Support argument destructuring for #[values(...)]

[nyurik]

In some cases, it may be good to combine #[values(...)] and #[cases(...)] approach - e.g. when a certain combination of parameters must be given together.

This code already works, and will execute 4 times (since both params are given as having two possible values). The second parameter's tuple will always be used together:

#[rstest]
fn my_tester(
    #[values(1, 2)] param1: i32,
    #[values(('x', "xxx"), ('y', "yyy"))] param2: (char, &'static str),
) {
  let (param2a, param2b) = param2;  // destructure second param into its components
  ...
}

Proposal

Support param destructuring in the fn declaration:

#[rstest]
fn my_tester(
    #[values(1, 2)] param1: i32,
    #[values(('x', "xxx"), ('y', "yyy"))] (param2a, param2b): (char, &'static str),
) {
  ...
}

[la10736]

Yeah, I've planned the support for destructuring both for values, case and fixture. But I cannot estimate when I'll do t.