Parser error resulting in "overloaded or recursive method needs return type"

[soronpo]

I also created a scastie link with the code.

object Main {
  def main(args: Array[String]) = println("")

  object Foo {
    def apply(t : Any)(block: => Unit) : Unit = {}
    def foo(t : Any)(block: => Unit) : Unit = {}
  }

  object Test {
    Foo(1){} //OK
    Foo.foo(1) {} //OK
    Foo foo(1) {} //overloaded or recursive method  needs return type
  }
}

Using -Xprint:parser, gives the following:

    parsed:
    package  {
      module object Main extends { 
         def main( args: Array[String]) = println("")
        module object Foo extends { 
           def apply( t: Any)( block: => Unit): Unit = 
            {
              
            }
           def foo( t: Any)( block: => Unit): Unit = 
            {
              
            }
        }
        module object Test extends { 
          Foo(1)(
            {
              
            }
          )
          Foo.foo(1)(
            {
              
            }
          )
          Foo foo 
            (1)(
              {
                
              }
            )
        }
      }
    }

[nicolasstucki]

Minimization

object Main {
  object Foo {
    def foo(a : Int)(b: Int): Unit = ()
  }
  Foo foo(1)(2)
}

-- [E044] Syntax Error: Foo.scala:7:10 -----------------------------------------
7 |  Foo foo(1)(2)
  |          ^
  |          overloaded or recursive method <none> needs return type

[nicolasstucki]

foo is parsed as an infix operator and then (1)(2) are parsed as 2 applied to 1.

InfixOp(
  Ident(Foo), 
  Ident(foo), 
  Apply(Parens(Literal(1)), List(Literal(2)))
)

[smarter]

The only issue I see here is the weird error message:

scala> 1(2) 
1 |1(2)
  |^
  |overloaded or recursive method <none> needs return type

The actual parsing is done exactly like scalac, changing the way we parse infix operators will require someone to come up with a specification of the changes and some good motivation.

[olafurpg]

The error message is a bit clearer in 2.12.4

scala> (1)(2)
<console>:12: error: Int(1) does not take parameters
       (1)(2)
          ^

[soronpo]

The actual parsing is done exactly like scalac,

Yes, this example was also added to an existing ticket on the scalac issue tracker: scala/bug#8859

changing the way we parse infix operators will require someone to come up with a specification of the changes and some good motivation.

Can you point me where in the spec I can find this (the error) is the required behavior?

[soronpo]

I should mention I have a use-case for this, but it's not a major-one to create a SIP and change the current intended behavior. I just wish for a confirmation that this is indeed the intended behavior, and I will close this issue. (and I can create a separate issue for the weird error message just for (1)(2)).

[smarter]

The syntax is described at http://www.scala-lang.org/files/archive/spec/2.12/13-syntax-summary.html for 2.12 and http://dotty.epfl.ch/docs/internals/syntax.html for dotty.

I think the current behavior matches the syntax description. Parsing Foo foo(1) {} is equivalent to parsing Foo foo (1) {}. The right-hand-side of an InfixExpr can be a SimpleExpr, and (1) {} is a valid SimpleExpr parsed as an application of (1) to {}.

[soronpo]

OK. After further thinking about this, I believe this is the required behavior. I'll open a new issue for the error message.