/mdtest/attributes.md
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@@ -32,7 +32,8 @@ class C:
c_instance = C(1)
# TODO: should be `Literal["value set in __init__"]` (or `str` which would probably be more generally useful)
# TODO: should be `Literal["value set in __init__"]`, or `Unknown | Literal[…]` to allow
# assignments to this unannotated attribute from other scopes.
reveal_type(c_instance.pure_instance_variable1) # revealed: @Todo(instance attributes)
# TODO: should be `int`
@@ -41,14 +42,17 @@ reveal_type(c_instance.pure_instance_variable2) # revealed: @Todo(instance attr
# TODO: should be `bytes`
reveal_type(c_instance.pure_instance_variable3) # revealed: @Todo(instance attributes)
# TODO: should be `Literal[True]` (or `bool`)
# TODO: should be `bool`
reveal_type(c_instance.pure_instance_variable4) # revealed: @Todo(instance attributes)
# TODO: should be `Literal["possibly set in __init__"]` (or `str`)
# TODO: should be `str`
# We probably don't want to emit a diagnostic for this being possibly undeclared/unbound.
# mypy and pyright do not show an error here.
reveal_type(c_instance.pure_instance_variable5) # revealed: @Todo(instance attributes)
# TODO: If we choose to infer a precise `Literal[…]` type for the instance attribute (see
# above), this should be an error: incompatible types in assignment. If we choose to infer
# a gradual `Unknown | Literal[…]` type, this assignment is fine.
c_instance.pure_instance_variable1 = "value set on instance"
# TODO: this should be an error (incompatible types in assignment)
@@ -63,9 +67,14 @@ reveal_type(C.pure_instance_variable1) # revealed: Unknown
# mypy shows no error here, but pyright raises "reportAttributeAccessIssue"
C.pure_instance_variable1 = "overwritten on class"
# TODO: should ideally be `Literal["value set on instance"]`
# (due to earlier assignment of the attribute from the global scope)
reveal_type(c_instance.pure_instance_variable1) # revealed: @Todo(instance attributes)
c_instance.pure_instance_variable4 = False
# TODO: After this assignment to the attribute within this scope, we may eventually want to narrow
# the `bool` type (see above) for this instance variable to `Literal[False]` here. This is unsound
# in general (we don't know what else happened to `c_instance` between the assignment and the use
# here), but mypy and pyright support this. In conclusion, this could be `bool` but should probably
# be `Literal[False]`.
reveal_type(c_instance.pure_instance_variable4) # revealed: @Todo(instance attributes)
```
#### Variable declared in class body and declared/bound in `__init__`
@@ -109,10 +118,11 @@ class C:
c_instance = C()
# for a more realistic example, let's actually call the method
# Not that we would use this in static analysis, but for a more realistic example, let's actually
# call the method, so that the attribute is bound if this example is actually run.
c_instance.set_instance_variable()
# TODO: should be `Literal["value set in method"]` or `str`
# TODO: should be `Literal["value set in method"]` or `Unknown | Literal[…]` (see above).
reveal_type(c_instance.pure_instance_variable) # revealed: @Todo(instance attributes)
# TODO: We already show an error here, but the message might be improved?
@@ -163,7 +173,7 @@ class C:
reveal_type(C.pure_class_variable1) # revealed: str
# TODO: this should be `Literal[1]`, `int`, or maybe `Unknown | Literal[1]` / `Unknown | int`
# TODO: this should be `Literal[1]`, or `Unknown | Literal[1]`.
reveal_type(C.pure_class_variable2) # revealed: @Todo(Unsupported or invalid type in a type expression)
c_instance = C()
@@ -176,9 +186,6 @@ c_instance.pure_class_variable1 = "value set on instance"
C.pure_class_variable1 = "overwritten on class"
# TODO: should ideally be `Literal["overwritten on class"]`, but not a priority
reveal_type(C.pure_class_variable1) # revealed: str
# TODO: should raise an error (incompatible types in assignment)
C.pure_class_variable1 = 1
@@ -214,7 +221,7 @@ C.pure_class_variable = "overwritten on class"
reveal_type(C.pure_class_variable) # revealed: Unknown
c_instance = C()
# TODO: should be `Literal["overwritten on class"]` or `str`
# TODO: should be `Literal["overwritten on class"]`
reveal_type(c_instance.pure_class_variable) # revealed: @Todo(instance attributes)
# TODO: should raise an error.
@@ -248,15 +255,17 @@ c_instance.variable_with_class_default = "value set on instance"
reveal_type(C.variable_with_class_default) # revealed: str
# TODO: should ideally be Literal["value set on instance"], or still `str`
# TODO: Could be Literal["value set on instance"], or still `str` if we choose not to
# narrow the type.
reveal_type(c_instance.variable_with_class_default) # revealed: @Todo(instance attributes)
C.variable_with_class_default = "overwritten on class"
# TODO: should ideally be `Literal["overwritten on class"]`
# TODO: Could be `Literal["overwritten on class"]`, or still `str` if we choose not to
# narrow the type.
reveal_type(C.variable_with_class_default) # revealed: str
# TODO: should still be `Literal["value set on instance"]`
# TODO: should still be `Literal["value set on instance"]`, or `str`.
reveal_type(c_instance.variable_with_class_default) # revealed: @Todo(instance attributes)
```