Revert "Make concat also work on lists of bytes."

This reverts commit a0c5d9a.

Author: spookylukey

src/parsy/__init__.py

@@ -166,23 +166,10 @@ def combine_dict(self, combine_fn: Callable) -> Parser:
 
     def concat(self) -> Parser:
         """
-        Returns a parser that concatenates together the previously produced values.
-
-        This parser will join the values using the type of the input stream, so
-        when feeding bytes to the parser, the items to be joined must also be bytes.
+        Returns a parser that concatenates together (as a string) the previously
+        produced values.
         """
-
-        @Parser
-        def parser(stream: bytes | str, index: int) -> Result:
-            joiner = type(stream)()
-            result = self(stream, index)
-            if result.status:
-                next_parser: Parser = success(joiner.join(result.value))
-                return next_parser(stream, result.index).aggregate(result)
-            else:
-                return result
-
-        return parser
+        return self.map("".join)
 
     def then(self, other: Parser) -> Parser:
         """

tests/test_parsy.py

@@ -157,16 +157,11 @@ def test_combine_dict_skip_underscores(self):
         ).combine_dict(Pair)
         self.assertEqual(parser.parse("ABC   123"), Pair(word="ABC", number=123))
 
-    def test_concat_str(self):
+    def test_concat(self):
         parser = letter.many().concat()
         self.assertEqual(parser.parse(""), "")
         self.assertEqual(parser.parse("abc"), "abc")
 
-    def test_concat_bytes(self):
-        parser = any_char.many().concat()
-        self.assertEqual(parser.parse(b""), b"")
-        self.assertEqual(parser.parse(b"abc"), b"abc")
-
     def test_generate(self):
         x = y = None