Merge pull request scala#595 from som-snytt/ticket/3761-overload-byname-only

lrytz · lrytz · commit 94e5d76fb863 · 2012-05-23T03:48:50.000-07:00
SI-3761: Overload resolution fails on by-name parameter
diff --git a/src/compiler/scala/tools/nsc/typechecker/Infer.scala b/src/compiler/scala/tools/nsc/typechecker/Infer.scala
@@ -305,9 +305,21 @@ trait Infer {
       }
 
 
-    def isCompatible(tp: Type, pt: Type): Boolean = {
+    /** "Compatible" means conforming after conversions.
+     *  "Raising to a thunk" is not implicit; therefore, for purposes of applicability and
+     *  specificity, an arg type `A` is considered compatible with cbn formal parameter type `=>A`.
+     *  For this behavior, the type `pt` must have cbn params preserved; for instance, `formalTypes(removeByName = false)`.
+     *
+     *  `isAsSpecific` no longer prefers A by testing applicability to A for both m(A) and m(=>A)
+     *  since that induces a tie between m(=>A) and m(=>A,B*) [SI-3761]
+     */
+    private def isCompatible(tp: Type, pt: Type): Boolean = {
+      def isCompatibleByName(tp: Type, pt: Type): Boolean = pt match {
+        case TypeRef(_, ByNameParamClass, List(res)) if !isByNameParamType(tp) => isCompatible(tp, res)
+        case _ => false
+      }
       val tp1 = normalize(tp)
-      (tp1 weak_<:< pt) || isCoercible(tp1, pt)
+      (tp1 weak_<:< pt) || isCoercible(tp1, pt) || isCompatibleByName(tp, pt)
     }
     def isCompatibleArgs(tps: List[Type], pts: List[Type]) =
       (tps corresponds pts)(isCompatible)
@@ -662,7 +674,7 @@ trait Infer {
         case ExistentialType(tparams, qtpe) =>
           isApplicable(undetparams, qtpe, argtpes0, pt)
         case MethodType(params, _) =>
-          val formals = formalTypes(params map { _.tpe }, argtpes0.length)
+          val formals = formalTypes(params map { _.tpe }, argtpes0.length, removeByName = false)
 
           def tryTupleApply: Boolean = {
             // if 1 formal, 1 argtpe (a tuple), otherwise unmodified argtpes0
diff --git a/test/files/run/t3761-overload-byname.check b/test/files/run/t3761-overload-byname.check
@@ -0,0 +1,6 @@
+hello!
+hello working world
+goodnight!
+goodnight moon, nobody, noises everywhere
+0
+1
diff --git a/test/files/run/t3761-overload-byname.scala b/test/files/run/t3761-overload-byname.scala
@@ -0,0 +1,23 @@
+
+class OverTheTop {
+  def info0(m: String) = m + "!"
+  def info0(m: String, args: Any*) = m +" "+ args.mkString(" ")
+
+  // as reported
+  def info1(m: =>String) = m + "!"
+  def info1(m: =>String, args: Any*) = m +" "+ args.mkString(", ")
+
+  // @lrytz
+  def m[A](x: => Int) = 0; def m[A](x: => Int, xs: Int*) = 1 
+}
+object Test {
+  def main(args: Array[String]) {
+    val top = new OverTheTop
+    println(top.info0("hello"))
+    println(top.info0("hello","working","world"))
+    println(top.info1("goodnight"))
+    println(top.info1("goodnight", "moon", "nobody", "noises everywhere"))
+    println(top.m(17))
+    println(top.m(17,19))
+  }
+}
