Disallow unwrapping tuples in an as clause (#4634)

CHANGES.md

@@ -13,6 +13,8 @@
 - Fix crash while formatting expressions using the walrus operator in complex
   `with` statements (#4630)
 - Handle `# fmt: skip` followed by a comment at the end of file (#4635)
+- Fix crash when a tuple appears in the `as` clause of a `with` statement
+  (#4634)
 
 ### Preview style
 

src/black/linegen.py

@@ -56,6 +56,7 @@
     is_rpar_token,
     is_stub_body,
     is_stub_suite,
+    is_tuple,
     is_tuple_containing_star,
     is_tuple_containing_walrus,
     is_type_ignore_comment_string,
@@ -1626,6 +1627,7 @@ def maybe_make_parens_invisible_in_atom(
         node.type not in (syms.atom, syms.expr)
         or is_empty_tuple(node)
         or is_one_tuple(node)
+        or (is_tuple(node) and parent.type == syms.asexpr_test)
         or (is_yield(node) and parent.type != syms.expr_stmt)
         or (
             # This condition tries to prevent removing non-optional brackets

src/black/nodes.py

@@ -603,6 +603,17 @@ def is_one_tuple(node: LN) -> bool:
     )
 
 
+def is_tuple(node: LN) -> bool:
+    """Return True if `node` holds a tuple."""
+    if node.type != syms.atom:
+        return False
+    gexp = unwrap_singleton_parenthesis(node)
+    if gexp is None or gexp.type != syms.testlist_gexp:
+        return False
+
+    return True
+
+
 def is_tuple_containing_walrus(node: LN) -> bool:
     """Return True if `node` holds a tuple that contains a walrus operator."""
     if node.type != syms.atom:

tests/data/cases/context_managers_39.py

@@ -84,6 +84,11 @@ async def func():
         pass
 
 
+
+# don't remove the brackets here, it changes the meaning of the code.
+with (x, y) as z:
+    pass
+
 # output
 
 
@@ -172,3 +177,8 @@ async def func():
         some_other_function(argument1, argument2, argument3="some_value"),
     ):
         pass
+
+
+# don't remove the brackets here, it changes the meaning of the code.
+with (x, y) as z:
+    pass