This Role defines the interface and basic behavior of Structured Type Constraints.
+Structured type constraints let you assign an internal pattern of type
+constraints to a 'container' constraint. The goal is to make it easier to
+declare constraints like "ArrayRef[Int, Int, Str]" where the constraint is an
+ArrayRef of three elements and the internal constraint on the three is Int, Int
+and Str.
+
+To accomplish this, we add an attribute to the base L<Moose::Meta::TypeConstraint>
+to hold a L</signature>, which is a reference to a pattern of type constraints.
+We then override L</constraint> to check our incoming value to the attribute
+against this signature pattern. Additionally we allow L</optional_signature> to
+hold any optional type constraints. The overall goal is to support something
+like:
+
+ has 'attr' => (isa=>'Tuple[Int, Str, Optional[Int, Int]]');
+
+These classes define how the underlying support for this works.
+
=head1 TYPES
The following types are defined in this class.