LambdaLift emits paramaccessor syms and defdefs

... instead of emitting ValDefs and field symbols, which are then
promptly unlinked and transformed by the "late trait methods"
logic in mixins...

Mixins still synthesizes implementations for these accessors
in subclasses.

A paramaccessor in a trait is a method without an underlying field.

1 files changed, 14 insertions, 6 deletions

diff --git a/src/compiler/scala/tools/nsc/transform/Constructors.scala b/src/compiler/scala/tools/nsc/transform/Constructors.scala
index ec8dc68834..0a87e358b4 100644
--- a/src/compiler/scala/tools/nsc/transform/Constructors.scala
+++ b/src/compiler/scala/tools/nsc/transform/Constructors.scala
@@ -506,7 +506,8 @@ abstract class Constructors extends Statics with Transform with TypingTransforme
       )
 
       /*
-       * whether `sym` denotes a param-accessor (ie a field) that fulfills all of:
+       * whether `sym` denotes a param-accessor (ie in a class a PARAMACCESSOR field, or in a trait a method with same flag)
+       * that fulfills all of:
        *   (a) has stationary value, ie the same value provided via the corresponding ctor-arg; and
        *   (b) isn't subject to specialization. We might be processing statements for:
        *         (b.1) the constructor in the generic   (super-)class; or
@@ -519,10 +520,11 @@ abstract class Constructors extends Statics with Transform with TypingTransforme
         case Apply(Select(This(_), _), List()) =>
           // references to parameter accessor methods of own class become references to parameters
           // outer accessors become references to $outer parameter
-          if (clazz.isTrait)
+          // println(s"to param ref in $clazz for ${tree.symbol} ${tree.symbol.debugFlagString} / ${tree.symbol.outerSource} / ${canBeSupplanted(tree.symbol)}")
+          if (clazz.isTrait && !(tree.symbol hasAllFlags (ACCESSOR | PARAMACCESSOR)))
             super.transform(tree)
           else if (canBeSupplanted(tree.symbol))
-            gen.mkAttributedIdent(parameter(tree.symbol.accessed)) setPos tree.pos
+            gen.mkAttributedIdent(parameter(tree.symbol)) setPos tree.pos
           else if (tree.symbol.outerSource == clazz)
             gen.mkAttributedIdent(parameterNamed(nme.OUTER)) setPos tree.pos
           else
@@ -700,7 +702,9 @@ abstract class Constructors extends Statics with Transform with TypingTransforme
       def omittableStat(stat: Tree) = omittableSym(stat.symbol)
 
       // The parameter accessor fields which are members of the class
-      val paramAccessors = clazz.constrParamAccessors
+      val paramAccessors =
+        if (clazz.isTrait) clazz.info.decls.toList.filter(sym => sym.hasAllFlags(STABLE | PARAMACCESSOR)) // since a trait does not have constructor parameters (yet), these can only come from lambdalift -- right?
+        else clazz.constrParamAccessors
 
       // Initialize all parameters fields that must be kept.
       val paramInits = paramAccessors filterNot omittableSym map { acc =>
@@ -708,11 +712,15 @@ abstract class Constructors extends Statics with Transform with TypingTransforme
         // It would be better to mangle the constructor parameter name since
         // it can only be used internally, but I think we need more robust name
         // mangling before we introduce more of it.
-        val conflict = clazz.info.nonPrivateMember(acc.name) filter (s => s.isGetter && !s.isOuterField && s.enclClass.isTrait)
+        val conflict = clazz.info.nonPrivateMember(acc.name) filter (s => (s ne acc) && s.isGetter && !s.isOuterField && s.enclClass.isTrait)
         if (conflict ne NoSymbol)
           reporter.error(acc.pos, "parameter '%s' requires field but conflicts with %s".format(acc.name, conflict.fullLocationString))
 
-        copyParam(acc, parameter(acc))
+        val accSetter =
+          if (clazz.isTrait) acc.setterIn(clazz, hasExpandedName = true)
+          else acc
+
+        copyParam(accSetter, parameter(acc))
       }
 
       // Return a pair consisting of (all statements up to and including superclass and trait constr calls, rest)