Fix #3010: Remove compiler-generated attributes for required members with custom ctors.

Author: siegfriedpammer

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

@@ -4,6 +4,9 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Pretty
 {
 	internal class AutoProperties
 	{
+#if CS110
+		public required int RequiredField;
+#endif
 		public int A { get; } = 1;
 
 		public int B { get; set; } = 2;
@@ -22,9 +25,23 @@ internal class AutoProperties
 
 		public int issue1319 { get; }
 
+#if CS110
+		public required int RequiredProperty { get; set; }
+#endif
+
 		public AutoProperties(int issue1319)
 		{
 			this.issue1319 = issue1319;
+#if CS110
+			RequiredProperty = 42;
+			RequiredField = 42;
+#endif
 		}
 	}
+#if !NET70
+	[AttributeUsage(AttributeTargets.Class | AttributeTargets.Struct | AttributeTargets.Property | AttributeTargets.Field, AllowMultiple = false, Inherited = false)]
+	internal sealed class RequiredMemberAttribute : Attribute
+	{
+	}
+#endif
 }

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

@@ -256,10 +256,13 @@ public CompilerFeatureRequiredAttribute(string featureName)
 	internal class IsExternalInit
 	{
 	}
-
+#endif
+#if !NET70
 	[AttributeUsage(AttributeTargets.Class | AttributeTargets.Struct | AttributeTargets.Property | AttributeTargets.Field, AllowMultiple = false, Inherited = false)]
 	internal sealed class RequiredMemberAttribute : Attribute
 	{
 	}
+#endif
+#if !NET60
 }
 #endif

ICSharpCode.Decompiler/CSharp/CSharpDecompiler.cs

@@ -1397,16 +1397,7 @@ EntityDeclaration DoDecompile(ITypeDefinition typeDef, DecompileRun decompileRun
 				}
 				if (settings.IntroduceRefModifiersOnStructs)
 				{
-					if (FindAttribute(typeDecl, KnownAttribute.Obsolete, out var attr))
-					{
-						if (obsoleteAttributePattern.IsMatch(attr))
-						{
-							if (attr.Parent is AttributeSection section && section.Attributes.Count == 1)
-								section.Remove();
-							else
-								attr.Remove();
-						}
-					}
+					RemoveObsoleteAttribute(typeDecl, "Types with embedded references are not supported in this version of your compiler.");
 					RemoveCompilerFeatureRequiredAttribute(typeDecl, "RefStructs");
 				}
 				if (settings.RequiredMembers)
@@ -1584,14 +1575,6 @@ EnumValueDisplayMode DetectBestEnumValueDisplayMode(ITypeDefinition typeDef, PEF
 			return firstValue == 0 ? EnumValueDisplayMode.None : EnumValueDisplayMode.FirstOnly;
 		}
 
-		static readonly Syntax.Attribute obsoleteAttributePattern = new Syntax.Attribute() {
-			Type = new TypePattern(typeof(ObsoleteAttribute)),
-			Arguments = {
-				new PrimitiveExpression("Types with embedded references are not supported in this version of your compiler."),
-				new Choice() { new PrimitiveExpression(true), new PrimitiveExpression(false) }
-			}
-		};
-
 		EntityDeclaration DoDecompile(IMethod method, DecompileRun decompileRun, ITypeResolveContext decompilationContext)
 		{
 			Debug.Assert(decompilationContext.CurrentMember == method);
@@ -1645,6 +1628,10 @@ EntityDeclaration DoDecompile(IMethod method, DecompileRun decompileRun, ITypeRe
 					methodDecl.Modifiers &= ~(Modifiers.New | Modifiers.Virtual);
 					methodDecl.Modifiers |= Modifiers.Override;
 				}
+				if (method.IsConstructor && settings.RequiredMembers && RemoveCompilerFeatureRequiredAttribute(methodDecl, "RequiredMembers"))
+				{
+					RemoveObsoleteAttribute(methodDecl, "Constructors of types with required members are not supported in this version of your compiler.");
+				}
 				return methodDecl;
 
 				bool IsTypeHierarchyKnown(IType type)
@@ -1877,6 +1864,30 @@ internal static bool RemoveCompilerFeatureRequiredAttribute(EntityDeclaration en
 			return found;
 		}
 
+		internal static bool RemoveObsoleteAttribute(EntityDeclaration entityDecl, string message)
+		{
+			bool found = false;
+			foreach (var section in entityDecl.Attributes)
+			{
+				foreach (var attr in section.Attributes)
+				{
+					var symbol = attr.Type.GetSymbol();
+					if (symbol is ITypeDefinition td && td.FullTypeName == KnownAttribute.Obsolete.GetTypeName()
+						&& attr.Arguments.Count >= 1 && attr.Arguments.First() is PrimitiveExpression pe
+						&& pe.Value is string s && s == message)
+					{
+						attr.Remove();
+						found = true;
+					}
+				}
+				if (section.Attributes.Count == 0)
+				{
+					section.Remove();
+				}
+			}
+			return found;
+		}
+
 		bool FindAttribute(EntityDeclaration entityDecl, KnownAttribute attributeType, out Syntax.Attribute attribute)
 		{
 			attribute = null;