gh-108455: Run `mypy` on `Tools/peg_generator` (#108456)

Co-authored-by: Hugo van Kemenade <hugovk@users.noreply.github.com>

4 files changed, 16 insertions, 9 deletions

diff --git a/Tools/peg_generator/mypy.ini b/Tools/peg_generator/mypy.ini
index 1732372..186e633 100644
--- a/Tools/peg_generator/mypy.ini
+++ b/Tools/peg_generator/mypy.ini
@@ -1,5 +1,6 @@
 [mypy]
-files = pegen
+files = Tools/peg_generator/pegen
+pretty = True
 
 follow_imports = error
 no_implicit_optional = True
@@ -24,3 +25,6 @@ show_error_codes = True
 
 [mypy-pegen.grammar_parser]
 strict_optional = False
+
+[mypy-setuptools.*]
+ignore_missing_imports = True
diff --git a/Tools/peg_generator/pegen/build.py b/Tools/peg_generator/pegen/build.py
index e41330f..81efcad 100644
--- a/Tools/peg_generator/pegen/build.py
+++ b/Tools/peg_generator/pegen/build.py
@@ -5,7 +5,7 @@ import sys
 import sysconfig
 import tempfile
 import tokenize
-from typing import IO, Dict, List, Optional, Set, Tuple
+from typing import IO, Any, Dict, List, Optional, Set, Tuple
 
 from pegen.c_generator import CParserGenerator
 from pegen.grammar import Grammar
@@ -18,6 +18,7 @@ from pegen.tokenizer import Tokenizer
 MOD_DIR = pathlib.Path(__file__).resolve().parent
 
 TokenDefinitions = Tuple[Dict[int, str], Dict[str, int], Set[str]]
+Incomplete = Any  # TODO: install `types-setuptools` and remove this alias
 
 
 def get_extra_flags(compiler_flags: str, compiler_py_flags_nodist: str) -> List[str]:
@@ -28,7 +29,7 @@ def get_extra_flags(compiler_flags: str, compiler_py_flags_nodist: str) -> List[
     return f"{flags} {py_flags_nodist}".split()
 
 
-def fixup_build_ext(cmd):
+def fixup_build_ext(cmd: Incomplete) -> None:
     """Function needed to make build_ext tests pass.
 
     When Python was built with --enable-shared on Unix, -L. is not enough to
@@ -74,7 +75,7 @@ def compile_c_extension(
     keep_asserts: bool = True,
     disable_optimization: bool = False,
     library_dir: Optional[str] = None,
-) -> str:
+) -> pathlib.Path:
     """Compile the generated source for a parser generator into an extension module.
 
     The extension module will be generated in the same directory as the provided path
diff --git a/Tools/peg_generator/pegen/keywordgen.py b/Tools/peg_generator/pegen/keywordgen.py
index bbf1326..82d717b 100644
--- a/Tools/peg_generator/pegen/keywordgen.py
+++ b/Tools/peg_generator/pegen/keywordgen.py
@@ -35,6 +35,7 @@ iskeyword = frozenset(kwlist).__contains__
 issoftkeyword = frozenset(softkwlist).__contains__
 '''.lstrip()
 
+
 def main() -> None:
     parser = argparse.ArgumentParser(
         description="Generate the Lib/keywords.py file from the grammar."
diff --git a/Tools/peg_generator/pegen/parser.py b/Tools/peg_generator/pegen/parser.py
index 034e8e6..eab48ef 100644
--- a/Tools/peg_generator/pegen/parser.py
+++ b/Tools/peg_generator/pegen/parser.py
@@ -10,7 +10,6 @@ from typing import Any, Callable, ClassVar, Dict, Optional, Tuple, Type, TypeVar
 from pegen.tokenizer import Mark, Tokenizer, exact_token_types
 
 T = TypeVar("T")
-P = TypeVar("P", bound="Parser")
 F = TypeVar("F", bound=Callable[..., Any])
 
 
@@ -21,7 +20,7 @@ def logger(method: F) -> F:
     """
     method_name = method.__name__
 
-    def logger_wrapper(self: P, *args: object) -> T:
+    def logger_wrapper(self: "Parser", *args: object) -> Any:
         if not self._verbose:
             return method(self, *args)
         argsr = ",".join(repr(arg) for arg in args)
@@ -41,7 +40,7 @@ def memoize(method: F) -> F:
     """Memoize a symbol method."""
     method_name = method.__name__
 
-    def memoize_wrapper(self: P, *args: object) -> T:
+    def memoize_wrapper(self: "Parser", *args: object) -> Any:
         mark = self._mark()
         key = mark, method_name, args
         # Fast path: cache hit, and not verbose.
@@ -74,11 +73,13 @@ def memoize(method: F) -> F:
     return cast(F, memoize_wrapper)
 
 
-def memoize_left_rec(method: Callable[[P], Optional[T]]) -> Callable[[P], Optional[T]]:
+def memoize_left_rec(
+    method: Callable[["Parser"], Optional[T]]
+) -> Callable[["Parser"], Optional[T]]:
     """Memoize a left-recursive symbol method."""
     method_name = method.__name__
 
-    def memoize_left_rec_wrapper(self: P) -> Optional[T]:
+    def memoize_left_rec_wrapper(self: "Parser") -> Optional[T]:
         mark = self._mark()
         key = mark, method_name, ()
         # Fast path: cache hit, and not verbose.