Replace `if let tuple = tuple` by a let chain

[ronnodas]

What it does

Replaces if let (Some(x), Ok(y)) = (x, y) by if let Some(x) = x && Ok(y) = y, i.e. when a tuple is constructed and then immediately matched against a destructuring pattern. Similarly for arrays.

Things like if let (Some(x), Some(y) = (y, x), albeit questionable, should not trigger the lint.

Advantage

• Separates independent checks
• Can short-circuit

Drawbacks

• Can short circuit
• With default formatting, can increase the number of lines

Example

if let (Some(x), Ok(y)) = (x, y) && let [Some(_), None] = [a, b] {
   ...
}

Could be written as:

if let Some(x) = x && let Ok(y) = y && let Some(_) = a && let None = b {
   ...
}

Comparison with existing lints

It seems likely that redundant_pattern_match can trigger as a follow-up.

Not a lint, but rust-analyzer's unwrap_tuple assist is the analog for assignments. Note that for assignments, (x, y) = (y, x); is entirely reasonable and idiomatic,

Additional Context

This pattern may have been used as a partial workaround before let chains were available.