1 files changed, 17 insertions, 11 deletions

diff --git a/compiler/src/dotty/tools/dotc/typer/Applications.scala b/compiler/src/dotty/tools/dotc/typer/Applications.scala
index 4e43e429b..c4d3e2292 100644
--- a/compiler/src/dotty/tools/dotc/typer/Applications.scala
+++ b/compiler/src/dotty/tools/dotc/typer/Applications.scala
@@ -20,6 +20,7 @@ import Trees._
 import config.Config
 import Names._
 import StdNames._
+import NameKinds.DefaultGetterName
 import ProtoTypes._
 import EtaExpansion._
 import Inferencing._
@@ -47,13 +48,15 @@ object Applications {
     ref.info.widenExpr.dealias
   }
 
+  def canProductMatch(tp: Type)(implicit ctx: Context) =
+    extractorMemberType(tp, nme._1).exists
+
   /** Does `tp` fit the "product match" conditions as an unapply result type
-   *  for a pattern with `numArgs` subpatterns>
-   *  This is the case of `tp` is a subtype of the Product<numArgs> class.
+   *  for a pattern with `numArgs` subpatterns?
+   *  This is the case of `tp` has members `_1` to `_N` where `N == numArgs`.
    */
   def isProductMatch(tp: Type, numArgs: Int)(implicit ctx: Context) =
-    0 <= numArgs && numArgs <= Definitions.MaxTupleArity &&
-    tp.derivesFrom(defn.ProductNType(numArgs).typeSymbol)
+    numArgs > 0 && productArity(tp) == numArgs
 
   /** Does `tp` fit the "get match" conditions as an unapply result type?
    *  This is the case of `tp` has a `get` member as well as a
@@ -68,6 +71,9 @@ object Applications {
     sels.takeWhile(_.exists).toList
   }
 
+  def productArity(tp: Type)(implicit ctx: Context) =
+    if (canProductMatch(tp)) productSelectorTypes(tp).size else -1
+
   def productSelectors(tp: Type)(implicit ctx: Context): List[Symbol] = {
     val sels = for (n <- Iterator.from(0)) yield tp.member(nme.selectorName(n)).symbol
     sels.takeWhile(_.exists).toList
@@ -108,7 +114,7 @@ object Applications {
         getUnapplySelectors(getTp, args, pos)
       else if (unapplyResult isRef defn.BooleanClass)
         Nil
-      else if (defn.isProductSubType(unapplyResult))
+      else if (canProductMatch(unapplyResult))
         productSelectorTypes(unapplyResult)
           // this will cause a "wrong number of arguments in pattern" error later on,
           // which is better than the message in `fail`.
@@ -345,7 +351,7 @@ trait Applications extends Compatibility { self: Typer with Dynamic =>
       }
       val getterPrefix =
         if ((meth is Synthetic) && meth.name == nme.apply) nme.CONSTRUCTOR else meth.name
-      def getterName = getterPrefix.defaultGetterName(n)
+      def getterName = DefaultGetterName(getterPrefix, n)
       if (!meth.hasDefaultParams)
         EmptyTree
       else if (receiver.isEmpty) {
@@ -395,15 +401,14 @@ trait Applications extends Compatibility { self: Typer with Dynamic =>
           def addTyped(arg: Arg, formal: Type): Type => Type = {
             addArg(typedArg(arg, formal), formal)
             if (methodType.isParamDependent)
-              _.substParam(methodType.newParamRef(n), typeOfArg(arg))
-            else
-              identity
+              safeSubstParam(_, methodType.paramRefs(n), typeOfArg(arg))
+            else identity
           }
 
           def missingArg(n: Int): Unit = {
             val pname = methodType.paramNames(n)
             fail(
-              if (pname contains '$') s"not enough arguments for $methString"
+              if (pname.firstPart contains '$') s"not enough arguments for $methString"
               else s"missing argument for parameter $pname of $methString")
           }
 
@@ -719,7 +724,8 @@ trait Applications extends Compatibility { self: Typer with Dynamic =>
       val lhs1 = typedExpr(lhs)
       val liftedDefs = new mutable.ListBuffer[Tree]
       val lhs2 = untpd.TypedSplice(liftAssigned(liftedDefs, lhs1))
-      val assign = untpd.Assign(lhs2, untpd.Apply(untpd.Select(lhs2, name.init), rhss))
+      val assign = untpd.Assign(lhs2,
+          untpd.Apply(untpd.Select(lhs2, name.asSimpleName.dropRight(1)), rhss))
       wrapDefs(liftedDefs, typed(assign))
     }