skipping trips to specializeTypes when not necessary in constructors

1 files changed, 13 insertions, 5 deletions

diff --git a/src/compiler/scala/tools/nsc/transform/Constructors.scala b/src/compiler/scala/tools/nsc/transform/Constructors.scala
index f93d26360e..cf2b6d39a2 100644
--- a/src/compiler/scala/tools/nsc/transform/Constructors.scala
+++ b/src/compiler/scala/tools/nsc/transform/Constructors.scala
@@ -279,7 +279,6 @@ abstract class Constructors extends Transform with ast.TreeDSL {
       delayedDD.asInstanceOf[DefDef]
     }
 
-    /* @see overview at `delayedEndpointDef()` of the translation scheme for DelayedInit */
     private def delayedInitClosure(delayedEndPointSym: MethodSymbol): ClassDef = {
       val satelliteClass = localTyper.typed {
         atPos(impl.pos) {
@@ -327,7 +326,6 @@ abstract class Constructors extends Transform with ast.TreeDSL {
       satelliteClass.asInstanceOf[ClassDef]
     }
 
-    /* @see overview at `delayedEndpointDef()` of the translation scheme for DelayedInit */
     private def delayedInitCall(closure: Tree) = localTyper.typedPos(impl.pos) {
       gen.mkMethodCall(This(clazz), delayedInitMethod, Nil, List(New(closure.symbol.tpe, This(clazz))))
     }
@@ -446,7 +444,7 @@ abstract class Constructors extends Transform with ast.TreeDSL {
       //   postfix = postfix.tail
       // }
 
-      if (usesSpecializedField && shouldGuard && stats.nonEmpty) {
+      if (shouldGuard && usesSpecializedField && stats.nonEmpty) {
         // save them for duplication in the specialized subclass
         guardedCtorStats(clazz) = stats
         ctorParams(clazz) = constrInfo.constrParams
@@ -526,6 +524,15 @@ abstract class Constructors extends Transform with ast.TreeDSL {
       }
     }
 
+    /*
+     * `usesSpecializedField` makes a difference in deciding whether constructor-statements
+     * should be guarded in a `shouldGuard` class, ie in a class that's the generic super-class of
+     * one or more specialized sub-classes.
+     *
+     * Given that `usesSpecializedField` isn't read for any other purpose than the one described above,
+     * we skip setting `usesSpecializedField` in case the current class isn't `shouldGuard` to start with.
+     * That way, trips to a map in `specializeTypes` are saved.
+     */
     var usesSpecializedField: Boolean = false
 
     /*
@@ -572,9 +579,10 @@ abstract class Constructors extends Transform with ast.TreeDSL {
           // references to parameter accessor field of own class become references to parameters
           gen.mkAttributedIdent(parameter(tree.symbol)) setPos tree.pos
 
-        case Select(_, _) =>
-          if (possiblySpecialized(tree.symbol))
+        case Select(_, _) if shouldGuard => // reasoning behind this guard in the docu of `usesSpecializedField`
+          if (possiblySpecialized(tree.symbol)) {
             usesSpecializedField = true
+          }
           super.transform(tree)
 
         case _ =>