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.

2 files changed, 8 insertions, 4 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)
diff --git a/src/dotty/tools/dotc/typer/Checking.scala b/src/dotty/tools/dotc/typer/Checking.scala
index 982b97f7e..fdc70e207 100644
--- a/src/dotty/tools/dotc/typer/Checking.scala
+++ b/src/dotty/tools/dotc/typer/Checking.scala
@@ -33,9 +33,9 @@ object Checking {
   /** A general checkBounds method that can be used for TypeApply nodes as
    *  well as for AppliedTypeTree nodes.
    */
-  def checkBounds(args: List[tpd.Tree], bounds: List[TypeBounds], instantiate: (Type, List[Type]) => Type)(implicit ctx: Context) = {
+  def checkBounds(args: List[tpd.Tree], boundss: List[TypeBounds], instantiate: (Type, List[Type]) => Type)(implicit ctx: Context) = {
     val argTypes = args.tpes
-    for ((arg, bounds) <- args zip bounds) {
+    for ((arg, bounds) <- args zip boundss) {
       def notConforms(which: String, bound: Type) = {
         ctx.error(
           d"Type argument ${arg.tpe} does not conform to $which bound $bound ${err.whyNoMatchStr(arg.tpe, bound)}",