Add a "no-boxing" test for specialised tuples

Author: dwijnand

compiler/src/dotty/tools/dotc/transform/SpecializeTuples.scala

@@ -32,10 +32,10 @@ class SpecializeTuples extends MiniPhase:
   end transformApply
 
   override def transformSelect(tree: Select)(using Context): Tree = tree match
-    case Select(qual, nme._1) if isAppliedSpecializableTuple(qual.tpe.widen)
-    => Select(qual, nme._1.specializedName(qual.tpe.widen.argInfos.slice(0, 1)))
-    case Select(qual, nme._2) if isAppliedSpecializableTuple(qual.tpe.widen)
-    => Select(qual, nme._2.specializedName(qual.tpe.widen.argInfos.slice(1, 2)))
+    case Select(qual, nme._1) if isAppliedSpecializableTuple(qual.tpe.widen) =>
+      Select(qual, nme._1.specializedName(qual.tpe.widen.argInfos.slice(0, 1)))
+    case Select(qual, nme._2) if isAppliedSpecializableTuple(qual.tpe.widen) =>
+      Select(qual, nme._2.specializedName(qual.tpe.widen.argInfos.slice(1, 2)))
     case _ => tree
 
   private def isAppliedSpecializableTuple(tp: Type)(using Context) = tp match

compiler/test/dotty/tools/dotc/transform/SpecializeTuplesTests.scala

@@ -0,0 +1,55 @@
+package dotty.tools
+package dotc
+package transform
+
+import org.junit.Test
+
+import dotty.tools.backend.jvm.DottyBytecodeTest
+
+import scala.jdk.CollectionConverters.*
+
+class SpecializeTuplesTests extends DottyBytecodeTest {
+  @Test def noBoxing = {
+    given source: String =
+      """|class Test {
+         |  def foo: (Int, Int) = (1, 1)
+         |  def bar: Int = foo._1
+         |}""".stripMargin
+
+    checkBCode(source) { dir =>
+      assertNoBoxing("foo", findClass("Test", dir).methods)
+      assertNoBoxing("bar", findClass("Test", dir).methods)
+    }
+  }
+
+  @Test def boxing = {
+    // Pick a tuple type that isn't specialised.
+    given source: String =
+      """|class Test {
+         |  def t: (Boolean, Byte, Short, Char, Int, Long, Float, Double, AnyRef) = (true, 8, 16, 'c', 32, 64L, 32.0f, 64.0, this)
+         |  def _1 = t._1
+         |  def _2 = t._2
+         |  def _3 = t._3
+         |  def _4 = t._4
+         |  def _5 = t._5
+         |  def _6 = t._6
+         |  def _7 = t._7
+         |  def _8 = t._8
+         |  def _9 = t._9
+         |}""".stripMargin
+
+    checkBCode(source) { dir =>
+      val methods = findClass("Test", dir).methods
+      assertBoxing("t", methods)
+      assertBoxing("_1", methods)
+      assertBoxing("_2", methods)
+      assertBoxing("_3", methods)
+      assertBoxing("_4", methods)
+      assertBoxing("_5", methods)
+      assertBoxing("_6", methods)
+      assertBoxing("_7", methods)
+      assertBoxing("_8", methods)
+      assertNoBoxing("_9", methods)
+    }
+  }
+}