add failing tests

crates/ty_python_semantic/resources/mdtest/type_properties/implies_subtype_of.md

@@ -341,4 +341,93 @@ def mutually_constrained[T, U]():
     static_assert(not given_int.implies_subtype_of(Invariant[T], Invariant[str]))
 ```
 
+## Generic callables
+
+A generic callable can be considered equivalent to an intersection of all of its possible
+specializations. That means that a generic callable is a subtype of any particular specialization.
+(If someone expects a function that works with a particular specialization, it's fine to hand them
+the generic callable.)
+
+```py
+from typing import Callable
+from ty_extensions import CallableTypeOf, ConstraintSet, TypeOf, is_subtype_of, static_assert
+
+def identity[T](t: T) -> T:
+    return t
+
+constraints = ConstraintSet.always()
+
+# TODO: no error
+# error: [static-assert-error]
+static_assert(constraints.implies_subtype_of(TypeOf[identity], Callable[[int], int]))
+# TODO: no error
+# error: [static-assert-error]
+static_assert(constraints.implies_subtype_of(TypeOf[identity], Callable[[str], str]))
+static_assert(not constraints.implies_subtype_of(TypeOf[identity], Callable[[str], int]))
+
+# TODO: no error
+# error: [static-assert-error]
+static_assert(constraints.implies_subtype_of(CallableTypeOf[identity], Callable[[int], int]))
+# TODO: no error
+# error: [static-assert-error]
+static_assert(constraints.implies_subtype_of(CallableTypeOf[identity], Callable[[str], str]))
+static_assert(not constraints.implies_subtype_of(CallableTypeOf[identity], Callable[[str], int]))
+```
+
+The reverse is not true — if someone expects a generic function that can be called with any
+specialization, we cannot hand them a function that only works with one specialization.
+
+```py
+static_assert(not constraints.implies_subtype_of(Callable[[int], int], TypeOf[identity]))
+static_assert(not constraints.implies_subtype_of(Callable[[str], str], TypeOf[identity]))
+static_assert(not constraints.implies_subtype_of(Callable[[str], int], TypeOf[identity]))
+
+static_assert(not constraints.implies_subtype_of(Callable[[int], int], CallableTypeOf[identity]))
+static_assert(not constraints.implies_subtype_of(Callable[[str], str], CallableTypeOf[identity]))
+static_assert(not constraints.implies_subtype_of(Callable[[str], int], CallableTypeOf[identity]))
+```
+
+Unrelated typevars in the constraint set do not affect whether the subtyping check succeeds or
+fails.
+
+```py
+def unrelated[T]():
+    # Note that even though this typevar is also named T, it is not the same typevar as T@identity!
+    constraints = ConstraintSet.range(bool, T, int)
+
+    # TODO: no error
+    # error: [static-assert-error]
+    static_assert(constraints.implies_subtype_of(TypeOf[identity], Callable[[int], int]))
+    # TODO: no error
+    # error: [static-assert-error]
+    static_assert(constraints.implies_subtype_of(TypeOf[identity], Callable[[str], str]))
+    static_assert(not constraints.implies_subtype_of(TypeOf[identity], Callable[[str], int]))
+
+    static_assert(not constraints.implies_subtype_of(Callable[[int], int], TypeOf[identity]))
+    static_assert(not constraints.implies_subtype_of(Callable[[str], str], TypeOf[identity]))
+    static_assert(not constraints.implies_subtype_of(Callable[[str], int], TypeOf[identity]))
+```
+
+The generic callable's typevar _also_ does not affect whether the subtyping check succeeds or fails!
+
+```py
+def identity2[T](t: T) -> T:
+    # This constraint set refers to the same typevar as the generic function types below!
+    constraints = ConstraintSet.range(bool, T, int)
+
+    # TODO: no error
+    # error: [static-assert-error]
+    static_assert(constraints.implies_subtype_of(TypeOf[identity2], Callable[[int], int]))
+    # TODO: no error
+    # error: [static-assert-error]
+    static_assert(constraints.implies_subtype_of(TypeOf[identity2], Callable[[str], str]))
+    static_assert(not constraints.implies_subtype_of(TypeOf[identity2], Callable[[str], int]))
+
+    static_assert(not constraints.implies_subtype_of(Callable[[int], int], TypeOf[identity2]))
+    static_assert(not constraints.implies_subtype_of(Callable[[str], str], TypeOf[identity2]))
+    static_assert(not constraints.implies_subtype_of(Callable[[str], int], TypeOf[identity2]))
+
+    return t
+```
+
 [subtyping]: https://typing.python.org/en/latest/spec/concepts.html#subtype-supertype-and-type-equivalence

crates/ty_python_semantic/resources/mdtest/type_properties/is_assignable_to.md

@@ -1,5 +1,10 @@
 # Assignable-to relation
 
+```toml
+[environment]
+python-version = "3.12"
+```
+
 The `is_assignable_to(S, T)` relation below checks if type `S` is assignable to type `T` (target).
 This allows us to check if a type `S` can be used in a context where a type `T` is expected
 (function arguments, variable assignments). See the [typing documentation] for a precise definition
@@ -1227,6 +1232,46 @@ from ty_extensions import static_assert, is_assignable_to
 static_assert(is_assignable_to(type, Callable[..., Any]))
 ```
 
+### Generic callables
+
+A generic callable can be considered equivalent to an intersection of all of its possible
+specializations. That means that a generic callable is assignable to any particular specialization.
+(If someone expects a function that works with a particular specialization, it's fine to hand them
+the generic callable.)
+
+```py
+from typing import Callable
+from ty_extensions import CallableTypeOf, TypeOf, is_assignable_to, static_assert
+
+def identity[T](t: T) -> T:
+    return t
+
+static_assert(is_assignable_to(TypeOf[identity], Callable[[int], int]))
+static_assert(is_assignable_to(TypeOf[identity], Callable[[str], str]))
+# TODO: no error
+# error: [static-assert-error]
+static_assert(not is_assignable_to(TypeOf[identity], Callable[[str], int]))
+
+static_assert(is_assignable_to(CallableTypeOf[identity], Callable[[int], int]))
+static_assert(is_assignable_to(CallableTypeOf[identity], Callable[[str], str]))
+# TODO: no error
+# error: [static-assert-error]
+static_assert(not is_assignable_to(CallableTypeOf[identity], Callable[[str], int]))
+```
+
+The reverse is not true — if someone expects a generic function that can be called with any
+specialization, we cannot hand them a function that only works with one specialization.
+
+```py
+static_assert(not is_assignable_to(Callable[[int], int], TypeOf[identity]))
+static_assert(not is_assignable_to(Callable[[str], str], TypeOf[identity]))
+static_assert(not is_assignable_to(Callable[[str], int], TypeOf[identity]))
+
+static_assert(not is_assignable_to(Callable[[int], int], CallableTypeOf[identity]))
+static_assert(not is_assignable_to(Callable[[str], str], CallableTypeOf[identity]))
+static_assert(not is_assignable_to(Callable[[str], int], CallableTypeOf[identity]))
+```
+
 ## Generics
 
 ### Assignability of generic types parameterized by gradual types

crates/ty_python_semantic/resources/mdtest/type_properties/is_subtype_of.md

@@ -2207,6 +2207,50 @@ static_assert(is_subtype_of(CallableTypeOf[overload_ab], CallableTypeOf[overload
 static_assert(is_subtype_of(CallableTypeOf[overload_ba], CallableTypeOf[overload_ab]))
 ```
 
+### Generic callables
+
+A generic callable can be considered equivalent to an intersection of all of its possible
+specializations. That means that a generic callable is a subtype of any particular specialization.
+(If someone expects a function that works with a particular specialization, it's fine to hand them
+the generic callable.)
+
+```py
+from typing import Callable
+from ty_extensions import CallableTypeOf, TypeOf, is_subtype_of, static_assert
+
+def identity[T](t: T) -> T:
+    return t
+
+# TODO: no error
+# error: [static-assert-error]
+static_assert(is_subtype_of(TypeOf[identity], Callable[[int], int]))
+# TODO: no error
+# error: [static-assert-error]
+static_assert(is_subtype_of(TypeOf[identity], Callable[[str], str]))
+static_assert(not is_subtype_of(TypeOf[identity], Callable[[str], int]))
+
+# TODO: no error
+# error: [static-assert-error]
+static_assert(is_subtype_of(CallableTypeOf[identity], Callable[[int], int]))
+# TODO: no error
+# error: [static-assert-error]
+static_assert(is_subtype_of(CallableTypeOf[identity], Callable[[str], str]))
+static_assert(not is_subtype_of(CallableTypeOf[identity], Callable[[str], int]))
+```
+
+The reverse is not true — if someone expects a generic function that can be called with any
+specialization, we cannot hand them a function that only works with one specialization.
+
+```py
+static_assert(not is_subtype_of(Callable[[int], int], TypeOf[identity]))
+static_assert(not is_subtype_of(Callable[[str], str], TypeOf[identity]))
+static_assert(not is_subtype_of(Callable[[str], int], TypeOf[identity]))
+
+static_assert(not is_subtype_of(Callable[[int], int], CallableTypeOf[identity]))
+static_assert(not is_subtype_of(Callable[[str], str], CallableTypeOf[identity]))
+static_assert(not is_subtype_of(Callable[[str], int], CallableTypeOf[identity]))
+```
+
 [gradual form]: https://typing.python.org/en/latest/spec/glossary.html#term-gradual-form
 [gradual tuple]: https://typing.python.org/en/latest/spec/tuples.html#tuple-type-form
 [special case for float and complex]: https://typing.python.org/en/latest/spec/special-types.html#special-cases-for-float-and-complex