[red-knot] Method calls and the descriptor protocol

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

@@ -73,12 +73,12 @@ qux = (foo, bar)
 reveal_type(qux)  # revealed: tuple[Literal["foo"], Literal["bar"]]
 
 # TODO: Infer "LiteralString"
-reveal_type(foo.join(qux))  # revealed: @Todo(Attribute access on `StringLiteral` types)
+reveal_type(foo.join(qux))  # revealed: @Todo(decorated method)
 
 template: LiteralString = "{}, {}"
 reveal_type(template)  # revealed: Literal["{}, {}"]
 # TODO: Infer `LiteralString`
-reveal_type(template.format(foo, bar))  # revealed: @Todo(Attribute access on `StringLiteral` types)
+reveal_type(template.format(foo, bar))  # revealed: @Todo(decorated method)
 ```
 
 ### Assignability

crates/red_knot_python_semantic/resources/mdtest/attributes.md

@@ -941,7 +941,7 @@ reveal_type(f.__kwdefaults__)  # revealed: @Todo(generics) | None
 Some attributes are special-cased, however:
 
 ```py
-reveal_type(f.__get__)  # revealed: @Todo(`__get__` method on functions)
+reveal_type(f.__get__)  # revealed: <function `__get__`>
 reveal_type(f.__call__)  # revealed: @Todo(`__call__` method on functions)
 ```
 
@@ -951,7 +951,7 @@ Most attribute accesses on int-literal types are delegated to `builtins.int`, si
 integers are instances of that class:
 
 ```py
-reveal_type((2).bit_length)  # revealed: @Todo(bound method)
+reveal_type((2).bit_length)  # revealed: <bound method: `bit_length` of `Literal[2]`>
 reveal_type((2).denominator)  # revealed: @Todo(@property)
 ```
 
@@ -968,8 +968,8 @@ Most attribute accesses on bool-literal types are delegated to `builtins.bool`,
 bols are instances of that class:
 
 ```py
-reveal_type(True.__and__)  # revealed: @Todo(bound method)
-reveal_type(False.__or__)  # revealed: @Todo(bound method)
+reveal_type(True.__and__)  # revealed: @Todo(decorated method)
+reveal_type(False.__or__)  # revealed: @Todo(decorated method)
 ```
 
 Some attributes are special-cased, however:
@@ -984,8 +984,8 @@ reveal_type(False.real)  # revealed: Literal[0]
 All attribute access on literal `bytes` types is currently delegated to `buitins.bytes`:
 
 ```py
-reveal_type(b"foo".join)  # revealed: @Todo(bound method)
-reveal_type(b"foo".endswith)  # revealed: @Todo(bound method)
+reveal_type(b"foo".join)  # revealed: <bound method: `join` of `Literal[b"foo"]`>
+reveal_type(b"foo".endswith)  # revealed: <bound method: `endswith` of `Literal[b"foo"]`>
 ```
 
 ## Instance attribute edge cases

crates/red_knot_python_semantic/resources/mdtest/binary/integers.md

@@ -51,7 +51,8 @@ reveal_type(1 ** (largest_u32 + 1))  # revealed: int
 reveal_type(2**largest_u32)  # revealed: int
 
 def variable(x: int):
-    reveal_type(x**2)  # revealed: @Todo(return type)
+    # TODO
+    reveal_type(x**2)  # revealed: Any
     reveal_type(2**x)  # revealed: @Todo(return type)
     reveal_type(x**x)  # revealed: @Todo(return type)
 ```

crates/red_knot_python_semantic/resources/mdtest/descriptor_protocol.md

@@ -26,18 +26,19 @@ class C:
 
 c = C()
 
-# TODO: this should be `Literal[10]`
-reveal_type(c.ten)  # revealed: Unknown | Ten
+reveal_type(c.ten)  # revealed: Literal[10]
 
-# TODO: This should `Literal[10]`
-reveal_type(C.ten)  # revealed: Unknown | Ten
+reveal_type(C.ten)  # revealed: Literal[10]
 
 # These are fine:
 c.ten = 10
 C.ten = 10
 
-# TODO: Both of these should be errors
+# TODO: This should be an error
 c.ten = 11
+
+# TODO: This is not the correct error message
+# error: [invalid-assignment] "Object of type `Literal[11]` is not assignable to attribute `ten` of type `Literal[10]`"
 C.ten = 11
 ```
 
@@ -61,20 +62,68 @@ class C:
 
 c = C()
 
-# TODO: should be `int | None`
-reveal_type(c.flexible_int)  # revealed: Unknown | FlexibleInt
+reveal_type(c.flexible_int)  # revealed: int | None
 
 c.flexible_int = 42  # okay
 c.flexible_int = "42"  # also okay!
 
-# TODO: should be `int | None`
-reveal_type(c.flexible_int)  # revealed: Unknown | FlexibleInt
+reveal_type(c.flexible_int)  # revealed: int | None
 
 # TODO: should be an error
 c.flexible_int = None  # not okay
 
-# TODO: should be `int | None`
-reveal_type(c.flexible_int)  # revealed: Unknown | FlexibleInt
+reveal_type(c.flexible_int)  # revealed: int | None
+```
+
+## Data and non-data descriptors
+
+Descriptors that define `__set__` or `__delete__` are called data descriptors (e.g. properties),
+while those that only define `__get__` are called non-data descriptors (e.g. `classmethod` or
+`staticmethod`).
+
+The precedence chain for attribute access is:
+
+- Data descriptors
+- Instance attributes
+- Non-data descriptors
+
+```py
+from typing import Literal
+
+class DataDescriptor:
+    def __get__(self, instance: object, owner: type | None = None) -> Literal["data descriptor"]:
+        return "data descriptor"
+
+    def __set__(self, instance: object, value) -> None:
+        pass
+
+class NonDataDescriptor:
+    def __get__(self, instance: object, owner: type | None = None) -> Literal["non-data descriptor"]:
+        return "non-data descriptor"
+
+class C:
+    data_descriptor = DataDescriptor()
+    non_data_descriptor = NonDataDescriptor()
+
+    def __init__(self):
+        self.data_descriptor = "instance attribute"
+        self.non_data_descriptor = "instance attribute"
+
+c = C()
+
+# TODO: Should be `Unknown | Literal["data descriptor"]`
+reveal_type(c.data_descriptor)  # revealed: Literal["data descriptor"]
+
+# TODO: Should be `Unknown | Literal["instance attribute"]`
+reveal_type(c.non_data_descriptor)  # revealed: Literal["non-data descriptor"]
+```
+
+Access on the class itself only sees the descriptors:
+
+```py
+reveal_type(C.data_descriptor)  # revealed: Literal["data descriptor"]
+
+reveal_type(C.non_data_descriptor)  # revealed: Literal["non-data descriptor"]
 ```
 
 ## Built-in `property` descriptor
@@ -101,10 +150,10 @@ c = C()
 reveal_type(c._name)  # revealed: str | None
 
 # Should be `str`
-reveal_type(c.name)  # revealed: @Todo(bound method)
+reveal_type(c.name)  # revealed: @Todo(decorated method)
 
 # Should be `builtins.property`
-reveal_type(C.name)  # revealed: Literal[name]
+reveal_type(C.name)  # revealed: <function `name`>
 
 # This is fine:
 c.name = "new"
@@ -142,7 +191,7 @@ reveal_type(c1)  # revealed: @Todo(return type)
 reveal_type(C.get_name())  # revealed: @Todo(return type)
 
 # TODO: should be `str`
-reveal_type(C("42").get_name())  # revealed: @Todo(bound method)
+reveal_type(C("42").get_name())  # revealed: @Todo(decorated method)
 ```
 
 ## Descriptors only work when used as class variables
@@ -162,7 +211,8 @@ class C:
     def __init__(self):
         self.ten = Ten()
 
-reveal_type(C().ten)  # revealed: Unknown | Ten
+# TODO: Should be Unknown | Ten
+reveal_type(C().ten)  # revealed: Literal[10]
 ```
 
 ## Descriptors distinguishing between class and instance access
@@ -189,10 +239,10 @@ class C:
     d = Descriptor()
 
 # TODO: should be `Literal["called on class object"]
-reveal_type(C.d)  # revealed: Unknown | Descriptor
+reveal_type(C.d)  # revealed: LiteralString
 
 # TODO: should be `Literal["called on instance"]
-reveal_type(C().d)  # revealed: Unknown | Descriptor
+reveal_type(C().d)  # revealed: LiteralString
 ```
 
 [descriptors]: https://docs.python.org/3/howto/descriptor.html

crates/red_knot_python_semantic/resources/mdtest/generics.md

@@ -41,7 +41,8 @@ reveal_type(secure_box)  # revealed: MySecureBox
 # TODO reveal int
 # The @Todo(…) is misleading here. We currently treat `MyBox[T]` as a dynamic base class because we
 # don't understand generics and therefore infer `Unknown` for the `MyBox[T]` base of `MySecureBox[T]`.
-reveal_type(secure_box.data)  # revealed: @Todo(instance attribute on class with dynamic base)
+# error: [unresolved-attribute]
+reveal_type(secure_box.data)  # revealed: Unknown
 ```
 
 ## Cyclical class definition

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

@@ -54,10 +54,10 @@ inside the module:
 import typing
 
 reveal_type(typing.__name__)  # revealed: str
-reveal_type(typing.__init__)  # revealed: @Todo(bound method)
+reveal_type(typing.__init__)  # revealed: <bound method: `__init__` of `ModuleType`>
 
 # These come from `builtins.object`, not `types.ModuleType`:
-reveal_type(typing.__eq__)  # revealed: @Todo(bound method)
+reveal_type(typing.__eq__)  # revealed: <bound method: `__eq__` of `ModuleType`>
 
 reveal_type(typing.__class__)  # revealed: Literal[ModuleType]
 

crates/red_knot_python_semantic/resources/mdtest/sys_platform.md

@@ -66,6 +66,6 @@ It is [recommended](https://docs.python.org/3/library/sys.html#sys.platform) to
 ```py
 import sys
 
-reveal_type(sys.platform.startswith("freebsd"))  # revealed: @Todo(Attribute access on `LiteralString` types)
-reveal_type(sys.platform.startswith("linux"))  # revealed: @Todo(Attribute access on `LiteralString` types)
+reveal_type(sys.platform.startswith("freebsd"))  # revealed: bool
+reveal_type(sys.platform.startswith("linux"))  # revealed: bool
 ```

crates/red_knot_python_semantic/resources/mdtest/type_of/dynamic.md

@@ -35,7 +35,7 @@ in strict mode.
 ```py
 def f(x: type):
     reveal_type(x)  # revealed: type
-    reveal_type(x.__repr__)  # revealed: @Todo(bound method)
+    reveal_type(x.__repr__)  # revealed: <bound method: `__repr__` of `type`>
 
 class A: ...
 
@@ -50,7 +50,7 @@ x: type = A()  # error: [invalid-assignment]
 ```py
 def f(x: type[object]):
     reveal_type(x)  # revealed: type
-    reveal_type(x.__repr__)  # revealed: @Todo(bound method)
+    reveal_type(x.__repr__)  # revealed: <bound method: `__repr__` of `type`>
 
 class A: ...