Handle TypeProxy of Named Tuples, minimal fix without refactoring

Author: aherlihy

compiler/src/dotty/tools/dotc/ast/Desugar.scala

@@ -1744,7 +1744,7 @@ object desugar {
   def adaptPatternArgs(elems: List[Tree], pt: Type)(using Context): List[Tree] =
 
     def reorderedNamedArgs(wildcardSpan: Span): List[untpd.Tree] =
-      var selNames = pt.namedTupleElementTypes.map(_(0))
+      var selNames = pt.namedTupleElementTypes(false).map(_(0))
       if selNames.isEmpty && pt.classSymbol.is(CaseClass) then
         selNames = pt.classSymbol.caseAccessors.map(_.name.asTermName)
       val nameToIdx = selNames.zipWithIndex.toMap

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

@@ -127,19 +127,33 @@ class TypeUtils:
         case Some(types) => TypeOps.nestedPairs(types)
         case None => throw new AssertionError("not a tuple")
 
-    def namedTupleElementTypesUpTo(bound: Int, normalize: Boolean = true)(using Context): List[(TermName, Type)] =
+    def namedTupleElementTypesUpTo(bound: Int, derived: Boolean, normalize: Boolean = true)(using Context): List[(TermName, Type)] =
       (if normalize then self.normalized else self).dealias match
         case defn.NamedTuple(nmes, vals) =>
           val names = nmes.tupleElementTypesUpTo(bound, normalize).getOrElse(Nil).map(_.dealias).map:
             case ConstantType(Constant(str: String)) => str.toTermName
             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 derived =>
+          tp.superType.namedTupleElementTypesUpTo(bound - 1, normalize)
+        case tp: OrType if derived =>
+          val lhs = tp.tp1.namedTupleElementTypesUpTo(bound - 1, normalize)
+          val rhs = tp.tp2.namedTupleElementTypesUpTo(bound - 1, normalize)
+          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 if derived =>
+          (tp.tp1.namedTupleElementTypesUpTo(bound - 1, normalize), tp.tp2.namedTupleElementTypesUpTo(bound - 1, normalize)) match
+            case (Nil, rhs) => rhs
+            case (lhs, Nil) => lhs
+            case (lhs, rhs) =>
+              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
 
-    def namedTupleElementTypes(using Context): List[(TermName, Type)] =
-      namedTupleElementTypesUpTo(Int.MaxValue)
+    def namedTupleElementTypes(derived: Boolean)(using Context): List[(TermName, Type)] =
+      namedTupleElementTypesUpTo(Int.MaxValue, derived)
 
     def isNamedTupleType(using Context): Boolean = self match
       case defn.NamedTuple(_, _) => true

compiler/src/dotty/tools/dotc/interactive/Completion.scala

@@ -532,7 +532,7 @@ object Completion:
       def namedTupleCompletionsFromType(tpe: Type): CompletionMap =
         val freshCtx = ctx.fresh.setExploreTyperState()
         inContext(freshCtx):
-          tpe.namedTupleElementTypes
+          tpe.namedTupleElementTypes(true)
             .map { (name, tpe) =>
               val symbol = newSymbol(owner = NoSymbol, name, EmptyFlags, tpe)
               val denot = SymDenotation(symbol, NoSymbol, name, EmptyFlags, tpe)

compiler/src/dotty/tools/dotc/printing/RefinedPrinter.scala

@@ -248,7 +248,7 @@ class RefinedPrinter(_ctx: Context) extends PlainPrinter(_ctx) {
     def appliedText(tp: Type): Text = tp match
       case tp @ AppliedType(tycon, args) =>
         val namedElems =
-          try tp.namedTupleElementTypesUpTo(200, normalize = false)
+          try tp.namedTupleElementTypesUpTo(200, false, normalize = false) // TODO: should the printer use derived or not?
           catch case ex: TypeError => Nil
         if namedElems.nonEmpty then
           toTextNamedTuple(namedElems)

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

@@ -799,7 +799,7 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
 
     // Otherwise, try to expand a named tuple selection
     def tryNamedTupleSelection() =
-      val namedTupleElems = qual.tpe.widenDealias.namedTupleElementTypes
+      val namedTupleElems = qual.tpe.widenDealias.namedTupleElementTypes(true)
       val nameIdx = namedTupleElems.indexWhere(_._1 == selName)
       if nameIdx >= 0 && Feature.enabled(Feature.namedTuples) then
         typed(
@@ -875,7 +875,7 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
       then
         val pre = if !TypeOps.isLegalPrefix(qual.tpe) then SkolemType(qual.tpe) else qual.tpe
         val fieldsType = pre.select(tpnme.Fields).widenDealias.simplified
-        val fields = fieldsType.namedTupleElementTypes
+        val fields = fieldsType.namedTupleElementTypes(true)
         typr.println(i"try dyn select $qual, $selName, $fields")
         fields.find(_._1 == selName) match
           case Some((_, fieldType)) =>

tests/run/i22150.check

@@ -0,0 +1,3 @@
+0
+1
+2

tests/run/i22150.scala

@@ -0,0 +1,26 @@
+//> 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
+
+object NT:
+//  def foo[T <: (x: Int, y: String)](tup: T): Int =
+//    tup.x
+
+  def union[T](tup: (x: Int, y: String) | (x: Int, y: String)): Int =
+    tup.x
+
+  def intersect[T](tup: (x: Int, y: String) & T): Int =
+    tup.x
+
+
+@main def Test =
+  println(UpNT.dx)
+  println(NT.union((1, "a")))
+  println(NT.intersect((2, "b")))