Map parents of ClassInfos when inlining

Otherwise base tyeps of inlined classes are wrong.

Author: odersky

compiler/src/dotty/tools/dotc/ast/TreeTypeMap.scala

@@ -80,7 +80,7 @@ final class TreeTypeMap(
       val tmap = withMappedSyms(localSyms(impl :: self :: Nil))
       cpy.Template(impl)(
           constr = tmap.transformSub(constr),
-          parents = parents mapconserve transform,
+          parents = parents.mapconserve(transform),
           self = tmap.transformSub(self),
           body = impl.body mapconserve
             (tmap.transform(_)(ctx.withOwner(mapOwner(impl.symbol.owner))))

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

@@ -3850,6 +3850,17 @@ object Types {
     protected def mapClassInfo(tp: ClassInfo): Type =
       derivedClassInfo(tp, this(tp.prefix))
 
+    /** A version of mapClassInfo which also maps parents and self type */
+    protected def mapFullClassInfo(tp: ClassInfo) =
+      tp.derivedClassInfo(
+        prefix = this(tp.prefix),
+        classParents = tp.classParents.mapConserve(this),
+        selfInfo = tp.selfInfo match {
+          case tp: Type => this(tp)
+          case sym => sym
+        }
+      )
+
     def andThen(f: Type => Type): TypeMap = new TypeMap {
       override def stopAtStatic = thisMap.stopAtStatic
       def apply(tp: Type) = f(thisMap(tp))

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

@@ -446,6 +446,7 @@ class Inliner(call: tpd.Tree, rhs: tpd.Tree)(implicit ctx: Context) {
         case t: SingletonType => paramProxy.getOrElse(t, mapOver(t))
         case t => mapOver(t)
       }
+      override def mapClassInfo(tp: ClassInfo) = mapFullClassInfo(tp)
     }
 
     // The tree map to apply to the inlined tree. This maps references to this-types

tests/pos/i3130b.scala

@@ -1,5 +1,5 @@
-trait F { def f(): Int }
 class Outer {
+  trait F { def f(): Int }
   inline def inner: F = {
     class InnerClass(x: Int) extends F {
       def this() = this(3)