Fix #1444: Add implicit arguments to supertraits

If a super trait is given as a type (i.e. no argument list), implicit args were
not passed. This is fixed now. Also, we now check for parameterized traits lacking
type arguments in Typer instead of in Mixin.

Fixes #1444.

1 files changed, 36 insertions, 1 deletions

diff --git a/src/dotty/tools/dotc/typer/Typer.scala b/src/dotty/tools/dotc/typer/Typer.scala
index 2b690ef51..81e6e9430 100644
--- a/src/dotty/tools/dotc/typer/Typer.scala
+++ b/src/dotty/tools/dotc/typer/Typer.scala
@@ -1132,8 +1132,43 @@ class Typer extends Namer with TypeAssigner with Applications with Implicits wit
   def typedClassDef(cdef: untpd.TypeDef, cls: ClassSymbol)(implicit ctx: Context) = track("typedClassDef") {
     val TypeDef(name, impl @ Template(constr, parents, self, _)) = cdef
     val superCtx = ctx.superCallContext
+
+    /** If `ref` is an implicitly parameterized trait, pass an implicit argument list.
+     *  Otherwise, if `ref` is a parameterized trait, error.
+     *  Note: Traits and classes currently always have at least an empty parameter list ()
+     *        before the implicit parameters (this is inserted if not given in source).
+     *        We skip this parameter list when deciding whether a trait is parameterless or not.
+     *  @param ref   The tree referring to the (parent) trait
+     *  @param psym  Its type symbol
+     *  @param cinfo The info of its constructor
+     */
+    def maybeCall(ref: Tree, psym: Symbol, cinfo: Type): Tree = cinfo match {
+      case cinfo: PolyType =>
+        maybeCall(ref, psym, cinfo.resultType)
+      case cinfo @ MethodType(Nil, _) if cinfo.resultType.isInstanceOf[ImplicitMethodType] =>
+        val icall = New(ref).select(nme.CONSTRUCTOR).appliedToNone
+        typedExpr(untpd.TypedSplice(icall))(superCtx)
+      case cinfo @ MethodType(Nil, _) if !cinfo.resultType.isInstanceOf[MethodType] =>
+        ref
+      case cinfo: MethodType =>
+        if (!ctx.erasedTypes) { // after constructors arguments are passed in super call.
+          typr.println(i"constr type: $cinfo")
+          ctx.error(em"parameterized $psym lacks argument list", ref.pos)
+        }
+        ref
+      case _ =>
+        ref
+    }
+
     def typedParent(tree: untpd.Tree): Tree =
-      if (tree.isType) typedType(tree)(superCtx)
+      if (tree.isType) {
+        val result = typedType(tree)(superCtx)
+        val psym = result.tpe.typeSymbol
+        if (psym.is(Trait) && !cls.is(Trait) && !cls.superClass.isSubClass(psym))
+          maybeCall(result, psym, psym.primaryConstructor.info)
+        else
+          result
+      }
       else {
         val result = typedExpr(tree)(superCtx)
         checkParentCall(result, cls)