[MLton] building mlton on Snow Leopard

[Matthew Fluet]

val { get : Var.t -> ((WordSize.t
                        * WordSize.t
                        * {signed:bool})
                       * Var.t) option,
       set, ... } =
    Property.getSetOnce (Var.plist, Property.initConst NONE)

Committed as r7229.

On Thu, 17 Sep 2009, John Reppy wrote:
> I understand the source of the error, but what is the correct type here so 
> that I can
> fix it?  A debate about the interpretation of the SML'97 semantics is not 
> useful (even
> though I actually agree with your position).
>
> 	- John
>
> On Sep 17, 2009, at 10:16 AM, Matthew Fluet wrote:
>
>> On Thu, 17 Sep 2009, John Reppy wrote:
>>> I'm trying to compile mlton (revision 7228) using the command
>>>
>>> 	make TARGET_ARCH=x86_64 smlnj-mlton
>>> 
>>> on Snow Leopard, but I'm hitting type errors in 
>>> ssa/combine-conversions.fun
>> 
>> Nothing to do with Snow Leopard.  Everything to do with SML/NJ using an 
>> overly restrictive context for type inference.
>> 
>>> ssa/combine-conversions.fun:57.5-58.60 Warning: type vars not generalized 
>>> because of value restriction are instantiated to dummy types (X1,X2,...)
>> 
>> The code in question is:
>> 
>> val { get, set, ... } =
>>  Property.getSetOnce (Var.plist, Property.initConst NONE)
>> 
>> Yes, the type of NONE (and get and set) are undetermined by this 
>> declaration.  However, subsequent use of get and set within the module 
>> determine the types.
>> 
>> For a smaller example:
>> 
>> structure S =
>> struct
>>  val z = (fn x => x) []
>>  val y = z :: [true] :: nil
>> end
>> 
>> Accepted by MLton, Poly/ML, and HaMLet; only rejected by SML/NJ.
>> 
>> Another example:
>> 
>> structure S : sig val z : bool list end =
>> struct
>>  val z = (fn x => x) []
>> end
>> 
>> Accepted by MLton, Poly/ML, and HaMLet; only rejected by SML/NJ.
>> 
>> 
>> Admittedly, we have attempted to keep the MLton sources compatible with 
>> SML/NJ, so we will probably put in an explicit type constraint (you'll see 
>> such a constraint in most uses of Property.* functions), but it's really 
>> SML/NJ's bug.
>> 
>
>
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-- 
============================================
Matthew Fluet
Assistant Professor
Department of Computer Science
Rochester Institute of Technology
102 Lomb Memorial Drive
Rochester, NY 14623-5608
Tel: +1.585.475.2854 ; Fax: +1.585.475.4935
mtf at cs.rit.edu ; http://www.cs.rit.edu/~mtf
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