Merge pull request #4373 from retronym/topic/indylambda-permutations-2

SI-8359 Adjust parameter order of accessor method in Delambdafy

5 files changed, 86 insertions, 3 deletions

diff --git a/src/compiler/scala/tools/nsc/transform/LambdaLift.scala b/src/compiler/scala/tools/nsc/transform/LambdaLift.scala
index 5e2fe21eec..d1be1558b9 100644
--- a/src/compiler/scala/tools/nsc/transform/LambdaLift.scala
+++ b/src/compiler/scala/tools/nsc/transform/LambdaLift.scala
@@ -376,7 +376,7 @@ abstract class LambdaLift extends InfoTransform {
 
     private def addFreeArgs(pos: Position, sym: Symbol, args: List[Tree]) = {
       free get sym match {
-        case Some(fvs) => args ++ (fvs.toList map (fv => atPos(pos)(proxyRef(fv))))
+        case Some(fvs) => addFree(sym, free = fvs.toList map (fv => atPos(pos)(proxyRef(fv))), original = args)
         case _         => args
       }
     }
@@ -388,9 +388,9 @@ abstract class LambdaLift extends InfoTransform {
           case DefDef(_, _, _, vparams :: _, _, _) =>
             val addParams = cloneSymbols(ps).map(_.setFlag(PARAM))
             sym.updateInfo(
-              lifted(MethodType(sym.info.params ::: addParams, sym.info.resultType)))
+              lifted(MethodType(addFree(sym, free = addParams, original = sym.info.params), sym.info.resultType)))
 
-            copyDefDef(tree)(vparamss = List(vparams ++ freeParams))
+            copyDefDef(tree)(vparamss = List(addFree(sym, free = freeParams, original = vparams)))
           case ClassDef(_, _, _, _) =>
             // SI-6231
             // Disabled attempt to to add getters to freeParams
@@ -571,4 +571,12 @@ abstract class LambdaLift extends InfoTransform {
     }
   } // class LambdaLifter
 
+  private def addFree[A](sym: Symbol, free: List[A], original: List[A]): List[A] = {
+    val prependFree = (
+         !sym.isConstructor // this condition is redundant for now. It will be needed if we remove the second condition in 2.12.x
+      && (settings.Ydelambdafy.value == "method" && sym.isDelambdafyTarget) // SI-8359 Makes the lambda body a viable as the target MethodHandle for a call to LambdaMetafactory
+    )
+    if (prependFree) free ::: original
+    else             original ::: free
+  }
 }
diff --git a/src/reflect/scala/reflect/internal/Symbols.scala b/src/reflect/scala/reflect/internal/Symbols.scala
index d85ec22a84..4a39712ad7 100644
--- a/src/reflect/scala/reflect/internal/Symbols.scala
+++ b/src/reflect/scala/reflect/internal/Symbols.scala
@@ -794,6 +794,7 @@ trait Symbols extends api.Symbols { self: SymbolTable =>
 
     final def isAnonymousFunction = isSynthetic && (name containsName tpnme.ANON_FUN_NAME)
     final def isDelambdafyFunction = isSynthetic && (name containsName tpnme.DELAMBDAFY_LAMBDA_CLASS_NAME)
+    final def isDelambdafyTarget  = isSynthetic && isMethod && (name containsName tpnme.ANON_FUN_NAME)
     final def isDefinedInPackage  = effectiveOwner.isPackageClass
     final def needsFlatClasses    = phase.flatClasses && rawowner != NoSymbol && !rawowner.isPackageClass
 
diff --git a/test/files/pos/t8359-closelim-crash.flags b/test/files/pos/t8359-closelim-crash.flags
new file mode 100644
index 0000000000..49d036a887
--- /dev/null
+++ b/test/files/pos/t8359-closelim-crash.flags
@@ -0,0 +1 @@
+-optimize
diff --git a/test/files/pos/t8359-closelim-crash.scala b/test/files/pos/t8359-closelim-crash.scala
new file mode 100644
index 0000000000..1413694d10
--- /dev/null
+++ b/test/files/pos/t8359-closelim-crash.scala
@@ -0,0 +1,23 @@
+package test
+
+// This is a minimization of code that crashed the compiler during bootstrapping
+// in the first iteration of https://github.com/scala/scala/pull/4373, the PR
+// that adjusted the order of free and declared params in LambdaLift.
+
+// Was:
+//  java.lang.AssertionError: assertion failed:
+//  Record Record(<$anon: Function1>,Map(value a$1 -> Deref(LocalVar(value b)))) does not contain a field value b$1
+// at scala.tools.nsc.Global.assert(Global.scala:262)
+// at scala.tools.nsc.backend.icode.analysis.CopyPropagation$copyLattice$State.getFieldNonRecordValue(CopyPropagation.scala:113)
+// at scala.tools.nsc.backend.icode.analysis.CopyPropagation$copyLattice$State.getFieldNonRecordValue(CopyPropagation.scala:122)
+// at scala.tools.nsc.backend.opt.ClosureElimination$ClosureElim$$anonfun$analyzeMethod$1$$anonfun$apply$2.replaceFieldAccess$1(ClosureElimination.scala:124)
+class Typer {
+  def bar(a: Boolean, b: Boolean): Unit = {
+    @inline
+    def baz(): Unit = {
+      ((_: Any) => (Typer.this, a, b)).apply("")
+    }
+    ((_: Any) => baz()).apply("")
+  }
+}
+
diff --git a/test/pending/run/delambdafy-lambdametafactory.scala b/test/pending/run/delambdafy-lambdametafactory.scala
new file mode 100644
index 0000000000..daea8a39fe
--- /dev/null
+++ b/test/pending/run/delambdafy-lambdametafactory.scala
@@ -0,0 +1,50 @@
+//
+// Tests that the static accessor method for lambda bodies
+// (generated under -Ydelambdafy:method) are compatible with
+// Java 8's LambdaMetafactory.
+//
+import java.lang.invoke._
+
+class C {
+  def test1: Unit = {
+    (x: String) => x.reverse
+  }
+  def test2: Unit = {
+    val capture1 = "capture1"
+    (x: String) => capture1 + " " + x.reverse
+  }
+  def test3: Unit = {
+    (x: String) => C.this + " " + x.reverse
+  }
+}
+trait T {
+  def test4: Unit = {
+    (x: String) => x.reverse
+  }
+}
+
+// A functional interface. Function1 contains abstract methods that are filled in by mixin 
+trait Function1ish[A, B] {
+  def apply(a: A): B
+}
+
+object Test {
+  def lambdaFactory[A, B](hostClass: Class[_], instantiatedParam: Class[A], instantiatedRet: Class[B], accessorName: String,
+                          capturedParams: Array[(Class[_], AnyRef)] = Array()) = {
+    val caller = MethodHandles.lookup
+    val methodType = MethodType.methodType(classOf[AnyRef], Array[Class[_]](classOf[AnyRef]))
+    val instantiatedMethodType = MethodType.methodType(instantiatedRet, Array[Class[_]](instantiatedParam))
+    val (capturedParamTypes, captured) = capturedParams.unzip
+    val targetMethodType = MethodType.methodType(instantiatedRet, capturedParamTypes :+ instantiatedParam)
+    val invokedType = MethodType.methodType(classOf[Function1ish[_, _]], capturedParamTypes)
+    val target = caller.findStatic(hostClass, accessorName, targetMethodType)
+    val site = LambdaMetafactory.metafactory(caller, "apply", invokedType, methodType, target, instantiatedMethodType)
+    site.getTarget.invokeWithArguments(captured: _*).asInstanceOf[Function1ish[A, B]]
+  }
+  def main(args: Array[String]) {
+    println(lambdaFactory(classOf[C], classOf[String], classOf[String], "accessor$1").apply("abc"))
+    println(lambdaFactory(classOf[C], classOf[String], classOf[String], "accessor$2", Array(classOf[String] -> "capture1")).apply("abc"))
+    println(lambdaFactory(classOf[C], classOf[String], classOf[String], "accessor$3", Array(classOf[C] -> new C)).apply("abc"))
+    println(lambdaFactory(Class.forName("T$class"), classOf[String], classOf[String], "accessor$4", Array(classOf[T] -> new T{})).apply("abc"))
+  }
+}