Fixed bug that resulted in incorrect type evaluation when bidirectional type inference was used along with a type alias that was involved in a circular declaration.

msfterictraut · msfterictraut · commit 6ad84aecfe1e · 2022-08-05T21:18:35.000-07:00
diff --git a/packages/pyright-internal/src/analyzer/constraintSolver.ts b/packages/pyright-internal/src/analyzer/constraintSolver.ts
@@ -54,6 +54,7 @@ import {
     mapSubtypes,
     specializeTupleClass,
     transformExpectedTypeForConstructor,
+    transformPossibleRecursiveTypeAlias,
 } from './typeUtils';
 import { TypeVarContext } from './typeVarContext';
 
@@ -868,7 +869,9 @@ export function populateTypeVarContextBasedOnExpectedType(
                 const targetTypeVar =
                     ClassType.getTypeParameters(specializedType)[synthTypeVar.details.synthesizedIndex];
                 if (index < expectedTypeArgs.length) {
-                    let expectedTypeArgValue: Type | undefined = expectedTypeArgs[index];
+                    let expectedTypeArgValue: Type | undefined = transformPossibleRecursiveTypeAlias(
+                        expectedTypeArgs[index]
+                    );
 
                     if (liveTypeVarScopes) {
                         expectedTypeArgValue = transformExpectedTypeForConstructor(
