From 069359240a902cc989553123a61db3f6abe8fd1a Mon Sep 17 00:00:00 2001
From: Paul Phillips <paulp@improving.org>
Date: Tue, 1 Jan 2013 16:27:48 -0800
Subject: Move escaping local logic into VarianceValidator.

---
 .../scala/tools/nsc/typechecker/RefChecks.scala        | 16 ++++------------
 src/reflect/scala/reflect/internal/Variances.scala     | 18 +++++++++++++++---
 2 files changed, 19 insertions(+), 15 deletions(-)

diff --git a/src/compiler/scala/tools/nsc/typechecker/RefChecks.scala b/src/compiler/scala/tools/nsc/typechecker/RefChecks.scala
index 750a4f65ec..8a34d58e6e 100644
--- a/src/compiler/scala/tools/nsc/typechecker/RefChecks.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/RefChecks.scala
@@ -1449,18 +1449,10 @@ abstract class RefChecks extends InfoTransform with scala.reflect.internal.trans
         checkMigration(sym, tree.pos)
       checkCompileTimeOnly(sym, tree.pos)
 
-      if (sym eq NoSymbol) {
-        unit.warning(tree.pos, "Select node has NoSymbol! " + tree + " / " + tree.tpe)
-      }
-      else if (currentClass != sym.owner && sym.hasLocalFlag) {
-        var o = currentClass
-        var hidden = false
-        while (!hidden && o != sym.owner && o != sym.owner.moduleClass && !o.isPackage) {
-          hidden = o.isTerm || o.isPrivateLocal
-          o = o.owner
-        }
-        if (!hidden) varianceValidator.escapedLocals += sym
-      }
+      if (sym eq NoSymbol)
+        devWarning("Select node has NoSymbol! " + tree + " / " + tree.tpe)
+      else if (sym.hasLocalFlag)
+        varianceValidator.checkForEscape(sym, currentClass)
 
       def checkSuper(mix: Name) =
         // term should have been eliminated by super accessors
diff --git a/src/reflect/scala/reflect/internal/Variances.scala b/src/reflect/scala/reflect/internal/Variances.scala
index a54420dd94..779d1ac0fe 100644
--- a/src/reflect/scala/reflect/internal/Variances.scala
+++ b/src/reflect/scala/reflect/internal/Variances.scala
@@ -8,6 +8,7 @@ package internal
 
 import Variance._
 import scala.collection.{ mutable, immutable }
+import scala.annotation.tailrec
 
 /** See comments at scala.reflect.internal.Variance.
  */
@@ -18,14 +19,25 @@ trait Variances {
    *  TODO - eliminate duplication with varianceInType
    */
   class VarianceValidator extends Traverser {
-    val escapedLocals = mutable.HashSet[Symbol]()
+    private val escapedLocals = mutable.HashSet[Symbol]()
+
+    /** Is every symbol in the owner chain between `site` and the owner of `sym`
+     *  either a term symbol or private[this]? If not, add `sym` to the set of
+     *  esacped locals.
+     *  @pre  sym.hasLocalFlag
+     */
+    @tailrec final def checkForEscape(sym: Symbol, site: Symbol) {
+      if (site == sym.owner || site == sym.owner.moduleClass || site.isPackage) () // done
+      else if (site.isTerm || site.isPrivateLocal) checkForEscape(sym, site.owner) // ok - recurse to owner
+      else escapedLocals += sym
+    }
 
     protected def issueVarianceError(base: Symbol, sym: Symbol, required: Variance): Unit = ()
 
     // Flip occurrences of type parameters and parameters, unless
     //  - it's a constructor, or case class factory or extractor
     //  - it's a type parameter of tvar's owner.
-    private def isFlipped(sym: Symbol, tvar: Symbol) = (
+    def shouldFlip(sym: Symbol, tvar: Symbol) = (
          sym.isParameter
       && !sym.owner.isConstructor
       && !sym.owner.isCaseApplyOrUnapply
@@ -56,7 +68,7 @@ trait Variances {
        */
       def relativeVariance(tvar: Symbol): Variance = {
         def nextVariance(sym: Symbol, v: Variance): Variance = (
-          if (isFlipped(sym, tvar)) v.flip
+          if (shouldFlip(sym, tvar)) v.flip
           else if (isLocalOnly(sym)) Bivariant
           else if (!sym.isAliasType) v
           else if (sym.isOverridingSymbol) Invariant
-- 
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