Normalize for underlyingClassRef

Test #15827 with a classpath dependency

Author: EugeneFlesselle

compiler/src/dotty/tools/dotc/core/Types.scala

@@ -1584,7 +1584,7 @@ object Types extends TypeUtils {
      *  a class, the class type ref, otherwise NoType.
      *  @param  refinementOK   If `true` we also skip refinements.
      */
-    def underlyingClassRef(refinementOK: Boolean)(using Context): Type = dealias match {
+    def underlyingClassRef(refinementOK: Boolean)(using Context): Type = dealiasNormalized match {
       case tp: TypeRef =>
         if (tp.symbol.isClass) tp
         else if (tp.symbol.isAliasType) tp.underlying.underlyingClassRef(refinementOK)

tests/pos/i15827.scala renamed to tests/pos/i15827a.scala

@@ -0,0 +1,7 @@
+
+case class Foo()
+
+type T = Tuple.Elem[(Foo, Any), 0]
+
+val x = new T() // ok
+

tests/pos/i15827b/A_1.scala

@@ -0,0 +1,2 @@
+
+val y = new T() // error before changes