Added special-case bidirectional type inference for the right operand of the "|" and "|=" operators (with an expected type based on the left operand). This supports the case where the left operand is a TypedDict and the right operand is a dict expression that conforms to the TypedDict type.

packages/pyright-internal/src/analyzer/typeEvaluator.ts

@@ -10563,6 +10563,10 @@ export function createTypeEvaluator(importLookup: ImportLookup, evaluatorOptions
                 // For the "+" operator , use this technique only if the right operand is
                 // a list expression. This heuristic handles the common case of `my_list + [0]`.
                 expectedOperandType = leftType;
+            } else if (node.operator === OperatorType.BitwiseOr) {
+                // If this is a bitwise or ("|"), use the type of the left operand. This allows
+                // us to support the case where a TypedDict is being updated with a dict expression.
+                expectedOperandType = leftType;
             }
         }
 
@@ -10732,7 +10736,15 @@ export function createTypeEvaluator(importLookup: ImportLookup, evaluatorOptions
 
         const leftTypeResult = getTypeOfExpression(node.leftExpression);
         const leftType = leftTypeResult.type;
-        const rightTypeResult = getTypeOfExpression(node.rightExpression);
+
+        let expectedOperandType: Type | undefined;
+        if (node.operator === OperatorType.BitwiseOrEqual) {
+            // If this is a bitwise or ("|="), use the type of the left operand. This allows
+            // us to support the case where a TypedDict is being updated with a dict expression.
+            expectedOperandType = leftType;
+        }
+
+        const rightTypeResult = getTypeOfExpression(node.rightExpression, expectedOperandType);
         const rightType = rightTypeResult.type;
         const isIncomplete = !!rightTypeResult.isIncomplete || !!leftTypeResult.isIncomplete;
 

packages/pyright-internal/src/tests/samples/typedDict17.py

@@ -0,0 +1,24 @@
+# This sample tests the handling of the "|" and "|=" operators
+# for TypedDicts.
+
+from typing import TypedDict
+
+
+class Person(TypedDict, total=False):
+    name: str
+    age: int
+
+
+person: Person = {}
+
+person.update({"name": "Michael"})
+
+person |= {"name": "Michael"}
+person = person | {"name": "Michael"}
+
+
+# This should generate an error.
+person |= {"name": "Michael", "other": 1}
+
+# This should generate an error.
+person = person | {"name": 1}

packages/pyright-internal/src/tests/typeEvaluator2.test.ts

@@ -1107,3 +1107,9 @@ test('TypedDict16', () => {
 
     TestUtils.validateResults(analysisResults, 9);
 });
+
+test('TypedDict17', () => {
+    const analysisResults = TestUtils.typeAnalyzeSampleFiles(['typedDict17.py']);
+
+    TestUtils.validateResults(analysisResults, 2);
+});