From 32e39698efd00dd3ddc3d72f62fc1f432d82d5c0 Mon Sep 17 00:00:00 2001
From: Jamie Thompson <bishbashboshjt@gmail.com>
Date: Fri, 31 May 2024 15:46:50 +0200
Subject: [PATCH] widenDealias before extracting namedTupleElementTypes

---
 compiler/src/dotty/tools/dotc/typer/Typer.scala |  2 +-
 tests/pos/named-tuple-selections.scala          | 12 ++++++++++++
 2 files changed, 13 insertions(+), 1 deletion(-)
 create mode 100644 tests/pos/named-tuple-selections.scala

diff --git a/compiler/src/dotty/tools/dotc/typer/Typer.scala b/compiler/src/dotty/tools/dotc/typer/Typer.scala
index 24d28aa8b4e6..c11a0d1f15d6 100644
--- a/compiler/src/dotty/tools/dotc/typer/Typer.scala
+++ b/compiler/src/dotty/tools/dotc/typer/Typer.scala
@@ -756,7 +756,7 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
       return typedSelect(tree, pt, qual)
 
     // Otherwise, try to expand a named tuple selection
-    val namedTupleElems = qual.tpe.widen.namedTupleElementTypes
+    val namedTupleElems = qual.tpe.widenDealias.namedTupleElementTypes
     val nameIdx = namedTupleElems.indexWhere(_._1 == selName)
     if nameIdx >= 0 && Feature.enabled(Feature.namedTuples) then
       return typed(
diff --git a/tests/pos/named-tuple-selections.scala b/tests/pos/named-tuple-selections.scala
new file mode 100644
index 000000000000..c3569f21b323
--- /dev/null
+++ b/tests/pos/named-tuple-selections.scala
@@ -0,0 +1,12 @@
+import scala.language.experimental.namedTuples
+
+object Test1:
+  // original code from issue https://github.com/scala/scala3/issues/20439
+  val bar = (a = 1, b = 2)
+
+  type ThatBar = bar.type
+  val thatBar: ThatBar = bar
+  val thatBar2: bar.type = bar
+
+  def test2 = thatBar.a // error
+  def test3 = thatBar2.a // ok