Fix problem related to cbn parameters in supercalls

The closures generated by elimByName did not get the InSuperCall
flag set. This caused problems in lambda lift which led to a
verify error for the new version CollectionStrawMan6. That version
replaces explicit function parameters in class LazyList by
by-name parameters.

Also: Clarify logic for liftLocals in LambdaLift (liftLocals caused the immediate
problem but was in the end not to blame).

4 files changed, 21 insertions, 18 deletions

diff --git a/src/dotty/tools/dotc/transform/ElimByName.scala b/src/dotty/tools/dotc/transform/ElimByName.scala
index b65a46249..192227261 100644
--- a/src/dotty/tools/dotc/transform/ElimByName.scala
+++ b/src/dotty/tools/dotc/transform/ElimByName.scala
@@ -77,8 +77,9 @@ class ElimByName extends MiniPhaseTransform with InfoTransformer { thisTransform
           if qual.tpe.derivesFrom(defn.FunctionClass(0)) && isPureExpr(qual) =>
             qual
           case _ =>
+            val inSuper = if (ctx.mode.is(Mode.InSuperCall)) InSuperCall else EmptyFlags
             val meth = ctx.newSymbol(
-                ctx.owner, nme.ANON_FUN, Synthetic | Method, MethodType(Nil, Nil, argType))
+                ctx.owner, nme.ANON_FUN, Synthetic | Method | inSuper, MethodType(Nil, Nil, argType))
             Closure(meth, _ => arg.changeOwner(ctx.owner, meth))
         }
         ref(defn.dummyApply).appliedToType(argType).appliedTo(argFun)
diff --git a/src/dotty/tools/dotc/transform/LambdaLift.scala b/src/dotty/tools/dotc/transform/LambdaLift.scala
index 5fbe0343f..18b030913 100644
--- a/src/dotty/tools/dotc/transform/LambdaLift.scala
+++ b/src/dotty/tools/dotc/transform/LambdaLift.scala
@@ -364,13 +364,15 @@ class LambdaLift extends MiniPhase with IdentityDenotTransformer { thisTransform
           if (lOwner is Package)  {
             val encClass = local.enclosingClass
             val topClass = local.topLevelClass
-              // member of a static object
-            if (encClass.isStatic && encClass.isProperlyContainedIn(topClass)) {
-               // though the second condition seems weird, it's not true for symbols which are defined in some
-               // weird combinations of super calls.
-              (encClass, EmptyFlags)
-            } else if (encClass.is(ModuleClass, butNot = Package) && encClass.isStatic) // needed to not cause deadlocks in classloader. see t5375.scala
-              (encClass, EmptyFlags)
+            val preferEncClass =
+              encClass.isStatic &&
+                // non-static classes can capture owners, so should be avoided
+              (encClass.isProperlyContainedIn(topClass) ||
+                // can be false for symbols which are defined in some weird combination of supercalls.
+               encClass.is(ModuleClass, butNot = Package)
+                // needed to not cause deadlocks in classloader. see t5375.scala
+              )
+            if (preferEncClass) (encClass, EmptyFlags)
             else (topClass, JavaStatic)
           }
           else (lOwner, EmptyFlags)
diff --git a/src/strawman/collections/CollectionStrawMan6.scala b/src/strawman/collections/CollectionStrawMan6.scala
index f4d5e006b..5889782d6 100644
--- a/src/strawman/collections/CollectionStrawMan6.scala
+++ b/src/strawman/collections/CollectionStrawMan6.scala
@@ -562,14 +562,14 @@ object CollectionStrawMan6 extends LowPriority {
     override def className = "ArrayBufferView"
   }
 
-  class LazyList[+A](expr: () => LazyList.Evaluated[A])
+  class LazyList[+A](expr: => LazyList.Evaluated[A])
   extends LinearSeq[A] with SeqLike[A, LazyList] { self =>
     private[this] var evaluated = false
     private[this] var result: LazyList.Evaluated[A] = _
 
     def force: LazyList.Evaluated[A] = {
       if (!evaluated) {
-        result = expr()
+        result = expr
         evaluated = true
       }
       result
@@ -579,7 +579,7 @@ object CollectionStrawMan6 extends LowPriority {
     override def head = force.get._1
     override def tail = force.get._2
 
-    def #:: [B >: A](elem: => B): LazyList[B] = new LazyList(() => Some((elem, self)))
+    def #:: [B >: A](elem: => B): LazyList[B] = new LazyList(Some((elem, self)))
 
     def fromIterable[B](c: Iterable[B]): LazyList[B] = LazyList.fromIterable(c)
 
@@ -600,10 +600,10 @@ object CollectionStrawMan6 extends LowPriority {
 
     def fromIterable[B](coll: Iterable[B]): LazyList[B] = coll match {
       case coll: LazyList[B] => coll
-      case _ => new LazyList(() => if (coll.isEmpty) None else Some((coll.head, fromIterable(coll.tail))))
+      case _ => new LazyList(if (coll.isEmpty) None else Some((coll.head, fromIterable(coll.tail))))
     }
 
-    object Empty extends LazyList[Nothing](() => None)
+    object Empty extends LazyList[Nothing](None)
 
     object #:: {
       def unapply[A](s: LazyList[A]): Evaluated[A] = s.force
diff --git a/tests/run/colltest6/CollectionStrawMan6_1.scala b/tests/run/colltest6/CollectionStrawMan6_1.scala
index f4d5e006b..5889782d6 100644
--- a/tests/run/colltest6/CollectionStrawMan6_1.scala
+++ b/tests/run/colltest6/CollectionStrawMan6_1.scala
@@ -562,14 +562,14 @@ object CollectionStrawMan6 extends LowPriority {
     override def className = "ArrayBufferView"
   }
 
-  class LazyList[+A](expr: () => LazyList.Evaluated[A])
+  class LazyList[+A](expr: => LazyList.Evaluated[A])
   extends LinearSeq[A] with SeqLike[A, LazyList] { self =>
     private[this] var evaluated = false
     private[this] var result: LazyList.Evaluated[A] = _
 
     def force: LazyList.Evaluated[A] = {
       if (!evaluated) {
-        result = expr()
+        result = expr
         evaluated = true
       }
       result
@@ -579,7 +579,7 @@ object CollectionStrawMan6 extends LowPriority {
     override def head = force.get._1
     override def tail = force.get._2
 
-    def #:: [B >: A](elem: => B): LazyList[B] = new LazyList(() => Some((elem, self)))
+    def #:: [B >: A](elem: => B): LazyList[B] = new LazyList(Some((elem, self)))
 
     def fromIterable[B](c: Iterable[B]): LazyList[B] = LazyList.fromIterable(c)
 
@@ -600,10 +600,10 @@ object CollectionStrawMan6 extends LowPriority {
 
     def fromIterable[B](coll: Iterable[B]): LazyList[B] = coll match {
       case coll: LazyList[B] => coll
-      case _ => new LazyList(() => if (coll.isEmpty) None else Some((coll.head, fromIterable(coll.tail))))
+      case _ => new LazyList(if (coll.isEmpty) None else Some((coll.head, fromIterable(coll.tail))))
     }
 
-    object Empty extends LazyList[Nothing](() => None)
+    object Empty extends LazyList[Nothing](None)
 
     object #:: {
       def unapply[A](s: LazyList[A]): Evaluated[A] = s.force