From adaf7fd65b9a53a8e127d41bf430e56001c6e472 Mon Sep 17 00:00:00 2001
From: Marek Safar <marek.safar@gmail.com>
Date: Tue, 3 Oct 2017 02:27:20 +0200
Subject: [PATCH] [mcs] Allow properties and indexers of by-ref values to be
 set without setter

---
 mcs/mcs/ecore.cs             |  5 +++++
 mcs/tests/test-ref-06.cs     | 24 ++++++++++++++++++++++++
 mcs/tests/ver-il-net_4_x.xml | 16 ++++++++++++++++
 3 files changed, 45 insertions(+)
 create mode 100644 mcs/tests/test-ref-06.cs

diff --git a/mcs/mcs/ecore.cs b/mcs/mcs/ecore.cs
index 490bcfb518e..34ff9a30dab 100644
--- a/mcs/mcs/ecore.cs
+++ b/mcs/mcs/ecore.cs
@@ -7394,6 +7394,11 @@ namespace Mono.CSharp {
 				if (ResolveAutopropertyAssignment (rc, right_side))
 					return this;
 
+				if (best_candidate.MemberType.Kind == MemberKind.ByRef) {
+					getter = CandidateToBaseOverride (rc, best_candidate.Get);
+					return ByRefDereference.Create(this).Resolve(rc);
+				}
+
 				rc.Report.Error (200, loc, "Property or indexer `{0}' cannot be assigned to (it is read-only)",
 					GetSignatureForError ());
 				return null;
diff --git a/mcs/tests/test-ref-06.cs b/mcs/tests/test-ref-06.cs
new file mode 100644
index 00000000000..74d35f44ed8
--- /dev/null
+++ b/mcs/tests/test-ref-06.cs
@@ -0,0 +1,24 @@
+using System;
+
+class X
+{
+	public static int Main ()
+	{
+		var x = new X ();
+		x [0] = 3;
+		if (x.field != 3)
+			return 1;
+		x.Prop = 5;
+		if (x.field != 5)
+			return 2;
+
+		return 0;
+	}
+
+	int field;
+
+	ref int this [int idx] => ref field;
+
+	ref int Prop => ref field;
+
+}
\ No newline at end of file
diff --git a/mcs/tests/ver-il-net_4_x.xml b/mcs/tests/ver-il-net_4_x.xml
index b111a7e3c5a..16a62d1ce87 100644
--- a/mcs/tests/ver-il-net_4_x.xml
+++ b/mcs/tests/ver-il-net_4_x.xml
@@ -72780,6 +72780,22 @@
       </method>
     </type>
   </test>
+  <test name="test-ref-06.cs">
+    <type name="X">
+      <method name="Int32 Main()" attrs="150">
+        <size>71</size>
+      </method>
+      <method name="Int32&amp; get_Item(Int32)" attrs="2177">
+        <size>14</size>
+      </method>
+      <method name="Int32&amp; get_Prop()" attrs="2177">
+        <size>14</size>
+      </method>
+      <method name="Void .ctor()" attrs="6278">
+        <size>7</size>
+      </method>
+    </type>
+  </test>
   <test name="test-static-using-01.cs">
     <type name="A.B.X">
       <method name="Int32 Test()" attrs="150">
-- 
2.25.1