Macro declare_arena

pub macro declare_arena([$($a:tt $name:ident: $ty:ty,)*]) {
    ...
}

Declare an Arena containing one dropless arena and many typed arenas (the types of the typed arenas are specified by the arguments).

There are three cases of interest.

• Types that are Copy: these need not be specified in the arguments. They will use the DroplessArena.
• Types that are !Copy and !Drop: these must be specified in the arguments. An empty TypedArena will be created for each one, but the DroplessArena will always be used and the TypedArena will stay empty. This is odd but harmless, because an empty arena allocates no memory.
• Types that are !Copy and Drop: these must be specified in the arguments. The TypedArena will be used for them.