Fix to checkBounds

Need to account for the fact that some argument types may be TypeBoudns themselves.
The change makes Jason's latest example work.

1 files changed, 6 insertions, 2 deletions

diff --git a/src/dotty/tools/dotc/transform/FirstTransform.scala b/src/dotty/tools/dotc/transform/FirstTransform.scala
index 0dac38a78..a58e8a643 100644
--- a/src/dotty/tools/dotc/transform/FirstTransform.scala
+++ b/src/dotty/tools/dotc/transform/FirstTransform.scala
@@ -141,8 +141,12 @@ class FirstTransform extends MiniPhaseTransform with IdentityDenotTransformer wi
       val tparams = tycon.tpe.typeSymbol.typeParams
       val bounds = tparams.map(tparam =>
         tparam.info.asSeenFrom(tycon.tpe.normalizedPrefix, tparam.owner.owner).bounds)
-      Checking.checkBounds(
-        args, bounds, (tp, argTypes) => tp.substDealias(tparams, argTypes))
+      def instantiateUpperBound(tp: Type, argTypes: List[Type]): Type = {
+        tp.substDealias(tparams, argTypes).bounds.hi
+          // not that argTypes can contain a TypeBounds type for arguments that are
+          // not fully determined. In that case we need to check against the hi bound.
+      }
+      Checking.checkBounds(args, bounds, instantiateUpperBound)
       normalizeType(tree)
     case tree =>
       normalizeType(tree)