Macro wdf_element 

macro_rules! wdf_element {
    (
        name: $name:ident<T>,
        params: { $($pname:ident: $ptype:ty),* },
        state: { $($sname:ident: $stype:ty),* },
        port_resistance: |$pr_self:ident| $pr:expr,
        scattering: |$p:ident, $a:ident| $scatter:expr,
        update: |$u:ident| $update:expr,
        reset: |$r:ident| $reset:expr,
    ) => { ... };
}

Generate a single WDF element struct implementing WdfElement.

Defines port resistance, scattering, state update, and reset behaviour via closures provided at the macro call site.