Allow same RHS expressions in annotated assignments as in regular assignments

CHANGES.md

@@ -21,6 +21,9 @@
 
 - Added support for PEP 614 relaxed decorator syntax on python 3.9 (#1711)
 
+- Added parsing support for unparenthesized tuples and yield expressions in annotated
+  assignments (#1835)
+
 - use lowercase hex strings (#1692)
 
 #### _Packaging_

src/blib2to3/Grammar.txt

@@ -77,7 +77,7 @@ small_stmt: (expr_stmt | print_stmt  | del_stmt | pass_stmt | flow_stmt |
              import_stmt | global_stmt | exec_stmt | assert_stmt)
 expr_stmt: testlist_star_expr (annassign | augassign (yield_expr|testlist) |
                      ('=' (yield_expr|testlist_star_expr))*)
-annassign: ':' test ['=' test]
+annassign: ':' test ['=' (yield_expr|testlist_star_expr)]
 testlist_star_expr: (test|star_expr) (',' (test|star_expr))* [',']
 augassign: ('+=' | '-=' | '*=' | '@=' | '/=' | '%=' | '&=' | '|=' | '^=' |
             '<<=' | '>>=' | '**=' | '//=')

tests/data/python38.py

@@ -11,6 +11,14 @@ def starred_yield():
     yield "value1", *my_list
 
 
+# all right hand side expressions allowed in regular assignments are now also allowed in
+# annotated assignments
+a : Tuple[ str, int] = "1", 2
+a: Tuple[int , ... ] = b,  *c, d
+def t():
+    a : str =  yield "a"
+
+
 # output
 
 
@@ -25,3 +33,13 @@ def starred_return():
 def starred_yield():
     my_list = ["value2", "value3"]
     yield "value1", *my_list
+
+
+# all right hand side expressions allowed in regular assignments are now also allowed in
+# annotated assignments
+a: Tuple[str, int] = "1", 2
+a: Tuple[int, ...] = b, *c, d
+
+
+def t():
+    a: str = yield "a"