From 6aaa9d784ab7d8f70a4cd34de994ec7d468b0d78 Mon Sep 17 00:00:00 2001
From: David Peter <mail@david-peter.de>
Date: Tue, 25 Nov 2025 11:13:22 +0100
Subject: [PATCH] Fix problem with np.array related to type[T]

---
 .../resources/mdtest/implicit_type_aliases.md | 24 +++++++++++++++++++
 crates/ty_python_semantic/src/types.rs        | 10 ++++++--
 2 files changed, 32 insertions(+), 2 deletions(-)

diff --git a/crates/ty_python_semantic/resources/mdtest/implicit_type_aliases.md b/crates/ty_python_semantic/resources/mdtest/implicit_type_aliases.md
index 93cdcf515f..c975b14db2 100644
--- a/crates/ty_python_semantic/resources/mdtest/implicit_type_aliases.md
+++ b/crates/ty_python_semantic/resources/mdtest/implicit_type_aliases.md
@@ -500,14 +500,27 @@ def _(
 A generic implicit type alias can also be used in another generic implicit type alias:
 
 ```py
+from typing_extensions import Any
+
+B = TypeVar("B", bound=int)
+
 MyOtherList = MyList[T]
+MyOtherType = MyType[T]
+TypeOrList = MyType[B] | MyList[B]
 
 reveal_type(MyOtherList)  # revealed: <class 'list[T@MyOtherList]'>
+reveal_type(MyOtherType)  # revealed: GenericAlias
+reveal_type(TypeOrList)  # revealed: types.UnionType
 
 def _(
     list_of_ints: MyOtherList[int],
+    subclass_of_int: MyOtherType[int],
+    type_or_list: TypeOrList[Any],
 ):
     reveal_type(list_of_ints)  # revealed: list[int]
+    reveal_type(subclass_of_int)  # revealed: type[int]
+    # TODO: Should be `type[Any] | list[Any]`
+    reveal_type(type_or_list)  # revealed: @Todo(type[T] for typevar T) | list[Any]
 ```
 
 If a generic implicit type alias is used unspecialized in a type expression, we treat it as an
@@ -1456,3 +1469,14 @@ def _(
     reveal_type(recursive_dict3)  # revealed: dict[Divergent, int]
     reveal_type(recursive_dict4)  # revealed: dict[Divergent, int]
 ```
+
+### Self-referential generic implicit type aliases
+
+<!-- expect-panic: execute: too many cycle iterations -->
+
+```py
+from typing import TypeVar
+
+T = TypeVar("T")
+NestedDict = dict[str, "NestedDict[T] | T"]
+```
diff --git a/crates/ty_python_semantic/src/types.rs b/crates/ty_python_semantic/src/types.rs
index 367ea11be5..fe4afa5356 100644
--- a/crates/ty_python_semantic/src/types.rs
+++ b/crates/ty_python_semantic/src/types.rs
@@ -6799,7 +6799,7 @@ impl<'db> Type<'db> {
                 }
                 KnownInstanceType::Literal(ty) => Ok(ty.inner(db)),
                 KnownInstanceType::Annotated(ty) => Ok(ty.inner(db)),
-                KnownInstanceType::TypeGenericAlias(ty) => {
+                KnownInstanceType::TypeGenericAlias(instance) => {
                     // When `type[…]` appears in a value position (e.g. in an implicit type alias),
                     // we infer its argument as a type expression. This ensures that we can emit
                     // diagnostics for invalid type expressions, and more importantly, that we can
@@ -6808,7 +6808,13 @@ impl<'db> Type<'db> {
                     // (`int` -> instance of `int` -> subclass of `int`) can be lossy, but it is
                     // okay for all valid arguments to `type[…]`.
 
-                    Ok(ty.inner(db).to_meta_type(db))
+                    let ty = instance.inner(db);
+
+                    if ty.is_type_var() {
+                        Ok(todo_type!("type[T] for typevar T"))
+                    } else {
+                        Ok(ty.to_meta_type(db))
+                    }
                 }
                 KnownInstanceType::Callable(instance) => {
                     Ok(Type::Callable(instance.callable_type(db)))