Macro adapton::eager

macro_rules! eager {
    ( $nm:expr =>> $f:ident :: < $( $ty:ty ),* > , $( $lab:ident : $arg:expr ),* ) => { ... };
    ( $nm:expr =>> $f:path , $( $lab:ident : $arg:expr ),* ) => { ... };
    ( $f:ident :: < $( $ty:ty ),* > , $( $lab:ident : $arg:expr ),* ) => { ... };
    ( $f:path , $( $lab:ident : $arg:expr ),* ) => { ... };
    ( $nm:expr =>> $f:ident =>> < $( $ty:ty ),* > , $( $lab1:ident : $arg1:expr ),* ;; $( $lab2:ident : $arg2:expr ),* ) => { ... };
}

Similar to memo!, except return both the thunk and its observed (forced) value.