Allow else branch to be omitted in certain cases.

[gdotdesign]

This PR contains three separate changes (sorry about that):

1. Allow omitting the else branch when the return type and value can be inferred. The reason for this is there are cases when the else branch is unnecessary like when working with Html (which could be omitted before) or next { } branches. The inferred return values for omitted else branches are:
   • String returns empty string ""
   • Array(a) returns empty array
   • Promise(Void) returns null (maybe it will need to return an actual promise we will see)
   • Maybe(a) returns Maybe::Nothing
   • Void returns null
   • Html returns null
2. next { } now compiles to null. Previously it would compile to something like this ( which essentially does nothing):

   new Promise((resolve) => { this.setState(new Record({})) })
   

3. Remove NEVER from the type checker and replace it with VOID

[jansul]

String might be the only one that's a little too magic for my taste 😅 (Can always use Maybe(String) for an optional string?)

Do you have any use cases for that one in mind?

[gdotdesign]

String might be the only one that's a little too magic for my taste sweat_smile (Can always use Maybe(String) for an optional string?)

Do you have any use cases for that one in mind?

It's mainly for Html (as it currently works):

<div>
  if condition {
    "value"
  }
</div>