From 2403548ce3479a7481c866ed17da3b551f0d81bf Mon Sep 17 00:00:00 2001
From: Siegfried Pammer <siegfriedpammer@gmail.com>
Date: Wed, 5 Aug 2020 22:10:32 +0200
Subject: [PATCH] Add tests for C# 9.0 lambda parameter discards

---
 ICSharpCode.Decompiler.Tests/Helpers/Tester.cs       |  7 ++++---
 ICSharpCode.Decompiler.Tests/PrettyTestRunner.cs     |  2 +-
 .../TestCases/Pretty/DelegateConstruction.cs         | 12 ++++++++++++
 3 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/ICSharpCode.Decompiler.Tests/Helpers/Tester.cs b/ICSharpCode.Decompiler.Tests/Helpers/Tester.cs
index b177b7ef9..6bc3c6a9f 100644
--- a/ICSharpCode.Decompiler.Tests/Helpers/Tester.cs
+++ b/ICSharpCode.Decompiler.Tests/Helpers/Tester.cs
@@ -251,15 +251,16 @@ namespace ICSharpCode.Decompiler.Tests.Helpers
 				preprocessorSymbols.Add("VB11");
 				preprocessorSymbols.Add("VB14");
 				preprocessorSymbols.Add("VB15");
+
+				if (flags.HasFlag(CompilerOptions.Preview)) {
+					preprocessorSymbols.Add("CS90");
+				}
 			} else if (flags.HasFlag(CompilerOptions.UseMcs)) {
 				preprocessorSymbols.Add("MCS");
 			} else {
 				preprocessorSymbols.Add("LEGACY_CSC");
 				preprocessorSymbols.Add("LEGACY_VBC");
 			}
-			if (flags.HasFlag(CompilerOptions.Preview)) {
-				preprocessorSymbols.Add("CS90");
-			}
 			return preprocessorSymbols;
 		}
 
diff --git a/ICSharpCode.Decompiler.Tests/PrettyTestRunner.cs b/ICSharpCode.Decompiler.Tests/PrettyTestRunner.cs
index ceeae1d1a..fa6fc7ccf 100644
--- a/ICSharpCode.Decompiler.Tests/PrettyTestRunner.cs
+++ b/ICSharpCode.Decompiler.Tests/PrettyTestRunner.cs
@@ -155,7 +155,7 @@ namespace ICSharpCode.Decompiler.Tests
 		[Test]
 		public void DelegateConstruction([ValueSource(nameof(defaultOptionsWithMcs))] CompilerOptions cscOptions)
 		{
-			RunForLibrary(cscOptions: cscOptions);
+			RunForLibrary(cscOptions: cscOptions | CompilerOptions.Preview);
 		}
 
 		[Test]
diff --git a/ICSharpCode.Decompiler.Tests/TestCases/Pretty/DelegateConstruction.cs b/ICSharpCode.Decompiler.Tests/TestCases/Pretty/DelegateConstruction.cs
index a73252ee0..8d5f6fdab 100644
--- a/ICSharpCode.Decompiler.Tests/TestCases/Pretty/DelegateConstruction.cs
+++ b/ICSharpCode.Decompiler.Tests/TestCases/Pretty/DelegateConstruction.cs
@@ -428,6 +428,18 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Pretty
 			return () => valueTuple.RenamedString;
 		}
 #endif
+
+		public static Func<T, T> Identity<T>()
+		{
+			return (T _) => _;
+		}
+
+#if CS90
+		public static Func<int, int, int, int> LambdaParameterDiscard()
+		{
+			return (int _, int _, int _) => 0;
+		}
+#endif
 	}
 
 	public class Issue1867