Re: [Caml-list] exhaustiveness checking within a submatch

[David House <dhouse@janestreet.com>]

This does actually work with polymorphic variants, as long as you
rename the thing in the submatch:

match f with `A -> 1 | `B -> 2 | (`C | `D as foo) -> match foo with `C
-> 3 | `D -> 4

On 10 October 2013 09:07, David Allsopp <dra-news@metastack.com> wrote:
> Martin DeMello wrote:
>> Just curious as to why the compiler can't handle this, since in theory
>> everything is statically deducible:
>>
>> # type test = A | B | C | D;;
>> type test = A | B | C | D
>>
>> # let f = A;;
>> val f : test = A
>>
>> # match f with A -> 1 | B -> 2 | C | D -> ( match f with C -> 3 | D ->
>> 4);;
>> Characters 40-71:
>>                                                                Warning
>> 8: this pattern-matching is not exhaustive.
>>                                                        Here is an
>> example of a value that is not matched:
>> (A|B)
>> Characters 40-71:
>> Warning 8: this pattern-matching is not exhaustive.
>> Here is an example of a value that is not matched:
>> (A|B)
>> - : int = 1
>
> http://caml.inria.fr/pub/ml-archives/caml-list/2007/02/d35648b13d76f1717edbf41101dc913f.en.html
>
>
> David
>
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