Fix grammar for type alias support (#3949)

Fixes #3948

Author: JelleZijlstra

CHANGES.md

@@ -37,6 +37,9 @@
 
 <!-- Changes to the parser or to version autodetection -->
 
+- Add support for PEP 695 type aliases containing lambdas and other unusual expressions
+  (#3949)
+
 ### Performance
 
 <!-- Changes that improve Black's performance. -->

src/blib2to3/Grammar.txt

@@ -108,7 +108,7 @@ dotted_as_names: dotted_as_name (',' dotted_as_name)*
 dotted_name: NAME ('.' NAME)*
 global_stmt: ('global' | 'nonlocal') NAME (',' NAME)*
 assert_stmt: 'assert' test [',' test]
-type_stmt: "type" NAME [typeparams] '=' expr
+type_stmt: "type" NAME [typeparams] '=' test
 
 compound_stmt: if_stmt | while_stmt | for_stmt | try_stmt | with_stmt | funcdef | classdef | decorated | async_stmt | match_stmt
 async_stmt: ASYNC (funcdef | with_stmt | for_stmt)

tests/data/cases/type_aliases.py

@@ -1,6 +1,10 @@
 # flags: --minimum-version=3.12
+
 type A=int
 type Gen[T]=list[T]
+type Alias[T]=lambda: T
+type And[T]=T and T
+type IfElse[T]=T if T else T
 
 type = aliased
 print(type(42))
@@ -9,6 +13,9 @@
 
 type A = int
 type Gen[T] = list[T]
+type Alias[T] = lambda: T
+type And[T] = T and T
+type IfElse[T] = T if T else T
 
 type = aliased
 print(type(42))