[red-knot] Remove Type::Unbound

crates/red_knot_python_semantic/resources/mdtest/assignment/annotations.md

@@ -33,6 +33,8 @@ b: tuple[int] = (42,)
 c: tuple[str, int] = ("42", 42)
 d: tuple[tuple[str, str], tuple[int, int]] = (("foo", "foo"), (42, 42))
 e: tuple[str, ...] = ()
+# TODO: we should not emit this error
+# error: [call-possibly-unbound-method] "Method `__class_getitem__` of type `Literal[tuple]` is possibly unbound"
 f: tuple[str, *tuple[int, ...], bytes] = ("42", b"42")
 g: tuple[str, Unpack[tuple[int, ...]], bytes] = ("42", b"42")
 h: tuple[list[int], list[int]] = ([], [])

crates/red_knot_python_semantic/resources/mdtest/assignment/augmented.md

@@ -80,9 +80,11 @@ class Foo:
             return 42
 
 f = Foo()
+
+# TODO: We should emit an `unsupported-operator` error here, possibly with the information
+# that `Foo.__iadd__` may be unbound as additional context.
 f += "Hello, world!"
 
-# TODO should emit a diagnostic warning that `Foo` might not have an `__iadd__` method
 reveal_type(f)  # revealed: int
 ```
 

crates/red_knot_python_semantic/resources/mdtest/assignment/unbound.md

@@ -6,11 +6,20 @@
 x = foo  # error: [unresolved-reference] "Name `foo` used when not defined"
 foo = 1
 
-# error: [unresolved-reference]
-# revealed: Unbound
+# No error `unresolved-reference` diagnostic is reported for `x`. This is
+# desirable because we would get a lot of cascading errors even though there
+# is only one root cause (the unbound variable `foo`).
+
+# revealed: Unknown
 reveal_type(x)
 ```
 
+Note: in this particular example, one could argue that the most likely error would
+be a wrong order of the `x`/`foo` definitions, and so it could be desirable to infer
+`Literal[1]` for the type of `x`. On the other hand, there might be a variable `fob`
+a little higher up in this file, and the actual error might have been just a typo.
+Inferring `Unknown` thus seems like the safest option.
+
 ## Unbound class variable
 
 Name lookups within a class scope fall back to globals, but lookups of class attributes don't.
@@ -30,3 +39,22 @@ class C:
 reveal_type(C.x)  # revealed: Literal[2]
 reveal_type(C.y)  # revealed: Literal[1]
 ```
+
+## Possibly unbound in class and global scope
+
+```py
+def bool_instance() -> bool:
+    return True
+
+if bool_instance():
+    x = "abc"
+
+class C:
+    if bool_instance():
+        x = 1
+
+    # error: [possibly-unresolved-reference]
+    y = x
+
+reveal_type(C.y)  # revealed: Literal[1] | Literal["abc"]
+```

crates/red_knot_python_semantic/resources/mdtest/boolean/short_circuit.md

@@ -12,11 +12,11 @@ def bool_instance() -> bool:
 
 if bool_instance() or (x := 1):
     # error: [possibly-unresolved-reference]
-    reveal_type(x)  # revealed: Unbound | Literal[1]
+    reveal_type(x)  # revealed: Literal[1]
 
 if bool_instance() and (x := 1):
     # error: [possibly-unresolved-reference]
-    reveal_type(x)  # revealed: Unbound | Literal[1]
+    reveal_type(x)  # revealed: Literal[1]
 ```
 
 ## First expression is always evaluated
@@ -36,14 +36,14 @@ if (x := 1) and bool_instance():
 
 ```py
 if True or (x := 1):
-    # TODO: infer that the second arm is never executed so type should be just "Unbound".
+    # TODO: infer that the second arm is never executed, and raise `unresolved-reference`.
     # error: [possibly-unresolved-reference]
-    reveal_type(x)  # revealed: Unbound | Literal[1]
+    reveal_type(x)  # revealed: Literal[1]
 
 if True and (x := 1):
-    # TODO: infer that the second arm is always executed so type should be just "Literal[1]".
+    # TODO: infer that the second arm is always executed, do not raise a diagnostic
     # error: [possibly-unresolved-reference]
-    reveal_type(x)  # revealed: Unbound | Literal[1]
+    reveal_type(x)  # revealed: Literal[1]
 ```
 
 ## Later expressions can always use variables from earlier expressions
@@ -55,7 +55,7 @@ def bool_instance() -> bool:
 bool_instance() or (x := 1) or reveal_type(x)  # revealed: Literal[1]
 
 # error: [unresolved-reference]
-bool_instance() or reveal_type(y) or (y := 1)  # revealed: Unbound
+bool_instance() or reveal_type(y) or (y := 1)  # revealed: Unknown
 ```
 
 ## Nested expressions
@@ -65,14 +65,14 @@ def bool_instance() -> bool:
     return True
 
 if bool_instance() or ((x := 1) and bool_instance()):
-    # error: "Name `x` used when possibly not defined"
-    reveal_type(x)  # revealed: Unbound | Literal[1]
+    # error: [possibly-unresolved-reference]
+    reveal_type(x)  # revealed: Literal[1]
 
 if ((y := 1) and bool_instance()) or bool_instance():
     reveal_type(y)  # revealed: Literal[1]
 
 # error: [possibly-unresolved-reference]
-if (bool_instance() and (z := 1)) or reveal_type(z):  # revealed: Unbound | Literal[1]
+if (bool_instance() and (z := 1)) or reveal_type(z):  # revealed: Literal[1]
     # error: [possibly-unresolved-reference]
-    reveal_type(z)  # revealed: Unbound | Literal[1]
+    reveal_type(z)  # revealed: Literal[1]
 ```

crates/red_knot_python_semantic/resources/mdtest/conditional/if_statement.md

@@ -37,11 +37,11 @@ x = y
 
 reveal_type(x)  # revealed: Literal[3, 4, 5]
 
-# revealed: Unbound | Literal[2]
+# revealed: Literal[2]
 # error: [possibly-unresolved-reference]
 reveal_type(r)
 
-# revealed: Unbound | Literal[5]
+# revealed: Literal[5]
 # error: [possibly-unresolved-reference]
 reveal_type(s)
 ```

crates/red_knot_python_semantic/resources/mdtest/conditional/match.md

@@ -21,7 +21,7 @@ match 0:
     case 2:
         y = 3
 
-# revealed: Unbound | Literal[2, 3]
+# revealed: Literal[2, 3]
 # error: [possibly-unresolved-reference]
 reveal_type(y)
 ```

crates/red_knot_python_semantic/resources/mdtest/exception/basic.md

@@ -41,7 +41,12 @@ except EXCEPTIONS as f:
 ## Dynamic exception types
 
 ```py
-def foo(x: type[AttributeError], y: tuple[type[OSError], type[RuntimeError]], z: tuple[type[BaseException], ...]):
+# TODO: we should not emit these `call-possibly-unbound-method` errors for `tuple.__class_getitem__`
+def foo(
+    x: type[AttributeError],
+    y: tuple[type[OSError], type[RuntimeError]],  # error: [call-possibly-unbound-method]
+    z: tuple[type[BaseException], ...],  # error: [call-possibly-unbound-method]
+):
     try:
         help()
     except x as e:

crates/red_knot_python_semantic/resources/mdtest/import/conditional.md

@@ -12,11 +12,10 @@ if flag:
 
 x = y  # error: [possibly-unresolved-reference]
 
-# revealed: Unbound | Literal[3]
-# error: [possibly-unresolved-reference]
+# revealed: Literal[3]
 reveal_type(x)
 
-# revealed: Unbound | Literal[3]
+# revealed: Literal[3]
 # error: [possibly-unresolved-reference]
 reveal_type(y)
 ```
@@ -40,11 +39,10 @@ if flag:
     y: int = 3
 x = y  # error: [possibly-unresolved-reference]
 
-# revealed: Unbound | Literal[3]
-# error: [possibly-unresolved-reference]
+# revealed: Literal[3]
 reveal_type(x)
 
-# revealed: Unbound | Literal[3]
+# revealed: Literal[3]
 # error: [possibly-unresolved-reference]
 reveal_type(y)
 ```
@@ -58,6 +56,24 @@ reveal_type(x)  # revealed: Literal[3]
 reveal_type(y)  # revealed: int
 ```
 
+## Maybe undeclared
+
+Importing a possibly undeclared name still gives us its declared type:
+
+```py path=maybe_undeclared.py
+def bool_instance() -> bool:
+    return True
+
+if bool_instance():
+    x: int
+```
+
+```py
+from maybe_undeclared import x
+
+reveal_type(x)  # revealed: int
+```
+
 ## Reimport
 
 ```py path=c.py

crates/red_knot_python_semantic/resources/mdtest/loops/async_for_loops.md

@@ -17,8 +17,8 @@ async def foo():
     async for x in Iterator():
         pass
 
-    # TODO: should reveal `Unbound | Unknown` because `__aiter__` is not defined
-    # revealed: Unbound | @Todo
+    # TODO: should reveal `Unknown` because `__aiter__` is not defined
+    # revealed: @Todo
     # error: [possibly-unresolved-reference]
     reveal_type(x)
 ```
@@ -40,6 +40,6 @@ async def foo():
         pass
 
     # error: [possibly-unresolved-reference]
-    # revealed: Unbound | @Todo
+    # revealed: @Todo
     reveal_type(x)
 ```

crates/red_knot_python_semantic/resources/mdtest/loops/for_loop.md

@@ -14,7 +14,7 @@ class IntIterable:
 for x in IntIterable():
     pass
 
-# revealed: Unbound | int
+# revealed: int
 # error: [possibly-unresolved-reference]
 reveal_type(x)
 ```
@@ -87,7 +87,7 @@ class OldStyleIterable:
 for x in OldStyleIterable():
     pass
 
-# revealed: Unbound | int
+# revealed: int
 # error: [possibly-unresolved-reference]
 reveal_type(x)
 ```
@@ -98,7 +98,7 @@ reveal_type(x)
 for x in (1, "a", b"foo"):
     pass
 
-# revealed: Unbound | Literal[1] | Literal["a"] | Literal[b"foo"]
+# revealed: Literal[1] | Literal["a"] | Literal[b"foo"]
 # error: [possibly-unresolved-reference]
 reveal_type(x)
 ```
@@ -120,7 +120,7 @@ class NotIterable:
 for x in NotIterable():  # error: "Object of type `NotIterable` is not iterable"
     pass
 
-# revealed: Unbound | Unknown
+# revealed: Unknown
 # error: [possibly-unresolved-reference]
 reveal_type(x)
 ```
@@ -240,7 +240,7 @@ def coinflip() -> bool:
 
 # TODO: we should emit a diagnostic here (it might not be iterable)
 for x in Test() if coinflip() else 42:
-    reveal_type(x)  # revealed: int | Unknown
+    reveal_type(x)  # revealed: int
 ```
 
 ## Union type as iterable where one union element has invalid `__iter__` method
@@ -261,9 +261,9 @@ class Test2:
 def coinflip() -> bool:
     return True
 
-# TODO: we should emit a diagnostic here (it might not be iterable)
+# error: "Object of type `Test | Test2` is not iterable"
 for x in Test() if coinflip() else Test2():
-    reveal_type(x)  # revealed: int | Unknown
+    reveal_type(x)  # revealed: Unknown
 ```
 
 ## Union type as iterator where one union element has no `__next__` method
@@ -277,7 +277,7 @@ class Test:
     def __iter__(self) -> TestIter | int:
         return TestIter()
 
-# TODO: we should emit a diagnostic here (it might not be iterable)
+# error: [not-iterable] "Object of type `Test` is not iterable"
 for x in Test():
-    reveal_type(x)  # revealed: int | Unknown
+    reveal_type(x)  # revealed: Unknown
 ```

crates/red_knot_python_semantic/resources/mdtest/scopes/moduletype_attrs.md

@@ -19,7 +19,7 @@ reveal_type(__path__)  # revealed: @Todo
 
 # TODO: this should probably be added to typeshed; not sure why it isn't?
 # error: [unresolved-reference]
-# revealed: Unbound
+# revealed: Unknown
 reveal_type(__doc__)
 
 class X:
@@ -34,15 +34,15 @@ module globals; these are excluded:
 
 ```py path=unbound_dunders.py
 # error: [unresolved-reference]
-# revealed: Unbound
+# revealed: Unknown
 reveal_type(__getattr__)
 
 # error: [unresolved-reference]
-# revealed: Unbound
+# revealed: Unknown
 reveal_type(__dict__)
 
 # error: [unresolved-reference]
-# revealed: Unbound
+# revealed: Unknown
 reveal_type(__init__)
 ```
 
@@ -61,10 +61,10 @@ reveal_type(typing.__init__)  # revealed: Literal[__init__]
 
 # These come from `builtins.object`, not `types.ModuleType`:
 # TODO: we don't currently understand `types.ModuleType` as inheriting from `object`;
-# these should not reveal `Unbound`:
-reveal_type(typing.__eq__)  # revealed: Unbound
-reveal_type(typing.__class__)  # revealed: Unbound
-reveal_type(typing.__module__)  # revealed: Unbound
+# these should not reveal `Unknown`:
+reveal_type(typing.__eq__)  # revealed: Unknown
+reveal_type(typing.__class__)  # revealed: Unknown
+reveal_type(typing.__module__)  # revealed: Unknown
 
 # TODO: needs support for attribute access on instances, properties and generics;
 # should be `dict[str, Any]`
@@ -78,7 +78,7 @@ where we know exactly which module we're dealing with:
 ```py path=__getattr__.py
 import typing
 
-reveal_type(typing.__getattr__)  # revealed: Unbound
+reveal_type(typing.__getattr__)  # revealed: Unknown
 ```
 
 ## `types.ModuleType.__dict__` takes precedence over global variable `__dict__`
@@ -120,7 +120,7 @@ if returns_bool():
     __name__ = 1
 
 reveal_type(__file__)  # revealed: Literal[42]
-reveal_type(__name__)  # revealed: str | Literal[1]
+reveal_type(__name__)  # revealed: Literal[1] | str
 ```
 
 ## Conditionally global or `ModuleType` attribute, with annotation
@@ -137,5 +137,5 @@ if returns_bool():
     __name__: int = 1
 
 reveal_type(__file__)  # revealed: Literal[42]
-reveal_type(__name__)  # revealed: str | Literal[1]
+reveal_type(__name__)  # revealed: Literal[1] | str
 ```

crates/red_knot_python_semantic/resources/mdtest/subscript/class.md

@@ -68,8 +68,8 @@ if flag:
 else:
     class Spam: ...
 
-# error: [call-non-callable] "Method `__class_getitem__` of type `Literal[__class_getitem__] | Unbound` is not callable on object of type `Literal[Spam, Spam]`"
-# revealed: str | Unknown
+# error: [call-possibly-unbound-method] "Method `__class_getitem__` of type `Literal[Spam, Spam]` is possibly unbound"
+# revealed: str
 reveal_type(Spam[42])
 ```