From acba8a231a8ebb5568d777aa32db85990caf714b Mon Sep 17 00:00:00 2001
From: "Aleksandr.Govenko" <aleksandr.govenko@jetbrains.com>
Date: Mon, 8 Sep 2025 18:16:05 +0200
Subject: [PATCH] PY-83348 Narrow `X | None` object to `X` after `object or x`

GitOrigin-RevId: d835132ade43a3f12b78f4029f584cad97180dc2
---
 .../controlflow/PyTypeAssertionEvaluator.java        |  2 ++
 .../python/psi/impl/PyBinaryExpressionImpl.java      | 11 +++++++++--
 python/testSrc/com/jetbrains/python/Py3TypeTest.java | 12 ++++++++++++
 3 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/python/python-psi-impl/src/com/jetbrains/python/codeInsight/controlflow/PyTypeAssertionEvaluator.java b/python/python-psi-impl/src/com/jetbrains/python/codeInsight/controlflow/PyTypeAssertionEvaluator.java
index 1589d7d26e82..2422c37e8aa3 100644
--- a/python/python-psi-impl/src/com/jetbrains/python/codeInsight/controlflow/PyTypeAssertionEvaluator.java
+++ b/python/python-psi-impl/src/com/jetbrains/python/codeInsight/controlflow/PyTypeAssertionEvaluator.java
@@ -392,6 +392,8 @@ public class PyTypeAssertionEvaluator extends PyRecursiveElementVisitor {
       return null;
     };
   }
+  
+
 
   private static boolean isIfReferenceStatement(@NotNull PyExpression node) {
     return PsiTreeUtil.skipParentsOfType(node, PyParenthesizedExpression.class) instanceof PyIfPart;
diff --git a/python/python-psi-impl/src/com/jetbrains/python/psi/impl/PyBinaryExpressionImpl.java b/python/python-psi-impl/src/com/jetbrains/python/psi/impl/PyBinaryExpressionImpl.java
index 09d53f29f2f5..d3f5f960338f 100644
--- a/python/python-psi-impl/src/com/jetbrains/python/psi/impl/PyBinaryExpressionImpl.java
+++ b/python/python-psi-impl/src/com/jetbrains/python/psi/impl/PyBinaryExpressionImpl.java
@@ -2,9 +2,11 @@
 package com.jetbrains.python.psi.impl;
 
 import com.intellij.lang.ASTNode;
+import com.intellij.openapi.util.Ref;
 import com.intellij.psi.PsiPolyVariantReference;
 import com.intellij.util.IncorrectOperationException;
 import com.jetbrains.python.PyNames;
+import com.jetbrains.python.codeInsight.controlflow.PyTypeAssertionEvaluator;
 import com.jetbrains.python.psi.PyBinaryExpression;
 import com.jetbrains.python.psi.PyElementVisitor;
 import com.jetbrains.python.psi.PyExpression;
@@ -53,14 +55,19 @@ public class PyBinaryExpressionImpl extends PyElementImpl implements PyBinaryExp
 
   @Override
   public @Nullable PyType getType(@NotNull TypeEvalContext context, @NotNull TypeEvalContext.Key key) {
-    if (isOperator("and") || isOperator("or")) {
+    if (isOperator(PyNames.AND) || isOperator(PyNames.OR)) {
       final PyExpression left = getLeftExpression();
-      final PyType leftType = left != null ? context.getType(left) : null;
+      PyType leftType = left != null ? context.getType(left) : null;
       final PyExpression right = getRightExpression();
       final PyType rightType = right != null ? context.getType(right) : null;
       if (leftType == null && rightType == null) {
         return null;
       }
+      if (isOperator(PyNames.OR)) {
+        // TODO: also exclude Literal[False, 0, ""]
+        leftType = Ref.deref(PyTypeAssertionEvaluator.createAssertionType(
+          leftType, PyBuiltinCache.getInstance(this).getNoneType(), false, true, context));
+      }
       return PyUnionType.union(leftType, rightType);
     }
     final String referencedName = getReferencedName();
diff --git a/python/testSrc/com/jetbrains/python/Py3TypeTest.java b/python/testSrc/com/jetbrains/python/Py3TypeTest.java
index 45b6fcd7aa83..99bf757e9ae3 100644
--- a/python/testSrc/com/jetbrains/python/Py3TypeTest.java
+++ b/python/testSrc/com/jetbrains/python/Py3TypeTest.java
@@ -150,6 +150,18 @@ public class Py3TypeTest extends PyTestCase {
              d = {}
              expr = d.pop("abc", None)""");
   }
+  
+  // PY-83348
+  public void testOrExpressionType() {
+    doTest("int | str", """
+             def foo(x: int | None):
+                 expr = x or "foo"
+             """);
+    doTest("str", """
+             def foo(x: None):
+                 expr = x or "foo"
+             """);
+  }
 
   public void testYieldInsideLambda() {
     // Checks that foo is not a generator