Avoid using ArraySeq.empty with fixed element type

scala · May 25, 2021 · 8fa1580 · 8fa1580
1 parent 3b1b2d1
commit 8fa1580
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Showing 2 changed files with 22 additions and 2 deletions.
diff --git a/src/library/scala/collection/StrictOptimizedSeqOps.scala b/src/library/scala/collection/StrictOptimizedSeqOps.scala
@@ -94,7 +94,7 @@ trait StrictOptimizedSeqOps [+A, +CC[_], +C]
     }
 
   override def intersect[B >: A](that: Seq[B]): C =
-    if (isEmpty || that.isEmpty) empty
+    if (isEmpty || that.isEmpty) newSpecificBuilder.result()
     else {
       val occ = occCounts(that)
       val b = newSpecificBuilder

diff --git a/test/junit/scala/collection/StrictOptimizedSeqTest.scala b/test/junit/scala/collection/StrictOptimizedSeqTest.scala
@@ -1,6 +1,6 @@
 package scala.collection
 
-import org.junit.Assert.assertEquals
+import org.junit.Assert.{assertEquals, assertTrue}
 import org.junit.Test
 import org.junit.runner.RunWith
 import org.junit.runners.JUnit4
@@ -20,4 +20,24 @@ class StrictOptimizedSeqTest {
 
     assertEquals(Vector("a", "aa", "aaa", "bbbb"), result)
   }
+
+  @Test
+  def `empty intersection has correct component type for array`(): Unit = {
+    val something = Array(3.14)
+    val nothing   = Array[Double]()
+    val empty     = Array.empty[Double]
+
+    assertEquals(classOf[Double], nothing.intersect(something).getClass.getComponentType)
+    assertTrue(nothing.intersect(something).isEmpty)
+
+    assertEquals(classOf[Double], empty.intersect(something).getClass.getComponentType)
+    assertTrue(empty.intersect(something).isEmpty)
+    assertEquals(classOf[Double], empty.intersect(nothing).getClass.getComponentType)
+    assertTrue(empty.intersect(nothing).isEmpty)
+
+    assertEquals(classOf[Double], something.intersect(nothing).getClass.getComponentType)
+    assertTrue(something.intersect(nothing).isEmpty)
+    assertEquals(classOf[Double], something.intersect(empty).getClass.getComponentType)
+    assertTrue(something.intersect(empty).isEmpty)
+  }
 }