Fix type substitution

Author: nicolasstucki

compiler/src/dotty/tools/dotc/quoted/TreeCleaner.scala

@@ -17,12 +17,14 @@ class TreeCleaner extends tpd.TreeMap {
   /** List of symbols and their types for type aliases `type T = U` */
   private[this] var aliasesSyms: List[Symbol] = Nil
   private[this] var aliasesTypes: List[Type] = Nil
+  private[this] val aliases = newMutableSymbolMap[Tree]
 
   override def transform(tree: Tree)(implicit ctx: Context): Tree = {
     val tree0 = tree match {
       case TypeDef(_, TypeBoundsTree(lo, hi)) if lo == hi =>
         aliasesSyms = tree.symbol :: aliasesSyms
         aliasesTypes = lo.tpe :: aliasesTypes
+        aliases(tree.symbol) = ref(lo.tpe.typeSymbol)
         Literal(Constant(()))
       case _ => tree
     }
@@ -40,6 +42,7 @@ class TreeCleaner extends tpd.TreeMap {
           case expr3 => Block(flatStats, expr3)
         }
       case tree1: TypeTree => TypeTree(tree1.tpe.subst(aliasesSyms, aliasesTypes))
+      case tree1: Ident => aliases.get(tree1.symbol).getOrElse(tree1)
       case tree1 => tree1
     }
   }

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

@@ -210,7 +210,10 @@ class ReifyQuotes extends MacroTransformWithImplicits with InfoTransformer {
         explicitTags.clear()
 
         // Maps type splices to type references of tags e.g., ~t -> some type T$1
-        val map: Map[Type, Type] = tagsExplicitTypeDefsPairs.map(x => (x._1, x._2.symbol.typeRef)).toMap
+        val map: Map[Type, Type] = {
+          tagsExplicitTypeDefsPairs.map(x => (x._1, x._2.symbol.typeRef)) ++
+          (itags.map(_._1) zip typeDefs.map(_.symbol.typeRef))
+        }.toMap
         val tMap = new TypeMap() {
           override def apply(tp: Type): Type = map.getOrElse(tp, mapOver(tp))
         }