Fix ++= in Lst.Buffer

Author: odersky

tests/run/lst/Lst.scala

@@ -464,6 +464,7 @@ object Lst {
             ensureSize(len + elems2.length)
             System.arraycopy(elems2, 0, elems, len, elems2.length)
           }
+          len += elems2.length
         case elem: T @unchecked => this += elem
       }
       this

tests/run/lst/LstTest.scala

@@ -277,17 +277,35 @@ object Test extends App {
     assert(zs1.eqElements(zs1))
     assert(zs1.eqElements(zs2))
     assert(!zs1.eqElements(zs3))
+
+    assert(is4.corresponds(is4)(_ == _))
+    assert(!is4.corresponds(is5)(_ == _))
+    assert(is1.corresponds(is1)(_ == _))
+    assert(!is1.corresponds(Lst(-1))(_ == _))
+    assert(is0.corresponds(is0)(_ == _))
+    assert(!is0.corresponds(is1)(_ == _))
   }
 
   def bufferTest() = {
-    val b = new Lst.Buffer[String]
-    b += "a"
-    assert(b.size == 1)
-    assert(b.toLst === Lst("a"))
-    b += "aa"
-    b ++= Lst.fill(20)("a")
-    assert(b.toLst.mkString("") == "a" * 23)
-    assert(b.size == 23)
+    { val b = new Lst.Buffer[String]
+      b += "a"
+      assert(b.size == 1)
+      assert(b.toLst === Lst("a"))
+      b += "aa"
+      b ++= Lst.fill(20)("a")
+      assert(b.toLst.mkString("") == "a" * 23)
+      assert(b.size == 22)
+    }
+
+    { val b = new Lst.Buffer[Int]
+      b += 1
+      assert(b.size == 1)
+      assert(b.toLst === Lst(1))
+      b += 11
+      b ++= Lst.fill(20)(1)
+      assert(b.toLst.mkString("") == "1" * 23)
+      assert(b.size == 22)
+    }
   }
 
   println("testing")
@@ -307,4 +325,5 @@ object Test extends App {
   sliceTest()
   zipWithTest()
   correspondsTest()
+  bufferTest()
 }