TypeConstraint/TypeVar refinement.

I zeroed in on the actual conditions under which the parameter bounds
can be utilized without poisoning the well. Also fixed a bug in
ClassfileParser where it would get confused and set Any as a lower
bound, as well as a bug or at least misbehavior where a TypeBounds with
only Any/Nothing as an upper/lower bound would be treated differently
than one with no bound at all.

Review by @moors.

1 files changed, 6 insertions, 1 deletions

diff --git a/src/compiler/scala/tools/nsc/symtab/classfile/ClassfileParser.scala b/src/compiler/scala/tools/nsc/symtab/classfile/ClassfileParser.scala
index ac72b4d22c..de11f3aa28 100644
--- a/src/compiler/scala/tools/nsc/symtab/classfile/ClassfileParser.scala
+++ b/src/compiler/scala/tools/nsc/symtab/classfile/ClassfileParser.scala
@@ -717,7 +717,12 @@ abstract class ClassfileParser {
                       index += 1
                       val bounds = variance match {
                         case '+' => TypeBounds.upper(objToAny(sig2type(tparams, skiptvs)))
-                        case '-' => TypeBounds.lower(sig2type(tparams, skiptvs))
+                        case '-' => 
+                          val tp = sig2type(tparams, skiptvs)
+                          // sig2type seems to return AnyClass regardless of the situation:
+                          // we don't want Any as a LOWER bound.
+                          if (tp.typeSymbol == definitions.AnyClass) TypeBounds.empty
+                          else TypeBounds.lower(tp)
                         case '*' => TypeBounds.empty
                       }
                       val newtparam = sym.newExistential(sym.pos, newTypeName("?"+i)) setInfo bounds