[Perl5-syntax] How to test for a role in a method signature

[Piers Cawley]

On Fri, Mar 4, 2011 at 7:16 AM, Reverend Chip <rev.chip at gmail.com> wrote:
> On 3/3/2011 10:32 PM, Piers Cawley wrote:
>> Personally, I prefer the flow of 'Typed $parameter does coerce', where
>> the constraint declaration is always to the left of the parameter name
>> and the right hand side is for declaring stuff about how the parameter
>> is initialized. I would encourage anyone wanting to constrain by type
>> to declare a type along the lines of "subtype DoesRole, as role_type
>> 'Role'" ...
>
> No, I don't buy it.  The "isa" and "does" tests are so fundamental and
> common that forcing people to type that much to get the test would
> violate Huffman.

That's why I think that the better solution is to delegate to the
package to find out if a particular value satisfies it. If the package
is a class, then obviously it does an 'isa' test, if a role, then it
does a 'does' check and, if a type constraint, it uses the type's
constraints. That way you'd use the same syntax to constrain the
argument whether it be a class, a role or a moose type, rather than
the proposed idea where you use one syntax if it's a class or a role,
and different syntax if it's a Role. Similar things should look
similar, after all.

>
> Count me as favoring "$x does Foo".
>
>
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