First the question is are Roles and Types are Symmetric. In Moose they are not, effectively Roles are a subset of Types in Moose. This means that just because an attribute has a Type, and a value that satisfies that Type is stored, that does not automatically mean that an attribute’s value does a Role equivalent to that Type. There may not be a Role that is equivalent to that type.

Second, and it took me a second to notice this, but he’s checking the Attribute MetaObject’s does(). The Type is a property of the value stored in the attribute, not necessarily a property of the attribute itself. So even if the first were resolved such that a Type automatically implied a Role on the value, this check wouldn’t be the proper one for it.

Third, if the poster is in fact looking to test a property of the MetaObject, and if we all agree that the best way to test/implement this is via a Role on the MetaObject, I’m not sure calling that trait after the Type name is the most intelligent design choice. It would lead to a collision with the way Moose’s implicit type auto-vivification happens.

In reply to Re^3: Introspection of Moose/Mouse attributes fails to find native trait with `does` by perigrin
in thread Introspection of Moose/Mouse attributes fails to find native trait with `does` by Your Mother

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