Function the 

pub fn the<T>(expr: T) -> T

Specify the type [T] of expression [expr]

Example

let foo: u8 = 0;
let items1 : [usize; 4] = [foo.into(); 4];

// won't compile becuase Into is a generic trait but self.into() is not a generic method
// let items2 = [foo.into::<usize>(): usize ; 4];
// an alternative way: 
let items3 = [usize::from(foo); 4];
// a more intuitive way:
let items4 = [the::<usize>(foo.into()); 4];