Allows to annotate instance as delegate (#266)

* WIP

* WIP

* Finishes with delegates

* Fixes CI

Author: sobolevn

CHANGELOG.md

@@ -8,8 +8,9 @@ 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 types that have `__instancecheck__` defined
+  via `delegate` argument #248
 - Adds support for multiple type arguments in `Supports` type #244
-- Adds support for types that have `__instancecheck__` defined #248
 
 ### Bugfixes
 

classes/_registry.py

@@ -1,4 +1,3 @@
-from types import MethodType
 from typing import Callable, Dict, NoReturn, Optional
 
 TypeRegistry = Dict[type, Callable]
@@ -11,7 +10,7 @@ def choose_registry(  # noqa: WPS211
     typ: type,
     is_protocol: bool,
     delegate: Optional[type],
-    concretes: TypeRegistry,
+    delegates: TypeRegistry,
     instances: TypeRegistry,
     protocols: TypeRegistry,
 ) -> TypeRegistry:
@@ -21,20 +20,12 @@ def choose_registry(  # noqa: WPS211
     It depends on how ``instance`` method is used and also on the type itself.
     """
     if is_protocol and delegate is not None:
-        raise ValueError('Both `is_protocol` and `delegated` are passed')
+        raise ValueError('Both `is_protocol` and `delegate` are passed')
 
     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
+    elif delegate is not None:
+        return delegates
     return instances
 
 

classes/_typeclass.py

@@ -312,7 +312,7 @@ class _TypeClass(  # noqa: WPS214
         '_associated_type',
 
         # Registry:
-        '_concretes',
+        '_delegates',
         '_instances',
         '_protocols',
 
@@ -361,7 +361,7 @@ def __init__(
         self._associated_type = associated_type
 
         # Registries:
-        self._concretes: TypeRegistry = {}
+        self._delegates: TypeRegistry = {}
         self._instances: TypeRegistry = {}
         self._protocols: TypeRegistry = {}
 
@@ -418,13 +418,13 @@ def __call__(
         And all typeclasses that match ``Callable[[int, int], int]`` signature
         will typecheck.
         """
-        # At first, we try all our concrete types,
-        # we don't cache it, because we cannot.
+        # At first, we try all our delegate types,
+        # we don't cache it, because it is impossible.
         # We only have runtime type info: `type([1]) == type(['a'])`.
         # It might be slow!
-        # Don't add concrete types unless
+        # Don't add any delegate types unless
         # you are absolutely know what you are doing.
-        impl = self._dispatch_concrete(instance)
+        impl = self._dispatch_delegate(instance)
         if impl is not None:
             return impl(instance, *args, **kwargs)
 
@@ -499,21 +499,21 @@ def supports(
         See also: https://www.python.org/dev/peps/pep-0647
         """
         # Here we first check that instance is already in the cache
-        # and only then we check concrete types.
+        # and only then we check delegate types.
         # Why?
         # Because if some type is already in the cache,
-        # it means that it is not concrete.
+        # it means that it is not a delegate.
         # So, this is simply faster.
         instance_type = type(instance)
         if instance_type in self._dispatch_cache:
             return True
 
-        # We never cache concrete types.
-        if self._dispatch_concrete(instance) is not None:
+        # We never cache delegate types.
+        if self._dispatch_delegate(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:
+        # and this is not a delegate type:
         impl = self._dispatch(instance, instance_type)
         if impl is None:
             return False
@@ -534,8 +534,9 @@ def instance(
         We use this method to store implementation for each specific type.
 
         Args:
-            is_protocol - required when passing protocols.
-            delegate - required when using concrete generics like ``List[str]``.
+            is_protocol: required when passing protocols.
+            delegate: required when using delegate types, for example,
+            when working with concrete generics like ``List[str]``.
 
         Returns:
             Decorator for instance handler.
@@ -570,7 +571,7 @@ def decorator(implementation):
                 typ=typ,
                 is_protocol=is_protocol,
                 delegate=delegate,
-                concretes=self._concretes,
+                delegates=self._delegates,
                 instances=self._instances,
                 protocols=self._protocols,
             )
@@ -600,9 +601,9 @@ def _dispatch(self, instance, instance_type: type) -> Optional[Callable]:
 
         return _find_impl(instance_type, self._instances)
 
-    def _dispatch_concrete(self, instance) -> Optional[Callable]:
-        for concrete, callback in self._concretes.items():
-            if isinstance(instance, concrete):
+    def _dispatch_delegate(self, instance) -> Optional[Callable]:
+        for delegate, callback in self._delegates.items():
+            if isinstance(instance, delegate):
                 return callback
         return None
 

classes/contrib/mypy/features/typeclass.py

@@ -21,9 +21,10 @@
     mro,
     type_loader,
 )
+from classes.contrib.mypy.typeops.instance_context import InstanceContext
 from classes.contrib.mypy.validation import (
     validate_associated_type,
-    validate_typeclass,
+    validate_instance,
     validate_typeclass_def,
 )
 
@@ -201,33 +202,21 @@ def __call__(self, ctx: MethodContext) -> MypyType:
         if not isinstance(instance_signature, CallableType):
             return ctx.default_return_type
 
-        # We need to add `Supports` metadata before typechecking,
-        # because it will affect type hierarchies.
-        metadata = mro.MetadataInjector(
-            typeclass.args[2],
-            instance_signature.arg_types[0],
-            ctx,
-        )
-        metadata.add_supports_metadata()
-
-        is_proper_typeclass = validate_typeclass.check_typeclass(
+        instance_context = InstanceContext.build(
             typeclass_signature=typeclass.args[1],
             instance_signature=instance_signature,
+            passed_args=ctx.type.args[0],
+            associated_type=typeclass.args[2],
             fullname=fullname,
-            passed_types=ctx.type.args[0],
             ctx=ctx,
         )
-        if not is_proper_typeclass:
-            # Since the typeclass is not valid,
-            # we undo the metadata manipulation,
-            # otherwise we would spam with invalid `Supports[]` base types:
-            metadata.remove_supports_metadata()
+        if not self._run_validation(instance_context):
             return AnyType(TypeOfAny.from_error)
 
         # If typeclass is checked, than it is safe to add new instance types:
         self._add_new_instance_type(
             typeclass=typeclass,
-            new_type=instance_signature.arg_types[0],
+            new_type=instance_context.instance_type,
             ctx=ctx,
         )
         return ctx.default_return_type
@@ -247,6 +236,25 @@ def _load_typeclass(
         assert isinstance(typeclass, Instance)
         return typeclass, typeclass_ref.args[3].value
 
+    def _run_validation(self, instance_context: InstanceContext) -> bool:
+        # We need to add `Supports` metadata before typechecking,
+        # because it will affect type hierarchies.
+        metadata = mro.MetadataInjector(
+            associated_type=instance_context.associated_type,
+            instance_type=instance_context.instance_type,
+            delegate=instance_context.delegate,
+            ctx=instance_context.ctx,
+        )
+        metadata.add_supports_metadata()
+
+        is_proper_instance = validate_instance.check_type(instance_context)
+        if not is_proper_instance:
+            # Since the typeclass is not valid,
+            # we undo the metadata manipulation,
+            # otherwise we would spam with invalid `Supports[]` base types:
+            metadata.remove_supports_metadata()
+        return is_proper_instance
+
     def _add_new_instance_type(
         self,
         typeclass: Instance,