Support as-expressions on dict items (GH-2686)

CHANGES.md

@@ -5,6 +5,8 @@
 ### _Black_
 
 - Improve error message for invalid regular expression (#2678)
+- Fix mapping cases that contain as-expressions, like `case {"key": 1 | 2 as password}`
+  (#2686)
 
 ## 21.12b0
 

src/blib2to3/Grammar.txt

@@ -168,8 +168,8 @@ subscript: test [':=' test] | [test] ':' [test] [sliceop]
 sliceop: ':' [test]
 exprlist: (expr|star_expr) (',' (expr|star_expr))* [',']
 testlist: test (',' test)* [',']
-dictsetmaker: ( ((test ':' test | '**' expr)
+dictsetmaker: ( ((test ':' asexpr_test | '**' expr)
-                 (comp_for | (',' (test ':' test | '**' expr))* [','])) |
+                 (comp_for | (',' (test ':' asexpr_test | '**' expr))* [','])) |
                 ((test [':=' test] | star_expr)
 		 (comp_for | (',' (test [':=' test] | star_expr))* [','])) )
 

tests/data/pattern_matching_extras.py

@@ -82,3 +82,13 @@ def func(match: case, case: match) -> case:
 match a, *b(), c:
     case d, *f, g:
         pass
+
+
+match something:
+    case {
+        "key": key as key_1,
+        "password": PASS.ONE | PASS.TWO | PASS.THREE as password,
+    }:
+        pass
+    case {"maybe": something(complicated as this) as that}:
+        pass