chyanged implicits so that implicit Builder pat...

chyanged implicits so that implicit Builder pattern works.

4 files changed, 20 insertions, 10 deletions

diff --git a/src/compiler/scala/tools/nsc/typechecker/Implicits.scala b/src/compiler/scala/tools/nsc/typechecker/Implicits.scala
index 6d91179c3d..0efdc6fbe2 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Implicits.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Implicits.scala
@@ -52,6 +52,16 @@ self: Analyzer =>
     search.result
   }
 
+  /** If type `pt` an instance of Manifest or OptManifest, or an abstract type lower-bounded
+   *  by such an instance?
+   */
+  def isManifest(pt: Type): Boolean = pt match {
+    case TypeRef(_, ManifestClass, List(_)) |
+         TypeRef(_, OptManifestClass, List(_)) => true
+    case TypeRef(_, tsym, _) => tsym.isAbstractType && isManifest(pt.bounds.lo)
+    case _ => false
+  }
+
   /** The result of an implicit search
    *  @param  tree    The tree representing the implicit
    *  @param  subst   A substituter that represents the undetermined type parameters
@@ -234,7 +244,7 @@ self: Analyzer =>
     private def typedImplicit(info: ImplicitInfo): SearchResult =
        context.openImplicits find (dominates(pt, _)) match {
          case Some(pending) =>
-           println("Pending implicit "+pending+" dominates "+pt)
+           //println("Pending implicit "+pending+" dominates "+pt+"/"+undetParams)
            throw DivergentImplicit
            SearchFailure
          case None =>
@@ -273,9 +283,7 @@ self: Analyzer =>
       def approximate(tp: Type) =
         tp.instantiateTypeParams(undetParams, undetParams map (_ => WildcardType))
 
-      /** Instantiated `pt' so that covariant occurrences of undetermined
-       *  type parameters are replaced by Any, and all other occurrences
-       *  are replaced by Nothing
+      /** Instantiated `pt' so that undetermined type parameters are replaced by wildcards
        */
       val wildPt = approximate(pt)
 
diff --git a/src/compiler/scala/tools/nsc/typechecker/Infer.scala b/src/compiler/scala/tools/nsc/typechecker/Infer.scala
index db43125ccc..1a07103e24 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Infer.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Infer.scala
@@ -524,7 +524,7 @@ trait Infer {
      */
     def adjustTypeArgs(tparams: List[Symbol], targs: List[Type], restpe: Type, uninstantiated: ListBuffer[Symbol]): List[Type] =
       List.map2(tparams, targs) {(tparam, targ) =>
-        if (targ.typeSymbol == NothingClass && (varianceInType(restpe)(tparam) & COVARIANT) == 0) {
+        if (targ.typeSymbol == NothingClass && (restpe == WildcardType || (varianceInType(restpe)(tparam) & COVARIANT) == 0)) {
           uninstantiated += tparam
           tparam.tpe
         } else if (targ.typeSymbol == RepeatedParamClass) {
@@ -943,12 +943,12 @@ trait Infer {
       val targs = exprTypeArgs(tparams, tree.tpe, pt)
       val uninstantiated = new ListBuffer[Symbol]
       val detargs = if (keepNothings) targs
-                    else adjustTypeArgs(tparams, targs, pt, uninstantiated)
+                    else adjustTypeArgs(tparams, targs, WildcardType, uninstantiated)
       val undetparams = uninstantiated.toList
       val detparams = tparams remove (undetparams contains _)
       substExpr(tree, detparams, detargs, pt)
       if (inferInfo)
-        println("inferred expr instance "+tree)
+        println("inferred expr instance "+tree+", detargs = "+detargs+", undetparams = "+undetparams)
       undetparams
     }
 
diff --git a/src/compiler/scala/tools/nsc/typechecker/Typers.scala b/src/compiler/scala/tools/nsc/typechecker/Typers.scala
index 955bd9ee4c..55ad496c94 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Typers.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Typers.scala
@@ -747,7 +747,11 @@ trait Typers { self: Analyzer =>
       case mt: ImplicitMethodType if ((mode & (EXPRmode | FUNmode | LHSmode)) == EXPRmode) => // (4.1)
         if (!context.undetparams.isEmpty && (mode & POLYmode) == 0) { // (9)
           context.undetparams = inferExprInstance(
-            tree, context.extractUndetparams(), pt, false)
+            tree, context.extractUndetparams(), pt, mt.paramTypes exists isManifest)
+              // if we are looking for a manifest, instantiate type to Nothing anyway,
+              // as we would get amnbiguity errors otherwise. Example
+              // Looking for a manifest of Nil: This mas many potential types,
+              // so we need to instantiate to minimal type List[Nothing].
         }
         val typer1 = constrTyperIf(treeInfo.isSelfOrSuperConstrCall(tree))
         typer1.typed(typer1.applyImplicitArgs(tree), mode, pt)
diff --git a/src/compiler/scala/tools/nsc/typechecker/Variances.scala b/src/compiler/scala/tools/nsc/typechecker/Variances.scala
index cc68373f40..a02b4b04a1 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Variances.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Variances.scala
@@ -74,8 +74,6 @@ trait Variances {
     varianceInType(attrib.atp)(tparam)
   }
 
-
-
   /** Compute variance of type parameter <code>tparam</code> in type <code>tp</code>. */
   def varianceInType(tp: Type)(tparam: Symbol): Int = tp match {
     case ErrorType | WildcardType | NoType | NoPrefix | ThisType(_) | ConstantType(_) =>