WIP

Author: odersky

compiler/src/dotty/tools/dotc/core/NameKinds.scala

@@ -343,6 +343,13 @@ object NameKinds {
     }
   }
 
+  /** Names of the form underlying$mapped$N. Used by overloading resolution for
+   *  mapped alternatives that have their parameters skipped.
+   */
+  val MappedAltName: NumberedNameKind = new NumberedNameKind(SHIFTED_ALT, "MappedAlt"):
+    def mkString(underlying: TermName, info: ThisInfo) =
+      s"$underlying${str.SHIFTED}${info.num}"
+
   /** Names of the form N_<outer>. Emitted by inliner, replaced by outer path
    *  in ExplicitOuter.
    */

compiler/src/dotty/tools/dotc/core/NameTags.scala

@@ -13,6 +13,9 @@ object NameTags extends TastyFormat.NameTags {
                                 // outer accessor that will be filled in by ExplicitOuter.
                                 // <num> indicates the number of hops needed to select the outer field.
 
+  inline val SHIFTED_ALT = 14    // A name `alt$shifted$n` for a mapped symbol in an overloading
+                                 // resolution where `n` term parameters have been stripped
+
   inline val PROTECTEDACCESSOR = 24 // The name of a protected accesor `protected$<name>` created by ProtectedAccessors.
 
   inline val INITIALIZER = 26    // A mixin initializer method

compiler/src/dotty/tools/dotc/core/StdNames.scala

@@ -22,6 +22,7 @@ object StdNames {
     inline val TOPLEVEL_SUFFIX          = "$package"
     inline val NAME_JOIN                = "$"
     inline val DEFAULT_GETTER           = "$default$"
+    inline val SHIFTED                  = "$shifted$"
     inline val LOCALDUMMY_PREFIX        = "<local "       // owner of local blocks
     inline val ANON_CLASS               = "$anon"
     inline val ANON_FUN                 = "$anonfun"

compiler/src/dotty/tools/dotc/typer/Applications.scala

@@ -18,7 +18,7 @@ import Trees._
 import Names._
 import StdNames._
 import ContextOps._
-import NameKinds.DefaultGetterName
+import NameKinds.{DefaultGetterName, MappedAltName}
 import ProtoTypes._
 import Inferencing._
 import reporting._
@@ -229,16 +229,19 @@ object Applications {
               EmptyTree
         }
       }
+      val (methName, skipped) = meth.name match
+        case MappedAltName(mname, n) => (mname, n)
+        case mname => (mname, 0)
       val getterPrefix =
-        if (meth.is(Synthetic) && meth.name == nme.apply) nme.CONSTRUCTOR else meth.name
-      def getterName = DefaultGetterName(getterPrefix, n + numArgs(fn))
+        if (meth.is(Synthetic) && methName == nme.apply) nme.CONSTRUCTOR else methName
+      def getterName = DefaultGetterName(getterPrefix, n + numArgs(fn) + skipped)
       if !meth.hasDefaultParams then
         EmptyTree
       else if (receiver.isEmpty) {
         def findGetter(cx: Context): Tree =
           if (cx eq NoContext) EmptyTree
           else if (cx.scope != cx.outer.scope &&
-            cx.denotNamed(meth.name).hasAltWith(_.symbol == meth)) {
+            cx.denotNamed(methName).hasAltWith(_.symbol == meth)) {
             val denot = cx.denotNamed(getterName)
             if (denot.exists) ref(TermRef(cx.owner.thisType, getterName, denot))
             else findGetter(cx.outer)