From b875cc098f8e6a5210021e8d20e95966b264811b Mon Sep 17 00:00:00 2001
From: odersky <odersky@gmail.com>
Date: Sat, 9 Jul 2022 11:34:32 +0200
Subject: [PATCH] Avoid assertion failure for illegal trait inheritance

Fixes #15629
---
 compiler/src/dotty/tools/dotc/typer/Namer.scala | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/compiler/src/dotty/tools/dotc/typer/Namer.scala b/compiler/src/dotty/tools/dotc/typer/Namer.scala
index 3a821f1dc65d..40f9906038f6 100644
--- a/compiler/src/dotty/tools/dotc/typer/Namer.scala
+++ b/compiler/src/dotty/tools/dotc/typer/Namer.scala
@@ -478,7 +478,7 @@ class Namer { typer: Typer =>
           if (child == other)
             annots // can happen if a class has several inaccessible children
           else {
-            assert(childStart != other.span.start, i"duplicate child annotation $child / $other")
+            assert(childStart != other.span.start || child.source != other.source, i"duplicate child annotation $child / $other")
             val (prefix, otherAnnot :: rest) = annots.span(_.symbol != defn.ChildAnnot): @unchecked
             prefix ::: otherAnnot :: insertInto(rest)
           }