Macro late_field 

macro_rules! late_field {
    (
        $($ty:ty [$ns:ty] $(=> $val:ty)?),*
        $(,)?
    ) => { ... };
}

Implements the LateField trait for the specified $ty type, turning it into a marker type that can be used to refer to a field within a late-initialized structure.

See the crate level documentation for examples of this macro in action as well as a step-by-step guide on how to use it.

The $ns type specifies a LateStruct (defined by an earlier late_struct! invocation) into which this field will be placed. The optional $val type specifies the type of the value this field stores. If $val is omitted, it will default to $ty.

$val (or $ty, if $val is omitted) is expected to live for 'static, be Sized, and implement Default. It is this Default trait implementation which is used to initialize the fields of a LateInstance. In addition, the field value must be able to coerce into the $ns structure type’s LateStruct::EraseTo associated type. By default, the LateStruct::EraseTo associated type is set to dyn 'static + fmt::Debug and thus $val will be expected to implement Debug as well.

If $val is distinct from $ty, the $ty type need only be Sized and live for 'static.

No types in this macro invocation may involve unbound generic parameters. You can specify more than one type onto which LateField should be implemented with this macro.