Tailrec patrol: src/library

  - mark methods that are tailrec as such
  - make some more methods tailrec by making them final

Author: retronym

src/library/scala/collection/Iterator.scala

@@ -530,6 +530,7 @@ trait Iterator[+A] extends IterableOnce[A] with IterableOnceOps[A, Iterator, Ite
     private[this] var nextElementDefined: Boolean = false
     private[this] var nextElement: A = _
 
+    @tailrec
     def hasNext: Boolean = nextElementDefined || (self.hasNext && {
       val a = self.next()
       if (traversedValues.add(f(a))) {
@@ -637,7 +638,7 @@ trait Iterator[+A] extends IterableOnce[A] with IterableOnceOps[A, Iterator, Ite
      * iterator is referring (the finish() method) and thus triggering
      * handling of structural calls. It's not what's intended here.
      */
-    class Leading extends AbstractIterator[A] {
+    final class Leading extends AbstractIterator[A] {
       private[this] var lookahead: mutable.Queue[A] = null
       private[this] var hd: A = _
       /* Status is kept with magic numbers
@@ -670,6 +671,7 @@ trait Iterator[+A] extends IterableOnce[A] with IterableOnceOps[A, Iterator, Ite
         }
         else Iterator.empty.next()
       }
+      @tailrec
       def finish(): Boolean = status match {
         case -2 => status = -1 ; true
         case -1 => false

src/library/scala/collection/StringParsers.scala

@@ -178,6 +178,7 @@ private[scala] object StringParsers {
     //some utilities for working with index bounds into the original string
     @inline
     def forAllBetween(start: Int, end: Int, pred: Char => Boolean): Boolean = {
+      @tailrec
       def rec(i: Int): Boolean = i >= end || pred(format.charAt(i)) && rec(i + 1)
       rec(start)
     }

src/library/scala/collection/View.scala

@@ -14,6 +14,7 @@ package scala.collection
 
 import java.io.{ObjectInputStream, ObjectOutputStream}
 
+import scala.annotation.tailrec
 import scala.collection.mutable.{ArrayBuffer, Builder}
 import scala.collection.immutable.LazyList
 
@@ -169,6 +170,7 @@ object View extends IterableFactory[View] {
       private[this] var hd: A1 = _
       private[this] var hdDefined: Boolean = false
       def hasNext = hdDefined || {
+        @tailrec
         def findNext(): Boolean =
           if (self.hasNext) {
             f(self.next()) match {
@@ -193,6 +195,7 @@ object View extends IterableFactory[View] {
         private[this] var hd: A2 = _
         private[this] var hdDefined: Boolean = false
         def hasNext = hdDefined || {
+          @tailrec
           def findNext(): Boolean =
             if (self.hasNext) {
               f(self.next()) match {

src/library/scala/collection/concurrent/TrieMap.scala

@@ -1038,7 +1038,7 @@ object TrieMap extends MapFactory[TrieMap] {
 }
 
 
-private[collection] class TrieMapIterator[K, V](var level: Int, private var ct: TrieMap[K, V], mustInit: Boolean = true) extends AbstractIterator[(K, V)] {
+private[collection] final class TrieMapIterator[K, V](var level: Int, private var ct: TrieMap[K, V], mustInit: Boolean = true) extends AbstractIterator[(K, V)] {
   private val stack = new Array[Array[BasicNode]](7)
   private val stackpos = new Array[Int](7)
   private var depth = -1
@@ -1088,6 +1088,7 @@ private[collection] class TrieMapIterator[K, V](var level: Int, private var ct:
     readin(r)
   }
 
+  @tailrec
   def advance(): Unit = if (depth >= 0) {
     val npos = stackpos(depth) + 1
     if (npos < stack(depth).length) {

src/library/scala/collection/immutable/IntMap.scala

@@ -133,6 +133,7 @@ private[immutable] abstract class IntMapIterator[V, T](it: IntMap[V]) extends Ab
   def valueOf(tip: IntMap.Tip[V]): T
 
   def hasNext = index != 0
+  @tailrec
   final def next(): T =
     pop match {
       case IntMap.Bin(_,_, t@IntMap.Tip(_, _), right) => {
@@ -285,19 +286,22 @@ sealed abstract class IntMap[+T] extends AbstractMap[Int, T]
     case IntMap.Bin(_, _, left, right) => left.size + right.size
   }
 
+  @tailrec
   final def get(key: Int): Option[T] = this match {
     case IntMap.Bin(prefix, mask, left, right) => if (zero(key, mask)) left.get(key) else right.get(key)
     case IntMap.Tip(key2, value) => if (key == key2) Some(value) else None
     case IntMap.Nil => None
   }
 
+  @tailrec
   final override def getOrElse[S >: T](key: Int, default: => S): S = this match {
     case IntMap.Nil => default
     case IntMap.Tip(key2, value) => if (key == key2) value else default
     case IntMap.Bin(prefix, mask, left, right) =>
       if (zero(key, mask)) left.getOrElse(key, default) else right.getOrElse(key, default)
   }
 
+  @tailrec
   final override def apply(key: Int): T = this match {
     case IntMap.Bin(prefix, mask, left, right) => if (zero(key, mask)) left(key) else right(key)
     case IntMap.Tip(key2, value) => if (key == key2) value else throw new IllegalArgumentException("Key not found")

src/library/scala/collection/immutable/List.scala

@@ -437,7 +437,7 @@ sealed abstract class List[+A]
   @`inline` final def mapConserve[B >: A <: AnyRef](f: A => B): List[B] = {
     // Note to developers: there exists a duplication between this function and `reflect.internal.util.Collections#map2Conserve`.
     // If any successful optimization attempts or other changes are made, please rehash them there too.
-    //@tailrec
+    @tailrec
     def loop(mappedHead: List[B], mappedLast: ::[B], unchanged: List[A], pending: List[A]): List[B] = {
       if (pending.isEmpty) {
         if (mappedHead eq null) unchanged

src/library/scala/collection/immutable/LongMap.scala

@@ -130,6 +130,7 @@ private[immutable] abstract class LongMapIterator[V, T](it: LongMap[V]) extends
   def valueOf(tip: LongMap.Tip[V]): T
 
   def hasNext = index != 0
+  @tailrec
   final def next(): T =
     pop() match {
       case LongMap.Bin(_,_, t@LongMap.Tip(_, _), right) => {
@@ -280,19 +281,22 @@ sealed abstract class LongMap[+T] extends AbstractMap[Long, T]
     case LongMap.Bin(_, _, left, right) => left.size + right.size
   }
 
+  @tailrec
   final def get(key: Long): Option[T] = this match {
     case LongMap.Bin(prefix, mask, left, right) => if (zero(key, mask)) left.get(key) else right.get(key)
     case LongMap.Tip(key2, value) => if (key == key2) Some(value) else None
     case LongMap.Nil => None
   }
 
+  @tailrec
   final override def getOrElse[S >: T](key: Long, default: => S): S = this match {
     case LongMap.Nil => default
     case LongMap.Tip(key2, value) => if (key == key2) value else default
     case LongMap.Bin(prefix, mask, left, right) =>
       if (zero(key, mask)) left.getOrElse(key, default) else right.getOrElse(key, default)
   }
 
+  @tailrec
   final override def apply(key: Long): T = this match {
     case LongMap.Bin(prefix, mask, left, right) => if (zero(key, mask)) left(key) else right(key)
     case LongMap.Tip(key2, value) => if (key == key2) value else throw new IllegalArgumentException("Key not found")

src/library/scala/collection/immutable/TreeSeqMap.scala

@@ -13,7 +13,9 @@
 package scala
 package collection
 package immutable
- 
+
+import scala.annotation.tailrec
+
 /** This class implements an immutable map that preserves order using
   * a hash map for the key to value mapping to provide efficient lookup,
   * and a tree for the ordering of the keys to provide efficient
@@ -383,6 +385,7 @@ object TreeSeqMap extends MapFactory[TreeSeqMap] {
       if (it != Zero) push(it)
 
       def hasNext = index != 0
+      @tailrec
       def next(): V =
         pop match {
           case Bin(_,_, Tip(_, v), right) =>

src/library/scala/reflect/ClassManifestDeprecatedApis.scala

@@ -13,8 +13,10 @@
 package scala
 package reflect
 
-import scala.collection.mutable.{ ArraySeq, ArrayBuilder }
-import java.lang.{ Class => jClass }
+import scala.collection.mutable.{ArrayBuilder, ArraySeq}
+import java.lang.{Class => jClass}
+
+import scala.annotation.tailrec
 
 @deprecated("use scala.reflect.ClassTag instead", "2.10.0")
 trait ClassManifestDeprecatedApis[T] extends OptManifest[T] {
@@ -25,6 +27,7 @@ trait ClassManifestDeprecatedApis[T] extends OptManifest[T] {
   def erasure: jClass[_] = runtimeClass
 
   private def subtype(sub: jClass[_], sup: jClass[_]): Boolean = {
+    @tailrec
     def loop(left: Set[jClass[_]], seen: Set[jClass[_]]): Boolean = {
       left.nonEmpty && {
         val next = left.head

src/library/scala/sys/process/BasicIO.scala

@@ -195,6 +195,7 @@ object BasicIO {
   def processLinesFully(processLine: String => Unit)(readLine: () => String): Unit = {
     def working = (Thread.currentThread.isInterrupted == false)
     def halting = { Thread.currentThread.interrupt(); null }
+    @tailrec
     def readFully(): Unit =
       if (working) {
         val line =