Support type inference on function parameters and class fields

[MaxGraey]

class Foo {
  a = 2.0
  static readonly PI = 3.14
  constructor(public b = 1, public c = 1.0) {}
}

[dcodeIO]

In 0e33806 I noticed that, at the current point, at least static fields must have a type annotation because these are compiled lazily but might become resolved before being compiled, and there isn't a proper resolveExpression for any expression yet that we could use if there wasn't a type annotation. Hence, implementing a full-fledged resolver seems to be one requirement to make this proposal work without exceptions.

[jarble]

It's probably possible to do this using TypeScript's compiler API.
It might also be possible to do this using Hegel, though it only works with a statically-typed subset of JavaScript.