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Merged
merged 7 commits into from
Mar 27, 2017
Merged

Allow instantiation of Type[A], if A is abstract #2853

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b0ff0cc
Some ideas
ilevkivskyi Nov 16, 2016
71ea62f
Work on corner cases, more tests
ilevkivskyi Feb 12, 2017
ec22e4d
Fix minor issues and lint
ilevkivskyi Feb 12, 2017
80c82e7
Formatting
ilevkivskyi Feb 12, 2017
f52a3bd
Merge branch 'master' into abstract-type-ok
ilevkivskyi Mar 9, 2017
65eab95
Apply review comments
ilevkivskyi Mar 21, 2017
4d2e6fd
Add test fixture; fix formatting
ilevkivskyi Mar 21, 2017
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Fix minor issues and lint
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@ilevkivskyi
ilevkivskyi committed Feb 12, 2017
commit ec22e4d3759335a36fdf4f1f8baf4bffb5b0924e
8 changes: 6 additions & 2 deletions mypy/checker.py
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Expand Up @@ -579,6 +579,8 @@ def is_implicit_any(t: Type) -> bool:
self.fail("The erased type of self '{}' "
"is not a supertype of its class '{}'"
.format(erased, ref_type), defn)
if defn.is_class and isinstance(arg_type, CallableType):
arg_type.is_classmethod_class = True
elif isinstance(arg_type, TypeVarType):
# Refuse covariant parameter type variables
# TODO: check recursively for inner type variables
Expand Down Expand Up @@ -1128,10 +1130,12 @@ def check_assignment(self, lvalue: Lvalue, rvalue: Expression, infer_lvalue_type
rvalue_type = self.check_simple_assignment(lvalue_type, rvalue, lvalue)

# Special case
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For what, exactly?

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I added a detailed comment here.

if (isinstance(rvalue_type, CallableType) and rvalue_type.is_type_obj() and
if (
isinstance(rvalue_type, CallableType) and rvalue_type.is_type_obj() and
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I'm not keen on this formatting.

rvalue_type.type_object().is_abstract and
isinstance(lvalue_type, TypeType) and
isinstance(lvalue_type.item, Instance) and lvalue_type.item.type.is_abstract):
isinstance(lvalue_type.item, Instance) and lvalue_type.item.type.is_abstract
):
self.fail("Cannot only assign non-abstract classes"
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"Cannot only" -> "Cannot" (I presume).

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Oh, sorry, it should be "Can only" (this is probably a worst kind of mistakes).

" to a variable of type '{}'".format(lvalue_type), rvalue)
return
Expand Down
13 changes: 7 additions & 6 deletions mypy/checkexpr.py
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Expand Up @@ -352,7 +352,8 @@ def check_call(self, callee: Type, args: List[Expression],
arg_messages = arg_messages or self.msg
if isinstance(callee, CallableType):
if (callee.is_type_obj() and callee.type_object().is_abstract
and not callee.from_type_type):
# Exceptions for Type[...] and classmethod first argument
and not callee.from_type_type and not callee.is_classmethod_class):
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Maybe also except static methods?

I found a case in our codebase that goes basically like this:

class Logger:
    @staticmethod
    def log(a: Type[C]): ...
class C:
    @classmethod
    def action(cls) -> None:
        Logger.log(cls)  #E: Only non-abstract class can be given where 'Type[C]' is expected
    @abstractmethod
    ...

(I'm far from positive that it's because of this line though.)

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This code looks reasonable, I added a corresponding exception to check_arg.

type = callee.type_object()
self.msg.cannot_instantiate_abstract_class(
callee.type_object().name(), type.abstract_attributes,
Expand Down Expand Up @@ -845,11 +846,11 @@ def check_arg(self, caller_type: Type, original_caller_type: Type,
elif isinstance(caller_type, DeletedType):
messages.deleted_as_rvalue(caller_type, context)
# Only non-abstract class could be given where Type[...] is expected
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could -> can (again :-)

elif isinstance(caller_type, CallableType) and isinstance(callee_type, TypeType):
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 (isinstance(caller_type, CallableType) and isinstance(callee_type, TypeType) and
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
Expand Down
1 change: 0 additions & 1 deletion mypy/checkmember.py
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Expand Up @@ -518,7 +518,6 @@ def class_callable(init_type: CallableType, info: TypeInfo, type_type: Instance,
ret_type=fill_typevars(info), fallback=type_type, name=None, variables=variables,
special_sig=special_sig)
c = callable_type.with_name('"{}"'.format(info.name()))
c.is_classmethod_class = True
return c


Expand Down
2 changes: 2 additions & 0 deletions test-data/unit/check-abstract.test
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Expand Up @@ -184,6 +184,8 @@ Alias = A
GoodAlias = C
Alias() # E: Cannot instantiate abstract class 'A' with abstract attribute 'm'
GoodAlias()
f(Alias) # E: Only non-abstract class can be given where 'Type[__main__.A]' is expected
f(GoodAlias)

var: Type[A]
var()
Expand Down
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