pep-484: sqlalchemy.sql pass one

sqlalchemy.sql will require many passes to get all
modules even gradually typed.  Will have to pick and
choose what modules can be strictly typed vs. which
can be gradual.

in this patch, emphasis is on visitors.py, cache_key.py,
annotations.py for strict typing, compiler.py is on gradual
typing but has much more structure, in particular where it
connects with the outside world.

The work within compiler.py also reached back out to
engine/cursor.py , default.py quite a bit.

References: #6810
Change-Id: I6e8a29f6013fd216e43d45091bc193f8be0368fd

1 files changed, 22 insertions, 2 deletions

diff --git a/lib/sqlalchemy/util/typing.py b/lib/sqlalchemy/util/typing.py
index 160eabd85..c089616e4 100644
--- a/lib/sqlalchemy/util/typing.py
+++ b/lib/sqlalchemy/util/typing.py
@@ -3,10 +3,11 @@ from __future__ import annotations
 import sys
 import typing
 from typing import Any
-from typing import Callable  # noqa
 from typing import cast
 from typing import Dict
 from typing import ForwardRef
+from typing import Iterable
+from typing import Tuple
 from typing import Type
 from typing import TypeVar
 from typing import Union
@@ -16,6 +17,11 @@ from typing_extensions import NotRequired as NotRequired  # noqa
 from . import compat
 
 _T = TypeVar("_T", bound=Any)
+_KT = TypeVar("_KT")
+_KT_co = TypeVar("_KT_co", covariant=True)
+_KT_contra = TypeVar("_KT_contra", contravariant=True)
+_VT = TypeVar("_VT")
+_VT_co = TypeVar("_VT_co", covariant=True)
 
 Self = TypeVar("Self", bound=Any)
 
@@ -45,6 +51,18 @@ else:
     from typing_extensions import Protocol as Protocol  # noqa F401
     from typing_extensions import TypedDict as TypedDict  # noqa F401
 
+# copied from TypeShed, required in order to implement
+# MutableMapping.update()
+
+
+class SupportsKeysAndGetItem(Protocol[_KT, _VT_co]):
+    def keys(self) -> Iterable[_KT]:
+        ...
+
+    def __getitem__(self, __k: _KT) -> _VT_co:
+        ...
+
+
 # work around https://github.com/microsoft/pyright/issues/3025
 _LiteralStar = Literal["*"]
 
@@ -120,7 +138,9 @@ def make_union_type(*types):
     return cast(Any, Union).__getitem__(types)
 
 
-def expand_unions(type_, include_union=False, discard_none=False):
+def expand_unions(
+    type_: Type[Any], include_union: bool = False, discard_none: bool = False
+) -> Tuple[Type[Any], ...]:
     """Return a type as as a tuple of individual types, expanding for
     ``Union`` types."""