Element-wise And/Or type

Author: aherlihy

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

@@ -140,15 +140,15 @@ class TypeUtils:
         case tp: OrType =>
           val lhs = tp.tp1.namedTupleElementTypesUpTo(bound, normalize)
           val rhs = tp.tp2.namedTupleElementTypesUpTo(bound, normalize)
-          if (lhs != rhs) throw TypeError(em"Malformed Union Type: Named Tuple elements must be the same, but $lhs and $rhs were found.")
-          lhs
+          if (lhs.map(_._1) != rhs.map(_._1)) throw TypeError(em"Malformed Union Type: Named Tuple elements must be the same, but $lhs and $rhs were found.")
+          lhs.zip(rhs).map((lhs, rhs) => (lhs._1, lhs._2 | rhs._2))
         case tp: AndType =>
           (tp.tp1.namedTupleElementTypesUpTo(bound, normalize), tp.tp2.namedTupleElementTypesUpTo(bound, normalize)) match
             case (Nil, rhs) => rhs
             case (lhs, Nil) => lhs
             case (lhs, rhs) =>
-              if (lhs != rhs) throw TypeError(em"Malformed Intersection Type: Named Tuple elements must be the same, but $lhs and $rhs were found.")
-              lhs
+              if (lhs.map(_._1) != rhs.map(_._1)) throw TypeError(em"Malformed Intersection Type: Named Tuple elements must be the same, but $lhs and $rhs were found.")
+              lhs.zip(rhs).map((lhs, rhs) => (lhs._1, lhs._2 & rhs._2))
         case t =>
           Nil