Drop AllowDependendFunctions mode bit

Tests indicate it's not needed anymore.

Also: fix neg test error position.

Author: odersky

compiler/src/dotty/tools/dotc/core/Mode.scala

@@ -48,12 +48,6 @@ object Mode {
   /** Allow GADTFlexType labelled types to have their bounds adjusted */
   val GADTflexible = newMode(8, "GADTflexible")
 
-  /** Allow dependent functions. This is currently necessary for unpickling, because
-   *  some dependent functions are passed through from the front end(s?), even though they
-   *  are technically speaking illegal.
-   */
-  val AllowDependentFunctions = newMode(9, "AllowDependentFunctions")
-
   /** We are currently printing something: avoid to produce more logs about
    *  the printing
    */

compiler/src/dotty/tools/dotc/core/Types.scala

@@ -1312,12 +1312,12 @@ object Types {
 // ----- misc -----------------------------------------------------------
 
     /** Turn type into a function type.
-     *  @pre this is a non-dependent method type.
+     *  @pre this is a method type without parameter dependencies.
      *  @param dropLast  The number of trailing parameters that should be dropped
      *                   when forming the function type.
      */
     def toFunctionType(dropLast: Int = 0)(implicit ctx: Context): Type = this match {
-      case mt: MethodType if !mt.isDependent || ctx.mode.is(Mode.AllowDependentFunctions) =>
+      case mt: MethodType if !mt.isDependent =>
         val formals1 = if (dropLast == 0) mt.paramInfos else mt.paramInfos dropRight dropLast
         defn.FunctionOf(
           formals1 mapConserve (_.underlyingIfRepeated(mt.isJavaMethod)), mt.resultType, mt.isImplicitMethod && !ctx.erasedTypes)

compiler/src/dotty/tools/dotc/core/tasty/TreeUnpickler.scala

@@ -74,7 +74,7 @@ class TreeUnpickler(reader: TastyReader, nameAtRef: NameRef => TermName, posUnpi
   /** The unpickled trees */
   def unpickle()(implicit ctx: Context): List[Tree] = {
     assert(roots != null, "unpickle without previous enterTopLevel")
-    new TreeReader(reader).readTopLevel()(ctx.addMode(Mode.AllowDependentFunctions))
+    new TreeReader(reader).readTopLevel()
   }
 
   class Completer(owner: Symbol, reader: TastyReader) extends LazyType {
@@ -1095,7 +1095,7 @@ class TreeUnpickler(reader: TastyReader, nameAtRef: NameRef => TermName, posUnpi
   class LazyReader[T <: AnyRef](reader: TreeReader, op: TreeReader => Context => T) extends Trees.Lazy[T] {
     def complete(implicit ctx: Context): T = {
       pickling.println(i"starting to read at ${reader.reader.currentAddr}")
-      op(reader)(ctx.addMode(Mode.AllowDependentFunctions).withPhaseNoLater(ctx.picklerPhase))
+      op(reader)(ctx.withPhaseNoLater(ctx.picklerPhase))
     }
   }
 

tests/neg/depfuns.scala

@@ -1,5 +1,5 @@
 object Test {
 
-  type T = (x: Int) // error: `=>' expected
+  type T = (x: Int)
 
-}
+}  // error: `=>' expected