Handle TypeProxy of Named Tuples, minimal fix without refactoring

Author: aherlihy

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

@@ -135,6 +135,8 @@ class TypeUtils:
             case t => throw TypeError(em"Malformed NamedTuple: names must be string types, but $t was found.")
           val values = vals.tupleElementTypesUpTo(bound, normalize).getOrElse(Nil)
           names.zip(values)
+        case tp: TypeProxy if tp.derivesFromNamedTuple =>
+          tp.superType.namedTupleElementTypesUpTo(bound, normalize)
         case t =>
           Nil
 

tests/run/i22150.check

@@ -0,0 +1 @@
+0

tests/run/i22150.scala

@@ -0,0 +1,12 @@
+//> using options -experimental -language:experimental.namedTuples
+import language.experimental.namedTuples
+
+val directionsNT = IArray(
+  (dx = 0, dy = 1), // up
+  (dx = 1, dy = 0), // right
+  (dx = 0, dy = -1), // down
+  (dx = -1, dy = 0), // left
+)
+val IArray(UpNT @ _, _, _, _) = directionsNT
+@main def Test =
+  println(UpNT.dx)