Fix handling of standalone match/case with newlines/comments

CHANGES.md

@@ -26,6 +26,8 @@
   be formatted. (#2526)
 - Speed-up the new backtracking parser about 4X in general (enabled when
   `--target-version` is set to 3.10 and higher). (#2728)
+- Fix handling of standalone `match()` or `case()` when there is a trailing newline or a
+  comment inside of the parentheses. (#2760)
 
 ### Packaging
 

src/blib2to3/pgen2/parse.py

@@ -269,6 +269,10 @@ def addtoken(self, type: int, value: Text, context: Context) -> bool:
                     break
 
                 next_token_type, next_token_value, *_ = proxy.eat(counter)
+                if next_token_type in (tokenize.COMMENT, tokenize.NL):
+                    counter += 1
+                    continue
+
                 if next_token_type == tokenize.OP:
                     next_token_type = grammar.opmap[next_token_value]
 

tests/data/pattern_matching_style.py

@@ -6,10 +6,52 @@
     ): print(1)
     case c(
         very_complex=True,
-        perhaps_even_loooooooooooooooooooooooooooooooooooooong=-1
+        perhaps_even_loooooooooooooooooooooooooooooooooooooong=-1,
     ): print(2)
     case a: pass
 
+match(
+    arg # comment
+)
+
+match(
+)
+
+match(
+
+
+)
+
+case(
+    arg # comment
+)
+
+case(
+)
+
+case(
+
+
+)
+
+
+re.match(
+    something # fast
+)
+re.match(
+
+
+
+)
+match match(
+
+
+):
+    case case(
+        arg, # comment
+    ):
+        pass
+
 # output
 
 match something:
@@ -20,8 +62,30 @@
     ):
         print(1)
     case c(
-        very_complex=True, perhaps_even_loooooooooooooooooooooooooooooooooooooong=-1
+        very_complex=True,
+        perhaps_even_loooooooooooooooooooooooooooooooooooooong=-1,
     ):
         print(2)
     case a:
         pass
+
+match(arg)  # comment
+
+match()
+
+match()
+
+case(arg)  # comment
+
+case()
+
+case()
+
+
+re.match(something)  # fast
+re.match()
+match match():
+    case case(
+        arg,  # comment
+    ):
+        pass