Merge pull request scala#4175 from Ichoran/issue/7981

SI-7981  toSeq on immutable Map and Set return ArrayBuffer

Author: lrytz

src/library/scala/collection/MapLike.scala

@@ -323,11 +323,20 @@ self =>
     res
   }
 
-  /* Overridden for efficiency. */
-  override def toSeq: Seq[(A, B)] = toBuffer[(A, B)]
+  override def toSeq: Seq[(A, B)] = {
+    if (isEmpty) Vector.empty[(A, B)]
+    else {
+      // Default appropriate for immutable collections; mutable collections override this
+      val vb = Vector.newBuilder[(A, B)]
+      foreach(vb += _)
+      vb.result
+    }
+  }  
+  
   override def toBuffer[C >: (A, B)]: mutable.Buffer[C] = {
     val result = new mutable.ArrayBuffer[C](size)
-    copyToBuffer(result)
+    // Faster to let the map iterate itself than to defer through copyToBuffer
+    foreach(result += _)
     result
   }
 

src/library/scala/collection/SetLike.scala

@@ -77,11 +77,20 @@ self =>
 
   protected[this] override def parCombiner = ParSet.newCombiner[A]
 
-  /* Overridden for efficiency. */
-  override def toSeq: Seq[A] = toBuffer[A]
+  // Default collection type appropriate for immutable collections; mutable collections override this
+  override def toSeq: Seq[A] = {
+    if (isEmpty) Vector.empty[A]
+    else {
+      val vb = Vector.newBuilder[A]
+      foreach(vb += _)
+      vb.result
+    }
+  }
+  
   override def toBuffer[A1 >: A]: mutable.Buffer[A1] = {
     val result = new mutable.ArrayBuffer[A1](size)
-    copyToBuffer(result)
+    // Faster to let the map iterate itself than to defer through copyToBuffer
+    foreach(result += _)
     result
   }
 

src/library/scala/collection/mutable/MapLike.scala

@@ -59,6 +59,18 @@ trait MapLike[A, B, +This <: MapLike[A, B, This] with Map[A, B]]
   override protected[this] def newBuilder: Builder[(A, B), This] = empty
 
   protected[this] override def parCombiner = ParMap.newCombiner[A, B]
+  
+  /** Converts this $coll to a sequence.
+    *
+    * ```Note```: assumes a fast `size` method.  Subclasses should override if this is not true.
+    */
+  override def toSeq: collection.Seq[(A, B)] = {
+    // ArrayBuffer for efficiency, preallocated to the right size.
+    val result = new ArrayBuffer[(A, B)](size)
+    foreach(result += _)
+    result
+  }
+
 
   /** Adds a new key/value pair to this map and optionally returns previously bound value.
    *  If the map already contains a

src/library/scala/collection/mutable/SetLike.scala

@@ -72,6 +72,17 @@ trait SetLike[A, +This <: SetLike[A, This] with Set[A]]
 
   protected[this] override def parCombiner = ParSet.newCombiner[A]
 
+  /** Converts this $coll to a sequence.
+    *
+    * ```Note```: assumes a fast `size` method.  Subclasses should override if this is not true.
+    */
+  override def toSeq: collection.Seq[A] = {
+    // ArrayBuffer for efficiency, preallocated to the right size.
+    val result = new ArrayBuffer[A](size)
+    foreach(result += _)
+    result
+  }
+
   /** Adds an element to this $coll.
    *
    *  @param elem the element to be added

test/files/run/inline-ex-handlers.check

@@ -123,12 +123,12 @@
      300	RETURN(UNIT)
 @@ -583,6 +603,6 @@
        with finalizer: null
--    catch (Throwable) in ArrayBuffer(7, 9, 10) starting at: 6
-+    catch (Throwable) in ArrayBuffer(7, 9, 10, 11) starting at: 6
+-    catch (Throwable) in Vector(7, 9, 10) starting at: 6
++    catch (Throwable) in Vector(7, 9, 10, 11) starting at: 6
        consisting of blocks: List(6)
        with finalizer: null
--    catch (Throwable) in ArrayBuffer(4, 6, 7, 9, 10) starting at: 3
-+    catch (Throwable) in ArrayBuffer(4, 6, 7, 9, 10, 11, 12) starting at: 3
+-    catch (Throwable) in Vector(4, 6, 7, 9, 10) starting at: 3
++    catch (Throwable) in Vector(4, 6, 7, 9, 10, 11, 12) starting at: 3
        consisting of blocks: List(3)
 @@ -618,3 +638,3 @@
    startBlock: 1
@@ -171,8 +171,8 @@
    }
 @@ -690,3 +730,3 @@
        with finalizer: null
--    catch (<none>) in ArrayBuffer(4, 5, 6, 8) starting at: 3
-+    catch (<none>) in ArrayBuffer(4, 5, 6, 8, 10) starting at: 3
+-    catch (<none>) in Vector(4, 5, 6, 8) starting at: 3
++    catch (<none>) in Vector(4, 5, 6, 8, 10) starting at: 3
        consisting of blocks: List(3)
 @@ -714,5 +754,5 @@
    def main(args: Array[String] (ARRAY[REF(class String)])): Unit {
@@ -276,12 +276,12 @@
    }
 @@ -852,6 +918,6 @@
        with finalizer: null
--    catch (Throwable) in ArrayBuffer(13, 14, 15, 18, 20, 21, 23) starting at: 4
-+    catch (Throwable) in ArrayBuffer(13, 14, 15, 18, 20, 21, 23, 25) starting at: 4
+-    catch (Throwable) in Vector(13, 14, 15, 18, 20, 21, 23) starting at: 4
++    catch (Throwable) in Vector(13, 14, 15, 18, 20, 21, 23, 25) starting at: 4
        consisting of blocks: List(9, 8, 6, 5, 4)
        with finalizer: null
--    catch (<none>) in ArrayBuffer(4, 5, 6, 9, 13, 14, 15, 18, 20, 21, 23) starting at: 3
-+    catch (<none>) in ArrayBuffer(4, 5, 6, 9, 13, 14, 15, 18, 20, 21, 23, 25, 26) starting at: 3
+-    catch (<none>) in Vector(4, 5, 6, 9, 13, 14, 15, 18, 20, 21, 23) starting at: 3
++    catch (<none>) in Vector(4, 5, 6, 9, 13, 14, 15, 18, 20, 21, 23, 25, 26) starting at: 3
        consisting of blocks: List(3)
 @@ -879,5 +945,5 @@
    def main(args: Array[String] (ARRAY[REF(class String)])): Unit {
@@ -317,8 +317,8 @@
      127	CALL_METHOD scala.Predef.println (dynamic)
 @@ -964,3 +1034,3 @@
        with finalizer: null
--    catch (IllegalArgumentException) in ArrayBuffer(6, 7, 8, 11, 13, 14, 16) starting at: 3
-+    catch (IllegalArgumentException) in ArrayBuffer(6, 7, 8, 11, 13, 14, 16, 17) starting at: 3
+-    catch (IllegalArgumentException) in Vector(6, 7, 8, 11, 13, 14, 16) starting at: 3
++    catch (IllegalArgumentException) in Vector(6, 7, 8, 11, 13, 14, 16, 17) starting at: 3
        consisting of blocks: List(3)
 @@ -988,5 +1058,5 @@
    def main(args: Array[String] (ARRAY[REF(class String)])): Unit {