Disallow `var` or `final` in front of initializing or super parameters.

The grammar today allows a constructor like `C(var this.x, final this.y)`.

They do so because we reuse grammar, so we end up with `` for the type.

The `var` and `final` make no difference, they do not affect the variable being initialized, they do not affect the implicit variable that is visible in the initializer list (that one's always `final`). In short, it's noise.

I also doubt anyone ever uses the syntax, so how about just disallowing it. The grammar of parameters might become a little less orthogonal, or we can simply do it in prose and say that it's a compile-time error if the `?` production preceding a `this.` or `super.` parameter is not just a `?`.

Start by locating the parameter grammar and specification prose for initializing and super parameters. Check how the existing production applies before this. and super. parameters, then define the compile-time-error wording or grammar change and verify that var this.x and final this.y are rejected.

Written by the indexing model from the issue text.