Changes to wildApprox

src/dotty/tools/dotc/typer/Implicits.scala

@@ -56,9 +56,9 @@ object Implicits {
               case mt: MethodType =>
                 mt.isImplicit ||
                 mt.paramTypes.length != 1 ||
-                !(argType relaxed_<:< wildApprox(mt.paramTypes.head)(ctx.fresh.setExploreTyperState))
+                !(argType relaxed_<:< wildApprox(mt.paramTypes.head, poly)(ctx.fresh.setExploreTyperState))
               case rtp =>
-                discardForView(wildApprox(rtp), argType)
+                discardForView(wildApprox(rtp, poly), argType)
             }
           case tpw: TermRef =>
             false // can't discard overloaded refs

src/dotty/tools/dotc/typer/ProtoTypes.scala

@@ -391,7 +391,10 @@ object ProtoTypes {
     case tp: TypeAlias => // default case, inlined for speed
       tp.derivedTypeAlias(wildApprox(tp.alias, theMap))
     case tp @ PolyParam(poly, pnum) =>
-      ctx.typerState.constraint.entry(tp) match {
+      val constrOrInst =
+        if (theMap != null && (poly eq theMap.disregarded)) NoType
+        else ctx.typerState.constraint.entry(tp)
+      constrOrInst match {
         case bounds: TypeBounds => wildApprox(WildcardType(bounds))
         case NoType => WildcardType(wildApprox(poly.paramBounds(pnum)).bounds)
         case inst => wildApprox(inst)
@@ -426,7 +429,20 @@ object ProtoTypes {
       (if (theMap != null) theMap else new WildApproxMap).mapOver(tp)
   }
 
-  private[ProtoTypes] class WildApproxMap(implicit ctx: Context) extends TypeMap {
+  /** Like unary wildApprox, but assume that all parameters of `disregarded` are not
+   *  bound in current constraint. This is necessary because an instance of
+   *  the type of a polymorphic function might already be part of the current
+   *  constraint when we try to check another occurrence of the same polymorphic
+   *  function for eligibility. An example is in i1044.scala where one expression
+   *  requires two implicit calls of the same refArrayOps method. When approximating
+   *  the parameter types of such a method we should always map the type parameters of
+   *  the method itself to wildcards, even though some of these parameters might still be
+   *  bound in the constraint.
+   */
+  final def wildApprox(tp: Type, disregarded: PolyType)(implicit ctx: Context): Type =
+    wildApprox(tp, new WildApproxMap(disregarded))
+
+  private[ProtoTypes] class WildApproxMap(val disregarded: Type = NoType)(implicit ctx: Context) extends TypeMap {
     def apply(tp: Type) = wildApprox(tp, this)
   }
 

tests/pos/i1044.scala

@@ -0,0 +1,3 @@
+object Test {
+  val x = ???.getClass.getMethods.head.getParameterTypes.mkString(",")
+}