Whether a type module defines an optional callback, loaded or not (spec/01 §9).
function_exported?/3 answers false for a module the VM hasn't loaded yet. Modules
load lazily in dev, test and iex, so a bare check can run before the type is loaded
and silently take the path of a type that lacks the callback. exported?/3 loads the
module first, so the answer is the module's, whatever has run before.
Summary
Functions
true when module defines name/arity, loading the module first. A module that
can't be loaded raises, as a type that doesn't exist is a mistake, not a type without
the callback.
Functions
true when module defines name/arity, loading the module first. A module that
can't be loaded raises, as a type that doesn't exist is a mistake, not a type without
the callback.
iex> Macaw.Layers.Callback.exported?(Macaw.Layers.Callback, :exported?, 3)
true