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|
_interface "085_provide.smi"
structure T :> sig
structure S1 : sig type 'a t end
structure S2 : sig type 'a t end
end
=
struct
structure S1 =
struct
datatype 'a t = X of 'a list
end
structure S2 =
struct
open S1
end
end
(*
2011-08-29 katsu
This causes an unexpected name error.
085_provide.smi:9.10-9.25 Error:
(name evaluation 139) Provide check fails (type definition) : T.S2.t
*)
(*
2011-08-31 ohori
I assert that this is an expected name error.
The open statement is the same effect as
datatype t = datatype S1.t
So without the signature constraint, S1.t and S2.t
are the same (generative) type.
The signature constraint hide this type. So a possible
interface would be:
structure T =
struct
structure S1 =
struct
datatype 'a t (= X of 'a list)
end
structure S2 =
struct
datatype 'a t (= X of 'a list)
end
end
For this, there are multiple instances, including:
(1)
structure T :> sig
structure S1 : sig type 'a t end
structure S2 : sig type 'a t end
end
=
struct
structure S1 =
struct
datatype 'a t = X of 'a list
end
structure S2 =
struct
open S1
end
end
(2)
structure T :> sig
structure S1 : sig type 'a t end
structure S2 : sig type 'a t end
end
=
struct
structure S1 =
struct
datatype 'a t = X of 'a list
end
structure S2 =
struct
datatype 'a t = X of 'a list
end
end
The current provide language cannot distinguish the two.
*)
|
