SI-10097 Error if no non-implicit case class param

Case class must have a non-implicit param list.

Error early, error often.

Also update spec to say that class implicitly gets
a non-implicit parameter section if it doesn't
have one, and that a case class must have one.

2 files changed, 11 insertions, 6 deletions

diff --git a/src/reflect/scala/reflect/internal/Printers.scala b/src/reflect/scala/reflect/internal/Printers.scala
index 9602a2859b..bb352e9d31 100644
--- a/src/reflect/scala/reflect/internal/Printers.scala
+++ b/src/reflect/scala/reflect/internal/Printers.scala
@@ -775,7 +775,7 @@ trait Printers extends api.Printers { self: SymbolTable =>
             }
             // constructor's params processing (don't print single empty constructor param list)
             vparamss match {
-              case Nil | List(Nil) if (!mods.isCase && !ctorMods.hasFlag(AccessFlags)) =>
+              case Nil | List(Nil) if !mods.isCase && !ctorMods.hasFlag(AccessFlags) =>
               case _ => vparamss foreach printConstrParams
             }
             parents
diff --git a/src/reflect/scala/reflect/internal/ReificationSupport.scala b/src/reflect/scala/reflect/internal/ReificationSupport.scala
index 026438e421..1b2be64654 100644
--- a/src/reflect/scala/reflect/internal/ReificationSupport.scala
+++ b/src/reflect/scala/reflect/internal/ReificationSupport.scala
@@ -266,7 +266,7 @@ trait ReificationSupport { self: SymbolTable =>
     }
 
     // undo gen.mkTemplate
-    protected object UnMkTemplate {
+    protected class UnMkTemplate(isCaseClass: Boolean) {
       def unapply(templ: Template): Option[(List[Tree], ValDef, Modifiers, List[List[ValDef]], List[Tree], List[Tree])] = {
         val Template(parents, selfType, _) = templ
         val tbody = treeInfo.untypecheckedTemplBody(templ)
@@ -296,8 +296,9 @@ trait ReificationSupport { self: SymbolTable =>
             result(ctorMods, Nil, edefs, body)
           else {
             // undo conversion from (implicit ... ) to ()(implicit ... ) when it's the only parameter section
+            // except that case classes require the explicit leading empty parameter list
             val vparamssRestoredImplicits = ctorVparamss match {
-              case Nil :: (tail @ ((head :: _) :: _)) if head.mods.isImplicit => tail
+              case Nil :: (tail @ ((head :: _) :: _)) if head.mods.isImplicit && !isCaseClass => tail
               case other => other
             }
             // undo flag modifications by merging flag info from constructor args and fieldDefs
@@ -314,7 +315,9 @@ trait ReificationSupport { self: SymbolTable =>
           }
         }
       }
+      def asCase = new UnMkTemplate(isCaseClass = true)
     }
+    protected object UnMkTemplate extends UnMkTemplate(isCaseClass = false)
 
     protected def mkSelfType(tree: Tree) = tree match {
       case vd: ValDef =>
@@ -346,9 +349,11 @@ trait ReificationSupport { self: SymbolTable =>
 
       def unapply(tree: Tree): Option[(Modifiers, TypeName, List[TypeDef], Modifiers, List[List[ValDef]],
                                        List[Tree], List[Tree], ValDef, List[Tree])] = tree match {
-        case ClassDef(mods, name, tparams, UnMkTemplate(parents, selfType, ctorMods, vparamss, earlyDefs, body))
-          if !ctorMods.isTrait && !ctorMods.hasFlag(JAVA) =>
-          Some((mods, name, tparams, ctorMods, vparamss, earlyDefs, parents, selfType, body))
+        case ClassDef(mods, name, tparams, impl) =>
+          val X = if (mods.isCase) UnMkTemplate.asCase else UnMkTemplate
+          val X(parents, selfType, ctorMods, vparamss, earlyDefs, body) = impl
+          if (ctorMods.isTrait || ctorMods.hasFlag(JAVA)) None
+          else Some((mods, name, tparams, ctorMods, vparamss, earlyDefs, parents, selfType, body))
         case _ =>
           None
       }