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package scala.tools.nsc.backend.jvm
import org.junit.Assert._
import org.junit.Test
import scala.collection.JavaConverters._
import scala.tools.asm.Handle
import scala.tools.asm.tree.InvokeDynamicInsnNode
import scala.tools.testing.BytecodeTesting
class IndyLambdaTest extends BytecodeTesting {
import compiler._
@Test def boxingBridgeMethodUsedSelectively(): Unit = {
def implMethodDescriptorFor(code: String): String = {
val method = compileAsmMethods(s"""def f = $code """).find(_.name == "f").get
val x = method.instructions.iterator.asScala.toList
x.flatMap {
case insn : InvokeDynamicInsnNode => insn.bsmArgs.collect { case h : Handle => h.getDesc }
case _ => Nil
}.head
}
val obj = "Ljava/lang/Object;"
val str = "Ljava/lang/String;"
// unspecialized functions that have a primitive in parameter or return position
// give rise to a "boxing bridge" method (which has the suffix `$adapted`).
// This is because Scala's unboxing of null values gives zero, whereas Java's throw a NPE.
// 1. Here we show that we are calling the boxing bridge (the lambda bodies here are compiled into
// methods of `(I)Ljava/lang/Object;` / `(I)Ljava/lang/Object;` respectively.)
assertEquals(s"($obj)$obj", implMethodDescriptorFor("(x: Int) => new Object"))
assertEquals(s"($obj)$obj", implMethodDescriptorFor("(x: Object) => 0"))
// 2a. We don't need such adaptations for parameters or return values with types that differ
// from Object due to other generic substitution, LambdaMetafactory will downcast the arguments.
assertEquals(s"($str)$str", implMethodDescriptorFor("(x: String) => x"))
// 2b. Testing 2a. in combination with 1.
assertEquals(s"($obj)$str", implMethodDescriptorFor("(x: Int) => \"\""))
assertEquals(s"($str)$obj", implMethodDescriptorFor("(x: String) => 0"))
// 3. Specialized functions, don't need any of this as they implement a method like `apply$mcII$sp`,
// and the (un)boxing is handled in the base class in code emitted by scalac.
assertEquals("(I)I", implMethodDescriptorFor("(x: Int) => x"))
// non-builtin sams are like specialized functions
compileToBytes("class VC(private val i: Int) extends AnyVal; trait FunVC { def apply(a: VC): VC }")
assertEquals("(I)I", implMethodDescriptorFor("((x: VC) => x): FunVC"))
compileToBytes("trait Fun1[T, U] { def apply(a: T): U }")
assertEquals(s"($obj)$str", implMethodDescriptorFor("(x => x.toString): Fun1[Int, String]"))
assertEquals(s"($obj)$obj", implMethodDescriptorFor("(x => println(x)): Fun1[Int, Unit]"))
assertEquals(s"($obj)$str", implMethodDescriptorFor("((x: VC) => \"\") : Fun1[VC, String]"))
assertEquals(s"($str)$obj", implMethodDescriptorFor("((x: String) => new VC(0)) : Fun1[String, VC]"))
compileToBytes("trait Coll[A, Repr] extends Any")
compileToBytes("final class ofInt(val repr: Array[Int]) extends AnyVal with Coll[Int, Array[Int]]")
assertEquals(s"([I)$obj", implMethodDescriptorFor("((xs: Array[Int]) => new ofInt(xs)): Array[Int] => Coll[Int, Array[Int]]"))
}
}
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