From 80f38711ecb29e7da60379199f87a0c0fa277e1e Mon Sep 17 00:00:00 2001
From: Marcus Mews <marcus.mews@jetbrains.com>
Date: Fri, 20 Feb 2026 16:52:31 +0000
Subject: [PATCH] PY-87831 incorrect (invariant) variance on subtype

(cherry picked from commit c0254d65914f2e6fab1b69eecc6fc4e4837b6ce7)

IJ-MR-192664

GitOrigin-RevId: b8d3a12e6774ccff04d368d30a0a49572e303e1e
---
 .../python/psi/types/PyInferredVarianceJudgment.kt     |  1 +
 .../jetbrains/python/PyInferredVarianceJudgmentTest.kt | 10 ++++++++++
 2 files changed, 11 insertions(+)

diff --git a/python/python-psi-impl/src/com/jetbrains/python/psi/types/PyInferredVarianceJudgment.kt b/python/python-psi-impl/src/com/jetbrains/python/psi/types/PyInferredVarianceJudgment.kt
index 62a0677e1f92..35fe8634c93e 100644
--- a/python/python-psi-impl/src/com/jetbrains/python/psi/types/PyInferredVarianceJudgment.kt
+++ b/python/python-psi-impl/src/com/jetbrains/python/psi/types/PyInferredVarianceJudgment.kt
@@ -107,6 +107,7 @@ object PyInferredVarianceJudgment {
       collector.usages.contains(COVARIANT) && collector.usages.contains(CONTRAVARIANT) -> INVARIANT
       collector.usages.contains(COVARIANT) -> COVARIANT
       collector.usages.contains(CONTRAVARIANT) -> CONTRAVARIANT
+      collector.usages.contains(BIVARIANT) -> BIVARIANT
       else -> INVARIANT
     }
   }
diff --git a/python/testSrc/com/jetbrains/python/PyInferredVarianceJudgmentTest.kt b/python/testSrc/com/jetbrains/python/PyInferredVarianceJudgmentTest.kt
index 1b1a34d4e5ea..00a0e59edf3d 100644
--- a/python/testSrc/com/jetbrains/python/PyInferredVarianceJudgmentTest.kt
+++ b/python/testSrc/com/jetbrains/python/PyInferredVarianceJudgmentTest.kt
@@ -139,6 +139,16 @@ internal class PyInferredVarianceJudgmentTest : PyTestCase() {
       """)
   }
 
+  fun `test Generic sub class unused`() {
+    // see comment about bivariance in: PyInferredVarianceJudgment.doGetInferredVariance
+    doTest("T", Variance.BIVARIANT, """
+      class A[S]:
+          ...
+      class B[T](A[T]):
+          def method(self): pass
+      """)
+  }
+
   fun `test Generic class unused TypeVar syntax`() {
     // see comment about bivariance in: PyInferredVarianceJudgment.doGetInferredVariance
     doTest("T])", Variance.BIVARIANT, PyReferenceExpression::class.java, """