Relocated redundant variance checking code.

The variance code in Refchecks is 75+% redundant with
our eventually canonical variance traversing code now in
Variances, but as usual it is time consuming to stamp out
this damaging redundancy so for the moment I am simply
moving it into close proximity with def variancesInType
to abet future work.

1 files changed, 3 insertions, 149 deletions

diff --git a/src/compiler/scala/tools/nsc/typechecker/RefChecks.scala b/src/compiler/scala/tools/nsc/typechecker/RefChecks.scala
index 71e04db24c..eeb76dced2 100644
--- a/src/compiler/scala/tools/nsc/typechecker/RefChecks.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/RefChecks.scala
@@ -11,7 +11,6 @@ import scala.collection.{ mutable, immutable }
 import transform.InfoTransform
 import scala.collection.mutable.ListBuffer
 import scala.language.postfixOps
-import scala.reflect.internal.Variance._
 
 /** <p>
  *    Post-attribution checking and transformation.
@@ -39,7 +38,7 @@ import scala.reflect.internal.Variance._
  *
  *  @todo    Check whether we always check type parameter bounds.
  */
-abstract class RefChecks extends InfoTransform with scala.reflect.internal.transform.RefChecks {
+abstract class RefChecks extends InfoTransform with scala.reflect.internal.transform.RefChecks with Variances {
 
   val global: Global               // need to repeat here because otherwise last mixin defines global as
                                    // SymbolTable. If we had DOT this would not be an issue
@@ -845,152 +844,7 @@ abstract class RefChecks extends InfoTransform with scala.reflect.internal.trans
 
   // Variance Checking --------------------------------------------------------
 
-    private val escapedPrivateLocals = new mutable.HashSet[Symbol]
-
-    val varianceValidator = new Traverser {
-
-      /** Validate variance of info of symbol `base` */
-      private def validateVariance(base: Symbol) {
-        // A flag for when we're in a refinement, meaning method parameter types
-        // need to be checked.
-        var inRefinement = false
-
-        /** The variance of a symbol occurrence of `tvar`
-         *  seen at the level of the definition of `base`.
-         *  The search proceeds from `base` to the owner of `tvar`.
-         *  Initially the state is covariant, but it might change along the search.
-         */
-        def relativeVariance(tvar: Symbol): Variance = {
-          val clazz = tvar.owner
-          var sym = base
-          var state: Variance = Covariant
-          while (sym != clazz && state != Bivariant) {
-            //Console.println("flip: " + sym + " " + sym.isParameter());//DEBUG
-            // 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.
-            if (sym.isParameter && !sym.owner.isConstructor && !sym.owner.isCaseApplyOrUnapply &&
-                !(tvar.isTypeParameterOrSkolem && sym.isTypeParameterOrSkolem &&
-                  tvar.owner == sym.owner)) state = state.flip
-            else if (!sym.owner.isClass ||
-                     sym.isTerm && ((sym.isPrivateLocal || sym.isProtectedLocal || sym.isSuperAccessor /* super accessors are implicitly local #4345*/) && !(escapedPrivateLocals contains sym))) {
-              // return AnyVariance if `sym` is local to a term
-              // or is private[this] or protected[this]
-              state = Bivariant
-            } else if (sym.isAliasType) {
-              // return Bivariant if `sym` is an alias type
-              // that does not override anything. This is OK, because we always
-              // expand aliases for variance checking.
-              // However, if `sym` does override a type in a base class
-              // we have to assume Invariant, as there might then be
-              // references to the type parameter that are not variance checked.
-              state = if (sym.isOverridingSymbol) Invariant else Bivariant
-            }
-            sym = sym.owner
-          }
-          state
-        }
-
-        /** Validate that the type `tp` is variance-correct, assuming
-         *  the type occurs itself at variance position given by `variance`
-         */
-        def validateVariance(tp: Type, variance: Variance): Unit = tp match {
-          case ErrorType =>
-          case WildcardType =>
-          case BoundedWildcardType(bounds) =>
-            validateVariance(bounds, variance)
-          case NoType =>
-          case NoPrefix =>
-          case ThisType(_) =>
-          case ConstantType(_) =>
-          case SingleType(pre, sym) =>
-            validateVariance(pre, variance)
-          case TypeRef(pre, sym, args) =>
-//            println("validate "+sym+" at "+relativeVariance(sym))
-            if (sym.isAliasType/* && relativeVariance(sym) == Bivariant*/)
-              validateVariance(tp.normalize, variance)
-            else if (!sym.variance.isInvariant) {
-              val v = relativeVariance(sym)
-              if (!v.isBivariant && sym.variance != v * variance) {
-                //Console.println("relativeVariance(" + base + "," + sym + ") = " + v);//DEBUG
-                def tpString(tp: Type) = tp match {
-                  case ClassInfoType(parents, _, clazz) => "supertype "+intersectionType(parents, clazz.owner)
-                  case _ => "type "+tp
-                }
-                unit.error(base.pos,
-                           sym.variance + " " + sym +
-                           " occurs in " + (v * variance) +
-                           " position in " + tpString(base.info) + " of " + base);
-              }
-            }
-            validateVariance(pre, variance)
-            // @M for higher-kinded typeref, args.isEmpty
-            // However, these args respect variances by construction anyway
-            // -- the interesting case is in type application, see checkKindBounds in Infer
-            if (args.nonEmpty)
-              validateVarianceArgs(args, variance, sym.typeParams)
-          case ClassInfoType(parents, decls, symbol) =>
-            validateVariances(parents, variance)
-          case RefinedType(parents, decls) =>
-            validateVariances(parents, variance)
-            val saved = inRefinement
-            inRefinement = true
-            for (sym <- decls)
-              validateVariance(sym.info, if (sym.isAliasType) Invariant else variance)
-            inRefinement = saved
-          case TypeBounds(lo, hi) =>
-            validateVariance(lo, variance.flip)
-            validateVariance(hi, variance)
-          case mt @ MethodType(formals, result) =>
-            if (inRefinement)
-              validateVariances(mt.paramTypes, variance.flip)
-            validateVariance(result, variance)
-          case NullaryMethodType(result) =>
-            validateVariance(result, variance)
-          case PolyType(tparams, result) =>
-            // type parameters will be validated separately, because they are defined explicitly.
-            validateVariance(result, variance)
-          case ExistentialType(tparams, result) =>
-            validateVariances(tparams map (_.info), variance)
-            validateVariance(result, variance)
-          case AnnotatedType(annots, tp, selfsym) =>
-            if (!annots.exists(_ matches uncheckedVarianceClass))
-              validateVariance(tp, variance)
-        }
-
-        def validateVariances(tps: List[Type], variance: Variance) {
-          tps foreach (tp => validateVariance(tp, variance))
-        }
-
-        def validateVarianceArgs(tps: List[Type], variance: Variance, tparams: List[Symbol]) {
-          foreach2(tps, tparams)((tp, tparam) => validateVariance(tp, variance * tparam.variance))
-        }
-
-        validateVariance(base.info, Covariant)
-      }
-
-      override def traverse(tree: Tree) {
-        tree match {
-          case ClassDef(_, _, _, _) | TypeDef(_, _, _, _) =>
-            validateVariance(tree.symbol)
-            super.traverse(tree)
-          // ModuleDefs need not be considered because they have been eliminated already
-          case ValDef(_, _, _, _) =>
-            if (!tree.symbol.hasLocalFlag)
-              validateVariance(tree.symbol)
-          case DefDef(_, _, tparams, vparamss, _, _) =>
-            // No variance check for object-private/protected methods/values.
-            if (!tree.symbol.hasLocalFlag) {
-              validateVariance(tree.symbol)
-              traverseTrees(tparams)
-              traverseTreess(vparamss)
-            }
-          case Template(_, _, _) =>
-            super.traverse(tree)
-          case _ =>
-        }
-      }
-    }
+    val varianceValidator = new VarianceValidator
 
 // Forward reference checking ---------------------------------------------------
 
@@ -1596,7 +1450,7 @@ abstract class RefChecks extends InfoTransform with scala.reflect.internal.trans
           hidden = o.isTerm || o.isPrivateLocal
           o = o.owner
         }
-        if (!hidden) escapedPrivateLocals += sym
+        if (!hidden) varianceValidator.escapedPrivateLocals += sym
       }
 
       def checkSuper(mix: Name) =