From c60e8a037a739db141cb8af096c0b6d68b42b6ad Mon Sep 17 00:00:00 2001
From: David Peter <sharkdp@users.noreply.github.com>
Date: Mon, 10 Mar 2025 13:24:13 +0100
Subject: [PATCH] =?UTF-8?q?[red-knot]=20Add=20support=20for=20calling=20`t?=
 =?UTF-8?q?ype[=E2=80=A6]`=20(#16597)?=
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## Summary

This fixes the non-diagnostics part of #15948.

## Test Plan

New Markdown tests.

Negative diff on the ecosystem checks:

```diff
zipp (https://github.com/jaraco/zipp)
- error: lint:call-non-callable
-    --> /tmp/mypy_primer/projects/zipp/zipp/__init__.py:393:16
-     |
- 392 |     def _next(self, at):
- 393 |         return self.__class__(self.root, at)
-     |                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Object of type `type[Unknown]` is not callable
- 394 |
- 395 |     def is_dir(self):
-     |
-
- Found 9 diagnostics
+ Found 8 diagnostics

arrow (https://github.com/arrow-py/arrow)
+     |
+     |
+ warning: lint:unused-ignore-comment
+    --> /tmp/mypy_primer/projects/arrow/arrow/arrow.py:576:66
+ 574 |                 values.append(1)
+ 575 |
+ 576 |             floor = self.__class__(*values, tzinfo=self.tzinfo)  # type: ignore[misc]
+     |                                                                  -------------------- Unused blanket `type: ignore` directive
+ 577 |
+ 578 |             if frame_absolute == "week":
- error: lint:call-non-callable
-     --> /tmp/mypy_primer/projects/arrow/arrow/arrow.py:1080:16
-      |
- 1078 |           dt = self._datetime.astimezone(tz)
- 1079 |
- 1080 |           return self.__class__(
-      |  ________________^
- 1081 | |             dt.year,
- 1082 | |             dt.month,
- 1083 | |             dt.day,
- 1084 | |             dt.hour,
- 1085 | |             dt.minute,
- 1086 | |             dt.second,
- 1087 | |             dt.microsecond,
- 1088 | |             dt.tzinfo,
- 1089 | |             fold=getattr(dt, "fold", 0),
- 1090 | |         )
-      | |_________^ Object of type `type[Unknown]` is not callable
- 1091 |
- 1092 |       # string output and formatting
-      |

black (https://github.com/psf/black)
-
-     |
-     |
- error: lint:call-non-callable
-    --> /tmp/mypy_primer/projects/black/src/blib2to3/pgen2/grammar.py:135:15
- 133 |         Copy the grammar.
- 134 |         """
- 135 |         new = self.__class__()
-     |               ^^^^^^^^^^^^^^^^ Object of type `type[@Todo]` is not callable
- 136 |         for dict_attr in (
- 137 |             "symbol2number",
- Found 328 diagnostics
+ Found 327 diagnostics
```
---
 .../resources/mdtest/call/subclass_of.md      | 50 +++++++++++++++++++
 crates/red_knot_python_semantic/src/types.rs  |  7 +++
 2 files changed, 57 insertions(+)
 create mode 100644 crates/red_knot_python_semantic/resources/mdtest/call/subclass_of.md

diff --git a/crates/red_knot_python_semantic/resources/mdtest/call/subclass_of.md b/crates/red_knot_python_semantic/resources/mdtest/call/subclass_of.md
new file mode 100644
index 0000000000..37082cfaa4
--- /dev/null
+++ b/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
+```
diff --git a/crates/red_knot_python_semantic/src/types.rs b/crates/red_knot_python_semantic/src/types.rs
index a6b1520e71..9041af59e8 100644
--- a/crates/red_knot_python_semantic/src/types.rs
+++ 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)