From 6d2a838bb861c51ad7a82a0f6561d9dd063686fc Mon Sep 17 00:00:00 2001
From: Jason Zaugg <jzaugg@gmail.com>
Date: Thu, 5 May 2016 12:47:28 +1000
Subject: [PATCH] Add impl restriction related to invokespecial to Java parents

---
 .../nsc/backend/jvm/BCodeBodyBuilder.scala    |  9 ++++++--
 test/files/neg/trait-defaults-super.check     |  4 ++++
 test/files/neg/trait-defaults-super.scala     | 21 +++++++++++++++++++
 test/files/pos/trait-defaults-super.scala     | 21 +++++++++++++++++++
 4 files changed, 53 insertions(+), 2 deletions(-)
 create mode 100644 test/files/neg/trait-defaults-super.check
 create mode 100644 test/files/neg/trait-defaults-super.scala
 create mode 100644 test/files/pos/trait-defaults-super.scala

diff --git a/src/compiler/scala/tools/nsc/backend/jvm/BCodeBodyBuilder.scala b/src/compiler/scala/tools/nsc/backend/jvm/BCodeBodyBuilder.scala
index 92aa75ef68f1..6cf23b063799 100644
--- a/src/compiler/scala/tools/nsc/backend/jvm/BCodeBodyBuilder.scala
+++ b/src/compiler/scala/tools/nsc/backend/jvm/BCodeBodyBuilder.scala
@@ -1077,10 +1077,15 @@ abstract class BCodeBodyBuilder extends BCodeSkelBuilder {
           if (needsInterfaceCall(receiverClass)) bc.invokeinterface(receiverName, jname, mdescr, pos)
           else                               bc.invokevirtual  (receiverName, jname, mdescr, pos)
         case Super   =>
-          if (receiverClass.isTraitOrInterface) {
+          if (receiverClass.isTrait && method.owner.isTrait && !method.owner.isJavaDefined) {
             val staticDesc = MethodBType(typeToBType(method.owner.info) :: method.info.paramTypes.map(typeToBType), typeToBType(method.info.resultType)).descriptor
             bc.invokestatic(receiverName, jname, staticDesc, pos)
-          } else bc.invokespecial  (receiverName, jname, mdescr, pos)
+          } else {
+            if (receiverClass.isTraitOrInterface && !cnode.interfaces.contains(receiverName))
+              reporter.error(pos, s"Implementation restriction: unable to emit a super call to ${receiverName}.${method.name} from ${cnode.name}. Add $receiverName as a direct parent of ${cnode.name}")
+            else
+              bc.invokespecial  (receiverName, jname, mdescr, pos)
+          }
       }
 
       bmType.returnType
diff --git a/test/files/neg/trait-defaults-super.check b/test/files/neg/trait-defaults-super.check
new file mode 100644
index 000000000000..9868049bc542
--- /dev/null
+++ b/test/files/neg/trait-defaults-super.check
@@ -0,0 +1,4 @@
+trait-defaults-super.scala:14: error: Implementation restriction: unable to emit a super call to java/lang/Iterable.spliterator from C. Add java/lang/Iterable as a direct parent of C
+class C extends T
+      ^
+one error found
diff --git a/test/files/neg/trait-defaults-super.scala b/test/files/neg/trait-defaults-super.scala
new file mode 100644
index 000000000000..def271e8e747
--- /dev/null
+++ b/test/files/neg/trait-defaults-super.scala
@@ -0,0 +1,21 @@
+trait T extends java.lang.Iterable[String] {
+
+  override def spliterator(): java.util.Spliterator[String] = {
+    super[Iterable].spliterator
+    super.spliterator
+    null
+  }
+  def foo = {
+    super[Iterable].spliterator
+    super.spliterator
+  }
+  def iterator(): java.util.Iterator[String] = java.util.Collections.emptyList().iterator()
+}
+class C extends T
+object Test {
+  def main(args: Array[String]): Unit = {
+    val t: T = new C
+    t.spliterator
+    t.foo
+  }
+}
diff --git a/test/files/pos/trait-defaults-super.scala b/test/files/pos/trait-defaults-super.scala
new file mode 100644
index 000000000000..8f867ab5632d
--- /dev/null
+++ b/test/files/pos/trait-defaults-super.scala
@@ -0,0 +1,21 @@
+trait T extends java.lang.Iterable[String] {
+
+  override def spliterator(): java.util.Spliterator[String] = {
+    super[Iterable].spliterator
+    super.spliterator
+    null
+  }
+  def foo = {
+    super[Iterable].spliterator
+    super.spliterator
+  }
+  def iterator(): java.util.Iterator[String] = java.util.Collections.emptyList().iterator()
+}
+class C extends T with java.lang.Iterable[String] // super accessor is okay with Iterable as a direct parent
+object Test {
+  def main(args: Array[String]): Unit = {
+    val t: T = new C
+    t.spliterator
+    t.foo
+  }
+}