Macro collection_impl

macro_rules! collection_impl {
    ({
    name: $name:ident,
    key: $key:ty,
    value: $value:ty,
    collection_type: $collection_type:expr,
    trace_field: $trace_field:ident,
    update: $update:expr,
}) => { ... };
}

Macro to simplify implementing Collection.

The arguments to collection_impl! are:

• $name, which will be the name of the implementing struct.
• $key, the type used to store keys.
• $value, the type used to store values.
• $collection_type, the CollectionType.
• $trace_field, the corresponding field name within a Trace.
• $update, the corresponding StateUpdateKind constructor.