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[red-knot] Use Unknown | T_inferred for undeclared public symbols #15674

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Jan 24, 2025
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[red-knot] Use Unknown | T_inferred for undeclared public symbols #15674

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f7f3d92
[red-knot] Use `Unknown | T_inferred` for undeclared public symbols
sharkdp Jan 22, 2025
9bf84e5
Extend description
sharkdp Jan 23, 2025
7a035b7
Adapt 'Public type' table
sharkdp Jan 23, 2025
5bf3c9b
Use helper to apply the same restrictions to instance_member
sharkdp Jan 23, 2025
49bcf53
Add TODO comment
sharkdp Jan 23, 2025
f29add5
Minor change in imports
sharkdp Jan 23, 2025
36b3af6
Add new test for '__slots__' modifications
sharkdp Jan 23, 2025
f4ca4b8
Union with Unknown for *possibly* undeclared types
sharkdp Jan 23, 2025
a1c5647
Revert change in symbol.rs
sharkdp Jan 23, 2025
1a1e08a
Revert possibly-undeclared changes
sharkdp Jan 24, 2025
edb295e
Add tests for modifications of external symbols
sharkdp Jan 24, 2025
96e8ae9
Add TODO
sharkdp Jan 24, 2025
f10e976
Clarifying comments
sharkdp Jan 24, 2025
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2 changes: 1 addition & 1 deletion crates/red_knot_python_semantic/resources/mdtest/annotations/literal.md
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Expand Up @@ -36,7 +36,7 @@ def f():
reveal_type(a7) # revealed: None
reveal_type(a8) # revealed: Literal[1]
# TODO: This should be Color.RED
reveal_type(b1) # revealed: Literal[0]
reveal_type(b1) # revealed: Unknown | Literal[0]

# error: [invalid-type-form]
invalid1: Literal[3 + 4]
Expand Down
17 changes: 8 additions & 9 deletions crates/red_knot_python_semantic/resources/mdtest/attributes.md
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Expand Up @@ -175,7 +175,7 @@ class C:

reveal_type(C.pure_class_variable1) # revealed: str

# TODO: this should be `Literal[1]`, or `Unknown | Literal[1]`.
# TODO: Should be `Unknown | Literal[1]`.
reveal_type(C.pure_class_variable2) # revealed: Unknown

c_instance = C()
Expand Down Expand Up @@ -252,8 +252,7 @@ class C:

reveal_type(C.variable_with_class_default1) # revealed: str

# TODO: this should be `Unknown | Literal[1]`.
reveal_type(C.variable_with_class_default2) # revealed: Literal[1]
reveal_type(C.variable_with_class_default2) # revealed: Unknown | Literal[1]

c_instance = C()

Expand Down Expand Up @@ -296,8 +295,8 @@ def _(flag: bool):
else:
x = 4

reveal_type(C1.x) # revealed: Literal[1, 2]
reveal_type(C2.x) # revealed: Literal[3, 4]
reveal_type(C1.x) # revealed: Unknown | Literal[1, 2]
reveal_type(C2.x) # revealed: Unknown | Literal[3, 4]
```

## Inherited class attributes
Expand All @@ -311,7 +310,7 @@ class A:
class B(A): ...
class C(B): ...

reveal_type(C.X) # revealed: Literal["foo"]
reveal_type(C.X) # revealed: Unknown | Literal["foo"]
```

### Multiple inheritance
Expand All @@ -334,7 +333,7 @@ class A(B, C): ...
reveal_type(A.__mro__)

# `E` is earlier in the MRO than `F`, so we should use the type of `E.X`
reveal_type(A.X) # revealed: Literal[42]
reveal_type(A.X) # revealed: Unknown | Literal[42]
```

## Unions with possibly unbound paths
Expand All @@ -356,7 +355,7 @@ def _(flag1: bool, flag2: bool):
C = C1 if flag1 else C2 if flag2 else C3

# error: [possibly-unbound-attribute] "Attribute `x` on type `Literal[C1, C2, C3]` is possibly unbound"
reveal_type(C.x) # revealed: Literal[1, 3]
reveal_type(C.x) # revealed: Unknown | Literal[1, 3]
```

### Possibly-unbound within a class
Expand All @@ -379,7 +378,7 @@ def _(flag: bool, flag1: bool, flag2: bool):
C = C1 if flag1 else C2 if flag2 else C3

# error: [possibly-unbound-attribute] "Attribute `x` on type `Literal[C1, C2, C3]` is possibly unbound"
reveal_type(C.x) # revealed: Literal[1, 2, 3]
reveal_type(C.x) # revealed: Unknown | Literal[1, 2, 3]
```

### Unions with all paths unbound
Expand Down
3 changes: 2 additions & 1 deletion crates/red_knot_python_semantic/resources/mdtest/binary/instances.md
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Expand Up @@ -262,7 +262,8 @@ class A:
class B:
__add__ = A()

reveal_type(B() + B()) # revealed: int
# TODO: this could be `int` if we declare `B.__add__` using a `Callable` type
reveal_type(B() + B()) # revealed: Unknown | int
```

## Integration test: numbers from typeshed
Expand Down
19 changes: 11 additions & 8 deletions crates/red_knot_python_semantic/resources/mdtest/boundness_declaredness/public.md
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Expand Up @@ -12,11 +12,11 @@ this behavior is questionable and might change in the future. See the TODOs in `
In particular, we should raise errors in the "possibly-undeclared-and-unbound" as well as the
"undeclared-and-possibly-unbound" cases (marked with a "?").

| **Public type** | declared | possibly-undeclared | undeclared |
| ---------------- | ------------ | -------------------------- | ------------ |
| bound | `T_declared` | `T_declared \| T_inferred` | `T_inferred` |
| possibly-unbound | `T_declared` | `T_declared \| T_inferred` | `T_inferred` |
| unbound | `T_declared` | `T_declared` | `Unknown` |
| **Public type** | declared | possibly-undeclared | undeclared |
| ---------------- | ------------ | -------------------------- | ----------------------- |
| bound | `T_declared` | `T_declared \| T_inferred` | `Unknown \| T_inferred` |
| possibly-unbound | `T_declared` | `T_declared \| T_inferred` | `Unknown \| T_inferred` |
| unbound | `T_declared` | `T_declared` | `Unknown` |

| **Diagnostic** | declared | possibly-undeclared | undeclared |
| ---------------- | -------- | ------------------------- | ------------------- |
Expand Down Expand Up @@ -160,7 +160,10 @@ reveal_type(x) # revealed: int

### Undeclared but bound

We use the inferred type as the public type, if a symbol has no declared type.
We use the union of `Unknown` with the inferred type as the public type, if a symbol has no declared
type. If there is no declaration, then the symbol can be reassigned to any type from another scope;
the union with `Unknown` reflects that its type must at least be as large as the type of the
assigned value, but could be arbitrarily larger.

```py path=mod.py
x = 1
Expand All @@ -169,7 +172,7 @@ x = 1
```py
from mod import x

reveal_type(x) # revealed: Literal[1]
reveal_type(x) # revealed: Unknown | Literal[1]
```

### Undeclared and possibly unbound
Expand All @@ -189,7 +192,7 @@ if flag:
# on top of this document.
from mod import x

reveal_type(x) # revealed: Literal[1]
reveal_type(x) # revealed: Unknown | Literal[1]
```

### Undeclared and unbound
Expand Down
2 changes: 1 addition & 1 deletion crates/red_knot_python_semantic/resources/mdtest/call/callable_instance.md
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Expand Up @@ -52,7 +52,7 @@ class NonCallable:
__call__ = 1

a = NonCallable()
# error: "Object of type `NonCallable` is not callable"
# error: "Object of type `Unknown | Literal[1]` is not callable (due to union element `Literal[1]`)"
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Another instance of the callable problem. Notice how the usefulness of the error message degrades.

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Yes, this is really begging for nested diagnostics (so you get both "Object of type NonCallable is not callable" and nested details explaining why.)

We could easily adjust the handling so you still get "Object of type NonCallable is not callable" here, but then you lose the details of which union element failed callability.

Even without nested diagnostics we could still provide all of the information here in a new error, it just requires more and more bespoke error-cases handling in the __call__ lookup code. (We would need to match on the case that callability of __call__ failed due to a union, and then write a new custom error message for that case which mentions both the outer NonCallable type and the details of why its __call__ isn't callable.) Nested diagnostics would just let us handle this kind of situation more generically, with less special casing.

cc @BurntSushi @MichaReiser re diagnostics considerations

reveal_type(a()) # revealed: Unknown
```

Expand Down
6 changes: 4 additions & 2 deletions crates/red_knot_python_semantic/resources/mdtest/comprehensions/basic.md
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Expand Up @@ -43,7 +43,8 @@ class IntIterable:
def __iter__(self) -> IntIterator:
return IntIterator()

# revealed: tuple[int, int]
# TODO: This could be a `tuple[int, int]` if we model that `y` can not be modified in the outer comprehension scope
# revealed: tuple[int, Unknown | int]
[[reveal_type((x, y)) for x in IntIterable()] for y in IntIterable()]
```

Expand All @@ -66,7 +67,8 @@ class IterableOfIterables:
def __iter__(self) -> IteratorOfIterables:
return IteratorOfIterables()

# revealed: tuple[int, IntIterable]
# TODO: This could be a `tuple[int, int]` (see above)
# revealed: tuple[int, Unknown | IntIterable]
[[reveal_type((x, y)) for x in y] for y in IterableOfIterables()]
```

Expand Down
17 changes: 12 additions & 5 deletions crates/red_knot_python_semantic/resources/mdtest/expression/attribute.md
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Expand Up @@ -5,22 +5,29 @@
```py
def _(flag: bool):
class A:
always_bound = 1
always_bound: int = 1

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

if flag:
possibly_unbound = "abc"
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.always_bound) # revealed: Literal[1]
reveal_type(A.union) # revealed: Unknown | Literal[1, "abc"]

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

# error: [possibly-unbound-attribute] "Attribute `possibly_unbound` on type `Literal[A]` is possibly unbound"
reveal_type(A.possibly_unbound) # revealed: Literal["abc"]
reveal_type(A.possibly_unbound) # revealed: str

# error: [unresolved-attribute] "Type `Literal[A]` has no attribute `non_existent`"
reveal_type(A.non_existent) # revealed: Unknown
Expand Down
2 changes: 1 addition & 1 deletion crates/red_knot_python_semantic/resources/mdtest/expression/boolean.md
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Expand Up @@ -55,7 +55,7 @@ reveal_type("x" or "y" and "") # revealed: Literal["x"]
## Evaluates to builtin

```py path=a.py
redefined_builtin_bool = bool
redefined_builtin_bool: type[bool] = bool

def my_bool(x) -> bool:
return True
Expand Down
4 changes: 2 additions & 2 deletions crates/red_knot_python_semantic/resources/mdtest/expression/len.md
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Expand Up @@ -172,10 +172,10 @@ class IntUnion:
def __len__(self) -> Literal[SomeEnum.INT, SomeEnum.INT_2]: ...

reveal_type(len(Auto())) # revealed: int
reveal_type(len(Int())) # revealed: Literal[2]
reveal_type(len(Int())) # revealed: int
reveal_type(len(Str())) # revealed: int
reveal_type(len(Tuple())) # revealed: int
reveal_type(len(IntUnion())) # revealed: Literal[2, 32]
reveal_type(len(IntUnion())) # revealed: int
```

### Negative integers
Expand Down
2 changes: 1 addition & 1 deletion crates/red_knot_python_semantic/resources/mdtest/generics.md
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Expand Up @@ -20,7 +20,7 @@ wrong_innards: MyBox[int] = MyBox("five")
# TODO reveal int, do not leak the typevar
reveal_type(box.data) # revealed: T

reveal_type(MyBox.box_model_number) # revealed: Literal[695]
reveal_type(MyBox.box_model_number) # revealed: Unknown | Literal[695]
```

## Subclassing
Expand Down
6 changes: 3 additions & 3 deletions crates/red_knot_python_semantic/resources/mdtest/import/conditional.md
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Expand Up @@ -23,8 +23,8 @@ reveal_type(y)
# error: [possibly-unbound-import] "Member `y` of module `maybe_unbound` is possibly unbound"
from maybe_unbound import x, y

reveal_type(x) # revealed: Literal[3]
reveal_type(y) # revealed: Literal[3]
reveal_type(x) # revealed: Unknown | Literal[3]
reveal_type(y) # revealed: Unknown | Literal[3]
```

## Maybe unbound annotated
Expand Down Expand Up @@ -52,7 +52,7 @@ Importing an annotated name prefers the declared type over the inferred type:
# error: [possibly-unbound-import] "Member `y` of module `maybe_unbound_annotated` is possibly unbound"
from maybe_unbound_annotated import x, y

reveal_type(x) # revealed: Literal[3]
reveal_type(x) # revealed: Unknown | Literal[3]
reveal_type(y) # revealed: int
```

Expand Down
6 changes: 3 additions & 3 deletions crates/red_knot_python_semantic/resources/mdtest/loops/for.md
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Expand Up @@ -109,9 +109,9 @@ reveal_type(x)
def _(flag: bool):
class NotIterable:
if flag:
__iter__ = 1
__iter__: int = 1
else:
__iter__ = None
__iter__: None = None

for x in NotIterable(): # error: "Object of type `NotIterable` is not iterable"
pass
Expand All @@ -135,7 +135,7 @@ for x in nonsense: # error: "Object of type `Literal[123]` is not iterable"
class NotIterable:
def __getitem__(self, key: int) -> int:
return 42
__iter__ = None
__iter__: None = None

for x in NotIterable(): # error: "Object of type `NotIterable` is not iterable"
pass
Expand Down
4 changes: 2 additions & 2 deletions crates/red_knot_python_semantic/resources/mdtest/narrow/type.md
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Expand Up @@ -99,9 +99,9 @@ def _(x: str | int):
class A: ...
class B: ...

alias_for_type = type

def _(x: A | B):
alias_for_type = type

if alias_for_type(x) is A:
reveal_type(x) # revealed: A
```
Expand Down
10 changes: 5 additions & 5 deletions crates/red_knot_python_semantic/resources/mdtest/scopes/nonlocal.md
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Expand Up @@ -6,7 +6,7 @@
def f():
x = 1
def g():
reveal_type(x) # revealed: Literal[1]
reveal_type(x) # revealed: Unknown | Literal[1]
```

## Two levels up
Expand All @@ -16,7 +16,7 @@ def f():
x = 1
def g():
def h():
reveal_type(x) # revealed: Literal[1]
reveal_type(x) # revealed: Unknown | Literal[1]
```

## Skips class scope
Expand All @@ -28,7 +28,7 @@ def f():
class C:
x = 2
def g():
reveal_type(x) # revealed: Literal[1]
reveal_type(x) # revealed: Unknown | Literal[1]
```

## Skips annotation-only assignment
Expand All @@ -41,7 +41,7 @@ def f():
# name is otherwise not defined; maybe should be an error?
x: int
def h():
reveal_type(x) # revealed: Literal[1]
reveal_type(x) # revealed: Unknown | Literal[1]
```

## Implicit global in function
Expand All @@ -52,5 +52,5 @@ A name reference to a never-defined symbol in a function is implicitly a global
x = 1

def f():
reveal_type(x) # revealed: Literal[1]
reveal_type(x) # revealed: Unknown | Literal[1]
```
6 changes: 3 additions & 3 deletions crates/red_knot_python_semantic/resources/mdtest/scopes/unbound.md
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Expand Up @@ -17,8 +17,8 @@ class C:
x = 2

# error: [possibly-unbound-attribute] "Attribute `x` on type `Literal[C]` is possibly unbound"
reveal_type(C.x) # revealed: Literal[2]
reveal_type(C.y) # revealed: Literal[1]
reveal_type(C.x) # revealed: Unknown | Literal[2]
reveal_type(C.y) # revealed: Unknown | Literal[1]
```

## Possibly unbound in class and global scope
Expand All @@ -37,7 +37,7 @@ class C:
# error: [possibly-unresolved-reference]
y = x

reveal_type(C.y) # revealed: Literal[1, "abc"]
reveal_type(C.y) # revealed: Unknown | Literal[1, "abc"]
```

## Unbound function local
Expand Down
3 changes: 2 additions & 1 deletion crates/red_knot_python_semantic/resources/mdtest/subscript/instance.md
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Expand Up @@ -14,7 +14,8 @@ a = NotSubscriptable()[0] # error: "Cannot subscript object of type `NotSubscri
class NotSubscriptable:
__getitem__ = None

a = NotSubscriptable()[0] # error: "Method `__getitem__` of type `None` is not callable on object of type `NotSubscriptable`"
# error: "Method `__getitem__` of type `Unknown | None` is not callable on object of type `NotSubscriptable`"
a = NotSubscriptable()[0]
```

## Valid getitem
Expand Down
2 changes: 1 addition & 1 deletion crates/red_knot_python_semantic/resources/mdtest/unary/not.md
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Expand Up @@ -139,7 +139,7 @@ reveal_type(not AlwaysFalse())

# We don't get into a cycle if someone sets their `__bool__` method to the `bool` builtin:
class BoolIsBool:
__bool__ = bool
__bool__: type[bool] = bool

# revealed: bool
reveal_type(not BoolIsBool())
Expand Down
8 changes: 4 additions & 4 deletions crates/red_knot_python_semantic/resources/mdtest/with/sync.md
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Expand Up @@ -76,11 +76,11 @@ with Manager():

```py
class Manager:
__enter__ = 42
__enter__: int = 42

def __exit__(self, exc_tpe, exc_value, traceback): ...

# error: [invalid-context-manager] "Object of type `Manager` cannot be used with `with` because the method `__enter__` of type `Literal[42]` is not callable"
# error: [invalid-context-manager] "Object of type `Manager` cannot be used with `with` because the method `__enter__` of type `int` is not callable"
with Manager():
...
```
Expand All @@ -91,9 +91,9 @@ with Manager():
class Manager:
def __enter__(self) -> Self: ...

__exit__ = 32
__exit__: int = 32

# error: [invalid-context-manager] "Object of type `Manager` cannot be used with `with` because the method `__exit__` of type `Literal[32]` is not callable"
# error: [invalid-context-manager] "Object of type `Manager` cannot be used with `with` because the method `__exit__` of type `int` is not callable"
with Manager():
...
```
Expand Down
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