[red-knot] Add support for calling type[…]

crates/red_knot_python_semantic/resources/mdtest/call/subclass_of.md

@@ -0,0 +1,50 @@
+# Call `type[...]`
+
+## Single class
+
+### Trivial constructor
+
+```py
+class C: ...
+
+def _(subclass_of_c: type[C]):
+    reveal_type(subclass_of_c())  # revealed: C
+```
+
+### Non-trivial constructor
+
+```py
+class C:
+    def __init__(self, x: int): ...
+
+def _(subclass_of_c: type[C]):
+    reveal_type(subclass_of_c(1))  # revealed: C
+
+    # TODO: Those should all be errors
+    reveal_type(subclass_of_c("a"))  # revealed: C
+    reveal_type(subclass_of_c())  # revealed: C
+    reveal_type(subclass_of_c(1, 2))  # revealed: C
+```
+
+## Dynamic base
+
+```py
+from typing import Any
+from knot_extensions import Unknown
+
+def _(subclass_of_any: type[Any], subclass_of_unknown: type[Unknown]):
+    reveal_type(subclass_of_any())  # revealed: Any
+    reveal_type(subclass_of_any("any", "args", 1, 2))  # revealed: Any
+    reveal_type(subclass_of_unknown())  # revealed: Unknown
+    reveal_type(subclass_of_unknown("any", "args", 1, 2))  # revealed: Unknown
+```
+
+## Unions of classes
+
+```py
+class A: ...
+class B: ...
+
+def _(subclass_of_ab: type[A | B]):
+    reveal_type(subclass_of_ab())  # revealed: A | B
+```

crates/red_knot_python_semantic/src/types.rs

@@ -2678,6 +2678,13 @@ impl<'db> Type<'db> {
                 )))
             }
 
+            Type::SubclassOf(subclass_of_type) => match subclass_of_type.subclass_of() {
+                ClassBase::Dynamic(dynamic_type) => Ok(CallOutcome::Single(
+                    CallBinding::from_return_type(Type::Dynamic(dynamic_type)),
+                )),
+                ClassBase::Class(class) => Type::class_literal(class).try_call(db, arguments),
+            },
+
             instance_ty @ Type::Instance(_) => {
                 instance_ty
                     .try_call_dunder(db, "__call__", arguments)