Overview of Overload Resolution¶

Overloads let several functions share a name while accepting different arguments:

::select FUNCTION(@ARG:value I32): I32 { RETURN 1; }
::select FUNCTION(@ARG:value I64): I32 { RETURN 2; }

ASSERT(select(4 AS I32) == 1);
ASSERT(select(4 AS I64) == 2);

Quxlang first maps named and positional arguments, removes candidates that cannot accept them, and selects the uniquely best type and reference fit.

Concrete and generic candidates¶

A concrete exact match normally outranks a broader generic match:

::describe FUNCTION(@ARG:value I32): I32 { RETURN 1; }
::describe FUNCTION(@ARG:value AUTO(t)): I32 { RETURN 2; }

Reference qualifiers also matter. Temporary-reference overloads can receive consumable values, while constant references are read-only fallbacks.

Constrained overloads¶

ENABLE_IF keeps a candidate only when its instantiated condition is true:

::width_class FUNCTION(@ARG:value AUTO(t))
  ENABLE_IF(BITS(t) < 32 AS I32): I32
{
  RETURN 1;
}

ENABLE_IF expresses call-dependent constraints. INCLUDE_IF applies when a declaration should not exist on a target at all.

Reference¶

If no candidate works, or two candidates are equally best, the call is a compilation error. For the exact value, reference, literal, template, receiver, and ambiguity ordering, see the Overload Resolution Reference.