Remove support for @builtinclass (#2294)

Following #599.

(As a followup, we should remove it from typeshed too.)

Author: elazarg

mypy/checker.py

@@ -50,7 +50,7 @@
 from mypy.visitor import NodeVisitor
 from mypy.join import join_types
 from mypy.treetransform import TransformVisitor
-from mypy.meet import meet_simple, nearest_builtin_ancestor, is_overlapping_types
+from mypy.meet import meet_simple, is_overlapping_types
 from mypy.binder import ConditionalTypeBinder
 from mypy.options import Options
 
@@ -959,7 +959,6 @@ def visit_class_def(self, defn: ClassDef) -> Type:
 
     def check_multiple_inheritance(self, typ: TypeInfo) -> None:
         """Check for multiple inheritance related errors."""
-
         if len(typ.bases) <= 1:
             # No multiple inheritance.
             return
@@ -973,13 +972,6 @@ def check_multiple_inheritance(self, typ: TypeInfo) -> None:
                     # checks suffice (these are implemented elsewhere).
                     if name in base2.names and base2 not in base.mro:
                         self.check_compatibility(name, base, base2, typ)
-        # Verify that base class layouts are compatible.
-        builtin_bases = [nearest_builtin_ancestor(base.type)
-                         for base in typ.bases]
-        for base1 in builtin_bases:
-            for base2 in builtin_bases:
-                if not (base1 in base2.mro or base2 in base1.mro):
-                    self.fail(messages.INSTANCE_LAYOUT_CONFLICT, typ)
 
     def check_compatibility(self, name: str, base1: TypeInfo,
                             base2: TypeInfo, ctx: Context) -> None:

mypy/meet.py

@@ -1,4 +1,4 @@
-from typing import cast, List
+from typing import List
 
 from mypy.join import is_similar_callables, combine_similar_callables
 from mypy.types import (
@@ -7,7 +7,6 @@
     DeletedType, UninhabitedType, TypeType
 )
 from mypy.subtypes import is_subtype
-from mypy.nodes import TypeInfo
 
 from mypy import experiments
 
@@ -114,14 +113,6 @@ class C(A, B): ...
     return True
 
 
-def nearest_builtin_ancestor(type: TypeInfo) -> TypeInfo:
-    for base in type.mro:
-        if base.defn.is_builtinclass:
-            return base
-    else:
-        return None
-
-
 class TypeMeetVisitor(TypeVisitor[Type]):
     def __init__(self, s: Type) -> None:
         self.s = s

mypy/messages.py

@@ -76,7 +76,6 @@
     'Overloaded method has both abstract and non-abstract variants'
 READ_ONLY_PROPERTY_OVERRIDES_READ_WRITE = \
     'Read-only property cannot override read-write property'
-INSTANCE_LAYOUT_CONFLICT = 'Instance layout conflict in multiple inheritance'
 FORMAT_REQUIRES_MAPPING = 'Format requires a mapping'
 GENERIC_TYPE_NOT_VALID_AS_EXPRESSION = \
     "Generic type is prohibited as a runtime expression (use a type alias or '# type:' comment)"

mypy/nodes.py

@@ -694,8 +694,6 @@ class ClassDef(Statement):
     info = None  # type: TypeInfo  # Related TypeInfo
     metaclass = ''
     decorators = None  # type: List[Expression]
-    # Built-in/extension class? (single implementation inheritance only)
-    is_builtinclass = False
     has_incompatible_baseclass = False
 
     def __init__(self,
@@ -724,7 +722,6 @@ def serialize(self) -> JsonDict:
                 'fullname': self.fullname,
                 'type_vars': [v.serialize() for v in self.type_vars],
                 'metaclass': self.metaclass,
-                'is_builtinclass': self.is_builtinclass,
                 }
 
     @classmethod
@@ -736,7 +733,6 @@ def deserialize(self, data: JsonDict) -> 'ClassDef':
                        metaclass=data['metaclass'],
                        )
         res.fullname = data['fullname']
-        res.is_builtinclass = data['is_builtinclass']
         return res
 
 

mypy/semanal.py

@@ -559,8 +559,6 @@ def visit_class_def(self, defn: ClassDef) -> None:
 
         self.enter_class(defn)
 
-        self.setup_is_builtinclass(defn)
-
         # Analyze class body.
         defn.defs.accept(self)
 
@@ -606,15 +604,6 @@ def unbind_class_type_vars(self) -> None:
     def analyze_class_decorator(self, defn: ClassDef, decorator: Expression) -> None:
         decorator.accept(self)
 
-    def setup_is_builtinclass(self, defn: ClassDef) -> None:
-        for decorator in defn.decorators:
-            if refers_to_fullname(decorator, 'typing.builtinclass'):
-                defn.is_builtinclass = True
-        if defn.fullname == 'builtins.object':
-            # Only 'object' is marked as a built-in class, as otherwise things elsewhere
-            # would break. We need a better way of dealing with built-in classes.
-            defn.is_builtinclass = True
-
     def calculate_abstract_status(self, typ: TypeInfo) -> None:
         """Calculate abstract status of a class.
 

mypy/strconv.py

@@ -141,8 +141,6 @@ def visit_class_def(self, o: 'mypy.nodes.ClassDef') -> str:
             a.insert(1, 'Metaclass({})'.format(o.metaclass))
         if o.decorators:
             a.insert(1, ('Decorators', o.decorators))
-        if o.is_builtinclass:
-            a.insert(1, 'Builtinclass')
         if o.info and o.info._promote:
             a.insert(1, 'Promote({})'.format(o.info._promote))
         if o.info and o.info.tuple_type:

mypy/treetransform.py

@@ -190,7 +190,6 @@ def visit_class_def(self, node: ClassDef) -> ClassDef:
         new.info = node.info
         new.decorators = [self.expr(decorator)
                           for decorator in node.decorators]
-        new.is_builtinclass = node.is_builtinclass
         return new
 
     def visit_global_decl(self, node: GlobalDecl) -> GlobalDecl:

test-data/unit/check-classes.test

@@ -894,26 +894,6 @@ a.f = a.f # E: Property "f" defined in "A" is read-only
 a.f.x # E: "int" has no attribute "x"
 [builtins fixtures/property.pyi]
 
-
--- Multiple inheritance, non-object built-in class as base
--- -------------------------------------------------------
-
-
-[case testInvalidMultipleInheritanceFromBuiltins-skip]
-import typing
-class A(int, str): pass # E: Instance layout conflict in multiple inheritance
-[out]
-main: note: In class "A":
-
-[case testInvalidMultipleInheritanceFromBuiltins-skip]
-import typing
-class S(str): pass
-class A(S, str): pass
-class B(S, int): pass # E: Instance layout conflict in multiple inheritance
-[out]
-main: note: In class "B":
-
-
 -- _promote decorators
 -- -------------------
 

test-data/unit/check-overloading.test

@@ -411,10 +411,10 @@ A() + B()
 A() + '' # E: No overload variant of "__add__" of "A" matches argument types [builtins.str]
 
 [case testOverrideOverloadedMethodWithMoreGeneralArgumentTypes]
-from typing import overload, builtinclass
-@builtinclass
+from typing import overload
+
 class IntSub(int): pass
-@builtinclass
+
 class StrSub(str): pass
 class A:
     @overload
@@ -429,10 +429,10 @@ class B(A):
 [out]
 
 [case testOverrideOverloadedMethodWithMoreSpecificArgumentTypes]
-from typing import overload, builtinclass
-@builtinclass
+from typing import overload
+
 class IntSub(int): pass
-@builtinclass
+
 class StrSub(str): pass
 class A:
     @overload
@@ -461,12 +461,10 @@ main: note: In class "C":
 main:17: error: Signature of "f" incompatible with supertype "A"
 
 [case testOverloadingAndDucktypeCompatibility]
-from typing import overload, _promote, builtinclass
+from typing import overload, _promote
 
-@builtinclass
 class A: pass
 
-@builtinclass
 @_promote(A)
 class B: pass
 

test-data/unit/semanal-classes.test

@@ -518,20 +518,6 @@ MypyFile:1(
       NameExpr(object [builtins.object]))
     PassStmt:3()))
 
-[case testBuiltinclassDecorator]
-from typing import builtinclass
-@builtinclass
-class A: pass
-[out]
-MypyFile:1(
-  ImportFrom:1(typing, [builtinclass])
-  ClassDef:2(
-    A
-    Builtinclass
-    Decorators(
-      NameExpr(builtinclass [typing.builtinclass]))
-    PassStmt:3()))
-
 [case testClassAttributeAsMethodDefaultArgumentValue]
 import typing
 class A:

test-data/unit/typexport-basic.test

@@ -136,8 +136,6 @@ import typing
 8 > 3
 4 < 6 > 2
 [file builtins.py]
-from typing import builtinclass
-@builtinclass
 class object:
     def __init__(self) -> None: pass
 class int: