Allow more complex pattern matching in match statement

[schoen]

Project

core

Describe the feature

According to https://docs.simplicity-lang.org/simplicityhl-reference/match_expression/

Match expressions don't support further pattern matching, in contrast to Rust.

For example, we can't destruct a tuple by matching its elements inside the match statement.

I think it would be good to be able to do this and developers would appreciate it (and expect it by default, if they're coming from Rust).

An example that I wanted to be able to do with tuple destructuring that doesn't work:

// We already know that the None case here cannot happen because
// num_outputs() is exactly 2.
let (out_asset, out_amount): (Asset1, Amount1) = match jet::output_amount(0) {
    Some((myasset, myamount): (Asset1, Amount1)) => (myasset, myamount),
    None => (0, 0),
};

We are instead allowed to do this:

let (out_asset, out_amount): (Asset1, Amount1) = unwrap(jet::output_amount(0));

This may actually be closer to what I want in this case because the None branch should be impossible, but in general I would like to be able to assign the elements of the tuple inside of the match.