diff --git a/.editorconfig b/.editorconfig
index 9516bd4f2..ec779b49f 100644
--- a/.editorconfig
+++ b/.editorconfig
@@ -152,6 +152,7 @@ dotnet_diagnostic.MEF006.severity = silent
 dotnet_diagnostic.IDE2003.severity = silent
 
 #cleared null error types
+dotnet_diagnostic.CS8714.severity = error
 dotnet_diagnostic.CS8765.severity = error
 dotnet_diagnostic.CS8766.severity = error
 dotnet_diagnostic.CS8767.severity = error
diff --git a/ICSharpCode.Decompiler/CSharp/CSharpDecompiler.cs b/ICSharpCode.Decompiler/CSharp/CSharpDecompiler.cs
index 20cecc2ce..64e2d090f 100644
--- a/ICSharpCode.Decompiler/CSharp/CSharpDecompiler.cs
+++ b/ICSharpCode.Decompiler/CSharp/CSharpDecompiler.cs
@@ -1799,7 +1799,8 @@ namespace ICSharpCode.Decompiler.CSharp
 		internal static void AddAnnotationsToDeclaration(IMethod method, EntityDeclaration entityDecl, ILFunction function)
 		{
 			int i = 0;
-			var parameters = function.Variables.Where(v => v.Kind == VariableKind.Parameter).ToDictionary(v => v.Index);
+			//if the variable is a parameter is a parameter then index "should not" be null, would indicate an deeper under lying problem if it is so we assert not null (!)
+			var parameters = function.Variables.Where(v => v.Kind == VariableKind.Parameter).ToDictionary(v => v.Index!.Value);
 			foreach (var parameter in entityDecl.GetChildrenByRole(Roles.Parameter))
 			{
 				if (parameters.TryGetValue(i, out var v))
diff --git a/ICSharpCode.Decompiler/CSharp/ExpressionBuilder.cs b/ICSharpCode.Decompiler/CSharp/ExpressionBuilder.cs
index 41fb3870e..5923a37a0 100644
--- a/ICSharpCode.Decompiler/CSharp/ExpressionBuilder.cs
+++ b/ICSharpCode.Decompiler/CSharp/ExpressionBuilder.cs
@@ -2544,7 +2544,8 @@ namespace ICSharpCode.Decompiler.CSharp
 
 		IEnumerable<ParameterDeclaration> MakeParameters(IReadOnlyList<IParameter> parameters, ILFunction function)
 		{
-			var variables = function.Variables.Where(v => v.Kind == VariableKind.Parameter).ToDictionary(v => v.Index);
+			//if the variable is a parameter is a parameter then index "should not" be null, would indicate an deeper under lying problem if it is so we assert not null (!)
+			var variables = function.Variables.Where(v => v.Kind == VariableKind.Parameter).ToDictionary(v => v.Index!.Value);
 			int i = 0;
 			foreach (var parameter in parameters)
 			{
diff --git a/ICSharpCode.Decompiler/CSharp/Syntax/AstNode.cs b/ICSharpCode.Decompiler/CSharp/Syntax/AstNode.cs
index b11edf399..73b76dc1f 100644
--- a/ICSharpCode.Decompiler/CSharp/Syntax/AstNode.cs
+++ b/ICSharpCode.Decompiler/CSharp/Syntax/AstNode.cs
@@ -340,7 +340,7 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 		/// Gets the first child with the specified role.
 		/// Returns the role's null object if the child is not found.
 		/// </summary>
-		public T GetChildByRole<T>(Role<T> role) where T : AstNode?
+		public T? GetChildByRole<T>(Role<T> role) where T : AstNode
 		{
 			if (role == null)
 				throw new ArgumentNullException(nameof(role));
@@ -348,7 +348,7 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 			for (var cur = firstChild; cur != null; cur = cur.nextSibling)
 			{
 				if ((cur.flags & roleIndexMask) == roleIndex)
-					return (T)cur;
+					return (T?)cur;
 			}
 			return role.NullObject;
 		}
@@ -368,16 +368,16 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 			return new AstNodeCollection<T>(this, role);
 		}
 
-		protected void SetChildByRole<T>(Role<T> role, T newChild) where T : AstNode
+		protected void SetChildByRole<T>(Role<T> role, T? newChild) where T : AstNode
 		{
-			AstNode oldChild = GetChildByRole(role);
-			if (oldChild.IsNull)
+			AstNode? oldChild = GetChildByRole(role);
+			if (oldChild?.IsNull != false)
 				AddChild(newChild, role);
 			else
 				oldChild.ReplaceWith(newChild);
 		}
 
-		public void AddChild<T>(T child, Role<T> role) where T : AstNode
+		public void AddChild<T>(T? child, Role<T> role) where T : AstNode
 		{
 			if (role == null)
 				throw new ArgumentNullException(nameof(role));
diff --git a/ICSharpCode.Decompiler/CSharp/Syntax/TypeMembers/ParameterDeclaration.cs b/ICSharpCode.Decompiler/CSharp/Syntax/TypeMembers/ParameterDeclaration.cs
index 98a86fd69..069e03e7a 100644
--- a/ICSharpCode.Decompiler/CSharp/Syntax/TypeMembers/ParameterDeclaration.cs
+++ b/ICSharpCode.Decompiler/CSharp/Syntax/TypeMembers/ParameterDeclaration.cs
@@ -97,7 +97,7 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 		bool isParams;
 		bool isScopedRef;
 
-		public CSharpTokenNode ThisKeyword {
+		public CSharpTokenNode? ThisKeyword {
 			get {
 				if (hasThisModifier)
 				{
@@ -141,21 +141,21 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 			}
 		}
 
-		public AstType Type {
+		public AstType? Type {
 			get { return GetChildByRole(Roles.Type); }
 			set { SetChildByRole(Roles.Type, value); }
 		}
 
 		public string Name {
 			get {
-				return GetChildByRole(Roles.Identifier).Name;
+				return GetChildByRole(Roles.Identifier)?.Name ?? "";
 			}
 			set {
 				SetChildByRole(Roles.Identifier, Identifier.Create(value));
 			}
 		}
 
-		public Identifier NameToken {
+		public Identifier? NameToken {
 			get {
 				return GetChildByRole(Roles.Identifier);
 			}
@@ -164,11 +164,11 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 			}
 		}
 
-		public CSharpTokenNode AssignToken {
+		public CSharpTokenNode? AssignToken {
 			get { return GetChildByRole(Roles.Assign); }
 		}
 
-		public Expression DefaultExpression {
+		public Expression? DefaultExpression {
 			get { return GetChildByRole(Roles.Expression); }
 			set { SetChildByRole(Roles.Expression, value); }
 		}