Possible more DRY suggestion for "as" cast

[leonardo-m]

Description

I am not sure if this is a good idea or if it can be done. But I think it's worth reporting here.

I'm using v.1.85 Nightly from the Playground. This code:

#![allow(dead_code)]
#![warn(clippy::all)]
#![warn(clippy::nursery)]
#![warn(clippy::pedantic)]

fn test1(x: u32) -> u16 {
    x as u16
}
fn main() {}

Gives:

warning: this could be a `const fn`
 --> src/main.rs:6:1
  |
6 | / fn test1(x: u32) -> u16 {
7 | |     x as u16
8 | | }
  | |_^
  |
  = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#missing_const_for_fn
note: the lint level is defined here
 --> src/main.rs:3:9
  |
3 | #![warn(clippy::nursery)]
  |         ^^^^^^^^^^^^^^^
  = note: `#[warn(clippy::missing_const_for_fn)]` implied by `#[warn(clippy::nursery)]`
help: make the function `const`
  |
6 | const fn test1(x: u32) -> u16 {
  | +++++

warning: casting `u32` to `u16` may truncate the value
 --> src/main.rs:7:5
  |
7 |     x as u16
  |     ^^^^^^^^
  |
  = help: if this is intentional allow the lint with `#[allow(clippy::cast_possible_truncation)]` ...
  = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#cast_possible_truncation
note: the lint level is defined here
 --> src/main.rs:4:9
  |
4 | #![warn(clippy::pedantic)]
  |         ^^^^^^^^^^^^^^^^
  = note: `#[warn(clippy::cast_possible_truncation)]` implied by `#[warn(clippy::pedantic)]`
help: ... or use `try_from` and handle the error accordingly
  |
7 |     u16::try_from(x)
  |

So replacing the "as" cast with try_from is safer, on the other hand, if the programmer wishes to keep the "as" cast, then an alternative more DRY (don't repeat yourself) way to write that code is:

#![allow(dead_code)]
#![warn(clippy::all)]
#![warn(clippy::nursery)]
#![warn(clippy::pedantic)]

fn test2(x: u32) -> u16 {
    x as _
}
fn main() {}

Sometimes it's better to write DRY code. It's also good for Clippy to show this syntax because it's less known than the common way to cast with "as".

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