Parboiled2: reference to position in source text from AST

Question

I am writing a DSL, and learning parboiled2, at the same time. Once my AST is built, I would like to run some semantic checks and, if there are any errors, output error messages that reference the offending positions in the source text.

I am writing things like the following, which, so far, do work:

case class CtxElem[A](start:Int, end:Int, elem:A)

def Identifier = rule {
  push(cursor) ~
  capture(Alpha ~ zeroOrMore(AlphaNum)) ~
  push(cursor) ~
  WhiteSpace
  ~> ((start, identifier, finish) => CtxElem(start, finish, identifier))
}

Is there a better or simpler way?

Answer 1

Parboiled 2 (for now) doesn't support parser recovery strategies. It means that if parser will fail - it will stop. As far as I remember it should print the symbol where it failed, or at least you could get the cursor

So if you're trying to build your own DSL and you need that kind of functionality, I would propose you to use a different tool like ANTLR. Parboiled1 supports parser recovery techniques, but for now it's dead in buried if favor of support for the second version. Parboiled 2 is good in parsing of log files or configuration files (that should correct by default), but it's not good for building DSLs.