Nice trick - but my 'problem' [1] regards arbitrary valid OCaml code and 
how to serialize code values.  The issue seems to be that one needs to 
attach an arbitrarily large typing environment to each part of a value, 
as there is no global typing environment which will do the job (because 
of shadowing).

Jacques

[1] Actually 'our' problem, in that this arose from some issues in 
metaocaml, and I am working with Oleg to figure out what is going on.  
Interestingly, this never arose in 3.09 and before.

Till Varoquaux wrote:
> AFAIK you are allowed to shadow just about anything in
> implementations. If you wanted to keep the exact same interface but
> retain the ability to avvoid the shadowing issue on the labels you
> could do:
>
> module Foo = struct
>   type t = Foo
> end
> type foo = Foo.t = Foo
>
> module Foo2 = struct
>   type t = Foo | Bar
> end
>
> type foo2 = Foo2.t = Foo | Bar
>
> HTH,
> Till
>
> On Mon, May 31, 2010 at 10:46 AM, Jacques Carette <carette@mcmaster.ca> wrote:
>   
>> type foo = Foo
>> let x = Foo
>>
>> type foo2 = Foo | Bar
>> let y = Foo
>> let z = (x,y) ;;
>>
>> I thought that re-using of algebraic labels was not allowed - but apparently
>> it is?  Note that this means that it is impossible to "text" print such
>> structures and hope to recover them uniquely.  This also causes very subtle
>> issues when Marshal'ing, and grave issues for code generation [think
>> metaocaml].
>>
>> Jacques
>>
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