From 420111125bd87604ca2a700181e73e17d33a4ba2 Mon Sep 17 00:00:00 2001
From: Claude <noreply@anthropic.com>
Date: Tue, 10 Nov 2026 17:25:22 +0000
Subject: [PATCH] WIP: Failing self-verifying test for ByRef parameterized
 property write-back (#909)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_019FEr8FVAmHV9bscZ82CChg
---
 .../VBToCS/ByRefParameterizedPropertyTests.vb | 48 +++++++++++++++++++
 1 file changed, 48 insertions(+)
 create mode 100644 Tests/TestData/SelfVerifyingTests/VBToCS/ByRefParameterizedPropertyTests.vb

diff --git a/Tests/TestData/SelfVerifyingTests/VBToCS/ByRefParameterizedPropertyTests.vb b/Tests/TestData/SelfVerifyingTests/VBToCS/ByRefParameterizedPropertyTests.vb
new file mode 100644
index 000000000..c5a164533
--- /dev/null
+++ b/Tests/TestData/SelfVerifyingTests/VBToCS/ByRefParameterizedPropertyTests.vb
@@ -0,0 +1,48 @@
+Imports System.Collections.Generic
+Imports Xunit
+
+Public Class ByRefParameterizedPropertyTests
+    <Fact>
+    Public Sub ParameterizedPropertyIsWrittenBackThroughItsSetterIssue909()
+        Dim db As New Db
+        db.Get_Equal(db.Qr(1, 21))
+        Assert.Equal("changed", db.Qr(1, 21))
+        Assert.Equal("get 1,21;set 1,21=changed;get 1,21", String.Join(";", db.Log))
+    End Sub
+
+    <Fact>
+    Public Sub IndexArgumentsAreEvaluatedOnce()
+        Dim db As New Db
+        Dim calls = 0
+        db.Get_Equal(db.Qr(NextIndex(calls), 21))
+        Assert.Equal(1, calls)
+        Assert.Equal("get 1,21;set 1,21=changed", String.Join(";", db.Log))
+    End Sub
+
+    Private Shared Function NextIndex(ByRef calls As Integer) As Integer
+        calls += 1
+        Return calls
+    End Function
+
+    Private Class Db
+        Public ReadOnly Log As New List(Of String)
+        Private ReadOnly _values As New Dictionary(Of String, String)
+
+        Public Sub Get_Equal(ByRef keyValue As String)
+            keyValue = "changed"
+        End Sub
+
+        Public Property Qr(tableBuffer As Integer, fieldNumber As Integer) As String
+            Get
+                Log.Add("get " & tableBuffer & "," & fieldNumber)
+                Dim value As String = Nothing
+                _values.TryGetValue(tableBuffer & "," & fieldNumber, value)
+                Return value
+            End Get
+            Set(value As String)
+                Log.Add("set " & tableBuffer & "," & fieldNumber & "=" & value)
+                _values(tableBuffer & "," & fieldNumber) = value
+            End Set
+        End Property
+    End Class
+End Class