Nested Destructuring

[gdotdesign]

This implements a recursive algorithm for destructuring and unifies statement and case branch destructuring checks. This allows:

• Destructuring with values in them
• Mixing and nesting destucturings
• Using complex destructurings in if expressions

Some examples:

case Test::Record(name: Maybe::Just({"John", "Doe"}), age: 32) {
  Test::Record(Maybe::Just({"John", a})) => a
  => "WTF"
}
    
case Result::Ok(Maybe::Just({"Hello", "Bello"})) {
  Result::Ok(Maybe::Just({"Hello", b})) => "Matches"
  Result::Ok(Maybe::Just({"JULIE"})) => "Not matches"
  Result::Err => "Error"
  => "Else branch"
}

case ["a", "b", "d"] {
  [a, ...b, d] => b
  ["a"] => ["one"]
  [a] => ["something else"]
  [] => ["empty"]
}

if Result::Ok(Maybe::Just({"Hello", b})) = result {
  ...
} else {
  ...
}

Top level exhaustiveness checking is still there but if any branch has nested destructuring or value ("string" for example) in it then it's excluded from the check.

Follow-up work (in separate PRs):

• Move _match and related functions into the runtime
• Allow named destructuring of records (including in enums)
• At some point implement exhaustiveness checking in sublevels

[Sija]

@gdotdesign Does it resolves #283?

[gdotdesign]

@gdotdesign Does it resolves #283?

Yes it will :)

[Sija]

✨