diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/compiler/scala/tools/nsc/Settings.scala | 1 | ||||
| -rw-r--r-- | src/compiler/scala/tools/nsc/transform/TailCalls.scala | 30 |
2 files changed, 25 insertions, 6 deletions
diff --git a/src/compiler/scala/tools/nsc/Settings.scala b/src/compiler/scala/tools/nsc/Settings.scala index 68bf6aeabf..c85242f937 100644 --- a/src/compiler/scala/tools/nsc/Settings.scala +++ b/src/compiler/scala/tools/nsc/Settings.scala @@ -834,6 +834,7 @@ trait ScalacSettings { val Ytyperdebug = BooleanSetting ("-Ytyper-debug", "Trace all type assignements") val Ypmatdebug = BooleanSetting ("-Ypmat-debug", "Trace all pattern matcher activity.") val Xwarnings = BooleanSetting ("-Xstrict-warnings", "Emit extra (usually spurious) warnings.") + val Ytailrec = BooleanSetting ("-Ytailrecommend", "Alert methods which would be tail-recursive if private or final.") /** * -P "Plugin" settings diff --git a/src/compiler/scala/tools/nsc/transform/TailCalls.scala b/src/compiler/scala/tools/nsc/transform/TailCalls.scala index c3cdc55ad6..93cb5baefa 100644 --- a/src/compiler/scala/tools/nsc/transform/TailCalls.scala +++ b/src/compiler/scala/tools/nsc/transform/TailCalls.scala @@ -163,19 +163,31 @@ abstract class TailCalls extends Transform newCtx.tailPos = true val isEligible = newCtx.currentMethod.isFinal || (newCtx.currentMethod.enclClass hasFlag Flags.MODULE) - if (isEligible) { + // If -Ytailrecommend is given, we speculatively try transforming ineligible methods and + // report where we would have been successful. + val recommend = settings.Ytailrec.value + val savedFlags: Option[Long] = if (recommend) Some(newCtx.currentMethod.flags) else None + + if (isEligible || recommend) { + if (recommend) + newCtx.currentMethod.flags |= Flags.FINAL + newCtx.tparams = Nil log(" Considering " + name + " for tailcalls") tree.symbol.tpe match { case PolyType(tpes, restpe) => newCtx.tparams = tparams map (_.symbol) newCtx.label.setInfo( - newCtx.label.tpe.substSym(tpes, tparams map (_.symbol))) + newCtx.label.tpe.substSym(tpes, tparams map (_.symbol))) case _ => } } - val t1 = treeCopy.DefDef(tree, mods, name, tparams, vparams, tpt, - transform(rhs, newCtx) match { + + val t1 = treeCopy.DefDef(tree, mods, name, tparams, vparams, tpt, { + val transformed = transform(rhs, newCtx) + savedFlags foreach (newCtx.currentMethod.flags = _) + + transformed match { case newRHS if isEligible && newCtx.accessed => log("Rewrote def " + newCtx.currentMethod) isTransformed = true @@ -188,9 +200,15 @@ abstract class TailCalls extends Transform List(ValDef(newThis, This(currentClass))), LabelDef(newCtx.label, newThis :: (vparams.flatten map (_.symbol)), newRHS) ))) - case rhs => rhs + case _ if recommend => + if (newCtx.accessed) + unit.warning(dd.pos, "method is tailrecommended") + // transform with the original flags restored + transform(rhs, newCtx) + + case rhs => rhs } - ) + }) if (!forMSIL && !isTransformed && tailrecRequired(dd)) unit.error(dd.pos, "could not optimize @tailrec annotated method") |