We are currently solving the following issue within our repository. Here is the issue text:
--- BEGIN ISSUE ---
unreachable code in `parsing.py`
**Describe the bug**

unreachable code in `src\black\parsing.py:170`: 
`raise AssertionError("INTERNAL ERROR: Tried parsing unsupported Python version!")`

**Expected behavior**

not having unreachable code 😝 

--- END ISSUE ---

Below are some code segments, each from a relevant file. One or more of these files may contain bugs.
--- BEGIN FILES ---
Path: `src/black/parsing.py`
Content:
```
1 """
2 Parse Python code and perform AST validation.
3 """
4 import ast
5 import platform
6 import sys
7 from typing import Any, Iterable, Iterator, List, Set, Tuple, Type, Union
8 
9 if sys.version_info < (3, 8):
10     from typing_extensions import Final
11 else:
12     from typing import Final
13 
14 from black.mode import Feature, TargetVersion, supports_feature
15 from black.nodes import syms
16 from blib2to3 import pygram
17 from blib2to3.pgen2 import driver
18 from blib2to3.pgen2.grammar import Grammar
19 from blib2to3.pgen2.parse import ParseError
20 from blib2to3.pgen2.tokenize import TokenError
21 from blib2to3.pytree import Leaf, Node
22 
23 ast3: Any
24 
25 _IS_PYPY = platform.python_implementation() == "PyPy"
26 
27 try:
28     from typed_ast import ast3
29 except ImportError:
30     if sys.version_info < (3, 8) and not _IS_PYPY:
31         print(
32             "The typed_ast package is required but not installed.\n"
33             "You can upgrade to Python 3.8+ or install typed_ast with\n"
34             "`python3 -m pip install typed-ast`.",
35             file=sys.stderr,
36         )
37         sys.exit(1)
38     else:
39         ast3 = ast
40 
41 
42 PY2_HINT: Final = "Python 2 support was removed in version 22.0."
43 
44 
45 class InvalidInput(ValueError):
46     """Raised when input source code fails all parse attempts."""
47 
48 
49 def get_grammars(target_versions: Set[TargetVersion]) -> List[Grammar]:
50     if not target_versions:
51         # No target_version specified, so try all grammars.
52         return [
53             # Python 3.7+
54             pygram.python_grammar_no_print_statement_no_exec_statement_async_keywords,
55             # Python 3.0-3.6
56             pygram.python_grammar_no_print_statement_no_exec_statement,
57             # Python 3.10+
58             pygram.python_grammar_soft_keywords,
59         ]
60 
61     grammars = []
62     # If we have to parse both, try to parse async as a keyword first
63     if not supports_feature(
64         target_versions, Feature.ASYNC_IDENTIFIERS
65     ) and not supports_feature(target_versions, Feature.PATTERN_MATCHING):
66         # Python 3.7-3.9
67         grammars.append(
68             pygram.python_grammar_no_print_statement_no_exec_statement_async_keywords
69         )
70     if not supports_feature(target_versions, Feature.ASYNC_KEYWORDS):
71         # Python 3.0-3.6
72         grammars.append(pygram.python_grammar_no_print_statement_no_exec_statement)
73     if supports_feature(target_versions, Feature.PATTERN_MATCHING):
74         # Python 3.10+
75         grammars.append(pygram.python_grammar_soft_keywords)
76 
77     # At least one of the above branches must have been taken, because every Python
78     # version has exactly one of the two 'ASYNC_*' flags
79     return grammars
80 
81 
82 def lib2to3_parse(src_txt: str, target_versions: Iterable[TargetVersion] = ()) -> Node:
83     """Given a string with source, return the lib2to3 Node."""
84     if not src_txt.endswith("\n"):
85         src_txt += "\n"
86 
87     grammars = get_grammars(set(target_versions))
88     errors = {}
89     for grammar in grammars:
90         drv = driver.Driver(grammar)
91         try:
92             result = drv.parse_string(src_txt, True)
93             break
94 
95         except ParseError as pe:
96             lineno, column = pe.context[1]
97             lines = src_txt.splitlines()
98             try:
99                 faulty_line = lines[lineno - 1]
100             except IndexError:
101                 faulty_line = "<line number missing in source>"
102             errors[grammar.version] = InvalidInput(
103                 f"Cannot parse: {lineno}:{column}: {faulty_line}"
104             )
105 
106         except TokenError as te:
107             # In edge cases these are raised; and typically don't have a "faulty_line".
108             lineno, column = te.args[1]
109             errors[grammar.version] = InvalidInput(
110                 f"Cannot parse: {lineno}:{column}: {te.args[0]}"
111             )
112 
113     else:
114         # Choose the latest version when raising the actual parsing error.
115         assert len(errors) >= 1
116         exc = errors[max(errors)]
117 
118         if matches_grammar(src_txt, pygram.python_grammar) or matches_grammar(
119             src_txt, pygram.python_grammar_no_print_statement
120         ):
121             original_msg = exc.args[0]
122             msg = f"{original_msg}\n{PY2_HINT}"
123             raise InvalidInput(msg) from None
124 
125         raise exc from None
126 
127     if isinstance(result, Leaf):
128         result = Node(syms.file_input, [result])
129     return result
130 
131 
132 def matches_grammar(src_txt: str, grammar: Grammar) -> bool:
133     drv = driver.Driver(grammar)
134     try:
135         drv.parse_string(src_txt, True)
136     except (ParseError, TokenError, IndentationError):
137         return False
138     else:
139         return True
140 
141 
142 def lib2to3_unparse(node: Node) -> str:
143     """Given a lib2to3 node, return its string representation."""
144     code = str(node)
145     return code
146 
147 
148 def parse_single_version(
149     src: str, version: Tuple[int, int]
150 ) -> Union[ast.AST, ast3.AST]:
151     filename = "<unknown>"
152     # typed-ast is needed because of feature version limitations in the builtin ast 3.8>
153     if sys.version_info >= (3, 8) and version >= (3,):
154         return ast.parse(src, filename, feature_version=version, type_comments=True)
155 
156     if _IS_PYPY:
157         # PyPy 3.7 doesn't support type comment tracking which is not ideal, but there's
158         # not much we can do as typed-ast won't work either.
159         if sys.version_info >= (3, 8):
160             return ast3.parse(src, filename, type_comments=True)
161         else:
162             return ast3.parse(src, filename)
163     else:
164         # Typed-ast is guaranteed to be used here and automatically tracks type
165         # comments separately.
166         return ast3.parse(src, filename, feature_version=version[1])
167 
168     raise AssertionError("INTERNAL ERROR: Tried parsing unsupported Python version!")
169 
170 
171 def parse_ast(src: str) -> Union[ast.AST, ast3.AST]:
172     # TODO: support Python 4+ ;)
173     versions = [(3, minor) for minor in range(3, sys.version_info[1] + 1)]
174 
175     first_error = ""
176     for version in sorted(versions, reverse=True):
177         try:
178             return parse_single_version(src, version)
179         except SyntaxError as e:
180             if not first_error:
181                 first_error = str(e)
182 
183     raise SyntaxError(first_error)
184 
185 
186 ast3_AST: Final[Type[ast3.AST]] = ast3.AST
187 
188 
189 def _normalize(lineend: str, value: str) -> str:
190     # To normalize, we strip any leading and trailing space from
191     # each line...
192     stripped: List[str] = [i.strip() for i in value.splitlines()]
193     normalized = lineend.join(stripped)
194     # ...and remove any blank lines at the beginning and end of
195     # the whole string
196     return normalized.strip()
197 
198 
199 def stringify_ast(node: Union[ast.AST, ast3.AST], depth: int = 0) -> Iterator[str]:
200     """Simple visitor generating strings to compare ASTs by content."""
201 
202     node = fixup_ast_constants(node)
203 
204     yield f"{'  ' * depth}{node.__class__.__name__}("
205 
206     type_ignore_classes: Tuple[Type[Any], ...]
207     for field in sorted(node._fields):  # noqa: F402
208         # TypeIgnore will not be present using pypy < 3.8, so need for this
209         if not (_IS_PYPY and sys.version_info < (3, 8)):
210             # TypeIgnore has only one field 'lineno' which breaks this comparison
211             type_ignore_classes = (ast3.TypeIgnore,)
212             if sys.version_info >= (3, 8):
213                 type_ignore_classes += (ast.TypeIgnore,)
214             if isinstance(node, type_ignore_classes):
215                 break
216 
217         try:
218             value: object = getattr(node, field)
219         except AttributeError:
220             continue
221 
222         yield f"{'  ' * (depth+1)}{field}="
223 
224         if isinstance(value, list):
225             for item in value:
226                 # Ignore nested tuples within del statements, because we may insert
227                 # parentheses and they change the AST.
228                 if (
229                     field == "targets"
230                     and isinstance(node, (ast.Delete, ast3.Delete))
231                     and isinstance(item, (ast.Tuple, ast3.Tuple))
232                 ):
233                     for elt in item.elts:
234                         yield from stringify_ast(elt, depth + 2)
235 
236                 elif isinstance(item, (ast.AST, ast3.AST)):
237                     yield from stringify_ast(item, depth + 2)
238 
239         # Note that we are referencing the typed-ast ASTs via global variables and not
240         # direct module attribute accesses because that breaks mypyc. It's probably
241         # something to do with the ast3 variables being marked as Any leading
242         # mypy to think this branch is always taken, leaving the rest of the code
243         # unanalyzed. Tighting up the types for the typed-ast AST types avoids the
244         # mypyc crash.
245         elif isinstance(value, (ast.AST, ast3_AST)):
246             yield from stringify_ast(value, depth + 2)
247 
248         else:
249             normalized: object
250             # Constant strings may be indented across newlines, if they are
251             # docstrings; fold spaces after newlines when comparing. Similarly,
252             # trailing and leading space may be removed.
253             if (
254                 isinstance(node, ast.Constant)
255                 and field == "value"
256                 and isinstance(value, str)
257             ):
258                 normalized = _normalize("\n", value)
259             else:
260                 normalized = value
261             yield f"{'  ' * (depth+2)}{normalized!r},  # {value.__class__.__name__}"
262 
263     yield f"{'  ' * depth})  # /{node.__class__.__name__}"
264 
265 
266 def fixup_ast_constants(node: Union[ast.AST, ast3.AST]) -> Union[ast.AST, ast3.AST]:
267     """Map ast nodes deprecated in 3.8 to Constant."""
268     if isinstance(node, (ast.Str, ast3.Str, ast.Bytes, ast3.Bytes)):
269         return ast.Constant(value=node.s)
270 
271     if isinstance(node, (ast.Num, ast3.Num)):
272         return ast.Constant(value=node.n)
273 
274     if isinstance(node, (ast.NameConstant, ast3.NameConstant)):
275         return ast.Constant(value=node.value)
276 
277     return node
278
```
--- END FILES ---

Please first localize the bug based on the issue statement, and then generate a patch according to the `git diff` format fenced by three backticks.

Here is an example:

```diff
diff --git a/examples/server_async.py b/examples/server_async.py
--- a/examples/server_async.py
+++ b/examples/server_async.py
@@ -313,4 +313,4 @@
 
 
 if __name__ == "__main__":
-    asyncio.run(run_async_server("."), debug=True)
+    asyncio.run(run_async_server(), debug=True)
diff --git a/examples/server_sync.py b/examples/server_sync.py
--- a/examples/server_sync.py
+++ b/examples/server_sync.py
@@ -313,5 +313,5 @@
 
 
 if __name__ == "__main__":
-    server = run_sync_server(".")
+    server = run_sync_server()
     server.shutdown()

```

diff --git a/src/black/parsing.py b/src/black/parsing.py
--- a/src/black/parsing.py
+++ b/src/black/parsing.py
@@ -165,8 +165,6 @@
         # comments separately.
         return ast3.parse(src, filename, feature_version=version[1])
 
-    raise AssertionError("INTERNAL ERROR: Tried parsing unsupported Python version!")
-
 
 def parse_ast(src: str) -> Union[ast.AST, ast3.AST]:
     # TODO: support Python 4+ ;)

{"golden_diff": "diff --git a/src/black/parsing.py b/src/black/parsing.py\n--- a/src/black/parsing.py\n+++ b/src/black/parsing.py\n@@ -165,8 +165,6 @@\n         # comments separately.\n         return ast3.parse(src, filename, feature_version=version[1])\n \n-    raise AssertionError(\"INTERNAL ERROR: Tried parsing unsupported Python version!\")\n-\n \n def parse_ast(src: str) -> Union[ast.AST, ast3.AST]:\n     # TODO: support Python 4+ ;)\n", "issue": "unreachable code in `parsing.py`\n**Describe the bug**\r\n\r\nunreachable code in `src\\black\\parsing.py:170`: \r\n`raise AssertionError(\"INTERNAL ERROR: Tried parsing unsupported Python version!\")`\r\n\r\n**Expected behavior**\r\n\r\nnot having unreachable code \ud83d\ude1d \n", "before_files": [{"content": "\"\"\"\nParse Python code and perform AST validation.\n\"\"\"\nimport ast\nimport platform\nimport sys\nfrom typing import Any, Iterable, Iterator, List, Set, Tuple, Type, Union\n\nif sys.version_info < (3, 8):\n    from typing_extensions import Final\nelse:\n    from typing import Final\n\nfrom black.mode import Feature, TargetVersion, supports_feature\nfrom black.nodes import syms\nfrom blib2to3 import pygram\nfrom blib2to3.pgen2 import driver\nfrom blib2to3.pgen2.grammar import Grammar\nfrom blib2to3.pgen2.parse import ParseError\nfrom blib2to3.pgen2.tokenize import TokenError\nfrom blib2to3.pytree import Leaf, Node\n\nast3: Any\n\n_IS_PYPY = platform.python_implementation() == \"PyPy\"\n\ntry:\n    from typed_ast import ast3\nexcept ImportError:\n    if sys.version_info < (3, 8) and not _IS_PYPY:\n        print(\n            \"The typed_ast package is required but not installed.\\n\"\n            \"You can upgrade to Python 3.8+ or install typed_ast with\\n\"\n            \"`python3 -m pip install typed-ast`.\",\n            file=sys.stderr,\n        )\n        sys.exit(1)\n    else:\n        ast3 = ast\n\n\nPY2_HINT: Final = \"Python 2 support was removed in version 22.0.\"\n\n\nclass InvalidInput(ValueError):\n    \"\"\"Raised when input source code fails all parse attempts.\"\"\"\n\n\ndef get_grammars(target_versions: Set[TargetVersion]) -> List[Grammar]:\n    if not target_versions:\n        # No target_version specified, so try all grammars.\n        return [\n            # Python 3.7+\n            pygram.python_grammar_no_print_statement_no_exec_statement_async_keywords,\n            # Python 3.0-3.6\n            pygram.python_grammar_no_print_statement_no_exec_statement,\n            # Python 3.10+\n            pygram.python_grammar_soft_keywords,\n        ]\n\n    grammars = []\n    # If we have to parse both, try to parse async as a keyword first\n    if not supports_feature(\n        target_versions, Feature.ASYNC_IDENTIFIERS\n    ) and not supports_feature(target_versions, Feature.PATTERN_MATCHING):\n        # Python 3.7-3.9\n        grammars.append(\n            pygram.python_grammar_no_print_statement_no_exec_statement_async_keywords\n        )\n    if not supports_feature(target_versions, Feature.ASYNC_KEYWORDS):\n        # Python 3.0-3.6\n        grammars.append(pygram.python_grammar_no_print_statement_no_exec_statement)\n    if supports_feature(target_versions, Feature.PATTERN_MATCHING):\n        # Python 3.10+\n        grammars.append(pygram.python_grammar_soft_keywords)\n\n    # At least one of the above branches must have been taken, because every Python\n    # version has exactly one of the two 'ASYNC_*' flags\n    return grammars\n\n\ndef lib2to3_parse(src_txt: str, target_versions: Iterable[TargetVersion] = ()) -> Node:\n    \"\"\"Given a string with source, return the lib2to3 Node.\"\"\"\n    if not src_txt.endswith(\"\\n\"):\n        src_txt += \"\\n\"\n\n    grammars = get_grammars(set(target_versions))\n    errors = {}\n    for grammar in grammars:\n        drv = driver.Driver(grammar)\n        try:\n            result = drv.parse_string(src_txt, True)\n            break\n\n        except ParseError as pe:\n            lineno, column = pe.context[1]\n            lines = src_txt.splitlines()\n            try:\n                faulty_line = lines[lineno - 1]\n            except IndexError:\n                faulty_line = \"<line number missing in source>\"\n            errors[grammar.version] = InvalidInput(\n                f\"Cannot parse: {lineno}:{column}: {faulty_line}\"\n            )\n\n        except TokenError as te:\n            # In edge cases these are raised; and typically don't have a \"faulty_line\".\n            lineno, column = te.args[1]\n            errors[grammar.version] = InvalidInput(\n                f\"Cannot parse: {lineno}:{column}: {te.args[0]}\"\n            )\n\n    else:\n        # Choose the latest version when raising the actual parsing error.\n        assert len(errors) >= 1\n        exc = errors[max(errors)]\n\n        if matches_grammar(src_txt, pygram.python_grammar) or matches_grammar(\n            src_txt, pygram.python_grammar_no_print_statement\n        ):\n            original_msg = exc.args[0]\n            msg = f\"{original_msg}\\n{PY2_HINT}\"\n            raise InvalidInput(msg) from None\n\n        raise exc from None\n\n    if isinstance(result, Leaf):\n        result = Node(syms.file_input, [result])\n    return result\n\n\ndef matches_grammar(src_txt: str, grammar: Grammar) -> bool:\n    drv = driver.Driver(grammar)\n    try:\n        drv.parse_string(src_txt, True)\n    except (ParseError, TokenError, IndentationError):\n        return False\n    else:\n        return True\n\n\ndef lib2to3_unparse(node: Node) -> str:\n    \"\"\"Given a lib2to3 node, return its string representation.\"\"\"\n    code = str(node)\n    return code\n\n\ndef parse_single_version(\n    src: str, version: Tuple[int, int]\n) -> Union[ast.AST, ast3.AST]:\n    filename = \"<unknown>\"\n    # typed-ast is needed because of feature version limitations in the builtin ast 3.8>\n    if sys.version_info >= (3, 8) and version >= (3,):\n        return ast.parse(src, filename, feature_version=version, type_comments=True)\n\n    if _IS_PYPY:\n        # PyPy 3.7 doesn't support type comment tracking which is not ideal, but there's\n        # not much we can do as typed-ast won't work either.\n        if sys.version_info >= (3, 8):\n            return ast3.parse(src, filename, type_comments=True)\n        else:\n            return ast3.parse(src, filename)\n    else:\n        # Typed-ast is guaranteed to be used here and automatically tracks type\n        # comments separately.\n        return ast3.parse(src, filename, feature_version=version[1])\n\n    raise AssertionError(\"INTERNAL ERROR: Tried parsing unsupported Python version!\")\n\n\ndef parse_ast(src: str) -> Union[ast.AST, ast3.AST]:\n    # TODO: support Python 4+ ;)\n    versions = [(3, minor) for minor in range(3, sys.version_info[1] + 1)]\n\n    first_error = \"\"\n    for version in sorted(versions, reverse=True):\n        try:\n            return parse_single_version(src, version)\n        except SyntaxError as e:\n            if not first_error:\n                first_error = str(e)\n\n    raise SyntaxError(first_error)\n\n\nast3_AST: Final[Type[ast3.AST]] = ast3.AST\n\n\ndef _normalize(lineend: str, value: str) -> str:\n    # To normalize, we strip any leading and trailing space from\n    # each line...\n    stripped: List[str] = [i.strip() for i in value.splitlines()]\n    normalized = lineend.join(stripped)\n    # ...and remove any blank lines at the beginning and end of\n    # the whole string\n    return normalized.strip()\n\n\ndef stringify_ast(node: Union[ast.AST, ast3.AST], depth: int = 0) -> Iterator[str]:\n    \"\"\"Simple visitor generating strings to compare ASTs by content.\"\"\"\n\n    node = fixup_ast_constants(node)\n\n    yield f\"{'  ' * depth}{node.__class__.__name__}(\"\n\n    type_ignore_classes: Tuple[Type[Any], ...]\n    for field in sorted(node._fields):  # noqa: F402\n        # TypeIgnore will not be present using pypy < 3.8, so need for this\n        if not (_IS_PYPY and sys.version_info < (3, 8)):\n            # TypeIgnore has only one field 'lineno' which breaks this comparison\n            type_ignore_classes = (ast3.TypeIgnore,)\n            if sys.version_info >= (3, 8):\n                type_ignore_classes += (ast.TypeIgnore,)\n            if isinstance(node, type_ignore_classes):\n                break\n\n        try:\n            value: object = getattr(node, field)\n        except AttributeError:\n            continue\n\n        yield f\"{'  ' * (depth+1)}{field}=\"\n\n        if isinstance(value, list):\n            for item in value:\n                # Ignore nested tuples within del statements, because we may insert\n                # parentheses and they change the AST.\n                if (\n                    field == \"targets\"\n                    and isinstance(node, (ast.Delete, ast3.Delete))\n                    and isinstance(item, (ast.Tuple, ast3.Tuple))\n                ):\n                    for elt in item.elts:\n                        yield from stringify_ast(elt, depth + 2)\n\n                elif isinstance(item, (ast.AST, ast3.AST)):\n                    yield from stringify_ast(item, depth + 2)\n\n        # Note that we are referencing the typed-ast ASTs via global variables and not\n        # direct module attribute accesses because that breaks mypyc. It's probably\n        # something to do with the ast3 variables being marked as Any leading\n        # mypy to think this branch is always taken, leaving the rest of the code\n        # unanalyzed. Tighting up the types for the typed-ast AST types avoids the\n        # mypyc crash.\n        elif isinstance(value, (ast.AST, ast3_AST)):\n            yield from stringify_ast(value, depth + 2)\n\n        else:\n            normalized: object\n            # Constant strings may be indented across newlines, if they are\n            # docstrings; fold spaces after newlines when comparing. Similarly,\n            # trailing and leading space may be removed.\n            if (\n                isinstance(node, ast.Constant)\n                and field == \"value\"\n                and isinstance(value, str)\n            ):\n                normalized = _normalize(\"\\n\", value)\n            else:\n                normalized = value\n            yield f\"{'  ' * (depth+2)}{normalized!r},  # {value.__class__.__name__}\"\n\n    yield f\"{'  ' * depth})  # /{node.__class__.__name__}\"\n\n\ndef fixup_ast_constants(node: Union[ast.AST, ast3.AST]) -> Union[ast.AST, ast3.AST]:\n    \"\"\"Map ast nodes deprecated in 3.8 to Constant.\"\"\"\n    if isinstance(node, (ast.Str, ast3.Str, ast.Bytes, ast3.Bytes)):\n        return ast.Constant(value=node.s)\n\n    if isinstance(node, (ast.Num, ast3.Num)):\n        return ast.Constant(value=node.n)\n\n    if isinstance(node, (ast.NameConstant, ast3.NameConstant)):\n        return ast.Constant(value=node.value)\n\n    return node\n", "path": "src/black/parsing.py"}], "after_files": [{"content": "\"\"\"\nParse Python code and perform AST validation.\n\"\"\"\nimport ast\nimport platform\nimport sys\nfrom typing import Any, Iterable, Iterator, List, Set, Tuple, Type, Union\n\nif sys.version_info < (3, 8):\n    from typing_extensions import Final\nelse:\n    from typing import Final\n\nfrom black.mode import Feature, TargetVersion, supports_feature\nfrom black.nodes import syms\nfrom blib2to3 import pygram\nfrom blib2to3.pgen2 import driver\nfrom blib2to3.pgen2.grammar import Grammar\nfrom blib2to3.pgen2.parse import ParseError\nfrom blib2to3.pgen2.tokenize import TokenError\nfrom blib2to3.pytree import Leaf, Node\n\nast3: Any\n\n_IS_PYPY = platform.python_implementation() == \"PyPy\"\n\ntry:\n    from typed_ast import ast3\nexcept ImportError:\n    if sys.version_info < (3, 8) and not _IS_PYPY:\n        print(\n            \"The typed_ast package is required but not installed.\\n\"\n            \"You can upgrade to Python 3.8+ or install typed_ast with\\n\"\n            \"`python3 -m pip install typed-ast`.\",\n            file=sys.stderr,\n        )\n        sys.exit(1)\n    else:\n        ast3 = ast\n\n\nPY2_HINT: Final = \"Python 2 support was removed in version 22.0.\"\n\n\nclass InvalidInput(ValueError):\n    \"\"\"Raised when input source code fails all parse attempts.\"\"\"\n\n\ndef get_grammars(target_versions: Set[TargetVersion]) -> List[Grammar]:\n    if not target_versions:\n        # No target_version specified, so try all grammars.\n        return [\n            # Python 3.7+\n            pygram.python_grammar_no_print_statement_no_exec_statement_async_keywords,\n            # Python 3.0-3.6\n            pygram.python_grammar_no_print_statement_no_exec_statement,\n            # Python 3.10+\n            pygram.python_grammar_soft_keywords,\n        ]\n\n    grammars = []\n    # If we have to parse both, try to parse async as a keyword first\n    if not supports_feature(\n        target_versions, Feature.ASYNC_IDENTIFIERS\n    ) and not supports_feature(target_versions, Feature.PATTERN_MATCHING):\n        # Python 3.7-3.9\n        grammars.append(\n            pygram.python_grammar_no_print_statement_no_exec_statement_async_keywords\n        )\n    if not supports_feature(target_versions, Feature.ASYNC_KEYWORDS):\n        # Python 3.0-3.6\n        grammars.append(pygram.python_grammar_no_print_statement_no_exec_statement)\n    if supports_feature(target_versions, Feature.PATTERN_MATCHING):\n        # Python 3.10+\n        grammars.append(pygram.python_grammar_soft_keywords)\n\n    # At least one of the above branches must have been taken, because every Python\n    # version has exactly one of the two 'ASYNC_*' flags\n    return grammars\n\n\ndef lib2to3_parse(src_txt: str, target_versions: Iterable[TargetVersion] = ()) -> Node:\n    \"\"\"Given a string with source, return the lib2to3 Node.\"\"\"\n    if not src_txt.endswith(\"\\n\"):\n        src_txt += \"\\n\"\n\n    grammars = get_grammars(set(target_versions))\n    errors = {}\n    for grammar in grammars:\n        drv = driver.Driver(grammar)\n        try:\n            result = drv.parse_string(src_txt, True)\n            break\n\n        except ParseError as pe:\n            lineno, column = pe.context[1]\n            lines = src_txt.splitlines()\n            try:\n                faulty_line = lines[lineno - 1]\n            except IndexError:\n                faulty_line = \"<line number missing in source>\"\n            errors[grammar.version] = InvalidInput(\n                f\"Cannot parse: {lineno}:{column}: {faulty_line}\"\n            )\n\n        except TokenError as te:\n            # In edge cases these are raised; and typically don't have a \"faulty_line\".\n            lineno, column = te.args[1]\n            errors[grammar.version] = InvalidInput(\n                f\"Cannot parse: {lineno}:{column}: {te.args[0]}\"\n            )\n\n    else:\n        # Choose the latest version when raising the actual parsing error.\n        assert len(errors) >= 1\n        exc = errors[max(errors)]\n\n        if matches_grammar(src_txt, pygram.python_grammar) or matches_grammar(\n            src_txt, pygram.python_grammar_no_print_statement\n        ):\n            original_msg = exc.args[0]\n            msg = f\"{original_msg}\\n{PY2_HINT}\"\n            raise InvalidInput(msg) from None\n\n        raise exc from None\n\n    if isinstance(result, Leaf):\n        result = Node(syms.file_input, [result])\n    return result\n\n\ndef matches_grammar(src_txt: str, grammar: Grammar) -> bool:\n    drv = driver.Driver(grammar)\n    try:\n        drv.parse_string(src_txt, True)\n    except (ParseError, TokenError, IndentationError):\n        return False\n    else:\n        return True\n\n\ndef lib2to3_unparse(node: Node) -> str:\n    \"\"\"Given a lib2to3 node, return its string representation.\"\"\"\n    code = str(node)\n    return code\n\n\ndef parse_single_version(\n    src: str, version: Tuple[int, int]\n) -> Union[ast.AST, ast3.AST]:\n    filename = \"<unknown>\"\n    # typed-ast is needed because of feature version limitations in the builtin ast 3.8>\n    if sys.version_info >= (3, 8) and version >= (3,):\n        return ast.parse(src, filename, feature_version=version, type_comments=True)\n\n    if _IS_PYPY:\n        # PyPy 3.7 doesn't support type comment tracking which is not ideal, but there's\n        # not much we can do as typed-ast won't work either.\n        if sys.version_info >= (3, 8):\n            return ast3.parse(src, filename, type_comments=True)\n        else:\n            return ast3.parse(src, filename)\n    else:\n        # Typed-ast is guaranteed to be used here and automatically tracks type\n        # comments separately.\n        return ast3.parse(src, filename, feature_version=version[1])\n\n\ndef parse_ast(src: str) -> Union[ast.AST, ast3.AST]:\n    # TODO: support Python 4+ ;)\n    versions = [(3, minor) for minor in range(3, sys.version_info[1] + 1)]\n\n    first_error = \"\"\n    for version in sorted(versions, reverse=True):\n        try:\n            return parse_single_version(src, version)\n        except SyntaxError as e:\n            if not first_error:\n                first_error = str(e)\n\n    raise SyntaxError(first_error)\n\n\nast3_AST: Final[Type[ast3.AST]] = ast3.AST\n\n\ndef _normalize(lineend: str, value: str) -> str:\n    # To normalize, we strip any leading and trailing space from\n    # each line...\n    stripped: List[str] = [i.strip() for i in value.splitlines()]\n    normalized = lineend.join(stripped)\n    # ...and remove any blank lines at the beginning and end of\n    # the whole string\n    return normalized.strip()\n\n\ndef stringify_ast(node: Union[ast.AST, ast3.AST], depth: int = 0) -> Iterator[str]:\n    \"\"\"Simple visitor generating strings to compare ASTs by content.\"\"\"\n\n    node = fixup_ast_constants(node)\n\n    yield f\"{'  ' * depth}{node.__class__.__name__}(\"\n\n    type_ignore_classes: Tuple[Type[Any], ...]\n    for field in sorted(node._fields):  # noqa: F402\n        # TypeIgnore will not be present using pypy < 3.8, so need for this\n        if not (_IS_PYPY and sys.version_info < (3, 8)):\n            # TypeIgnore has only one field 'lineno' which breaks this comparison\n            type_ignore_classes = (ast3.TypeIgnore,)\n            if sys.version_info >= (3, 8):\n                type_ignore_classes += (ast.TypeIgnore,)\n            if isinstance(node, type_ignore_classes):\n                break\n\n        try:\n            value: object = getattr(node, field)\n        except AttributeError:\n            continue\n\n        yield f\"{'  ' * (depth+1)}{field}=\"\n\n        if isinstance(value, list):\n            for item in value:\n                # Ignore nested tuples within del statements, because we may insert\n                # parentheses and they change the AST.\n                if (\n                    field == \"targets\"\n                    and isinstance(node, (ast.Delete, ast3.Delete))\n                    and isinstance(item, (ast.Tuple, ast3.Tuple))\n                ):\n                    for elt in item.elts:\n                        yield from stringify_ast(elt, depth + 2)\n\n                elif isinstance(item, (ast.AST, ast3.AST)):\n                    yield from stringify_ast(item, depth + 2)\n\n        # Note that we are referencing the typed-ast ASTs via global variables and not\n        # direct module attribute accesses because that breaks mypyc. It's probably\n        # something to do with the ast3 variables being marked as Any leading\n        # mypy to think this branch is always taken, leaving the rest of the code\n        # unanalyzed. Tighting up the types for the typed-ast AST types avoids the\n        # mypyc crash.\n        elif isinstance(value, (ast.AST, ast3_AST)):\n            yield from stringify_ast(value, depth + 2)\n\n        else:\n            normalized: object\n            # Constant strings may be indented across newlines, if they are\n            # docstrings; fold spaces after newlines when comparing. Similarly,\n            # trailing and leading space may be removed.\n            if (\n                isinstance(node, ast.Constant)\n                and field == \"value\"\n                and isinstance(value, str)\n            ):\n                normalized = _normalize(\"\\n\", value)\n            else:\n                normalized = value\n            yield f\"{'  ' * (depth+2)}{normalized!r},  # {value.__class__.__name__}\"\n\n    yield f\"{'  ' * depth})  # /{node.__class__.__name__}\"\n\n\ndef fixup_ast_constants(node: Union[ast.AST, ast3.AST]) -> Union[ast.AST, ast3.AST]:\n    \"\"\"Map ast nodes deprecated in 3.8 to Constant.\"\"\"\n    if isinstance(node, (ast.Str, ast3.Str, ast.Bytes, ast3.Bytes)):\n        return ast.Constant(value=node.s)\n\n    if isinstance(node, (ast.Num, ast3.Num)):\n        return ast.Constant(value=node.n)\n\n    if isinstance(node, (ast.NameConstant, ast3.NameConstant)):\n        return ast.Constant(value=node.value)\n\n    return node\n", "path": "src/black/parsing.py"}]}