WIP: concrete generics (#256)

* WIP

* Adds concrete generics support

* Fixes bug with `ABC` instances, annotates tests

* Ignores phantom-types for python3.7

Author: sobolevn

.readthedocs.yml

@@ -1,7 +1,7 @@
 version: 2
 
 python:
-  version: 3.7
+  version: 3.8
   install:
     - requirements: docs/requirements.txt
 

CHANGELOG.md

@@ -7,13 +7,15 @@ We follow Semantic Versions since the `0.1.0` release.
 
 ### Features
 
+- Adds support for concrete generic types like `List[str]` and `Set[int]` #24
 - Adds support for multiple type arguments in `Supports` type #244
 - Adds support for types that have `__instancecheck__` defined #248
 
 ### Bugfixes
 
 - Fixes that types referenced in multiple typeclasses
   were not handling `Supports` properly #249
+- Fixes typing bug with `ABC` and mutable typeclass signature #259
 
 
 ## Version 0.3.0

classes/_registry.py

@@ -0,0 +1,44 @@
+from types import MethodType
+from typing import Callable, Dict, NoReturn, Optional
+
+TypeRegistry = Dict[type, Callable]
+
+
+def choose_registry(  # noqa: WPS211
+    # It has multiple arguments, but I don't see an easy and performant way
+    # to refactor it: I don't want to create extra structures
+    # and I don't want to create a class with methods.
+    typ: type,
+    is_protocol: bool,
+    delegate: Optional[type],
+    concretes: TypeRegistry,
+    instances: TypeRegistry,
+    protocols: TypeRegistry,
+) -> TypeRegistry:
+    """
+    Returns the appropriate registry to store the passed type.
+
+    It depends on how ``instance`` method is used and also on the type itself.
+    """
+    if is_protocol:
+        return protocols
+
+    is_concrete = (
+        delegate is not None or
+        isinstance(getattr(typ, '__instancecheck__', None), MethodType)
+    )
+    if is_concrete:
+        # This means that this type has `__instancecheck__` defined,
+        # which allows dynamic checks of what `isinstance` of this type.
+        # That's why we also treat this type as a concrete.
+        return concretes
+    return instances
+
+
+def default_implementation(instance, *args, **kwargs) -> NoReturn:
+    """By default raises an exception."""
+    raise NotImplementedError(
+        'Missing matched typeclass instance for type: {0}'.format(
+            type(instance).__qualname__,
+        ),
+    )

classes/_typeclass.py

@@ -114,16 +114,12 @@
 
 See our `official docs <https://classes.readthedocs.io>`_ to learn more!
 """
-
-from abc import get_cache_token
 from functools import _find_impl  # type: ignore  # noqa: WPS450
-from types import MethodType
 from typing import (  # noqa: WPS235
     TYPE_CHECKING,
     Callable,
     Dict,
     Generic,
-    NoReturn,
     Optional,
     Type,
     TypeVar,
@@ -134,6 +130,12 @@
 
 from typing_extensions import TypeGuard, final
 
+from classes._registry import (
+    TypeRegistry,
+    choose_registry,
+    default_implementation,
+)
+
 _InstanceType = TypeVar('_InstanceType')
 _SignatureType = TypeVar('_SignatureType', bound=Callable)
 _AssociatedType = TypeVar('_AssociatedType')
@@ -305,12 +307,17 @@ class _TypeClass(  # noqa: WPS214
     """
 
     __slots__ = (
+        # Str:
         '_signature',
         '_associated_type',
+
+        # Registry:
+        '_concretes',
         '_instances',
         '_protocols',
+
+        # Cache:
         '_dispatch_cache',
-        '_cache_token',
     )
 
     _dispatch_cache: Dict[type, Callable]
@@ -349,16 +356,17 @@ def __init__(
           The only exception is the first argument: it is polymorfic.
 
         """
-        self._instances: Dict[type, Callable] = {}
-        self._protocols: Dict[type, Callable] = {}
-
         # We need this for `repr`:
         self._signature = signature
         self._associated_type = associated_type
 
+        # Registries:
+        self._concretes: TypeRegistry = {}
+        self._instances: TypeRegistry = {}
+        self._protocols: TypeRegistry = {}
+
         # Cache parts:
         self._dispatch_cache = WeakKeyDictionary()  # type: ignore
-        self._cache_token = None
 
     def __call__(
         self,
@@ -410,7 +418,16 @@ def __call__(
         And all typeclasses that match ``Callable[[int, int], int]`` signature
         will typecheck.
         """
-        self._control_abc_cache()
+        # At first, we try all our concrete types,
+        # we don't cache it, because we cannot.
+        # We only have runtime type info: `type([1]) == type(['a'])`.
+        # It might be slow!
+        # Don't add concrete types unless
+        # you are absolutely know what you are doing.
+        impl = self._dispatch_concrete(instance)
+        if impl is not None:
+            return impl(instance, *args, **kwargs)
+
         instance_type = type(instance)
 
         try:
@@ -419,7 +436,7 @@ def __call__(
             impl = self._dispatch(
                 instance,
                 instance_type,
-            ) or self._default_implementation
+            ) or default_implementation
             self._dispatch_cache[instance_type] = impl
         return impl(instance, *args, **kwargs)
 
@@ -481,16 +498,24 @@ def supports(
 
         See also: https://www.python.org/dev/peps/pep-0647
         """
-        self._control_abc_cache()
-
+        # Here we first check that instance is already in the cache
+        # and only then we check concrete types.
+        # Why?
+        # Because if some type is already in the cache,
+        # it means that it is not concrete.
+        # So, this is simply faster.
         instance_type = type(instance)
         if instance_type in self._dispatch_cache:
             return True
 
-        # This only happens when we don't have a cache in place:
+        # We never cache concrete types.
+        if self._dispatch_concrete(instance) is not None:
+            return True
+
+        # This only happens when we don't have a cache in place
+        # and this is not a concrete generic:
         impl = self._dispatch(instance, instance_type)
         if impl is None:
-            self._dispatch_cache[instance_type] = self._default_implementation
             return False
 
         self._dispatch_cache[instance_type] = impl
@@ -503,14 +528,36 @@ def instance(
         # TODO: at one point I would like to remove `is_protocol`
         # and make this function decide whether this type is protocol or not.
         is_protocol: bool = False,
+        delegate: Optional[type] = None,
     ) -> '_TypeClassInstanceDef[_NewInstanceType, _TypeClassType]':
         """
         We use this method to store implementation for each specific type.
 
-        The only setting we provide is ``is_protocol`` which is required
-        when passing protocols. See our ``mypy`` plugin for that.
+        Args:
+            is_protocol - required when passing protocols.
+            delegate - required when using concrete generics like ``List[str]``.
+
+        Returns:
+            Decorator for instance handler.
+
+        .. note::
+
+            ``is_protocol`` and ``delegate`` are mutually exclusive.
+
+        We don't use ``@overload`` decorator here
+        (which makes our ``mypy`` plugin even more complex)
+        because ``@overload`` functions do not
+        work well with ``ctx.api.fail`` inside the plugin.
+        They start to try other overloads, which produces wrong results.
         """
-        typ = type_argument or type(None)  # `None` is a special case
+        # This might seem like a strange line at first, let's dig into it:
+        #
+        # First, if `delegate` is passed, then we use delegate, not a real type.
+        # We use delegates for concrete generics.
+        # Then, we have a regular `type_argument`. It is used for most types.
+        # Lastly, we have `type(None)` to handle cases
+        # when we want to register `None` as a type / singleton value.
+        typ = delegate or type_argument or type(None)
 
         # That's how we check for generics,
         # generics that look like `List[int]` or `set[T]` will fail this check,
@@ -519,34 +566,20 @@ def instance(
         isinstance(object(), typ)
 
         def decorator(implementation):
-            container = self._protocols if is_protocol else self._instances
+            container = choose_registry(
+                typ=typ,
+                is_protocol=is_protocol,
+                delegate=delegate,
+                concretes=self._concretes,
+                instances=self._instances,
+                protocols=self._protocols,
+            )
             container[typ] = implementation
 
-            if isinstance(getattr(typ, '__instancecheck__', None), MethodType):
-                # This means that this type has `__instancecheck__` defined,
-                # which allows dynamic checks of what `isinstance` of this type.
-                # That's why we also treat this type as a protocol.
-                self._protocols[typ] = implementation
-
-            if self._cache_token is None:  # pragma: no cover
-                if getattr(typ, '__abstractmethods__', None):
-                    self._cache_token = get_cache_token()
-
             self._dispatch_cache.clear()
             return implementation
-        return decorator
 
-    def _control_abc_cache(self) -> None:
-        """
-        Required to drop cache if ``abc`` type got new subtypes in runtime.
-
-        Copied from ``cpython``.
-        """
-        if self._cache_token is not None:
-            current_token = get_cache_token()
-            if self._cache_token != current_token:
-                self._dispatch_cache.clear()
-                self._cache_token = current_token
+        return decorator
 
     def _dispatch(self, instance, instance_type: type) -> Optional[Callable]:
         """
@@ -567,13 +600,11 @@ def _dispatch(self, instance, instance_type: type) -> Optional[Callable]:
 
         return _find_impl(instance_type, self._instances)
 
-    def _default_implementation(self, instance, *args, **kwargs) -> NoReturn:
-        """By default raises an exception."""
-        raise NotImplementedError(
-            'Missing matched typeclass instance for type: {0}'.format(
-                type(instance).__qualname__,
-            ),
-        )
+    def _dispatch_concrete(self, instance) -> Optional[Callable]:
+        for concrete, callback in self._concretes.items():
+            if isinstance(instance, concrete):
+                return callback
+        return None
 
 
 if TYPE_CHECKING:

classes/contrib/mypy/features/typeclass.py

@@ -11,7 +11,7 @@
     TupleType,
 )
 from mypy.types import Type as MypyType
-from mypy.types import TypeOfAny
+from mypy.types import TypeOfAny, UninhabitedType
 from typing_extensions import final
 
 from classes.contrib.mypy.typeops import (
@@ -150,15 +150,21 @@ def instance_return_type(ctx: MethodContext) -> MypyType:
     assert isinstance(ctx.default_return_type, Instance)
     assert isinstance(ctx.type, Instance)
 
+    # We need to unify how we represent passed arguments to our internals.
+    # We use this convention: passed args are added as-is,
+    # missing ones are passed as `NoReturn` (because we cannot pass `None`).
+    passed_types = []
+    for arg_pos in ctx.arg_types:
+        if arg_pos:
+            passed_types.extend(arg_pos)
+        else:
+            passed_types.append(UninhabitedType())
+
     instance_args.mutate_typeclass_instance_def(
         ctx.default_return_type,
         ctx=ctx,
         typeclass=ctx.type,
-        passed_types=[
-            type_
-            for args in ctx.arg_types
-            for type_ in args
-        ],
+        passed_types=passed_types,
     )
     return ctx.default_return_type
 

classes/contrib/mypy/typeops/call_signatures.py

@@ -43,7 +43,7 @@ def __init__(
         ctx: MethodSigContext,
     ) -> None:
         """Context that we need."""
-        self._signature = signature
+        self._signature = signature.copy_modified()
         self._instance_type = instance_type
         self._associated_type = associated_type
         self._ctx = ctx