Pattern completions without `:` could also add it

[FMorschel]

Pattern completions without : could also add : TypeName , so we can simply write down the new variable name. Currently, it simply ends the current word but does nothing. Since we already know the user will need the type or the var/final` keyword, we can handle that to make this easier.

Repro:

void f(C c) {
  if (c case C(gett))
}

abstract class C {
  int get getter;
}

CC @bwilkerson @DanTup @srawlins

[bwilkerson]

It would make sense to add the colon (:), but we don't know that the next token will be either final or a type name. It could be an expression returning a value to be compared to the value of the property. I don't think we want to add anything more than the colon.

[FMorschel]

Makes sense to me.