[antlr-interest] How do you use template output with backtracking on in a validating semantic predicate?

[Richard Clark]

Whoa...so William could write this?

^('==' left=expression right=expression)
  -> { isString($left.st} && isString($right.st) }?
stringEqual(left={$left.st}, right={$right.st})
  -> equal(left={$left.st}, right={$right.st})

...R