SI-9515 closure elimination also for non-Scala-Function SAM types

Also logged in as SD-162

The optimizer had conservative checks in place to perform closure
elimination only for Scala Function types. We can eliminate IndyLambda
instructions for any functional interface. LambdaMetaFactory only
constructs lambda objects for interface types, which don't have any
side-effects on construction - they don't have a constructor.

1 files changed, 20 insertions, 0 deletions

diff --git a/test/junit/scala/tools/nsc/backend/jvm/opt/MethodLevelOptsTest.scala b/test/junit/scala/tools/nsc/backend/jvm/opt/MethodLevelOptsTest.scala
index 938bc7b846..2c697bfe50 100644
--- a/test/junit/scala/tools/nsc/backend/jvm/opt/MethodLevelOptsTest.scala
+++ b/test/junit/scala/tools/nsc/backend/jvm/opt/MethodLevelOptsTest.scala
@@ -750,4 +750,24 @@ class MethodLevelOptsTest extends BytecodeTesting {
       -1, LDC, ASTORE,
       -1, ALOAD, ARETURN))
   }
+
+  @Test
+  def elimSamLambda(): Unit = {
+    val code =
+      """class C {
+        |  def t1(x: Int) = {
+        |    val fun: java.util.function.IntFunction[Int] = y => y + 1
+        |    fun(x)
+        |  }
+        |  def t2(x: Int) = {
+        |    val fun: T = i => i + 1
+        |    fun.f(x)
+        |  }
+        |}
+        |trait T { def f(x: Int): Int }
+      """.stripMargin
+    val List(c, t) = compileClasses(code)
+    assertSameSummary(getMethod(c, "t1"), List(ILOAD, "$anonfun$t1$1", IRETURN))
+    assertSameSummary(getMethod(c, "t2"), List(ILOAD, "$anonfun$t2$1", IRETURN))
+  }
 }