I like the idea of using special syntax to denote the type — $T signals that it is a higher-order placeholder. It means there's no ambiguity to the reader or the compiler.

It also means that for a function that requires no type constraints, nothing more is needed:

  func WorksWithAllTypes(val $T) {
    ...
  }

I don't like the type constraint syntax, though. I think it could be done like this:

  func Max(a, b $T Comparable) $T {
    ...
  }

The idea here is that we only need to annotate the first instance of $T; all others will implicitly share the same type constraint.