Macro circuit_cache_key 

macro_rules! circuit_cache_key {
    ($constructor:ident$(<$($typearg:ident $(:$trait_bound:tt)? ),*>)?($key_type:ty => $val_type:ty)) => { ... };
    (local $vis:vis $constructor:ident$(<$($typearg:ident $(:$trait_bound:tt)?),*>)?($key_type:ty => $val_type:ty)) => { ... };
    (@inner $vis:vis [$type_key:path] $constructor:ident$(<$($typearg:ident $(:$trait_bound:tt)?),*>)?($key_type:ty => $val_type:ty)) => { ... };
}

Declare an anonymous struct type to be used as a key in the cache and associated value type.

Example

circuit_cache_key!(IntegralId<C, D>(NodeId => Stream<C, D>));

declares struct IntegralId(NodeId) key type with associated value type Stream<C, D>.