From 5f2865267cbd457fe9c1274eb7a397520735048f Mon Sep 17 00:00:00 2001
From: stakx <stakx@eml.cc>
Date: Sat, 2 Jan 2021 10:43:32 +0100
Subject: [PATCH] Switch to C# language version 9.0

...and make a small change to verify compilation actually succeeds.
---
 buildscripts/common.props                                      | 1 +
 src/Castle.Core.Tests/Castle.Core.Tests.csproj                 | 1 -
 src/Castle.Core/DynamicProxy/Generators/ClassProxyGenerator.cs | 2 +-
 3 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/buildscripts/common.props b/buildscripts/common.props
index ff301b775d..c2d455ba2b 100644
--- a/buildscripts/common.props
+++ b/buildscripts/common.props
@@ -1,6 +1,7 @@
 <Project>
 
 	<PropertyGroup>
+		<LangVersion>9.0</LangVersion>
 		<NoWarn>$(NoWarn);CS1591;CS3014;CS3003;CS3001;CS3021</NoWarn>
 		<NoWarn>$(NoWarn);CS0612;CS0618</NoWarn> <!-- TODO: Remove this line once `[Obsolete]` members have been dealt with. -->
 		<RepositoryType>git</RepositoryType>
diff --git a/src/Castle.Core.Tests/Castle.Core.Tests.csproj b/src/Castle.Core.Tests/Castle.Core.Tests.csproj
index f3f0bb1b03..a6b73851b1 100644
--- a/src/Castle.Core.Tests/Castle.Core.Tests.csproj
+++ b/src/Castle.Core.Tests/Castle.Core.Tests.csproj
@@ -16,7 +16,6 @@
 		<SignAssembly>True</SignAssembly>
 		<AssemblyOriginatorKeyFile>..\..\buildscripts\CastleKey.snk</AssemblyOriginatorKeyFile>
 		<PublicSign Condition="'$(OS)'=='Unix'">true</PublicSign>
-		<LangVersion>7.2</LangVersion>
 		<StartupObject>Program</StartupObject>
 	</PropertyGroup>
 
diff --git a/src/Castle.Core/DynamicProxy/Generators/ClassProxyGenerator.cs b/src/Castle.Core/DynamicProxy/Generators/ClassProxyGenerator.cs
index 112f416d64..f0ba3e41f3 100644
--- a/src/Castle.Core/DynamicProxy/Generators/ClassProxyGenerator.cs
+++ b/src/Castle.Core/DynamicProxy/Generators/ClassProxyGenerator.cs
@@ -142,7 +142,7 @@ protected virtual Type GenerateType(string name, Type[] interfaces, INamingScope
 				}
 			}
 			var additionalInterfacesContributor = new InterfaceProxyWithoutTargetContributor(namingScope,
-																							 (c, m) => NullExpression.Instance)
+																							 static (c, m) => NullExpression.Instance)
 			{ Logger = Logger };
 			// 3. then additional interfaces
 			foreach (var @interface in additionalInterfaces)