Suggest `uN::midpoint` over overflow prone `(a + b) / 2` expressions

[Urgau]

What it does

This lint is would suggest rewrite the not quite correct (a + b) / 2 expression to the (recently stabilized) uN::midpoint/iN::midpoint/fN::midpoint functions, in order to prevent overflow of a + b, which the midpoint functions handle appropriately.

Advantage

• Eliminate a potential source of overflow
  • Java’s binary search implementation and Mozilla had the overflow bug
• Bring awareness to the surprisingly subtleness of midpoint

Drawbacks

• Introduce a function call (but at the same the implementation is very small and the functions are inlined 🤷)

Example

let a = 10_i32;
let b = 10_000_i32;

let mid = (a + b) / 2;

Should be written as:

let a = 10_i32;
let b = 10_000_i32;

let mid = a.midpoint(b);

[samueltardieu]

Interesting

@rustbot claim