Closed
Description
Parser generator
def rep1[T](first: => Parser[T], p: => Parser[T]): Parser[List[T]]in scala.util.parsing.combinator.Parsers never returns error. So if first or p parser returns error this error is not propagated further.
It is almost obvious from code of this method:
def rep1[T](first: => Parser[T], p: => Parser[T]): Parser[List[T]] = Parser{ in0 =>
val xs = new scala.collection.mutable.ListBuffer[T]
var in = in0
var res = first(in)
while(res.successful) {
xs += res.get
in = res.next
res = p(in)
}
// assert(res.isInstanceOf[NoSuccess])
if (!xs.isEmpty) {
// the next parser should start parsing where p failed,
// since `!p(in).successful', the next input to be consumed is `in'
Success(xs.toList, in) // TODO: I don't think in == res.next holds
}
else {
Failure(res.asInstanceOf[NoSuccess].msg, in0)
}
}Suppose that after while finished res is an Error. This error is not propagated further - the result of rep1 depends only on emptiness of list xs!
res should be tested. The implementation of this method should be changed to something like this:
def rep1[T](first: => Parser[T], p: => Parser[T]): Parser[List[T]] = Parser{ in0 =>
val xs = new scala.collection.mutable.ListBuffer[T]
var in = in0
var res = first(in)
while(res.successful) {
xs += res.get
in = res.next
res = p(in)
}
res match {
case e: Error => e
case _ => if (!xs.isEmpty) Success(xs.toList, in) else Failure(res.asInstanceOf[NoSuccess].msg, in0)
}
}As a result of incorrect rep1, combinators * and + work also incorrectly (they finally call mentioned method).