Overview of Generics

Generics describe a set of object operations while erasing the concrete object type.

Generic references

GENERIC_REF is a non-owning erased reference:

::mutable_counter_ref GENERIC_REF
{
  .add FUNCTION(@ARG I32) MUT: I32;
  .read FUNCTION() CONST: I32;
}

::readable_ref GENERIC_REF CONST
{
  .read FUNCTION() CONST: I32;
}

The receiver suffix states the access required by each operation. A GENERIC_REF CONST surface itself carries only constant access.

Owning generics

GENERIC owns the erased object and manages its lifetime:

::owning_counter GENERIC
{
  .add FUNCTION(@ARG I32) MUT: I32;
  .read FUNCTION() CONST: I32;
}

An object whose member functions satisfy the surface can initialize the generic. Copying, moving, comparing, and destroying the generic apply the corresponding supported operation to its current concrete value.

GENERIC MOVE_ONLY suppresses copying. GENERIC INCOMPARABLE suppresses the generated cross-value comparison surface.

Surface reuse

IMPLEMENTS includes another generic or generic-reference surface:

::implemented_counter GENERIC
{
  IMPLEMENTS mutable_counter_ref;
}

The included operations remain part of the declaring generic's public surface.

Explicit receiver form

The suffix form follows the same function model as an explicit receiver:

.read FUNCTION(@THIS CONST& THISTYPE): I32;

For ordinary declarations, .read FUNCTION() CONST: I32; is the preferred compact spelling. Both retain formal THISTYPE; a concrete object type is used when the operation is instantiated.

Generics expose their public object contract only. Their storage and dispatch representation is not a source-language interface.

Reference

See the Generics Reference for the complete language rules, constraints, and technical edge cases.