Merge pull request #2145 from paulp/pr/value-class-extractors

Boxing cleanup: erasure, post-erasure, value classes.

3 files changed, 99 insertions, 99 deletions

diff --git a/src/compiler/scala/tools/nsc/ast/TreeInfo.scala b/src/compiler/scala/tools/nsc/ast/TreeInfo.scala
index f53f99a279..6a0f4407fc 100644
--- a/src/compiler/scala/tools/nsc/ast/TreeInfo.scala
+++ b/src/compiler/scala/tools/nsc/ast/TreeInfo.scala
@@ -14,6 +14,65 @@ package ast
 abstract class TreeInfo extends scala.reflect.internal.TreeInfo {
   val global: Global
   import global._
+  import definitions._
+
+  // arg1.op(arg2) returns (arg1, op.symbol, arg2)
+  object BinaryOp {
+    def unapply(t: Tree): Option[(Tree, Symbol, Tree)] = t match {
+      case Apply(sel @ Select(arg1, _), arg2 :: Nil) => Some((arg1, sel.symbol, arg2))
+      case _                                         => None
+    }
+  }
+  // recv.op[T1, ...] returns (recv, op.symbol, type argument types)
+  object TypeApplyOp {
+    def unapply(t: Tree): Option[(Tree, Symbol, List[Type])] = t match {
+      case TypeApply(sel @ Select(recv, _), targs) => Some((recv, sel.symbol, targs map (_.tpe)))
+      case _                                       => None
+    }
+  }
+
+  // x.asInstanceOf[T] returns (x, typeOf[T])
+  object AsInstanceOf {
+    def unapply(t: Tree): Option[(Tree, Type)] = t match {
+      case Apply(TypeApplyOp(recv, Object_asInstanceOf, tpe :: Nil), Nil) => Some((recv, tpe))
+      case _                                                              => None
+    }
+  }
+
+  // Extractors for value classes.
+  object ValueClass {
+    def isValueClass(tpe: Type)                  = enteringErasure(tpe.typeSymbol.isDerivedValueClass)
+    def valueUnbox(tpe: Type)                    = enteringErasure(tpe.typeSymbol.derivedValueClassUnbox)
+
+    // B.unbox. Returns B.
+    object Unbox {
+      def unapply(t: Tree): Option[Tree] = t match {
+        case Apply(sel @ Select(ref, _), Nil) if valueUnbox(ref.tpe) == sel.symbol => Some(ref)
+        case _                                                                     => None
+      }
+    }
+    // new B(v). Returns B and v.
+    object Box {
+      def unapply(t: Tree): Option[(Tree, Type)] = t match {
+        case Apply(sel @ Select(New(tpt), nme.CONSTRUCTOR), v :: Nil) => Some((v, tpt.tpe.finalResultType))
+        case _                                                        => None
+      }
+    }
+    // (new B(v)).unbox. returns v.
+    object BoxAndUnbox {
+      def unapply(t: Tree): Option[Tree] = t match {
+        case Unbox(Box(v, tpe)) if isValueClass(tpe) => Some(v)
+        case _                                       => None
+      }
+    }
+    // new B(v1) op new B(v2) where op is == or !=. Returns v1, op, v2.
+    object BoxAndCompare {
+      def unapply(t: Tree): Option[(Tree, Symbol, Tree)] = t match {
+        case BinaryOp(Box(v1, tpe1), op @ (Object_== | Object_!=), Box(v2, tpe2)) if isValueClass(tpe1) && tpe1 =:= tpe2 => Some((v1, op, v2))
+        case _                                                                                                           => None
+      }
+    }
+  }
 
   /** Is tree legal as a member definition of an interface?
    */
diff --git a/src/compiler/scala/tools/nsc/transform/Erasure.scala b/src/compiler/scala/tools/nsc/transform/Erasure.scala
index f380b9d04f..8287c1f631 100644
--- a/src/compiler/scala/tools/nsc/transform/Erasure.scala
+++ b/src/compiler/scala/tools/nsc/transform/Erasure.scala
@@ -21,6 +21,7 @@ abstract class Erasure extends AddInterfaces
   import global._
   import definitions._
   import CODE._
+  import treeInfo._
 
   val phaseName: String = "erasure"
 
@@ -357,41 +358,10 @@ abstract class Erasure extends AddInterfaces
 
   override def newTyper(context: Context) = new Eraser(context)
 
-  private def safeToRemoveUnbox(cls: Symbol): Boolean =
-    (cls == definitions.NullClass) || isBoxedValueClass(cls)
-
-  /** An extractor object for unboxed expressions (maybe subsumed by posterasure?) */
-  object Unboxed {
-    def unapply(tree: Tree): Option[Tree] = tree match {
-      case Apply(fn, List(arg)) if isUnbox(fn.symbol) && safeToRemoveUnbox(arg.tpe.typeSymbol) =>
-        Some(arg)
-      case Apply(
-        TypeApply(
-          cast @ Select(
-            Apply(
-              sel @ Select(arg, acc),
-              List()),
-            asinstanceof),
-          List(tpt)),
-        List())
-      if cast.symbol == Object_asInstanceOf &&
-        tpt.tpe.typeSymbol.isDerivedValueClass &&
-        sel.symbol == tpt.tpe.typeSymbol.derivedValueClassUnbox =>
-        Some(arg)
-      case _ =>
-        None
-    }
-  }
-
-  /** An extractor object for boxed expressions (maybe subsumed by posterasure?) */
-  object Boxed {
-    def unapply(tree: Tree): Option[Tree] = tree match {
-      case Apply(Select(New(tpt), nme.CONSTRUCTOR), List(arg)) if (tpt.tpe.typeSymbol.isDerivedValueClass) =>
-        Some(arg)
-      case LabelDef(name, params, Boxed(rhs)) =>
-        Some(treeCopy.LabelDef(tree, name, params, rhs) setType rhs.tpe)
-      case _ =>
-        None
+  private def isSafelyRemovableUnbox(fn: Tree, arg: Tree): Boolean = {
+    isUnbox(fn.symbol) && {
+      val cls = arg.tpe.typeSymbol
+      (cls == definitions.NullClass) || isBoxedValueClass(cls)
     }
   }
 
@@ -578,12 +548,7 @@ abstract class Erasure extends AddInterfaces
         val tree1 = tree.tpe match {
           case ErasedValueType(tref) =>
             val clazz = tref.sym
-            tree match {
-              case Unboxed(arg) if arg.tpe.typeSymbol == clazz =>
-                log("shortcircuiting unbox -> box "+arg); arg
-              case _ =>
-                New(clazz, cast(tree, underlyingOfValueClass(clazz)))
-            }
+            New(clazz, cast(tree, underlyingOfValueClass(clazz)))
           case _ =>
             tree.tpe.typeSymbol match {
           case UnitClass  =>
@@ -599,7 +564,7 @@ abstract class Erasure extends AddInterfaces
                *  This is important for specialization: calls to the super constructor should not box/unbox specialized
                *  fields (see TupleX). (ID)
                */
-              case Apply(boxFun, List(arg)) if isUnbox(tree.symbol) && safeToRemoveUnbox(arg.tpe.typeSymbol) =>
+              case Apply(boxFun, List(arg)) if isSafelyRemovableUnbox(tree, arg) =>
                 log(s"boxing an unbox: ${tree.symbol} -> ${arg.tpe}")
                 arg
               case _ =>
@@ -634,24 +599,18 @@ abstract class Erasure extends AddInterfaces
       case _ =>
         val tree1 = pt match {
           case ErasedValueType(tref) =>
-            tree match {
-              case Boxed(arg) if arg.tpe.isInstanceOf[ErasedValueType] =>
-                log("shortcircuiting box -> unbox "+arg)
-                arg
-              case _ =>
-                val clazz = tref.sym
-                log("not boxed: "+tree)
-                lazy val underlying = underlyingOfValueClass(clazz)
-                val tree0 =
-                  if (tree.tpe.typeSymbol == NullClass &&
-                      isPrimitiveValueClass(underlying.typeSymbol)) {
-                    // convert `null` directly to underlying type, as going
-                    // via the unboxed type would yield a NPE (see SI-5866)
-                    unbox1(tree, underlying)
-                  } else
-                    Apply(Select(adaptToType(tree, clazz.tpe), clazz.derivedValueClassUnbox), List())
-                cast(tree0, pt)
-            }
+            val clazz = tref.sym
+            log("not boxed: "+tree)
+            lazy val underlying = underlyingOfValueClass(clazz)
+            val tree0 =
+              if (tree.tpe.typeSymbol == NullClass &&
+                  isPrimitiveValueClass(underlying.typeSymbol)) {
+                // convert `null` directly to underlying type, as going
+                // via the unboxed type would yield a NPE (see SI-5866)
+                unbox1(tree, underlying)
+              } else
+                Apply(Select(adaptToType(tree, clazz.tpe), clazz.derivedValueClassUnbox), List())
+            cast(tree0, pt)
           case _ =>
             pt.typeSymbol match {
               case UnitClass  =>
diff --git a/src/compiler/scala/tools/nsc/transform/PostErasure.scala b/src/compiler/scala/tools/nsc/transform/PostErasure.scala
index a8dc47046b..2a86d711f1 100644
--- a/src/compiler/scala/tools/nsc/transform/PostErasure.scala
+++ b/src/compiler/scala/tools/nsc/transform/PostErasure.scala
@@ -9,10 +9,10 @@ package transform
  *  performs peephole optimizations.
  */
 trait PostErasure extends InfoTransform with TypingTransformers {
-
   val global: Global
+
   import global._
-  import definitions._
+  import treeInfo._
 
   val phaseName: String = "posterasure"
 
@@ -21,51 +21,33 @@ trait PostErasure extends InfoTransform with TypingTransformers {
 
   object elimErasedValueType extends TypeMap {
     def apply(tp: Type) = tp match {
-      case ConstantType(Constant(tp: Type)) =>
-        ConstantType(Constant(apply(tp)))
-      case ErasedValueType(tref) =>
-        enteringPhase(currentRun.erasurePhase)(erasure.erasedValueClassArg(tref))
-      case _ => mapOver(tp)
+      case ConstantType(Constant(tp: Type)) => ConstantType(Constant(apply(tp)))
+      case ErasedValueType(tref)            => enteringErasure(erasure.erasedValueClassArg(tref))
+      case _                                => mapOver(tp)
     }
   }
 
   def transformInfo(sym: Symbol, tp: Type) = elimErasedValueType(tp)
 
   class PostErasureTransformer(unit: CompilationUnit) extends TypingTransformer(unit) {
+    override def transform(tree: Tree) = {
+      def finish(res: Tree) = logResult(s"Posterasure reduction\n  Old: $tree\n  New")(res)
+
+      /** We use the name of the operation being performed and not the symbol
+       *  itself because the symbol hails from the boxed class, and this transformation
+       *  exists to operate directly on the values. So we are for instance looking
+       *  up == on an lhs of type Int, whereas the symbol which has been passed in
+       *  is from java.lang.Integer.
+       */
+      def binop(lhs: Tree, op: Symbol, rhs: Tree) =
+        finish(localTyper typed (Apply(Select(lhs, op.name) setPos tree.pos, rhs :: Nil) setPos tree.pos))
 
-    override def transform(tree: Tree) =
       super.transform(tree) setType elimErasedValueType(tree.tpe) match {
-        case // new C(arg).underlying  ==>  arg
-          Apply(sel @ Select(
-            Apply(Select(New(tpt), nme.CONSTRUCTOR), List(arg)),
-            acc), List())
-        if enteringPhase(currentRun.erasurePhase) {
-          tpt.tpe.typeSymbol.isDerivedValueClass &&
-          sel.symbol == tpt.tpe.typeSymbol.derivedValueClassUnbox
-        } =>
-          if (settings.debug.value) log("Removing "+tree+" -> "+arg)
-          arg
-        case // new C(arg1) == new C(arg2)  ==>  arg1 == arg2
-          Apply(sel @ Select(
-            Apply(Select(New(tpt1), nme.CONSTRUCTOR), List(arg1)),
-            cmp),
-            List(Apply(Select(New(tpt2), nme.CONSTRUCTOR), List(arg2))))
-        if enteringPhase(currentRun.erasurePhase) {
-          tpt1.tpe.typeSymbol.isDerivedValueClass &&
-          (sel.symbol == Object_== || sel.symbol == Object_!=) &&
-          tpt2.tpe.typeSymbol == tpt1.tpe.typeSymbol
-        } =>
-          val result = Apply(Select(arg1, cmp) setPos sel.pos, List(arg2)) setPos tree.pos
-          log("shortcircuiting equality "+tree+" -> "+result)
-          localTyper.typed(result)
-
-        case // arg.asInstanceOf[T]  ==>  arg      if arg.tpe == T
-          Apply(TypeApply(cast @ Select(arg, asinstanceof), List(tpt)), List())
-        if cast.symbol == Object_asInstanceOf && arg.tpe =:= tpt.tpe => // !!! <:< ?
-          if (settings.debug.value) log("Shortening "+tree+" -> "+arg)
-          arg
-        case tree1 =>
-          tree1
+        case AsInstanceOf(v, tpe) if v.tpe <:< tpe => finish(v)          // x.asInstanceOf[X]       ==> x
+        case ValueClass.BoxAndUnbox(v)             => finish(v)          // (new B(v)).unbox        ==> v
+        case ValueClass.BoxAndCompare(v1, op, v2)  => binop(v1, op, v2)  // new B(v1) == new B(v2)  ==> v1 == v2
+        case tree                                  => tree
       }
+    }
   }
 }