Add test for C# 11 generic attribute

ICSharpCode.Decompiler.Tests/Helpers/Tester.cs

@@ -348,7 +348,7 @@ namespace ICSharpCode.Decompiler.Tests.Helpers
 					preprocessorSymbols.Add("CS100");
 					if (flags.HasFlag(CompilerOptions.Preview))
 					{
-
+						preprocessorSymbols.Add("CS110");
 					}
 				}
 			}

ICSharpCode.Decompiler.Tests/PrettyTestRunner.cs

@@ -616,6 +616,11 @@ namespace ICSharpCode.Decompiler.Tests
 		[Test]
 		public async Task CustomAttributes([ValueSource(nameof(defaultOptions))] CompilerOptions cscOptions)
 		{
+			if (cscOptions.HasFlag(CompilerOptions.UseRoslynLatest))
+			{
+				// Test C# 11 generic attributes
+				cscOptions |= CompilerOptions.Preview;
+			}
 			await RunForLibrary(cscOptions: cscOptions);
 		}
 

ICSharpCode.Decompiler.Tests/TestCases/Pretty/CustomAttributes.cs

@@ -40,6 +40,18 @@ namespace CustomAttributes
 			{
 			}
 		}
+#if CS110
+		[AttributeUsage(AttributeTargets.All, AllowMultiple = true)]
+		public class GenericAttribute<T> : Attribute
+		{
+			public GenericAttribute()
+			{
+			}
+			public GenericAttribute(T val)
+			{
+			}
+		}
+#endif
 		[My(ULongEnum.MaxUInt64)]
 		public enum ULongEnum : ulong
 		{
@@ -145,5 +157,14 @@ namespace CustomAttributes
 		public static void BoxedLiteralsArray()
 		{
 		}
+#if CS110
+		[Generic<int>]
+		[Generic<string>]
+		public static void UseGenericAttribute()
+		{
+		}
+		// TODO: add test for generic attributes with arguments of type T
+		// This is blocked by https://github.com/dotnet/runtime/issues/58073
+#endif
 	}
 }

ICSharpCode.Decompiler/CSharp/CSharpLanguageVersion.cs

@@ -33,7 +33,8 @@ namespace ICSharpCode.Decompiler.CSharp
 		CSharp8_0 = 800,
 		CSharp9_0 = 900,
 		CSharp10_0 = 1000,
-		Preview = 1000,
+		CSharp11_0 = 1100,
+		Preview = 1100,
 		Latest = 0x7FFFFFFF
 	}
 }