Remove substDealias

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

@@ -73,35 +73,6 @@ trait Substituters { this: Context =>
     }
   }
 
-  final def substDealias(tp: Type, from: List[Symbol], to: List[Type], theMap: SubstDealiasMap): Type = {
-    tp match {
-      case tp: NamedType =>
-        val sym = tp.symbol
-        var fs = from
-        var ts = to
-        while (fs.nonEmpty) {
-          if (fs.head eq sym) return ts.head
-          fs = fs.tail
-          ts = ts.tail
-        }
-        if (sym.isStatic && !existsStatic(from) || (tp.prefix `eq` NoPrefix)) tp
-        else {
-          tp.info match {
-            case TypeAlias(alias) =>
-              val alias1 = substDealias(alias, from, to, theMap)
-              if (alias1 ne alias) return alias1
-            case _ =>
-          }
-          tp.derivedSelect(substDealias(tp.prefix, from, to, theMap))
-        }
-      case _: ThisType | _: BoundType =>
-        tp
-      case _ =>
-        (if (theMap != null) theMap else new SubstDealiasMap(from, to))
-          .mapOver(tp)
-    }
-  }
-
   final def substSym(tp: Type, from: List[Symbol], to: List[Symbol], theMap: SubstSymMap): Type =
     tp match {
       case tp: NamedType =>
@@ -210,10 +181,6 @@ trait Substituters { this: Context =>
     def apply(tp: Type): Type = subst(tp, from, to, this)
   }
 
-  final class SubstDealiasMap(from: List[Symbol], to: List[Type]) extends DeepTypeMap {
-    override def apply(tp: Type): Type = substDealias(tp, from, to, this)
-  }
-
   final class SubstSymMap(from: List[Symbol], to: List[Symbol]) extends DeepTypeMap {
     def apply(tp: Type): Type = substSym(tp, from, to, this)
   }

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

@@ -1307,17 +1307,6 @@ object Types {
         }
       }
 
-    /** Same as `subst` but follows aliases as a fallback. When faced with a reference
-     *  to an alias type, where normal substitution does not yield a new type, the
-     *  substitution is instead applied to the alias. If that yields a new type,
-     *  this type is returned, otherwise the original type (not the alias) is returned.
-     *  A use case for this method is if one wants to substitute the type parameters
-     *  of a class and also wants to substitute any parameter accessors that alias
-     *  the type parameters.
-     */
-    final def substDealias(from: List[Symbol], to: List[Type])(implicit ctx: Context): Type =
-      ctx.substDealias(this, from, to, null)
-
     /** Substitute all types of the form `TypeParamRef(from, N)` by
      *  `TypeParamRef(to, N)`.
      */

compiler/src/dotty/tools/dotc/transform/FullParameterization.scala

@@ -113,7 +113,7 @@ trait FullParameterization {
     /** Replace class type parameters by the added type parameters of the polytype `pt` */
     def mapClassParams(tp: Type, pt: PolyType): Type = {
       val classParamsRange = (mtparamCount until mtparamCount + ctparams.length).toList
-      tp.substDealias(ctparams, classParamsRange map (pt.paramRefs(_)))
+      tp.subst(ctparams, classParamsRange map (pt.paramRefs(_)))
     }
 
     /** The bounds for the added type parameters of the polytype `pt` */
@@ -206,8 +206,7 @@ trait FullParameterization {
 
       new TreeTypeMap(
         typeMap = rewireType(_)
-          .substDealias(origTParams, trefs)
-          .subst(origVParams, argRefs.map(_.tpe))
+          .subst(origTParams ++ origVParams, trefs ++ argRefs.map(_.tpe))
           .substThisUnlessStatic(origClass, thisRef.tpe),
         treeMap = {
           case tree: This if tree.symbol == origClass => thisRef

compiler/src/dotty/tools/dotc/transform/TailRec.scala

@@ -136,9 +136,8 @@ class TailRec extends MiniPhase with FullParameterization {
                 val origVParams = tree.vparamss.flatten map (_.symbol)
                 new TreeTypeMap(
                   typeMap = identity(_)
-                    .substDealias(origTParams, trefs)
-                    .subst(origVParams, vrefss.flatten.map(_.tpe)),
-                    oldOwners = origMeth :: Nil,
+                    .subst(origTParams ++ origVParams, trefs ++ vrefss.flatten.map(_.tpe)),
+                  oldOwners = origMeth :: Nil,
                   newOwners = label :: Nil
                 ).transform(rhsSemiTransformed)
               })