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Allow instantiation of Type[A], if A is abstract #2853
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Original file line number | Diff line number | Diff line change |
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@@ -1080,7 +1080,6 @@ def check_assignment(self, lvalue: Lvalue, rvalue: Expression, infer_lvalue_type | |
infer_lvalue_type) | ||
else: | ||
lvalue_type, index_lvalue, inferred = self.check_lvalue(lvalue) | ||
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if isinstance(lvalue, NameExpr): | ||
if self.check_compatibility_all_supers(lvalue, lvalue_type, rvalue): | ||
# We hit an error on this line; don't check for any others | ||
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@@ -1128,6 +1127,14 @@ def check_assignment(self, lvalue: Lvalue, rvalue: Expression, infer_lvalue_type | |
else: | ||
rvalue_type = self.check_simple_assignment(lvalue_type, rvalue, lvalue) | ||
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# Special case | ||
if (isinstance(rvalue_type, CallableType) and rvalue_type.is_type_obj() and | ||
rvalue_type.type_object().is_abstract and | ||
isinstance(lvalue_type, TypeType) and | ||
isinstance(lvalue_type.item, Instance) and lvalue_type.item.type.is_abstract): | ||
self.fail("Cannot only assign non-abstract classes" | ||
There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. "Cannot only" -> "Cannot" (I presume). There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. Oh, sorry, it should be "Can only" (this is probably a worst kind of mistakes). |
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" to a variable of type '{}'".format(lvalue_type), rvalue) | ||
return | ||
if rvalue_type and infer_lvalue_type: | ||
self.binder.assign_type(lvalue, | ||
rvalue_type, | ||
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Original file line number | Diff line number | Diff line change |
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@@ -351,7 +351,7 @@ def check_call(self, callee: Type, args: List[Expression], | |
""" | ||
arg_messages = arg_messages or self.msg | ||
if isinstance(callee, CallableType): | ||
if (callee.is_concrete_type_obj() and callee.type_object().is_abstract | ||
if (callee.is_type_obj() and callee.type_object().is_abstract | ||
and not callee.from_type_type): | ||
type = callee.type_object() | ||
self.msg.cannot_instantiate_abstract_class( | ||
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@@ -440,7 +440,7 @@ def analyze_type_type_callee(self, item: Type, context: Context) -> Type: | |
if isinstance(item, Instance): | ||
res = type_object_type(item.type, self.named_type) | ||
if isinstance(res, CallableType): | ||
res.from_type_type = True | ||
res = res.copy_modified(from_type_type=True) | ||
return res | ||
if isinstance(item, UnionType): | ||
return UnionType([self.analyze_type_type_callee(item, context) | ||
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@@ -846,10 +846,10 @@ def check_arg(self, caller_type: Type, original_caller_type: Type, | |
messages.deleted_as_rvalue(caller_type, context) | ||
# Only non-abstract class could be given where Type[...] is expected | ||
There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. could -> can (again :-) |
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elif isinstance(caller_type, CallableType) and isinstance(callee_type, TypeType): | ||
tp = caller_type.type_object() | ||
if caller_type.is_concrete_type_obj() and tp.is_abstract: | ||
messages.cannot_instantiate_abstract_class(tp.name(), | ||
tp.abstract_attributes, context) | ||
if (caller_type.is_type_obj() and caller_type.type_object().is_abstract and | ||
isinstance(callee_type.item, Instance) and callee_type.item.type.is_abstract): | ||
messages.fail("Only non-abstract class can be given where '{}' is expected" | ||
.format(callee_type), context) | ||
elif not is_subtype(caller_type, callee_type): | ||
if self.chk.should_suppress_optional_error([caller_type, callee_type]): | ||
return | ||
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Original file line number | Diff line number | Diff line change |
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@@ -158,6 +158,7 @@ B()# E: Cannot instantiate abstract class 'B' with abstract attributes 'f' and ' | |
[out] | ||
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[case testInstantiationAbstractsInType] | ||
# flags: --python-version 3.6 | ||
There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. I take it this is only because of the There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. Since recently |
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from typing import Type | ||
from abc import abstractmethod | ||
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@@ -173,15 +174,23 @@ def f(cls: Type[A]) -> A: | |
return cls() # OK | ||
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def g() -> A: | ||
return A() # Error, see out | ||
return A() # E: Cannot instantiate abstract class 'A' with abstract attribute 'm' | ||
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f(A) # E: Cannot instantiate abstract class 'A' with abstract attribute 'm' | ||
f(B) # E: Cannot instantiate abstract class 'B' with abstract attribute 'm' | ||
f(A) # E: Only non-abstract class can be given where 'Type[__main__.A]' is expected | ||
f(B) # E: Only non-abstract class can be given where 'Type[__main__.A]' is expected | ||
f(C) # OK | ||
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Alias = A | ||
GoodAlias = C | ||
Alias() # E: Cannot instantiate abstract class 'A' with abstract attribute 'm' | ||
GoodAlias() | ||
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var: Type[A] | ||
var() | ||
var = A # E: Cannot only assign non-abstract classes to a variable of type 'Type[__main__.A]' | ||
var = B # E: Cannot only assign non-abstract classes to a variable of type 'Type[__main__.A]' | ||
var = C # OK | ||
[out] | ||
main: note: In function "g": | ||
main:16: error: Cannot instantiate abstract class 'A' with abstract attribute 'm' | ||
main: note: At top level: | ||
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[case testInstantiatingClassWithInheritedAbstractMethodAndSuppression] | ||
from abc import abstractmethod, ABCMeta | ||
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For what, exactly?
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I added a detailed comment here.