More Typing Problems
neal at gafter.com
Tue Sep 7 14:55:54 PDT 2010
On Tuesday, September 7, 2010, Maurizio Cimadamore
<maurizio.cimadamore at oracle.com> wrote:
> On 07/09/10 14:55, Florian Weimer wrote:
>> * Maurizio Cimadamore:
>>> with an actual argument of the kind:
>>> So, given that there's no explicit type on 'c' and given that the method
>>> 'select' is accepting *any* subtype of SAM<T,U> for any U, I'm having
>>> hard times in imagining an inference scheme that can infer something
>>> meaningful (not Object) for 'c'.
>> This particular case isn't really a problem. OCaml infers its type as
>> < getName : 'a; ..> -> 'a
>> meaning "a function from an object which has got a getName method (and
>> possibly other methods) returning a value of type 'a to a value of
>> type 'a". There are probably some issues if you treat SAM conversion
>> as a variant of ML type ascription, but those can probably be solved.
> Smells of structural subtyping ;-) ?
Indeed, generics with wildcards is structural subtyping. The problem
is that SAMs can't be generic (i.e. have the abstract method be
generic), which excludes the ML solution.
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