syntax - scala coalesces multiple function call parameters into a Tuple -- can this be disabled?

Question

This is a troublesome violation of type safety in my project, so I'm looking for a way to disable it. It seems that if a function takes an AnyRef (or a java.lang.Object), you can call the function with any combination of parameters, and Scala will coalesce the parameters into a Tuple object and invoke the function.

In my case the function isn't expecting a Tuple, and fails at runtime. I would expect this situation to be caught at compile time.

object WhyTuple {
 def main(args: Array[String]): Unit = {
  fooIt("foo", "bar")
 }
 def fooIt(o: AnyRef) {
  println(o.toString)
 }
}

Output:

(foo,bar)

Answer 1

No implicits or Predef at play here at all -- just good old fashioned compiler magic. You can find it in the type checker. I can't locate it in the spec right now.

If you're motivated enough, you could add a -X option to the compiler prevent this.

Alternatively, you could avoid writing arity-1 methods that accept a supertype of TupleN.