Eliminate outer selections in separate phase

Needs to be done after ExplicitOuter to make sure all needed
outer accessors have been installed.

Author: odersky

compiler/src/dotty/tools/dotc/Compiler.scala

@@ -75,6 +75,7 @@ class Compiler {
            new InterceptedMethods,  // Special handling of `==`, `|=`, `getClass` methods
            new Getters,             // Replace non-private vals and vars with getter defs (fields are added later)
            new ElimByName,          // Expand by-name parameter references
+           new ElimOuterSelect,     // Expand outer selections
            new AugmentScala2Traits, // Expand traits defined in Scala 2.x to simulate old-style rewritings
            new ResolveSuper,        // Implement super accessors and add forwarders to trait methods
            new Simplify,            // Perform local optimizations, simplified versions of what linker does.

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

@@ -0,0 +1,49 @@
+package dotty.tools.dotc
+package transform
+
+import core._
+import TreeTransforms._
+import Contexts.Context
+import Flags._
+import SymUtils._
+import Symbols._
+import SymDenotations._
+import Types._
+import Decorators._
+import DenotTransformers._
+import StdNames._
+import NameOps._
+import NameKinds.OuterSelectName
+import ast.Trees._
+import dotty.tools.dotc.ast.tpd
+import util.Positions._
+import Names._
+
+import collection.mutable
+import ResolveSuper._
+
+import scala.collection.immutable.::
+
+/** This phase rewrites outer selects `E.n_<outer>` which were introduced by
+ *  inlining to outer paths.
+ */
+class ElimOuterSelect extends MiniPhaseTransform { thisTransform =>
+  import ast.tpd._
+
+  override def phaseName: String = "elimOuterSelect"
+
+  override def runsAfterGroupsOf = Set(classOf[ExplicitOuter])
+    // ExplicitOuter needs to have run to completion before so that all classes
+    // that need an outer accessor have one.
+
+  /** Convert a selection of the form `qual.n_<outer>` to an outer path from `qual` of
+   *  length `n`.
+   */
+  override def transformSelect(tree: Select)(implicit ctx: Context, info: TransformerInfo) =
+    tree.name match {
+      case OuterSelectName(_, nhops) =>
+        val SkolemType(tp) = tree.tpe
+        ExplicitOuter.outer.path(start = tree.qualifier, count = nhops).ensureConforms(tp)
+      case _ => tree
+    }
+}

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

@@ -11,7 +11,6 @@ import core.Decorators._
 import core.StdNames.nme
 import core.Names._
 import core.NameOps._
-import core.NameKinds.OuterSelectName
 import ast.Trees._
 import SymUtils._
 import dotty.tools.dotc.ast.tpd
@@ -62,14 +61,6 @@ class ExplicitOuter extends MiniPhaseTransform with InfoTransformer { thisTransf
 
   override def mayChange(sym: Symbol)(implicit ctx: Context): Boolean = sym.isClass
 
-  /** Convert a selection of the form `qual.C_<OUTER>` to an outer path from `qual` to `C` */
-  override def transformSelect(tree: Select)(implicit ctx: Context, info: TransformerInfo) =
-    tree.name match {
-      case OuterSelectName(_, nhops) =>
-        outer.path(start = tree.qualifier, count = nhops).ensureConforms(tree.tpe)
-      case _ => tree
-    }
-
   /** First, add outer accessors if a class does not have them yet and it references an outer this.
    *  If the class has outer accessors, implement them.
    *  Furthermore, if a parent trait might have an outer accessor,

tests/pos/i3130a.scala

@@ -0,0 +1,10 @@
+object O {
+  new D(2).DD.apply()
+}
+
+ class D(val x: Int) {
+  class DD()
+  object DD {
+   inline def apply() = x // new DD()
+  }
+}

tests/pos/i3130c.scala

@@ -0,0 +1,23 @@
+trait Test {
+  trait Global {
+    type Tree
+    def get: Tree
+  }
+
+  trait TreeBuilder {
+    val global: Global
+    inline def set(tree: global.Tree) = {}
+  }
+
+  val nsc: Global
+
+  trait FileImpl {
+    object treeBuilder extends TreeBuilder {
+      val global: nsc.type = nsc
+    }
+    treeBuilder.set(nsc.get)
+  }
+  def file: FileImpl
+
+  file.treeBuilder.set(nsc.get)
+}