Merge pull request #1766 from dotty-staging/fix-#1756

Fix #1756: Use lexically enclosing class as start of outer path.

Author: odersky

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

@@ -94,7 +94,7 @@ class Erasure extends Phase with DenotTransformer { thisTransformer =>
     assertErased(tree)
     tree match {
       case res: tpd.This =>
-        assert(!ExplicitOuter.referencesOuter(ctx.owner.enclosingClass, res),
+        assert(!ExplicitOuter.referencesOuter(ctx.owner.lexicallyEnclosingClass, res),
           i"Reference to $res from ${ctx.owner.showLocated}")
       case ret: tpd.Return =>
         // checked only after erasure, as checking before erasure is complicated
@@ -412,7 +412,7 @@ object Erasure extends TypeTestsCasts{
     }
 
     override def typedThis(tree: untpd.This)(implicit ctx: Context): Tree =
-      if (tree.symbol == ctx.owner.enclosingClass || tree.symbol.isStaticOwner) promote(tree)
+      if (tree.symbol == ctx.owner.lexicallyEnclosingClass || tree.symbol.isStaticOwner) promote(tree)
       else {
         ctx.log(i"computing outer path from ${ctx.owner.ownersIterator.toList}%, % to ${tree.symbol}, encl class = ${ctx.owner.enclosingClass}")
         outer.path(tree.symbol)

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

@@ -330,7 +330,7 @@ object ExplicitOuter {
     /** The path of outer accessors that references `toCls.this` starting from
      *  the context owner's this node.
      */
-    def path(toCls: Symbol, start: Tree = This(ctx.owner.enclosingClass.asClass)): Tree = try {
+    def path(toCls: Symbol, start: Tree = This(ctx.owner.lexicallyEnclosingClass.asClass)): Tree = try {
       def loop(tree: Tree): Tree = {
         val treeCls = tree.tpe.widen.classSymbol
         val outerAccessorCtx = ctx.withPhaseNoLater(ctx.lambdaLiftPhase) // lambdalift mangles local class names, which means we cannot reliably find outer acessors anymore

tests/pos/i1756.scala

@@ -0,0 +1,20 @@
+class A { { val x = this } }
+class B(x: Int) {
+  class C(x: Int)
+      extends B({
+        val test = this
+        x
+      }) {
+    def this() = {
+      this({
+        1
+      })
+    }
+  }
+}
+
+// Minimized version
+class D(x: Int) {
+  class E(x: Int) extends D({val test = D.this; x})
+}
+