Fixed bug that results in a crash when an empty tuple is used to specialize a generic type alias parameterized by a ParamSpec. This addresses #8694.

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

@@ -6814,7 +6814,7 @@ export function createTypeEvaluator(
                 typeArgs = [
                     {
                         type: UnknownType.create(),
-                        node: typeArgs[0].node,
+                        node: typeArgs.length > 0 ? typeArgs[0].node : node,
                         typeList: typeArgs,
                     },
                 ];

packages/pyright-internal/src/tests/samples/paramSpec13.py

@@ -2,8 +2,16 @@
 # for a generic type alias, a generic function, and a generic class.
 
 import asyncio
-from typing import Any, Callable, Concatenate, Coroutine, Generic, ParamSpec, TypeVar
-
+from typing import (
+    Any,
+    Callable,
+    Concatenate,
+    Coroutine,
+    Generic,
+    ParamSpec,
+    TypeAlias,
+    TypeVar,
+)
 
 _P = ParamSpec("_P")
 _R = TypeVar("_R")
@@ -101,3 +109,11 @@ asyncio.run(takes_check_func(my_check_func, 1, "2"))
 
 # This should generate an error because the signature doesn't match.
 asyncio.run(takes_check_func(my_check_func, 1, 2))
+
+
+TA1: TypeAlias = Callable[_P, Any]
+
+ta1_1: TA1[()] = lambda: 0
+
+# This should generate an error.
+ta1_2: TA1[()] = lambda x: x

packages/pyright-internal/src/tests/typeEvaluator4.test.ts

@@ -626,7 +626,7 @@ test('ParamSpec12', () => {
 
 test('ParamSpec13', () => {
     const results = TestUtils.typeAnalyzeSampleFiles(['paramSpec13.py']);
-    TestUtils.validateResults(results, 6);
+    TestUtils.validateResults(results, 7);
 });
 
 test('ParamSpec14', () => {