WIP widen 4

Author: odersky

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

@@ -1255,7 +1255,7 @@ class Typer extends Namer
                 // The resulting class `class $anon extends C[?] {...}` would be illegal,
                 // since type arguments to `C`'s super constructor cannot be constructed.
                 def isWildcardClassSAM =
-                  !pt.classSymbol.is(Trait) && pt.argInfos.exists(_.isInstanceOf[TypeBounds])
+                  !pt.widen.classSymbol.is(Trait) && pt.argInfos.exists(_.isInstanceOf[TypeBounds])
                 val targetTpe =
                   if isFullyDefined(pt, ForceDegree.all) && !isWildcardClassSAM then
                     pt
@@ -1265,9 +1265,9 @@ class Typer extends Namer
                   else
                     report.error(ex"result type of lambda is an underspecified SAM type $pt", tree.srcPos)
                     pt
-                if (pt.classSymbol.isOneOf(FinalOrSealed)) {
-                  val offendingFlag = pt.classSymbol.flags & FinalOrSealed
-                  report.error(ex"lambda cannot implement $offendingFlag ${pt.classSymbol}", tree.srcPos)
+                if (pt.widen.classSymbol.isOneOf(FinalOrSealed)) {
+                  val offendingFlag = pt.widen.classSymbol.flags & FinalOrSealed
+                  report.error(ex"lambda cannot implement $offendingFlag ${pt.widen.classSymbol}", tree.srcPos)
                 }
                 TypeTree(targetTpe)
               case _ =>
@@ -2190,11 +2190,11 @@ class Typer extends Namer
         case nil => defn.ObjectClass
       }
     def improve(candidate: ClassSymbol, parent: Type): ClassSymbol = {
-      val pcls = realClassParent(parent.classSymbol)
+      val pcls = realClassParent(parent.widen.classSymbol)
       if (pcls derivesFrom candidate) pcls else candidate
     }
     parents match {
-      case p :: _ if p.classSymbol.isRealClass => parents
+      case p :: _ if p.widen.classSymbol.isRealClass => parents
       case _ =>
         val pcls = parents.foldLeft(defn.ObjectClass)(improve)
         typr.println(i"ensure first is class $parents%, % --> ${parents map (_ baseType pcls)}%, %")
@@ -2205,7 +2205,7 @@ class Typer extends Namer
 
   /** Ensure that first parent tree refers to a real class. */
   def ensureFirstTreeIsClass(parents: List[Tree], span: Span)(using Context): List[Tree] = parents match {
-    case p :: ps if p.tpe.classSymbol.isRealClass => parents
+    case p :: ps if p.tpe.widen.classSymbol.isRealClass => parents
     case _ => TypeTree(ensureFirstIsClass(parents.tpes, span).head).withSpan(span.focus) :: parents
   }
 
@@ -3207,7 +3207,7 @@ class Typer extends Namer
           !(isSyntheticApply(tree) && !isExpandableApply)) {
         if (!defn.isFunctionType(pt))
           pt match {
-            case SAMType(_) if !pt.classSymbol.hasAnnotation(defn.FunctionalInterfaceAnnot) =>
+            case SAMType(_) if !pt.widen.classSymbol.hasAnnotation(defn.FunctionalInterfaceAnnot) =>
               report.warning(ex"${tree.symbol} is eta-expanded even though $pt does not have the @FunctionalInterface annotation.", tree.srcPos)
             case _ =>
           }
@@ -3226,7 +3226,7 @@ class Typer extends Namer
         isContextFunctionRef(parent) // apply refinements indicate a dependent CFT
       case _ =>
         val underlying = wtp.underlyingClassRef(refinementOK = false) // other refinements are not OK
-        defn.isContextFunctionClass(underlying.classSymbol)
+        defn.isContextFunctionClass(underlying.widen.classSymbol)
     }
 
     def adaptNoArgsOther(wtp: Type): Tree = {

compiler/src/dotty/tools/dotc/util/Signatures.scala

@@ -88,7 +88,7 @@ object Signatures {
           if (res.resultType.isParameterless &&
               res.isImplicitMethod &&
               res.paramInfos.forall(info =>
-                info.classSymbol.derivesFrom(ctx.definitions.DummyImplicitClass)))
+                info.widen.classSymbol.derivesFrom(ctx.definitions.DummyImplicitClass)))
             Nil
           else
             toParamss(res)