From a08789a7ef5eec67c28551611792c1dc8f573b8d Mon Sep 17 00:00:00 2001
From: odersky <odersky@gmail.com>
Date: Sun, 4 Sep 2022 13:33:53 +0200
Subject: [PATCH] Harden canAssign

Fixes #15897
---
 compiler/src/dotty/tools/dotc/typer/Typer.scala | 2 +-
 tests/neg/i15897.scala                          | 8 ++++++++
 tests/pos/i15897.scala                          | 8 ++++++++
 3 files changed, 17 insertions(+), 1 deletion(-)
 create mode 100644 tests/neg/i15897.scala
 create mode 100644 tests/pos/i15897.scala

diff --git a/compiler/src/dotty/tools/dotc/typer/Typer.scala b/compiler/src/dotty/tools/dotc/typer/Typer.scala
index d802ef0df973..628dcc5a9d92 100644
--- a/compiler/src/dotty/tools/dotc/typer/Typer.scala
+++ b/compiler/src/dotty/tools/dotc/typer/Typer.scala
@@ -989,7 +989,7 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
 
         def canAssign(sym: Symbol) =
           sym.is(Mutable, butNot = Accessor) ||
-          ctx.owner.isPrimaryConstructor && !sym.is(Method) && sym.owner == ctx.owner.owner ||
+          ctx.owner.isPrimaryConstructor && !sym.is(Method) && sym.maybeOwner == ctx.owner.owner ||
             // allow assignments from the primary constructor to class fields
           ctx.owner.name.is(TraitSetterName) || ctx.owner.isStaticConstructor
 
diff --git a/tests/neg/i15897.scala b/tests/neg/i15897.scala
new file mode 100644
index 000000000000..d9dbe94c4eef
--- /dev/null
+++ b/tests/neg/i15897.scala
@@ -0,0 +1,8 @@
+object O {
+  class AC(code: => Unit)
+
+  val action = new AC({mode = ???}) {} // error
+
+  def mode: AnyRef = ???
+  def mode=(em: AnyRef): Unit = {} // error // error // error
+}
\ No newline at end of file
diff --git a/tests/pos/i15897.scala b/tests/pos/i15897.scala
new file mode 100644
index 000000000000..b039401a6519
--- /dev/null
+++ b/tests/pos/i15897.scala
@@ -0,0 +1,8 @@
+object O {
+  class AC(code: => Unit)
+
+  val action = new AC({mode = ???}) {}
+
+  def mode: AnyRef = ???
+  def mode_=(em: AnyRef): Unit = {}
+}
\ No newline at end of file