From c90d779a53755075b8a1cb06cb5540b2ff52cc74 Mon Sep 17 00:00:00 2001
From: Dale Wijnand <dale.wijnand@gmail.com>
Date: Sun, 22 Aug 2021 18:56:06 +0100
Subject: [PATCH] Avoid crash by handling by-names under Typed

---
 .../dotc/transform/TransformByNameApply.scala |  3 +-
 tests/pos/i13349.scala                        | 31 +++++++++++++++++++
 tests/pos/i13349min.scala                     |  3 ++
 3 files changed, 36 insertions(+), 1 deletion(-)
 create mode 100644 tests/pos/i13349.scala
 create mode 100644 tests/pos/i13349min.scala

diff --git a/compiler/src/dotty/tools/dotc/transform/TransformByNameApply.scala b/compiler/src/dotty/tools/dotc/transform/TransformByNameApply.scala
index dab1d8f25ca2..af0998293904 100644
--- a/compiler/src/dotty/tools/dotc/transform/TransformByNameApply.scala
+++ b/compiler/src/dotty/tools/dotc/transform/TransformByNameApply.scala
@@ -45,7 +45,8 @@ abstract class TransformByNameApply extends MiniPhase { thisPhase: DenotTransfor
           if (argType.isBottomType) argType = formal.widenExpr
           def wrap(arg: Tree) =
             ref(defn.cbnArg).appliedToType(argType).appliedTo(arg).withSpan(arg.span)
-          arg match {
+          def unTyped(t: Tree): Tree = t match { case Typed(expr, _) => unTyped(expr) case _ => t }
+          unTyped(arg) match {
             case Apply(Select(qual, nme.apply), Nil)
             if qual.tpe.derivesFrom(defn.Function0) && (isPureExpr(qual) || qual.symbol.isAllOf(Inline | Param)) =>
               wrap(qual)
diff --git a/tests/pos/i13349.scala b/tests/pos/i13349.scala
new file mode 100644
index 000000000000..e4048424db24
--- /dev/null
+++ b/tests/pos/i13349.scala
@@ -0,0 +1,31 @@
+sealed trait Stream[+A]{
+    import Stream.*;
+
+    def foldRight[B](z: => B)(f: (A, => B) => B): B =
+      this match {
+        case Cons(h,t) => f(h(), t().foldRight(z)(f))
+        case _ => z
+      }
+
+    def append[B >: A](other : => Stream[B]) : Stream[B] =
+      foldRight(other : Stream[B])((elem, stream) => cons(elem, stream))
+
+}
+
+case object Empty extends Stream[Nothing]
+case class Cons[+A](h: () => A, t: () => Stream[A]) extends Stream[A]
+
+object Stream {
+
+  def cons[A](hd: => A, tl: => Stream[A]): Stream[A] = {
+    lazy val head = hd
+    lazy val tail = tl
+    Cons(() => head, () => tail)
+  }
+
+  def empty[A]: Stream[A] = Empty
+
+  def apply[A](as: A*): Stream[A] =
+    if (as.isEmpty) empty else cons(as.head, apply(as.tail: _*))
+
+}
diff --git a/tests/pos/i13349min.scala b/tests/pos/i13349min.scala
new file mode 100644
index 000000000000..da434744b638
--- /dev/null
+++ b/tests/pos/i13349min.scala
@@ -0,0 +1,3 @@
+class Foo:
+  def foo(x: => Foo) = bar(x: Foo)
+  def bar(x: => Foo) = x