Fix eta expansion for deeply curried methods

Eta expansion yielded incorrect result if the eta expanded method
has more than one parameter sections and the expected result type
is a unary function type. In that case a postfix `_' needs to be appended.

1 files changed, 112 insertions, 0 deletions

diff --git a/tests/run/tcpoly_parseridioms.scala b/tests/run/tcpoly_parseridioms.scala
new file mode 100644
index 000000000..e86af0caa
--- /dev/null
+++ b/tests/run/tcpoly_parseridioms.scala
@@ -0,0 +1,112 @@
+
+import scala.language.{ higherKinds, implicitConversions, postfixOps }
+
+trait Parsers {
+  type Input = List[Char]
+
+  sealed class ParseResult[+t](val next: Input)
+    case class Success[+t](override val next: Input, result: t) extends ParseResult[t](next)
+    case class Failure(override val next: Input, msg: String) extends ParseResult[Nothing](next)
+
+  abstract class Parser[+t] {
+    def apply(in: Input): ParseResult[t]
+  }
+
+  // sequence
+  def sq[T, U](a: => Parser[T], b: => Parser[U]): Parser[Tuple2[T, U]] =  new Parser[Tuple2[T, U]] {
+      def apply(in: Input): ParseResult[Tuple2[T, U]] = a(in) match {
+        case Success(next, x) => b(next) match {
+          case Success(next2, y) => Success(next2, (x,y))
+          case Failure(_, msg) => Failure(in, msg)
+        }
+        case Failure(_, msg) => Failure(in, msg)
+      }
+    }
+
+  // ordered choice
+  def or[T, U <: T](a: => Parser[T], b: => Parser[U]): Parser[T] =  new Parser[T] {
+    def apply(in: Input): ParseResult[T] = a(in) match {
+      case Success(next, x) => Success(next, x)
+      case Failure(_, _) => b(in) match {
+        case Success(next, y) => Success(next, y)
+        case Failure(_, msg) => Failure(in, msg)
+      }
+    }
+  }
+
+  // lifting
+  def lift[T, U](f: T => U)(a: => Parser[T]): Parser[U] = new Parser[U] {
+    def apply(in: Input): ParseResult[U] = a(in) match {
+      case Success(n, x) => Success(n, f(x))
+      case Failure(n, msg) => Failure(n, msg)
+    }
+  }
+
+  def accept[T](c: Char, r: T): Parser[T] = new Parser[T] {
+    def apply(in: Input) = in match {
+      case c2 :: n if c2 == c => Success(n, r)
+      case n => Failure(n, "expected "+c+" at the head of "+n)
+    }
+  }
+
+  def apply_++[s, tt](fun: Parser[s => tt], arg: Parser[s]): Parser[tt] = lift[Tuple2[s=>tt, s], tt]({case (f, a) => f(a)})(sq(fun, arg))
+
+  def success[u](v: u): Parser[u] = new Parser[u] {
+    def apply(in: Input) = Success(in, v)
+  }
+
+}
+
+trait Idioms {
+  trait Idiom[idi[x]] {
+    def liftedApply[s, t](fun: idi[s => t])(arg: idi[s]): idi[t]
+    def pure[a](x: a): idi[a]
+    def pureMethod[a](name: String, x: a): idi[a] = pure(x) // hack for Mirrors: allow passing of method names
+  }
+
+  class IdiomaticTarget[idi[x], idiom <: Idiom[idi], s](i: idiom, tgt: s) {
+    def dot [t](fun: s => t, name: String) = new IdiomaticApp2[idi, idiom, t](i, i.liftedApply(i.pureMethod(name, fun))(i.pure(tgt)))
+  } // TODO: `.` -->  java.lang.ClassFormatError: Illegal method name "." in class Idioms$Id$
+
+  class IdiomaticFunction[idi[x], idiom <: Idiom[idi], s, t](i: idiom, fun: s => t) {
+    def <| (a: idi[s]) = new IdiomaticApp[idi, idiom, t](i, i.liftedApply(i.pure(fun))(a))
+  }
+
+  class IdiomaticApp[idi[x], idiom <: Idiom[idi], x](i: idiom, a: idi[x]) {
+    // where x <: s=>t -- TODO can this be expressed without generalised constraints?
+    def <> [s, t](b: idi[s]) = new IdiomaticApp[idi, idiom, t](i, i.liftedApply(a.asInstanceOf[idi[s=>t]])(b))
+
+    def |> : idi[x] = a
+  }
+
+  class IdiomaticApp2[idi[x], idiom <: Idiom[idi], x](i: idiom, a: idi[x]) extends IdiomaticApp[idi, idiom, x](i, a) {
+    def <| [s, t](b: idi[s]) = <>[s,t](b)
+  }
+}
+
+trait ParserIdioms extends Parsers with Idioms {
+  object ParserIdiom extends Idiom[Parser] {
+    def liftedApply[s, t](fun: Parser[s => t])(arg: Parser[s]): Parser[t] = apply_++(fun, arg)
+    def pure[a](x: a): Parser[a] = success(x)
+  }
+
+  implicit def parserIdiomFun[s, t](fun: s=>t): IdiomaticFunction[Parser, ParserIdiom.type, s, t] =
+    new IdiomaticFunction[Parser, ParserIdiom.type, s, t](ParserIdiom, fun)
+  implicit def parserIdiomTgt[s](tgt: s): IdiomaticTarget[Parser, ParserIdiom.type, s] =
+    new IdiomaticTarget[Parser, ParserIdiom.type, s](ParserIdiom, tgt)
+
+  trait Expr
+  case class Plus(a: Int, b: Int) extends Expr
+
+  def num = or(accept('0', 0), or(accept('1', 1),accept('2', 2)))
+
+  // TODO: how can parserIdiom(curry2(_)) be omitted?
+  def expr: Parser[Expr] = parserIdiomFun(curry2(Plus)) <| num <> num |>
+
+  implicit def curry2[s,t,u](fun: (s, t)=>u)(a: s)(b: t): u = fun(a, b)
+  implicit def curry3[r,s,t,u](fun: (r,s, t)=>u)(a: r)(b: s)(c: t): u = fun(a, b, c)
+}
+
+object Test extends ParserIdioms with App {
+  assert(expr("12".toList).toString == "Success(List(),Plus(1,2))")
+}