Macro modify

macro_rules! modify {
    ($file:ident + $heap:ident: -> $y:ident) => { ... };
    ($file:ident + $heap:ident: & $y:ident) => { ... };
    ($file:ident + $heap:ident: mut $y:ident) => { ... };
    ($file:ident + $heap:ident: str $y:ident) => { ... };
}