address review: resolve type args in fresh context

Author: Jasper-M

compiler/src/dotty/tools/dotc/typer/Implicits.scala

@@ -704,6 +704,7 @@ trait Implicits { self: Typer =>
           params,
           args)
       }
+    def resolveTypes(targs: List[tpd.Tree])(implicit ctx: Context) = targs.map(a => fullyDefinedType(a.typeOpt, "type parameter", a.pos))
     arg.tpe match {
       case ambi: AmbiguousImplicits =>
         val maybeAnnot = ambi.alt1.ref.symbol.getAnnotation(defn.ImplicitAmbiguousAnnot).map(
@@ -718,11 +719,10 @@ trait Implicits { self: Typer =>
             case lambda: TypeLambda => lambda.typeParams.map(_.paramName.unexpandedName.toString)
             case _                  => Nil
           }
-          alt.tstate.commit()
           val args = alt.tree match {
             case TypeApply(_, targs) if params.nonEmpty =>
-              targs.map(a => fullyDefinedType(a.typeOpt, "type parameter", a.pos))
-            case _ => 
+              resolveTypes(targs)(ctx.fresh.setTyperState(alt.tstate))
+            case _ =>
               Nil
           }
           userDefinedMessage(annot, params, args)