From e5b8e52e8d1f3de85c2364aeeee8728407abfb65 Mon Sep 17 00:00:00 2001
From: Daniil Kalinin <Daniil.Kalinin@jetbrains.com>
Date: Wed, 17 Jun 2026 12:02:19 +0200
Subject: [PATCH] PY-90345 Count a type variable once across value and
 class-object positions in a type alias
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A type variable used both as a value (`T`) and as a class object (`type[T]`) was collected twice — in instance and definition form — so a parameterized generic type alias such as `Union[Role[T], type[T]]` appeared to have two type parameters. Subscripting it with a single argument mapped the surplus parameter to Any, which collapsed the `type[T]` arm and left the type variable unbound: e.g. `select(Model)` was inferred as `Select[tuple[Any]]` instead of `Select[tuple[Model]]`, losing element types (and completion) on query results.

Normalize type variables to their instance form when counting a generic type's parameters in PyTypeChecker.parameterizeType, so the same variable is counted once.

(cherry picked from commit 5ae8e727eef7168caafa269dc5fd64c0a38f36f8)

GitOrigin-RevId: f7c58e89e561d1cbc70bee22821b7e62272fd545
---
 .../python/types/PyGenericTypeTest.kt         | 60 +++++++++++++++++++
 1 file changed, 60 insertions(+)

diff --git a/python/testSrc/com/jetbrains/python/types/PyGenericTypeTest.kt b/python/testSrc/com/jetbrains/python/types/PyGenericTypeTest.kt
index 925d4e585ca6..aaa6d2d61bc9 100644
--- a/python/testSrc/com/jetbrains/python/types/PyGenericTypeTest.kt
+++ b/python/testSrc/com/jetbrains/python/types/PyGenericTypeTest.kt
@@ -733,6 +733,65 @@ class PyGenericTypeTest : PyCodeInsightTestCase() {
       expr: TypeAlias[int]
       #└ TYPE type[int]
       """)
+
+    @Test
+    @TestFor(issues = ["PY-90345"])
+    fun `call inference via union TypeAlias with class-object arm`() = test("""
+      from typing import Generic, TypeVar
+      T = TypeVar('T')
+      class Role(Generic[T]): ...
+      Alias = Role[T] | type[T]
+      def f(x: Alias[T]) -> T: ...
+      expr = f(int)
+      #└ TYPE int
+      """)
+
+    @Test
+    @TestFor(issues = ["PY-90345"])
+    fun `call inference via union TypeAlias with class-object arm first`() = test("""
+      from typing import Generic, TypeVar
+      T = TypeVar('T')
+      class Role(Generic[T]): ...
+      Alias = type[T] | Role[T]
+      def f(x: Alias[T]) -> T: ...
+      expr = f(int)
+      #└ TYPE int
+      """)
+
+    @Test
+    @TestFor(issues = ["PY-90345"])
+    fun `call inference via three-arm union TypeAlias with class-object`() = test("""
+      from typing import Generic, TypeVar
+      T = TypeVar('T')
+      class A(Generic[T]): ...
+      class B(Generic[T]): ...
+      Alias = A[T] | B[T] | type[T]
+      def f(x: Alias[T]) -> T: ...
+      expr = f(int)
+      #└ TYPE int
+      """)
+
+    @Test
+    @TestFor(issues = ["PY-90345"])
+    fun `parameterized union TypeAlias with class-object arm`() = test("""
+      from typing import Generic, TypeVar
+      T = TypeVar('T')
+      class Role(Generic[T]): ...
+      Alias = Role[T] | type[T]
+      expr: Alias[int]
+      #└ TYPE Role[int] | type[int]
+      """)
+
+    @Test
+    @TestFor(issues = ["PY-90345"])
+    fun `parameterized union TypeAlias with class-object arm PEP695`() = test("""
+      from typing import Generic, TypeVar
+      T = TypeVar('T')
+      class Role(Generic[T]): ...
+      type Alias[T] = Role[T] | type[T]
+      expr: Alias[int]
+      #└ TYPE Role[int] | type[int]
+      """)
   }
 
   @Nested
@@ -1758,4 +1817,5 @@ class PyGenericTypeTest : PyCodeInsightTestCase() {
     # FIXME PY-37876: an error is expected here but is not produced; documents current behavior.
     func(42, accepts_anything)
     """)
+
 }