Delete the Role hierarchy; key the child API on SlotKind

Slot identity already lived in node.Slot/CSharpSlotInfo/SlotKind after
the storage flip, so the parallel Role/Role<T> child model was redundant.
The Role-keyed mutation/query API is reexpressed over SlotKind, and the
role-index packing on AstNode flags is gone.

Because a node's Slot is now derived from its index in its parent rather
than stored on the child, the located-AST reattach in
InsertMissingTokensDecorator must capture the child's slot kind before
Remove() detaches it.

Assisted-by: Claude:claude-opus-4-8:Claude Code

ICSharpCode.Decompiler.Generators/DecompilerSyntaxTreeGenerator.cs

@@ -314,7 +314,7 @@ internal class DecompilerSyntaxTreeGenerator : IIncrementalGenerator
 				if (isCollection)
 				{
 					builder.AppendLine($"\tAstNodeCollection<{elementType}>? {field};");
-					builder.AppendLine($"\tpublic {(isOverride ? "override " : "")}{partialKw}AstNodeCollection<{elementType}> {name} => {field} ??= new AstNodeCollection<{elementType}>(this, {roleExpr});");
+					builder.AppendLine($"\tpublic {(isOverride ? "override " : "")}{partialKw}AstNodeCollection<{elementType}> {name} => {field} ??= new AstNodeCollection<{elementType}>(this, SlotKind.{kindName});");
 				}
 				else
 				{
@@ -322,7 +322,7 @@ internal class DecompilerSyntaxTreeGenerator : IIncrementalGenerator
 					builder.AppendLine($"\tpublic {(isOverride ? "override " : "")}{partialKw}{type}{(isNullable ? "?" : "")} {name}");
 					builder.AppendLine("\t{");
 					builder.AppendLine($"\t\tget => {field}{(isNullable ? "" : "!")};");
-					builder.AppendLine($"\t\tset => SetChildNode(ref {field}, value, {roleExpr});");
+					builder.AppendLine($"\t\tset => SetChildNode(ref {field}, value);");
 					builder.AppendLine("\t}");
 				}
 				builder.AppendLine();
@@ -389,27 +389,13 @@ internal class DecompilerSyntaxTreeGenerator : IIncrementalGenerator
 				}
 				else
 				{
-					builder.AppendLine($"\t\tif (i == 0) {{ SetChildNode(ref {FieldName(s.PropertyName)}, ({s.PropertyType}?)value, {s.RoleExpr}); return; }} i -= 1;");
+					builder.AppendLine($"\t\tif (i == 0) {{ SetChildNode(ref {FieldName(s.PropertyName)}, ({s.PropertyType}?)value); return; }} i -= 1;");
 				}
 			}
 			builder.AppendLine("\t\tthrow new System.ArgumentOutOfRangeException(nameof(index));");
 			builder.AppendLine("\t}");
 			builder.AppendLine();
 
-			builder.AppendLine("\tinternal override Role GetChildSlot(int index)");
-			builder.AppendLine("\t{");
-			builder.AppendLine("\t\tint i = index;");
-			foreach (var s in slots)
-			{
-				if (s.IsCollection)
-					builder.AppendLine($"\t\t{{ int n = {FieldName(s.PropertyName)}?.Count ?? 0; if (i < n) return {s.RoleExpr}; i -= n; }}");
-				else
-					builder.AppendLine($"\t\tif (i == 0) return {s.RoleExpr}; i -= 1;");
-			}
-			builder.AppendLine("\t\tthrow new System.ArgumentOutOfRangeException(nameof(index));");
-			builder.AppendLine("\t}");
-			builder.AppendLine();
-
 			// One CSharpSlotInfo static per slot; node.Slot compares against these by object identity.
 			foreach (var s in slots)
 				builder.AppendLine($"\tpublic static readonly CSharpSlotInfo {s.PropertyName}Slot = new CSharpSlotInfo(\"{s.PropertyName}\", typeof({s.ElementType}), {(s.IsCollection ? "true" : "false")}, SlotKind.{s.KindName});");
@@ -431,11 +417,11 @@ internal class DecompilerSyntaxTreeGenerator : IIncrementalGenerator
 
 			if (slots.Any(s => s.IsCollection))
 			{
-				builder.AppendLine("\tinternal override AstNodeCollection? GetCollectionByRole(Role role)");
+				builder.AppendLine("\tinternal override AstNodeCollection? GetCollectionByKind(SlotKind kind)");
 				builder.AppendLine("\t{");
 				foreach (var s in slots.Where(s => s.IsCollection))
-					builder.AppendLine($"\t\tif (role == {s.RoleExpr}) return {s.PropertyName};");
-				builder.AppendLine("\t\treturn base.GetCollectionByRole(role);");
+					builder.AppendLine($"\t\tif (kind == SlotKind.{s.KindName}) return {s.PropertyName};");
+				builder.AppendLine("\t\treturn base.GetCollectionByKind(kind);");
 				builder.AppendLine("\t}");
 				builder.AppendLine();
 			}

ICSharpCode.Decompiler/CSharp/CSharpDecompiler.cs

@@ -806,7 +806,7 @@ namespace ICSharpCode.Decompiler.CSharp
 				}
 				currentNamespace = typeDef.Namespace;
 				var typeDecl = DoDecompile(typeDef, decompileRun, decompilationContext.WithCurrentTypeDefinition(typeDef));
-				groupNode.AddChild(typeDecl, SyntaxTree.MemberRole);
+				groupNode.AddChild(typeDecl, SlotKind.Member);
 			}
 		}
 
@@ -1349,11 +1349,11 @@ namespace ICSharpCode.Decompiler.CSharp
 					RemoveAttribute(prop, KnownAttribute.ExtensionMarker);
 					if (propDef.Getter != null)
 					{
-						RemoveAttribute(prop.GetChildByRole(PropertyDeclaration.GetterRole), KnownAttribute.ExtensionMarker);
+						RemoveAttribute(prop.GetChildByRole<Accessor>(SlotKind.Getter), KnownAttribute.ExtensionMarker);
 					}
 					if (propDef.Setter != null)
 					{
-						RemoveAttribute(prop.GetChildByRole(PropertyDeclaration.SetterRole), KnownAttribute.ExtensionMarker);
+						RemoveAttribute(prop.GetChildByRole<Accessor>(SlotKind.Setter), KnownAttribute.ExtensionMarker);
 					}
 					RunTransforms(syntaxTree, decompileRun, new SimpleTypeResolveContext(propDef.DeclaringTypeDefinition));
 					break;
@@ -1406,7 +1406,7 @@ namespace ICSharpCode.Decompiler.CSharp
 			EntityDeclaration memberDecl, IMethod method,
 			TypeSystemAstBuilder astBuilder)
 		{
-			if (memberDecl.GetChildByRole(EntityDeclaration.PrivateImplementationTypeRole) is not null)
+			if (memberDecl.GetChildByRole<AstType>(SlotKind.PrivateImplementationType) is not null)
 			{
 				yield break; // cannot create forwarder for existing explicit interface impl
 			}
@@ -1430,9 +1430,9 @@ namespace ICSharpCode.Decompiler.CSharp
 				methodDecl.ReturnType = memberDecl.ReturnType?.Clone();
 				methodDecl.PrivateImplementationType = astBuilder.ConvertType(m.DeclaringType);
 				methodDecl.Name = m.Name;
-				methodDecl.TypeParameters.AddRange(memberDecl.GetChildrenByRole(Roles.TypeParameter)
+				methodDecl.TypeParameters.AddRange(memberDecl.GetChildrenByRole<TypeParameterDeclaration>(SlotKind.TypeParameter)
 												   .Select(n => (TypeParameterDeclaration)n.Clone()));
-				methodDecl.Parameters.AddRange(memberDecl.GetChildrenByRole(Roles.Parameter).Select(n => n.Clone()));
+				methodDecl.Parameters.AddRange(memberDecl.GetChildrenByRole<ParameterDeclaration>(SlotKind.Parameter).Select(n => n.Clone()));
 				// Constraints are not copied because explicit interface implementations cannot have constraints. CS0460
 
 				methodDecl.Body = new BlockStatement();
@@ -1548,7 +1548,7 @@ namespace ICSharpCode.Decompiler.CSharp
 		void FixParameterNames(EntityDeclaration entity)
 		{
 			int i = 0;
-			foreach (var parameter in entity.GetChildrenByRole(Roles.Parameter))
+			foreach (var parameter in entity.GetChildrenByRole<ParameterDeclaration>(SlotKind.Parameter))
 			{
 				if (string.IsNullOrWhiteSpace(parameter.Name) && !parameter.Type.IsArgList())
 				{
@@ -1845,11 +1845,11 @@ namespace ICSharpCode.Decompiler.CSharp
 							RemoveAttribute(prop, KnownAttribute.ExtensionMarker);
 							if (p.Getter != null)
 							{
-								RemoveAttribute(prop.GetChildByRole(PropertyDeclaration.GetterRole), KnownAttribute.ExtensionMarker);
+								RemoveAttribute(prop.GetChildByRole<Accessor>(SlotKind.Getter), KnownAttribute.ExtensionMarker);
 							}
 							if (p.Setter != null)
 							{
-								RemoveAttribute(prop.GetChildByRole(PropertyDeclaration.SetterRole), KnownAttribute.ExtensionMarker);
+								RemoveAttribute(prop.GetChildByRole<Accessor>(SlotKind.Setter), KnownAttribute.ExtensionMarker);
 							}
 							extMemberDecl = prop;
 							break;
@@ -2053,7 +2053,7 @@ namespace ICSharpCode.Decompiler.CSharp
 					var commentStatement = new EmptyStatement();
 					commentStatement.AddTrailingTrivia(new Comment("Invalid MethodBodyBlock: " + ex.Message));
 					body.Statements.Add(commentStatement);
-					entityDecl.AddChild(body, Roles.Body);
+					entityDecl.AddChild(body, SlotKind.Body);
 					return;
 				}
 				var function = ilReader.ReadIL((MethodDefinitionHandle)method.MetadataToken, methodBody, cancellationToken: CancellationToken);
@@ -2112,7 +2112,7 @@ namespace ICSharpCode.Decompiler.CSharp
 							body.Statements.Add(warningStatement);
 					}
 
-					entityDecl.AddChild(body, Roles.Body);
+					entityDecl.AddChild(body, SlotKind.Body);
 				}
 
 				CleanUpMethodDeclaration(entityDecl, body, function, localSettings.DecompileMemberBodies);
@@ -2127,7 +2127,7 @@ namespace ICSharpCode.Decompiler.CSharp
 		{
 			int i = parameterOffset;
 			var parameters = function.Variables.Where(v => v.Kind == VariableKind.Parameter).ToDictionary(v => v.Index);
-			foreach (var parameter in entityDecl.GetChildrenByRole(Roles.Parameter))
+			foreach (var parameter in entityDecl.GetChildrenByRole<ParameterDeclaration>(SlotKind.Parameter))
 			{
 				if (parameters.TryGetValue(i, out var v))
 					parameter.AddAnnotation(new ILVariableResolveResult(v, method.Parameters[i].Type));

ICSharpCode.Decompiler/CSharp/OutputVisitor/CSharpAmbience.cs

@@ -123,7 +123,7 @@ namespace ICSharpCode.Decompiler.CSharp.OutputVisitor
 			if ((ConversionFlags & ConversionFlags.PlaceReturnTypeAfterParameterList) != ConversionFlags.PlaceReturnTypeAfterParameterList
 				&& (ConversionFlags & ConversionFlags.ShowReturnType) == ConversionFlags.ShowReturnType)
 			{
-				var rt = node.GetChildByRole(Roles.Type);
+				var rt = node.GetChildByRole<AstType>(SlotKind.Type);
 				if (rt is not null)
 				{
 					rt.AcceptVisitor(new CSharpOutputVisitor(writer, formattingPolicy));
@@ -150,7 +150,7 @@ namespace ICSharpCode.Decompiler.CSharp.OutputVisitor
 				}
 				else
 				{
-					parameters = node.GetChildrenByRole(Roles.Parameter);
+					parameters = node.GetChildrenByRole<ParameterDeclaration>(SlotKind.Parameter);
 				}
 				foreach (var param in parameters)
 				{
@@ -181,7 +181,7 @@ namespace ICSharpCode.Decompiler.CSharp.OutputVisitor
 			if ((ConversionFlags & ConversionFlags.PlaceReturnTypeAfterParameterList) == ConversionFlags.PlaceReturnTypeAfterParameterList
 				&& (ConversionFlags & ConversionFlags.ShowReturnType) == ConversionFlags.ShowReturnType)
 			{
-				var rt = node.GetChildByRole(Roles.Type);
+				var rt = node.GetChildByRole<AstType>(SlotKind.Type);
 				if (rt is not null)
 				{
 					writer.Space();
@@ -309,7 +309,7 @@ namespace ICSharpCode.Decompiler.CSharp.OutputVisitor
 			else
 			{
 				writer.WriteIdentifier(node.NameToken);
-				WriteTypeParameters(node.GetChildrenByRole(Roles.TypeParameter), writer, formattingPolicy);
+				WriteTypeParameters(node.GetChildrenByRole<TypeParameterDeclaration>(SlotKind.TypeParameter), writer, formattingPolicy);
 			}
 		}
 
@@ -412,7 +412,7 @@ namespace ICSharpCode.Decompiler.CSharp.OutputVisitor
 					writer.WriteIdentifier(Identifier.Create(name));
 					break;
 			}
-			WriteTypeParameters(node.GetChildrenByRole(Roles.TypeParameter), writer, formattingPolicy);
+			WriteTypeParameters(node.GetChildrenByRole<TypeParameterDeclaration>(SlotKind.TypeParameter), writer, formattingPolicy);
 		}
 
 		void WriteTypeParameters(IEnumerable<TypeParameterDeclaration> typeParameters, TokenWriter writer, CSharpFormattingOptions formattingPolicy)

ICSharpCode.Decompiler/CSharp/OutputVisitor/CSharpOutputVisitor.cs

@@ -1910,7 +1910,7 @@ namespace ICSharpCode.Decompiler.CSharp.OutputVisitor
 		public virtual void VisitLabelStatement(LabelStatement labelStatement)
 		{
 			StartNode(labelStatement);
-			WriteIdentifier(labelStatement.GetChildByRole(Roles.Identifier));
+			WriteIdentifier(labelStatement.GetChildByRole<Identifier>(SlotKind.Identifier));
 			WriteToken(Roles.Colon);
 			bool foundLabelledStatement = false;
 			for (AstNode tmp = labelStatement.NextSibling; tmp != null; tmp = tmp.NextSibling)

ICSharpCode.Decompiler/CSharp/OutputVisitor/InsertMissingTokensDecorator.cs

@@ -91,8 +91,11 @@ namespace ICSharpCode.Decompiler.CSharp.OutputVisitor
 				foreach (var child in currentList)
 				{
 					System.Diagnostics.Debug.Assert(child.Parent == null || node == child.Parent);
+					// Slot is derived from the child's index in its parent, so it must be read before
+					// Remove() detaches the child (which would otherwise leave it as SlotKind.None).
+					SlotKind kind = child.Slot?.Kind ?? SlotKind.None;
 					child.Remove();
-					node.AddChildWithExistingRole(child);
+					node.AddChildUnsafe(child, kind);
 				}
 				currentList = nodes.Pop();
 			}

ICSharpCode.Decompiler/CSharp/Syntax/AstNode.cs

@@ -40,22 +40,15 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 	[DecompilerAstNode(hasNullNode: true, hasPatternPlaceholder: true)]
 	public abstract partial class AstNode : AbstractAnnotatable, IFreezable, INode, ICloneable
 	{
-		// the Root role must be available when creating the null nodes, so we can't put it in the Roles class
-		internal static readonly Role<AstNode?> RootRole = new Role<AstNode?>("Root", null);
-
 		AstNode? parent;
 		// Flattened index of this node within its parent's child-index space (-1 when unparented).
 		// Recomputed lazily by the parent (EnsureChildIndices) after a structural mutation.
 		internal int childIndex = -1;
 
-		// Flags, from least significant to most significant bits:
-		// - Role.RoleIndexBits: role index
-		protected uint flags = RootRole.Index;
-		// Derived classes may also use a few bits,
-		// for example Identifier uses 1 bit for IsVerbatim
+		// Flag bits used by derived classes (e.g. Identifier uses 1 bit for IsVerbatim).
+		protected uint flags = 0;
 
-		const uint roleIndexMask = (1u << Role.RoleIndexBits) - 1;
-		protected const int AstNodeFlagsUsedBits = Role.RoleIndexBits;
+		protected const int AstNodeFlagsUsedBits = 0;
 
 		TextLocation startLocation = TextLocation.Empty;
 		TextLocation endLocation = TextLocation.Empty;
@@ -158,28 +151,6 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 			get { return parent; }
 		}
 
-		public Role Role {
-			get {
-				return Role.GetByIndex(flags & roleIndexMask);
-			}
-			set {
-				if (value == null)
-					throw new ArgumentNullException(nameof(value));
-				if (!value.IsValid(this))
-					throw new ArgumentException("This node is not valid in the new role.");
-				SetRole(value);
-			}
-		}
-
-		internal uint RoleIndex {
-			get { return flags & roleIndexMask; }
-		}
-
-		void SetRole(Role role)
-		{
-			flags = (flags & ~roleIndexMask) | role.Index;
-		}
-
 		public AstNode? NextSibling {
 			get {
 				if (parent == null)
@@ -336,20 +307,18 @@ 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>(SlotKind kind) where T : AstNode?
 		{
-			if (role == null)
-				throw new ArgumentNullException(nameof(role));
 			int count = GetChildCount();
 			for (int i = 0; i < count; i++)
 			{
-				if (GetChildSlot(i) == role)
+				if (GetChildSlotInfo(i).Kind == kind)
 				{
 					AstNode? c = GetChild(i);
-					return c != null ? (T)c : role.NullObject;
+					return c != null ? (T)c : default!;
 				}
 			}
-			return role.NullObject;
+			return default!;
 		}
 
 		public T? GetParent<T>() where T : AstNode
@@ -362,20 +331,18 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 			return pred != null ? Ancestors.FirstOrDefault(pred) : Ancestors.FirstOrDefault();
 		}
 
-		public AstNodeCollection<T> GetChildrenByRole<T>(Role<T> role) where T : AstNode
+		public AstNodeCollection<T> GetChildrenByRole<T>(SlotKind kind) where T : AstNode
 		{
-			if (role == null)
-				throw new ArgumentNullException(nameof(role));
-			AstNodeCollection? collection = GetCollectionByRole(role);
-			// A node has no children of a role it does not declare a collection slot for. Reads of such
-			// a role (e.g. the parameters of a non-indexer property) get a detached empty collection;
-			// writes go through AddChild/SetChildByRole, which reject a missing role.
-			return collection != null ? (AstNodeCollection<T>)collection : new AstNodeCollection<T>(this, role);
+			AstNodeCollection? collection = GetCollectionByKind(kind);
+			// A node has no children of a kind it does not declare a collection slot for. Reads of such
+			// a kind (e.g. the parameters of a non-indexer property) get a detached empty collection;
+			// writes go through AddChild/SetChildByRole, which reject a missing slot.
+			return collection != null ? (AstNodeCollection<T>)collection : new AstNodeCollection<T>(this, kind);
 		}
 
-		protected void SetChildByRole<T>(Role<T> role, T? newChild) where T : AstNode
+		protected void SetChildByRole<T>(SlotKind kind, T? newChild) where T : AstNode
 		{
-			SetChildByRoleUntyped(role, newChild);
+			SetChildByRoleUntyped(kind, newChild);
 		}
 
 		#region Slot storage contract
@@ -391,8 +358,6 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 
 		internal virtual void SetChild(int index, AstNode? value) => throw new ArgumentOutOfRangeException(nameof(index));
 
-		internal virtual Role GetChildSlot(int index) => throw new ArgumentOutOfRangeException(nameof(index));
-
 		// The CSharpSlotInfo for the slot at the given flattened index; generator-emitted per leaf.
 		internal virtual CSharpSlotInfo GetChildSlotInfo(int index) => throw new ArgumentOutOfRangeException(nameof(index));
 
@@ -409,9 +374,9 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 			}
 		}
 
-		// Returns the collection occupying the slot with the given role, or null if there is none.
+		// Returns the collection occupying the slot with the given kind, or null if there is none.
 		// Overridden by the generator for nodes that have collection slots.
-		internal virtual AstNodeCollection? GetCollectionByRole(Role role) => null;
+		internal virtual AstNodeCollection? GetCollectionByKind(SlotKind kind) => null;
 
 		// Deep-copies this node's children into the (memberwise-cloned) copy, which initially shares
 		// this node's child references. Overridden by the generator for nodes that have slots.
@@ -465,14 +430,14 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 					continue; // empty optional single slot
 				Debug.Assert(child.parent == this, "child's Parent must point back to this node");
 				Debug.Assert(child.childIndex == i, "child's flattened index must match its slot position");
-				Debug.Assert(GetChildSlot(i).IsValid(child), "child's type must be valid in its slot's role");
+				Debug.Assert(GetChildSlotInfo(i).ChildType.IsInstanceOfType(child), "child's type must be valid in its slot");
 				child.CheckInvariant();
 			}
 		}
 
 		// Writes a single-slot backing field: detaches the old child, attaches the new one, renumbers.
 		// A null or null-object value empties the slot. Called by generated single-slot property setters.
-		internal void SetChildNode<T>(ref T? field, T? value, Role role) where T : AstNode
+		internal void SetChildNode<T>(ref T? field, T? value) where T : AstNode
 		{
 			T? newValue = value;
 			if (field == newValue)
@@ -493,14 +458,13 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 			}
 			field?.ClearParentAndIndex();
 			field = newValue;
-			newValue?.SetParentAndRole(this, role);
+			newValue?.SetParent(this);
 			InvalidateChildIndices();
 		}
 
-		internal void SetParentAndRole(AstNode newParent, Role role)
+		internal void SetParent(AstNode newParent)
 		{
 			parent = newParent;
-			SetRole(role);
 		}
 
 		internal void ClearParentAndIndex()
@@ -510,85 +474,72 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 		}
 		#endregion
 
-		public void AddChild<T>(T child, Role<T> role) where T : AstNode
-		{
-			if (role == null)
-				throw new ArgumentNullException(nameof(role));
-			if (child == null)
-				return;
-			AddChildUnsafe(child, role);
-		}
-
-		public void AddChildWithExistingRole(AstNode? child)
+		public void AddChild<T>(T child, SlotKind kind) where T : AstNode
 		{
 			if (child == null)
 				return;
-			AddChildUnsafe(child, child.Role);
+			AddChildUnsafe(child, kind);
 		}
 
 		/// <summary>
-		/// Adds a child into the slot matching <paramref name="role"/> (appending to a collection slot,
+		/// Adds a child into the slot matching <paramref name="kind"/> (appending to a collection slot,
 		/// or filling a single slot).
 		/// </summary>
-		internal void AddChildUnsafe(AstNode child, Role role)
+		internal void AddChildUnsafe(AstNode child, SlotKind kind)
 		{
-			AstNodeCollection? collection = GetCollectionByRole(role);
+			AstNodeCollection? collection = GetCollectionByKind(kind);
 			if (collection != null)
 				collection.AddNode(child);
 			else
-				SetChildByRoleUntyped(role, child);
+				SetChildByRoleUntyped(kind, child);
 		}
 
 		// Sets the single slot matching the role (used by the non-generic mutation API). Symmetric with
 		// GetChildByRole, which returns the null object for a role this node does not declare a slot for:
 		// a node has no child of a role it has no slot for, so writing one is a no-op.
-		internal void SetChildByRoleUntyped(Role role, AstNode? child)
+		internal void SetChildByRoleUntyped(SlotKind kind, AstNode? child)
 		{
 			int count = GetChildCount();
 			for (int i = 0; i < count; i++)
 			{
-				if (GetChildSlot(i) == role)
+				if (GetChildSlotInfo(i).Kind == kind)
 				{
 					SetChild(i, child);
 					return;
 				}
 			}
-			throw new InvalidOperationException($"{GetType().Name} has no slot for role '{role}'.");
+			throw new InvalidOperationException($"{GetType().Name} has no slot of kind '{kind}'.");
 		}
 
-		public void InsertChildBefore<T>(AstNode? nextSibling, T child, Role<T> role) where T : AstNode
+		public void InsertChildBefore<T>(AstNode? nextSibling, T child, SlotKind kind) where T : AstNode
 		{
-			if (role == null)
-				throw new ArgumentNullException(nameof(role));
 			if (child == null)
 				return;
-			AstNodeCollection? collection = GetCollectionByRole(role);
+			AstNodeCollection? collection = GetCollectionByKind(kind);
 			if (collection != null)
 				collection.InsertNodeBefore(nextSibling, child);
 			else
-				SetChildByRoleUntyped(role, child);
+				SetChildByRoleUntyped(kind, child);
 		}
 
-		internal void InsertChildBeforeUnsafe(AstNode nextSibling, AstNode child, Role role)
+		internal void InsertChildBeforeUnsafe(AstNode nextSibling, AstNode child, SlotKind kind)
 		{
-			AstNodeCollection? collection = GetCollectionByRole(role);
+			AstNodeCollection? collection = GetCollectionByKind(kind);
 			if (collection != null)
 				collection.InsertNodeBefore(nextSibling, child);
 			else
-				SetChildByRoleUntyped(role, child);
+				SetChildByRoleUntyped(kind, child);
 		}
 
-		public void InsertChildAfter<T>(AstNode? prevSibling, T child, Role<T> role) where T : AstNode
+		public void InsertChildAfter<T>(AstNode? prevSibling, T child, SlotKind kind) where T : AstNode
 		{
-			if (role == null)
-				throw new ArgumentNullException(nameof(role));
 			if (child == null)
 				return;
-			AstNodeCollection? collection = GetCollectionByRole(role);
+			AstNodeCollection? collection = GetCollectionByKind(kind);
 			if (collection != null)
 				collection.InsertNodeAfter(prevSibling, child);
 			else
-				SetChildByRoleUntyped(role, child);
+				SetChildByRoleUntyped(kind, child);
 		}
 
 		/// <summary>
@@ -599,8 +550,8 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 			if (parent == null)
 				return;
 			parent.EnsureChildIndices();
-			Role role = parent.GetChildSlot(childIndex);
-			AstNodeCollection? collection = parent.GetCollectionByRole(role);
+			SlotKind kind = parent.GetChildSlotInfo(childIndex).Kind;
+			AstNodeCollection? collection = parent.GetCollectionByKind(kind);
 			if (collection != null)
 				collection.RemoveNode(this);
 			else
@@ -624,12 +575,12 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 				throw new InvalidOperationException("Cannot replace the root node");
 			}
 			parent.EnsureChildIndices();
-			Role role = parent.GetChildSlot(childIndex);
-			// Because this method doesn't statically check the new node's type with the role,
+			CSharpSlotInfo slot = parent.GetChildSlotInfo(childIndex);
+			// Because this method doesn't statically check the new node's type with the slot,
 			// we perform a runtime test:
-			if (!role.IsValid(newNode))
+			if (!slot.ChildType.IsInstanceOfType(newNode))
 			{
-				throw new ArgumentException(string.Format("The new node '{0}' is not valid in the role {1}", newNode.GetType().Name, role.ToString()), nameof(newNode));
+				throw new ArgumentException(string.Format("The new node '{0}' is not valid in the slot {1}", newNode.GetType().Name, slot.ToString()), nameof(newNode));
 			}
 			if (newNode.parent != null)
 			{
@@ -658,7 +609,8 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 			}
 			AstNode oldParent = parent;
 			AstNode? oldSuccessor = NextSibling;
-			Role oldRole = this.Role;
+			CSharpSlotInfo? oldSlot = this.Slot;
+			SlotKind oldKind = oldSlot?.Kind ?? SlotKind.None;
 			Remove();
 			AstNode? replacement = replaceFunction(this);
 			if (oldSuccessor != null && oldSuccessor.parent != oldParent)
@@ -667,15 +619,15 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 			{
 				if (replacement.parent != null)
 					throw new InvalidOperationException("replace function must return the root of a tree");
-				if (!oldRole.IsValid(replacement))
+				if (oldSlot != null && !oldSlot.ChildType.IsInstanceOfType(replacement))
 				{
-					throw new InvalidOperationException(string.Format("The new node '{0}' is not valid in the role {1}", replacement.GetType().Name, oldRole.ToString()));
+					throw new InvalidOperationException(string.Format("The new node '{0}' is not valid in the slot {1}", replacement.GetType().Name, oldSlot.ToString()));
 				}
 
 				if (oldSuccessor != null)
-					oldParent.InsertChildBeforeUnsafe(oldSuccessor, replacement, oldRole);
+					oldParent.InsertChildBeforeUnsafe(oldSuccessor, replacement, oldKind);
 				else
-					oldParent.AddChildUnsafe(replacement, oldRole);
+					oldParent.AddChildUnsafe(replacement, oldKind);
 			}
 			return replacement;
 		}
@@ -786,17 +738,10 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 				prev = prev.GetPrevNode();
 			return prev;
 		}
-		// filters all non c# nodes (comments, white spaces or pre processor directives)
+		// Comments and directives are trivia, not sibling nodes, so the previous sibling is always a C# node.
 		public AstNode? GetCSharpNodeBefore(AstNode node)
 		{
-			var n = node.PrevSibling;
-			while (n != null)
-			{
-				if (n.Role != Roles.Comment)
-					return n;
-				n = n.GetPrevNode();
-			}
-			return null;
+			return node.PrevSibling;
 		}
 
 		/// <summary>

ICSharpCode.Decompiler/CSharp/Syntax/AstNodeCollection.cs

@@ -72,13 +72,13 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 		where T : AstNode
 	{
 		readonly AstNode parent;
-		readonly Role<T> role;
+		readonly SlotKind kind;
 		readonly List<T> list = new List<T>();
 
-		public AstNodeCollection(AstNode parent, Role<T> role)
+		public AstNodeCollection(AstNode parent, SlotKind kind)
 		{
 			this.parent = parent ?? throw new ArgumentNullException(nameof(parent));
-			this.role = role ?? throw new ArgumentNullException(nameof(role));
+			this.kind = kind;
 		}
 
 		public int Count {
@@ -97,7 +97,7 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 				ValidateNewChild(value);
 				old.ClearParentAndIndex();
 				list[index] = value;
-				value.SetParentAndRole(parent, role);
+				value.SetParent(parent);
 				parent.InvalidateChildIndices();
 			}
 		}
@@ -118,7 +118,7 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 				return;
 			ValidateNewChild(element);
 			list.Add(element);
-			element.SetParentAndRole(parent, role);
+			element.SetParent(parent);
 			parent.InvalidateChildIndices();
 		}
 
@@ -169,7 +169,7 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 
 		public bool Contains(T element)
 		{
-			return element != null && element.Parent == parent && element.RoleIndex == role.Index;
+			return element != null && element.Parent == parent && list.Contains(element);
 		}
 
 		public int IndexOf(T element)
@@ -247,7 +247,7 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 			foreach (T item in list)
 				if (predicate == null || predicate(item))
 					return item;
-			return role.NullObject;
+			return null!;
 		}
 
 		/// <summary>
@@ -256,7 +256,7 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 		/// </summary>
 		public T LastOrNullObject(Func<T, bool>? predicate = null)
 		{
-			T result = role.NullObject;
+			T result = null!;
 			foreach (T item in list)
 				if (predicate == null || predicate(item))
 					result = item;
@@ -289,12 +289,12 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 		#region Equals and GetHashCode implementation
 		public override int GetHashCode()
 		{
-			return parent.GetHashCode() ^ role.GetHashCode();
+			return parent.GetHashCode() ^ kind.GetHashCode();
 		}
 
 		public override bool Equals(object? obj)
 		{
-			return obj is AstNodeCollection<T> other && this.parent == other.parent && this.role == other.role;
+			return obj is AstNodeCollection<T> other && this.parent == other.parent && this.kind == other.kind;
 		}
 		#endregion
 
@@ -322,7 +322,7 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 				return;
 			ValidateNewChild(newItem);
 			list.Insert(index, newItem);
-			newItem.SetParentAndRole(parent, role);
+			newItem.SetParent(parent);
 			parent.InvalidateChildIndices();
 		}
 

ICSharpCode.Decompiler/CSharp/Syntax/ComposedType.cs

@@ -41,12 +41,10 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 	[DecompilerAstNode(hasNullNode: false)]
 	public partial class ComposedType : AstType
 	{
-		public static readonly Role<AttributeSection> AttributeRole = EntityDeclaration.AttributeRole;
 		public static readonly TokenRole RefRole = new TokenRole("ref");
 		public static readonly TokenRole ReadonlyRole = new TokenRole("readonly");
 		public static readonly TokenRole NullableRole = new TokenRole("?");
 		public static readonly TokenRole PointerRole = new TokenRole("*");
-		public static readonly Role<ArraySpecifier> ArraySpecifierRole = new Role<ArraySpecifier>("ArraySpecifier", null);
 		[Slot("AttributeRole")]
 		public partial AstNodeCollection<AttributeSection> Attributes { get; }
 
@@ -120,7 +118,7 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 
 		public override AstType MakeArrayType(int dimensions)
 		{
-			InsertChildBefore(this.ArraySpecifiers.FirstOrDefault(), new ArraySpecifier(dimensions), ArraySpecifierRole);
+			InsertChildBefore(this.ArraySpecifiers.FirstOrDefault(), new ArraySpecifier(dimensions), SlotKind.ArraySpecifier);
 			return this;
 		}
 

ICSharpCode.Decompiler/CSharp/Syntax/DocumentationReference.cs

@@ -34,8 +34,6 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 	[DecompilerAstNode(hasNullNode: false)]
 	public partial class DocumentationReference : AstNode
 	{
-		public static readonly Role<AstType> DeclaringTypeRole = new Role<AstType>("DeclaringType", null);
-		public static readonly Role<AstType> ConversionOperatorReturnTypeRole = new Role<AstType>("ConversionOperatorReturnType", null);
 
 		SymbolKind symbolKind;
 		OperatorType operatorType;

ICSharpCode.Decompiler/CSharp/Syntax/Expressions/AnonymousMethodExpression.cs

@@ -70,10 +70,10 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 				hasParameterList = true;
 				foreach (var parameter in parameters)
 				{
-					AddChild(parameter, Roles.Parameter);
+					AddChild(parameter, SlotKind.Parameter);
 				}
 			}
-			AddChild(body, Roles.Body);
+			AddChild(body, SlotKind.Body);
 		}
 
 		public AnonymousMethodExpression(BlockStatement body, params ParameterDeclaration[] parameters) : this(body, (IEnumerable<ParameterDeclaration>)parameters)

ICSharpCode.Decompiler/CSharp/Syntax/Expressions/AnonymousTypeCreateExpression.cs

@@ -46,7 +46,7 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 		{
 			foreach (var ini in initializers)
 			{
-				AddChild(ini, Roles.Expression);
+				AddChild(ini, SlotKind.Expression);
 			}
 		}
 

ICSharpCode.Decompiler/CSharp/Syntax/Expressions/ArrayCreateExpression.cs

@@ -27,8 +27,6 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 	public partial class ArrayCreateExpression : Expression
 	{
 		public readonly static TokenRole NewKeywordRole = new TokenRole("new");
-		public readonly static Role<ArraySpecifier> AdditionalArraySpecifierRole = new Role<ArraySpecifier>("AdditionalArraySpecifier", null);
-		public readonly static Role<ArrayInitializerExpression> InitializerRole = new Role<ArrayInitializerExpression>("Initializer", null);
 
 		[Slot("Roles.Type")]
 		public partial AstType? Type { get; set; }

ICSharpCode.Decompiler/CSharp/Syntax/Expressions/AsExpression.cs

@@ -46,8 +46,8 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 
 		public AsExpression(Expression expression, AstType type)
 		{
-			AddChild(expression, Roles.Expression);
-			AddChild(type, Roles.Type);
+			AddChild(expression, SlotKind.Expression);
+			AddChild(type, SlotKind.Type);
 		}
 	}
 }

ICSharpCode.Decompiler/CSharp/Syntax/Expressions/AssignmentExpression.cs

@@ -38,8 +38,6 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 	public partial class AssignmentExpression : Expression
 	{
 		// reuse roles from BinaryOperatorExpression
-		public readonly static Role<Expression> LeftRole = BinaryOperatorExpression.LeftRole;
-		public readonly static Role<Expression> RightRole = BinaryOperatorExpression.RightRole;
 
 		public readonly static TokenRole AssignRole = new TokenRole("=");
 		public readonly static TokenRole AddRole = new TokenRole("+=");

ICSharpCode.Decompiler/CSharp/Syntax/Expressions/BinaryOperatorExpression.cs

@@ -62,8 +62,6 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 		public readonly static TokenRole RangeRole = new TokenRole("..");
 		public readonly static TokenRole IsKeywordRole = IsExpression.IsKeywordRole;
 
-		public readonly static Role<Expression> LeftRole = new Role<Expression>("Left", null);
-		public readonly static Role<Expression> RightRole = new Role<Expression>("Right", null);
 
 		public BinaryOperatorExpression()
 		{
@@ -81,10 +79,10 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 			set;
 		}
 
-		[Slot(nameof(LeftRole))]
+		[Slot("LeftRole")]
 		public partial Expression? Left { get; set; }
 
-		[Slot(nameof(RightRole))]
+		[Slot("RightRole")]
 		public partial Expression? Right { get; set; }
 
 		public static TokenRole GetOperatorRole(BinaryOperatorType op)

ICSharpCode.Decompiler/CSharp/Syntax/Expressions/CastExpression.cs

@@ -43,8 +43,8 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 
 		public CastExpression(AstType castToType, Expression expression)
 		{
-			AddChild(castToType, Roles.Type);
-			AddChild(expression, Roles.Expression);
+			AddChild(castToType, SlotKind.Type);
+			AddChild(expression, SlotKind.Expression);
 		}
 	}
 }

ICSharpCode.Decompiler/CSharp/Syntax/Expressions/CheckedExpression.cs

@@ -43,7 +43,7 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 
 		public CheckedExpression(Expression expression)
 		{
-			AddChild(expression, Roles.Expression);
+			AddChild(expression, SlotKind.Expression);
 		}
 	}
 }

ICSharpCode.Decompiler/CSharp/Syntax/Expressions/ConditionalExpression.cs

@@ -32,11 +32,8 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 	[DecompilerAstNode(hasNullNode: false)]
 	public partial class ConditionalExpression : Expression
 	{
-		public readonly static Role<Expression> ConditionRole = Roles.Condition;
 		public readonly static TokenRole QuestionMarkRole = new TokenRole("?");
-		public readonly static Role<Expression> TrueRole = new Role<Expression>("True", null);
 		public readonly static TokenRole ColonRole = Roles.Colon;
-		public readonly static Role<Expression> FalseRole = new Role<Expression>("False", null);
 
 		[Slot("ConditionRole")]
 		public partial Expression Condition { get; set; }
@@ -53,9 +50,9 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 
 		public ConditionalExpression(Expression condition, Expression trueExpression, Expression falseExpression)
 		{
-			AddChild(condition, ConditionRole);
-			AddChild(trueExpression, TrueRole);
-			AddChild(falseExpression, FalseRole);
+			AddChild(condition, SlotKind.Condition);
+			AddChild(trueExpression, SlotKind.True);
+			AddChild(falseExpression, SlotKind.False);
 		}
 	}
 }

ICSharpCode.Decompiler/CSharp/Syntax/Expressions/DefaultValueExpression.cs

@@ -43,7 +43,7 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 
 		public DefaultValueExpression(AstType type)
 		{
-			AddChild(type, Roles.Type);
+			AddChild(type, SlotKind.Type);
 		}
 	}
 }

ICSharpCode.Decompiler/CSharp/Syntax/Expressions/DirectionExpression.cs

@@ -59,7 +59,7 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 		public DirectionExpression(FieldDirection direction, Expression expression)
 		{
 			this.FieldDirection = direction;
-			AddChild(expression, Roles.Expression);
+			AddChild(expression, SlotKind.Expression);
 		}
 	}
 }

ICSharpCode.Decompiler/CSharp/Syntax/Expressions/IdentifierExpression.cs

@@ -43,7 +43,7 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 
 		public IdentifierExpression(string identifier, TextLocation location)
 		{
-			SetChildByRole(Roles.Identifier, Decompiler.CSharp.Syntax.Identifier.Create(identifier, location));
+			SetChildByRole(SlotKind.Identifier, Decompiler.CSharp.Syntax.Identifier.Create(identifier, location));
 		}
 
 		[NameSlot("Roles.Identifier")]

ICSharpCode.Decompiler/CSharp/Syntax/Expressions/IndexerExpression.cs

@@ -53,7 +53,7 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 			{
 				foreach (var arg in arguments)
 				{
-					AddChild(arg, Roles.Argument);
+					AddChild(arg, SlotKind.Argument);
 				}
 			}
 		}

ICSharpCode.Decompiler/CSharp/Syntax/Expressions/InterpolatedStringExpression.cs

@@ -36,7 +36,6 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 	[DecompilerAstNode(hasNullNode: true)]
 	public abstract partial class InterpolatedStringContent : AstNode
 	{
-		public new static readonly Role<InterpolatedStringContent> Role = new Role<InterpolatedStringContent>("InterpolatedStringContent", null);
 
 	}
 

ICSharpCode.Decompiler/CSharp/Syntax/Expressions/InvocationExpression.cs

@@ -46,12 +46,12 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 
 		public InvocationExpression(Expression target, IEnumerable<Expression> arguments)
 		{
-			AddChild(target, Roles.TargetExpression);
+			AddChild(target, SlotKind.TargetExpression);
 			if (arguments != null)
 			{
 				foreach (var arg in arguments)
 				{
-					AddChild(arg, Roles.Argument);
+					AddChild(arg, SlotKind.Argument);
 				}
 			}
 		}

ICSharpCode.Decompiler/CSharp/Syntax/Expressions/IsExpression.cs

@@ -47,8 +47,8 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 
 		public IsExpression(Expression expression, AstType type)
 		{
-			AddChild(expression, Roles.Expression);
-			AddChild(type, Roles.Type);
+			AddChild(expression, SlotKind.Expression);
+			AddChild(type, SlotKind.Type);
 		}
 	}
 }

ICSharpCode.Decompiler/CSharp/Syntax/Expressions/LambdaExpression.cs

@@ -32,9 +32,7 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 	[DecompilerAstNode(hasNullNode: false)]
 	public partial class LambdaExpression : Expression
 	{
-		public static readonly Role<AttributeSection> AttributeRole = new Role<AttributeSection>("Attribute", null);
 		public readonly static TokenRole AsyncModifierRole = new TokenRole("async");
-		public static readonly Role<AstNode> BodyRole = new Role<AstNode>("Body", null);
 
 		bool isAsync;
 

ICSharpCode.Decompiler/CSharp/Syntax/Expressions/MemberReferenceExpression.cs

@@ -49,13 +49,13 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 
 		public MemberReferenceExpression(Expression target, string memberName, IEnumerable<AstType> arguments = null)
 		{
-			AddChild(target, Roles.TargetExpression);
+			AddChild(target, SlotKind.TargetExpression);
 			MemberName = memberName;
 			if (arguments != null)
 			{
 				foreach (var arg in arguments)
 				{
-					AddChild(arg, Roles.TypeArgument);
+					AddChild(arg, SlotKind.TypeArgument);
 				}
 			}
 		}

ICSharpCode.Decompiler/CSharp/Syntax/Expressions/ObjectCreateExpression.cs

@@ -37,7 +37,6 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 	public partial class ObjectCreateExpression : Expression
 	{
 		public readonly static TokenRole NewKeywordRole = new TokenRole("new");
-		public readonly static Role<ArrayInitializerExpression> InitializerRole = ArrayCreateExpression.InitializerRole;
 
 		[Slot("Roles.Type")]
 		public partial AstType Type { get; set; }
@@ -54,12 +53,12 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 
 		public ObjectCreateExpression(AstType type, IEnumerable<Expression>? arguments = null)
 		{
-			AddChild(type, Roles.Type);
+			AddChild(type, SlotKind.Type);
 			if (arguments != null)
 			{
 				foreach (var arg in arguments)
 				{
-					AddChild(arg, Roles.Argument);
+					AddChild(arg, SlotKind.Argument);
 				}
 			}
 		}

ICSharpCode.Decompiler/CSharp/Syntax/Expressions/QueryExpression.cs

@@ -26,7 +26,6 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 	[DecompilerAstNode(hasNullNode: true)]
 	public partial class QueryExpression : Expression
 	{
-		public static readonly Role<QueryClause> ClauseRole = new Role<QueryClause>("Clause", null);
 
 		[Slot("ClauseRole")]
 		public partial AstNodeCollection<QueryClause> Clauses { get; }
@@ -45,7 +44,6 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 	[DecompilerAstNode(hasNullNode: false)]
 	public partial class QueryContinuationClause : QueryClause
 	{
-		public static readonly Role<QueryExpression> PrecedingQueryRole = new Role<QueryExpression>("PrecedingQuery", null);
 		public static readonly TokenRole IntoKeywordRole = new TokenRole("into");
 
 		[Slot("PrecedingQueryRole")]
@@ -115,16 +113,10 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 	public partial class QueryJoinClause : QueryClause
 	{
 		public static readonly TokenRole JoinKeywordRole = new TokenRole("join");
-		public static readonly Role<AstType> TypeRole = Roles.Type;
-		public static readonly Role<Identifier> JoinIdentifierRole = Roles.Identifier;
 		public static readonly TokenRole InKeywordRole = new TokenRole("in");
-		public static readonly Role<Expression> InExpressionRole = Roles.Expression;
 		public static readonly TokenRole OnKeywordRole = new TokenRole("on");
-		public static readonly Role<Expression> OnExpressionRole = new Role<Expression>("OnExpression", null);
 		public static readonly TokenRole EqualsKeywordRole = new TokenRole("equals");
-		public static readonly Role<Expression> EqualsExpressionRole = new Role<Expression>("EqualsExpression", null);
 		public static readonly TokenRole IntoKeywordRole = new TokenRole("into");
-		public static readonly Role<Identifier> IntoIdentifierRole = new Role<Identifier>("IntoIdentifier", null);
 
 		// Derived from IntoIdentifier (which DoMatch already compares); exclude it to avoid a redundant compare.
 		[ExcludeFromMatch]
@@ -158,7 +150,6 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 	public partial class QueryOrderClause : QueryClause
 	{
 		public static readonly TokenRole OrderbyKeywordRole = new TokenRole("orderby");
-		public static readonly Role<QueryOrdering> OrderingRole = new Role<QueryOrdering>("Ordering", null);
 
 		[Slot("OrderingRole")]
 		public partial AstNodeCollection<QueryOrdering> Orderings { get; }
@@ -208,9 +199,7 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 	public partial class QueryGroupClause : QueryClause
 	{
 		public static readonly TokenRole GroupKeywordRole = new TokenRole("group");
-		public static readonly Role<Expression> ProjectionRole = new Role<Expression>("Projection", null);
 		public static readonly TokenRole ByKeywordRole = new TokenRole("by");
-		public static readonly Role<Expression> KeyRole = new Role<Expression>("Key", null);
 
 		[Slot("ProjectionRole")]
 		public partial Expression Projection { get; set; }

ICSharpCode.Decompiler/CSharp/Syntax/Expressions/RecursivePatternExpression.cs

@@ -31,7 +31,6 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 	[DecompilerAstNode(hasNullNode: false)]
 	public partial class RecursivePatternExpression : Expression
 	{
-		public static readonly Role<Expression> SubPatternRole = new Role<Expression>("SubPattern", null);
 
 		[Slot("Roles.Type")]
 		public partial AstType? Type { get; set; }

ICSharpCode.Decompiler/CSharp/Syntax/Expressions/SizeOfExpression.cs

@@ -43,7 +43,7 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 
 		public SizeOfExpression(AstType type)
 		{
-			AddChild(type, Roles.Type);
+			AddChild(type, SlotKind.Type);
 		}
 	}
 }

ICSharpCode.Decompiler/CSharp/Syntax/Expressions/StackAllocExpression.cs

@@ -42,7 +42,6 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 	public partial class StackAllocExpression : Expression
 	{
 		public readonly static TokenRole StackallocKeywordRole = new TokenRole("stackalloc");
-		public readonly static Role<ArrayInitializerExpression> InitializerRole = new Role<ArrayInitializerExpression>("Initializer", null);
 
 		[Slot("Roles.Type")]
 		public partial AstType? Type { get; set; }

ICSharpCode.Decompiler/CSharp/Syntax/Expressions/SwitchExpression.cs

@@ -26,7 +26,6 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 	public partial class SwitchExpression : Expression
 	{
 		public static readonly TokenRole SwitchKeywordRole = new TokenRole("switch");
-		public static readonly Role<SwitchExpressionSection> SwitchSectionRole = new Role<SwitchExpressionSection>("SwitchSection", null);
 
 		[Slot("Roles.Expression")]
 		public partial Expression Expression { get; set; }
@@ -41,8 +40,6 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 	[DecompilerAstNode(hasNullNode: false)]
 	public partial class SwitchExpressionSection : AstNode
 	{
-		public static readonly Role<Expression> PatternRole = new Role<Expression>("Pattern", null);
-		public static readonly Role<Expression> BodyRole = new Role<Expression>("Body", null);
 
 		[Slot("PatternRole")]
 		public partial Expression Pattern { get; set; }

ICSharpCode.Decompiler/CSharp/Syntax/Expressions/ThrowExpression.cs

@@ -35,7 +35,7 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 
 		public ThrowExpression(Expression expression)
 		{
-			AddChild(expression, Roles.Expression);
+			AddChild(expression, SlotKind.Expression);
 		}
 	}
 }

ICSharpCode.Decompiler/CSharp/Syntax/Expressions/TypeOfExpression.cs

@@ -43,7 +43,7 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 
 		public TypeOfExpression(AstType type)
 		{
-			AddChild(type, Roles.Type);
+			AddChild(type, SlotKind.Type);
 		}
 	}
 }

ICSharpCode.Decompiler/CSharp/Syntax/Expressions/TypeReferenceExpression.cs

@@ -34,7 +34,7 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 
 		public TypeReferenceExpression(AstType type)
 		{
-			AddChild(type, Roles.Type);
+			AddChild(type, SlotKind.Type);
 		}
 	}
 }

ICSharpCode.Decompiler/CSharp/Syntax/Expressions/UncheckedExpression.cs

@@ -43,7 +43,7 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 
 		public UncheckedExpression(Expression expression)
 		{
-			AddChild(expression, Roles.Expression);
+			AddChild(expression, SlotKind.Expression);
 		}
 	}
 }

ICSharpCode.Decompiler/CSharp/Syntax/Expressions/WithInitializerExpression.cs

@@ -26,7 +26,6 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 	public partial class WithInitializerExpression : Expression
 	{
 		public readonly static TokenRole WithKeywordRole = new TokenRole("with");
-		public readonly static Role<ArrayInitializerExpression> InitializerRole = ArrayCreateExpression.InitializerRole;
 
 		[Slot("Roles.Expression")]
 		public partial Expression Expression { get; set; }

ICSharpCode.Decompiler/CSharp/Syntax/FunctionPointerAstType.cs

@@ -33,7 +33,6 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 	public partial class FunctionPointerAstType : AstType
 	{
 		public static readonly TokenRole PointerRole = new TokenRole("*");
-		public static readonly Role<AstType> CallingConventionRole = new Role<AstType>("CallConv", null);
 
 		public bool HasUnmanagedCallingConvention { get; set; }
 

ICSharpCode.Decompiler/CSharp/Syntax/GeneralScope/AttributeSection.cs

@@ -35,10 +35,10 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 
 		public string AttributeTarget {
 			get {
-				return GetChildByRole(Roles.Identifier)?.Name ?? string.Empty;
+				return GetChildByRole<Identifier>(SlotKind.Identifier)?.Name ?? string.Empty;
 			}
 			set {
-				SetChildByRole(Roles.Identifier, Identifier.Create(value));
+				SetChildByRole(SlotKind.Identifier, Identifier.Create(value));
 			}
 		}
 

ICSharpCode.Decompiler/CSharp/Syntax/GeneralScope/NamespaceDeclaration.cs

@@ -39,8 +39,6 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 	[DecompilerAstNode(hasNullNode: false)]
 	public partial class NamespaceDeclaration : AstNode
 	{
-		public static readonly Role<AstNode> MemberRole = SyntaxTree.MemberRole;
-		public static readonly Role<AstType> NamespaceNameRole = new Role<AstType>("NamespaceName", null);
 
 		public bool IsFileScoped { get; set; }
 
@@ -123,7 +121,7 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 
 		public void AddMember(AstNode child)
 		{
-			AddChild(child, MemberRole);
+			AddChild(child, SlotKind.Member);
 		}
 	}
 };

ICSharpCode.Decompiler/CSharp/Syntax/GeneralScope/PreProcessorDirective.cs

@@ -67,7 +67,6 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 	[DecompilerAstNode(hasNullNode: false)]
 	public partial class PragmaWarningPreprocessorDirective : PreProcessorDirective
 	{
-		public static readonly Role<PrimitiveExpression> WarningRole = new Role<PrimitiveExpression>("Warning", null);
 
 		public static readonly TokenRole PragmaKeywordRole = new TokenRole("#pragma");
 		public static readonly TokenRole WarningKeywordRole = new TokenRole("warning");

ICSharpCode.Decompiler/CSharp/Syntax/GeneralScope/TypeParameterDeclaration.cs

@@ -29,7 +29,6 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 	[DecompilerAstNode(hasNullNode: false)]
 	public partial class TypeParameterDeclaration : AstNode
 	{
-		public static readonly Role<AttributeSection> AttributeRole = EntityDeclaration.AttributeRole;
 		public static readonly TokenRole OutVarianceKeywordRole = new TokenRole("out");
 		public static readonly TokenRole InVarianceKeywordRole = new TokenRole("in");
 

ICSharpCode.Decompiler/CSharp/Syntax/GeneralScope/UsingAliasDeclaration.cs

@@ -33,8 +33,6 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 	public partial class UsingAliasDeclaration : AstNode
 	{
 		public static readonly TokenRole UsingKeywordRole = new TokenRole("using");
-		public static readonly Role<Identifier> AliasRole = new Role<Identifier>("Alias", null);
-		public static readonly Role<AstType> ImportRole = UsingDeclaration.ImportRole;
 
 		[NameSlot("AliasRole")]
 		public partial string Alias { get; set; }
@@ -48,14 +46,14 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 
 		public UsingAliasDeclaration(string alias, string nameSpace)
 		{
-			AddChild(Identifier.Create(alias), AliasRole);
-			AddChild(new SimpleType(nameSpace), ImportRole);
+			AddChild(Identifier.Create(alias), SlotKind.Alias);
+			AddChild(new SimpleType(nameSpace), SlotKind.Import);
 		}
 
 		public UsingAliasDeclaration(string alias, AstType import)
 		{
-			AddChild(Identifier.Create(alias), AliasRole);
-			AddChild(import, ImportRole);
+			AddChild(Identifier.Create(alias), SlotKind.Alias);
+			AddChild(import, SlotKind.Import);
 		}
 	}
 }

ICSharpCode.Decompiler/CSharp/Syntax/GeneralScope/UsingDeclaration.cs

@@ -41,7 +41,6 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 	public partial class UsingDeclaration : AstNode
 	{
 		public static readonly TokenRole UsingKeywordRole = new TokenRole("using");
-		public static readonly Role<AstType> ImportRole = new Role<AstType>("Import", null);
 
 		[Slot("ImportRole")]
 		public partial AstType Import { get; set; }
@@ -84,12 +83,12 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 
 		public UsingDeclaration(string nameSpace)
 		{
-			AddChild(AstType.Create(nameSpace), ImportRole);
+			AddChild(AstType.Create(nameSpace), SlotKind.Import);
 		}
 
 		public UsingDeclaration(AstType import)
 		{
-			AddChild(import, ImportRole);
+			AddChild(import, SlotKind.Import);
 		}
 	}
 }

ICSharpCode.Decompiler/CSharp/Syntax/MemberType.cs

@@ -34,7 +34,6 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 	[DecompilerAstNode(hasNullNode: false)]
 	public partial class MemberType : AstType
 	{
-		public static readonly Role<AstType> TargetRole = new Role<AstType>("Target", null);
 
 		bool isDoubleColon;
 
@@ -70,7 +69,7 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 			this.MemberName = memberName;
 			foreach (var arg in typeArguments)
 			{
-				AddChild(arg, Roles.TypeArgument);
+				AddChild(arg, SlotKind.TypeArgument);
 			}
 		}
 

ICSharpCode.Decompiler/CSharp/Syntax/Role.cs

@@ -1,112 +0,0 @@
-// Copyright (c) 2010-2013 AlphaSierraPapa for the SharpDevelop Team
-// 
-// Permission is hereby granted, free of charge, to any person obtaining a copy of this
-// software and associated documentation files (the "Software"), to deal in the Software
-// without restriction, including without limitation the rights to use, copy, modify, merge,
-// publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons
-// to whom the Software is furnished to do so, subject to the following conditions:
-// 
-// The above copyright notice and this permission notice shall be included in all copies or
-// substantial portions of the Software.
-// 
-// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
-// INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
-// PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
-// FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
-// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
-// DEALINGS IN THE SOFTWARE.
-
-#nullable enable
-
-using System;
-using System.Threading;
-
-namespace ICSharpCode.Decompiler.CSharp.Syntax
-{
-	/// <summary>
-	/// Represents the role a node plays within its parent.
-	/// </summary>
-	public abstract class Role
-	{
-		public const int RoleIndexBits = 9;
-
-		static readonly Role[] roles = new Role[1 << RoleIndexBits];
-		static int nextRoleIndex = 0;
-
-		readonly uint index;
-
-		public uint Index {
-			get { return index; }
-		}
-
-		// don't allow NRefactory consumers to derive from Role
-		internal Role()
-		{
-			this.index = (uint)Interlocked.Increment(ref nextRoleIndex);
-			if (this.index >= roles.Length)
-				throw new InvalidOperationException("Too many roles");
-			roles[this.index] = this;
-		}
-
-		/// <summary>
-		/// Gets whether the specified node is valid in this role.
-		/// </summary>
-		public abstract bool IsValid(object node);
-
-		/// <summary>
-		/// Gets the role's null object as a non-generic reference, or null if the role has none.
-		/// Used by the transitional slot layer, which works with the non-generic <see cref="Role"/> base type.
-		/// </summary>
-		internal abstract object? NullObjectUntyped { get; }
-
-		/// <summary>
-		/// Gets the role with the specified index.
-		/// </summary>
-		public static Role GetByIndex(uint index)
-		{
-			return roles[index];
-		}
-	}
-
-	/// <summary>
-	/// Represents the role a node plays within its parent.
-	/// All nodes with this role have type T.
-	/// </summary>
-	public class Role<T> : Role where T : class?
-	{
-		readonly string name; // helps with debugging the AST
-		readonly T nullObject;
-
-		/// <summary>
-		/// Gets the null object used when there's no node with this role.
-		/// Not every role has a null object; this property returns null for roles without a null object.
-		/// </summary>
-		/// <remarks>
-		/// Roles used for non-collections should always have a null object, so that no AST property returns null.
-		/// However, if a role used for collections only, it may leave out the null object.
-		/// </remarks>
-		public T NullObject {
-			get { return nullObject; }
-		}
-
-		internal override object? NullObjectUntyped => nullObject;
-
-		public override bool IsValid(object node)
-		{
-			return node is T;
-		}
-
-		public Role(string name, T? nullObject)
-		{
-			this.name = name ?? throw new ArgumentNullException(nameof(name));
-			// Roles used only for collections may omit the null object (pass null); NullObject then
-			// returns null, matching the documented contract. Single-value roles always pass one.
-			this.nullObject = nullObject!;
-		}
-
-		public override string ToString()
-		{
-			return name;
-		}
-	}
-}

ICSharpCode.Decompiler/CSharp/Syntax/Roles.cs

@@ -28,25 +28,9 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 {
 	public static class Roles
 	{
-		public static readonly Role<AstNode> Root = AstNode.RootRole;
 
 		// some pre defined constants for common roles
-		public static readonly Role<Identifier> Identifier = new Role<Identifier>("Identifier", null);
-		public static readonly Role<BlockStatement> Body = new Role<BlockStatement>("Body", null);
-		public static readonly Role<ParameterDeclaration> Parameter = new Role<ParameterDeclaration>("Parameter", null);
-		public static readonly Role<Expression> Argument = new Role<Expression>("Argument", null);
-		public static readonly Role<AstType> Type = new Role<AstType>("Type", null);
-		public static readonly Role<Expression> Expression = new Role<Expression>("Expression", null);
-		public static readonly Role<Expression> TargetExpression = new Role<Expression>("Target", null);
-		public readonly static Role<Expression> Condition = new Role<Expression>("Condition", null);
-		public static readonly Role<TypeParameterDeclaration> TypeParameter = new Role<TypeParameterDeclaration>("TypeParameter", null);
-		public static readonly Role<AstType> TypeArgument = new Role<AstType>("TypeArgument", null);
-		public readonly static Role<Constraint> Constraint = new Role<Constraint>("Constraint", null);
-		public static readonly Role<VariableInitializer> Variable = new Role<VariableInitializer>("Variable", null);
-		public static readonly Role<Statement> EmbeddedStatement = new Role<Statement>("EmbeddedStatement", null);
-		public readonly static Role<EntityDeclaration> TypeMemberRole = new Role<EntityDeclaration>("TypeMember", null);
 
-		public static readonly Role<VariableDesignation> VariableDesignationRole = new Role<VariableDesignation>("VariableDesignation", null);
 
 		// some pre defined constants for most used punctuation
 		public static readonly TokenRole LPar = new TokenRole("(");
@@ -64,15 +48,10 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 		public static readonly TokenRole Colon = new TokenRole(":");
 		public static readonly TokenRole DoubleColon = new TokenRole("::");
 		public static readonly TokenRole Arrow = new TokenRole("=>");
-		public static readonly Role<Comment> Comment = new Role<Comment>("Comment", null);
-		public static readonly Role<PreProcessorDirective> PreProcessorDirective = new Role<PreProcessorDirective>("PreProcessorDirective", null);
 
-		public readonly static Role<AstType> BaseType = new Role<AstType>("BaseType", null);
 
-		public static readonly Role<Attribute> Attribute = new Role<Attribute>("Attribute", null);
 
 		public readonly static TokenRole WhereKeyword = new TokenRole("where");
-		public readonly static Role<SimpleType> ConstraintTypeParameter = new Role<SimpleType>("TypeParameter", null);
 		public readonly static TokenRole DelegateKeyword = new TokenRole("delegate");
 		public static readonly TokenRole ExternKeyword = new TokenRole("extern");
 		public static readonly TokenRole AliasKeyword = new TokenRole("alias");

ICSharpCode.Decompiler/CSharp/Syntax/SimpleType.cs

@@ -50,7 +50,7 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 
 		public SimpleType(string identifier, TextLocation location)
 		{
-			SetChildByRole(Roles.Identifier, Syntax.Identifier.Create(identifier, location));
+			SetChildByRole(SlotKind.Identifier, Syntax.Identifier.Create(identifier, location));
 		}
 
 		public SimpleType(string identifier, IEnumerable<AstType> typeArguments)
@@ -58,7 +58,7 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 			this.Identifier = identifier;
 			foreach (var arg in typeArguments)
 			{
-				AddChild(arg, Roles.TypeArgument);
+				AddChild(arg, SlotKind.TypeArgument);
 			}
 		}
 

ICSharpCode.Decompiler/CSharp/Syntax/Statements/BlockStatement.cs

@@ -34,19 +34,18 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 	[DecompilerAstNode(hasNullNode: true, hasPatternPlaceholder: true)]
 	public partial class BlockStatement : Statement, IEnumerable<Statement>
 	{
-		public static readonly Role<Statement> StatementRole = new Role<Statement>("Statement", null);
 
 		[Slot("StatementRole")]
 		public partial AstNodeCollection<Statement> Statements { get; }
 
 		public void Add(Statement statement)
 		{
-			AddChild(statement, StatementRole);
+			AddChild(statement, SlotKind.Statement);
 		}
 
 		public void Add(Expression expression)
 		{
-			AddChild(new ExpressionStatement(expression), StatementRole);
+			AddChild(new ExpressionStatement(expression), SlotKind.Statement);
 		}
 
 		IEnumerator<Statement> IEnumerable<Statement>.GetEnumerator()

ICSharpCode.Decompiler/CSharp/Syntax/Statements/CheckedStatement.cs

@@ -43,7 +43,7 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 
 		public CheckedStatement(BlockStatement body)
 		{
-			AddChild(body, Roles.Body);
+			AddChild(body, SlotKind.Body);
 		}
 	}
 }

ICSharpCode.Decompiler/CSharp/Syntax/Statements/ForStatement.cs

@@ -35,8 +35,6 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 	public partial class ForStatement : Statement
 	{
 		public static readonly TokenRole ForKeywordRole = new TokenRole("for");
-		public readonly static Role<Statement> InitializerRole = new Role<Statement>("Initializer", null);
-		public readonly static Role<Statement> IteratorRole = new Role<Statement>("Iterator", null);
 
 		/// <summary>
 		/// Gets the list of initializer statements.

ICSharpCode.Decompiler/CSharp/Syntax/Statements/IfElseStatement.cs

@@ -35,10 +35,7 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 	public partial class IfElseStatement : Statement
 	{
 		public readonly static TokenRole IfKeywordRole = new TokenRole("if");
-		public readonly static Role<Expression> ConditionRole = Roles.Condition;
-		public readonly static Role<Statement> TrueRole = new Role<Statement>("True", null);
 		public readonly static TokenRole ElseKeywordRole = new TokenRole("else");
-		public readonly static Role<Statement> FalseRole = new Role<Statement>("False", null);
 
 		[Slot("ConditionRole")]
 		public partial Expression Condition { get; set; }

ICSharpCode.Decompiler/CSharp/Syntax/Statements/LocalFunctionDeclarationStatement.cs

@@ -24,14 +24,13 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 	[DecompilerAstNode(hasNullNode: false)]
 	public partial class LocalFunctionDeclarationStatement : Statement
 	{
-		public static readonly Role<MethodDeclaration> MethodDeclarationRole = new Role<MethodDeclaration>("Method", null);
 
 		[Slot("MethodDeclarationRole")]
 		public partial MethodDeclaration Declaration { get; set; }
 
 		public LocalFunctionDeclarationStatement(MethodDeclaration methodDeclaration)
 		{
-			AddChild(methodDeclaration, MethodDeclarationRole);
+			AddChild(methodDeclaration, SlotKind.MethodDeclaration);
 		}
 	}
 }

ICSharpCode.Decompiler/CSharp/Syntax/Statements/ReturnStatement.cs

@@ -45,7 +45,7 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 
 		public ReturnStatement(Expression returnExpression)
 		{
-			AddChild(returnExpression, Roles.Expression);
+			AddChild(returnExpression, SlotKind.Expression);
 		}
 	}
 }

ICSharpCode.Decompiler/CSharp/Syntax/Statements/SwitchStatement.cs

@@ -35,7 +35,6 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 	public partial class SwitchStatement : Statement
 	{
 		public static readonly TokenRole SwitchKeywordRole = new TokenRole("switch");
-		public static readonly Role<SwitchSection> SwitchSectionRole = new Role<SwitchSection>("SwitchSection", null);
 
 		[Slot("Roles.Expression")]
 		public partial Expression Expression { get; set; }
@@ -50,7 +49,6 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 	[DecompilerAstNode(hasNullNode: false, hasPatternPlaceholder: true)]
 	public partial class SwitchSection : AstNode
 	{
-		public static readonly Role<CaseLabel> CaseLabelRole = new Role<CaseLabel>("CaseLabel", null);
 
 		[Slot("CaseLabelRole")]
 		public partial AstNodeCollection<CaseLabel> CaseLabels { get; }

ICSharpCode.Decompiler/CSharp/Syntax/Statements/ThrowStatement.cs

@@ -45,7 +45,7 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 
 		public ThrowStatement(Expression expression)
 		{
-			AddChild(expression, Roles.Expression);
+			AddChild(expression, SlotKind.Expression);
 		}
 	}
 }

ICSharpCode.Decompiler/CSharp/Syntax/Statements/TryCatchStatement.cs

@@ -35,10 +35,7 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 	public partial class TryCatchStatement : Statement
 	{
 		public static readonly TokenRole TryKeywordRole = new TokenRole("try");
-		public static readonly Role<BlockStatement> TryBlockRole = new Role<BlockStatement>("TryBlock", null);
-		public static readonly Role<CatchClause> CatchClauseRole = new Role<CatchClause>("CatchClause", null);
 		public static readonly TokenRole FinallyKeywordRole = new TokenRole("finally");
-		public static readonly Role<BlockStatement> FinallyBlockRole = new Role<BlockStatement>("FinallyBlock", null);
 
 		[Slot("TryBlockRole")]
 		public partial BlockStatement TryBlock { get; set; }
@@ -58,7 +55,6 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 	{
 		public static readonly TokenRole CatchKeywordRole = new TokenRole("catch");
 		public static readonly TokenRole WhenKeywordRole = new TokenRole("when");
-		public static readonly Role<Expression> ConditionRole = Roles.Condition;
 		public static readonly TokenRole CondLPar = new TokenRole("(");
 		public static readonly TokenRole CondRPar = new TokenRole(")");
 

ICSharpCode.Decompiler/CSharp/Syntax/Statements/UncheckedStatement.cs

@@ -43,7 +43,7 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 
 		public UncheckedStatement(BlockStatement body)
 		{
-			AddChild(body, Roles.Body);
+			AddChild(body, SlotKind.Body);
 		}
 	}
 }

ICSharpCode.Decompiler/CSharp/Syntax/Statements/UsingStatement.cs

@@ -34,7 +34,6 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 	{
 		public static readonly TokenRole UsingKeywordRole = new TokenRole("using");
 		public static readonly TokenRole AwaitRole = UnaryOperatorExpression.AwaitRole;
-		public static readonly Role<AstNode> ResourceAcquisitionRole = new Role<AstNode>("ResourceAcquisition", null);
 
 		public bool IsAsync { get; set; }
 

ICSharpCode.Decompiler/CSharp/Syntax/SyntaxTree.cs

@@ -36,7 +36,6 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 	[DecompilerAstNode(hasNullNode: false)]
 	public partial class SyntaxTree : AstNode
 	{
-		public static readonly Role<AstNode> MemberRole = new Role<AstNode>("Member", null);
 
 		[Slot("MemberRole")]
 		public partial AstNodeCollection<AstNode> Members { get; }

ICSharpCode.Decompiler/CSharp/Syntax/TupleAstType.cs

@@ -24,7 +24,6 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 	[DecompilerAstNode(hasNullNode: false)]
 	public partial class TupleAstType : AstType
 	{
-		public static readonly Role<TupleTypeElement> ElementRole = new Role<TupleTypeElement>("Element", null);
 
 		[Slot("ElementRole")]
 		public partial AstNodeCollection<TupleTypeElement> Elements { get; }

ICSharpCode.Decompiler/CSharp/Syntax/TypeMembers/ConstructorDeclaration.cs

@@ -36,7 +36,6 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 	[DecompilerAstNode(hasNullNode: false)]
 	public partial class ConstructorDeclaration : EntityDeclaration
 	{
-		public static readonly Role<ConstructorInitializer> InitializerRole = new Role<ConstructorInitializer>("Initializer", null);
 
 		public override SymbolKind SymbolKind {
 			get { return SymbolKind.Constructor; }

ICSharpCode.Decompiler/CSharp/Syntax/TypeMembers/EntityDeclaration.cs

@@ -25,18 +25,16 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 {
 	public abstract class EntityDeclaration : AstNode
 	{
-		public static readonly Role<AttributeSection> AttributeRole = new Role<AttributeSection>("Attribute", null);
 		// Modifiers are stored in the Modifiers scalar; this role only tags the keyword tokens the
 		// output visitor emits (e.g. for the override-link reference in TextTokenWriter).
 		// Identity marker for modifier keywords in the output (modifiers are scalars, not child nodes);
 		// the token writer uses it to make the 'override' modifier a go-to-definition reference.
 		public static readonly TokenRole ModifierRole = new TokenRole("modifier");
-		public static readonly Role<AstType> PrivateImplementationTypeRole = new Role<AstType>("PrivateImplementationType", null);
 
 		public abstract SymbolKind SymbolKind { get; }
 
 		public virtual AstNodeCollection<AttributeSection> Attributes {
-			get { return base.GetChildrenByRole(AttributeRole); }
+			get { return base.GetChildrenByRole<AttributeSection>(SlotKind.Attribute); }
 		}
 
 		public Modifiers Modifiers { get; set; }
@@ -48,21 +46,21 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 
 		public virtual string Name {
 			get {
-				return GetChildByRole(Roles.Identifier)?.Name ?? string.Empty;
+				return GetChildByRole<Identifier>(SlotKind.Identifier)?.Name ?? string.Empty;
 			}
 			set {
-				SetChildByRole(Roles.Identifier, Identifier.Create(value, TextLocation.Empty));
+				SetChildByRole(SlotKind.Identifier, Identifier.Create(value, TextLocation.Empty));
 			}
 		}
 
 		public virtual Identifier NameToken {
-			get { return GetChildByRole(Roles.Identifier); }
-			set { SetChildByRole(Roles.Identifier, value); }
+			get { return GetChildByRole<Identifier>(SlotKind.Identifier); }
+			set { SetChildByRole(SlotKind.Identifier, value); }
 		}
 
 		public virtual AstType ReturnType {
-			get { return GetChildByRole(Roles.Type); }
-			set { SetChildByRole(Roles.Type, value); }
+			get { return GetChildByRole<AstType>(SlotKind.Type); }
+			set { SetChildByRole(SlotKind.Type, value); }
 		}
 
 		protected bool MatchAttributesAndModifiers(EntityDeclaration o, PatternMatching.Match match)

ICSharpCode.Decompiler/CSharp/Syntax/TypeMembers/EnumMemberDeclaration.cs

@@ -36,7 +36,6 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 	[DecompilerAstNode(hasNullNode: false)]
 	public partial class EnumMemberDeclaration : EntityDeclaration
 	{
-		public static readonly Role<Expression> InitializerRole = new Role<Expression>("Initializer", null);
 
 		public override SymbolKind SymbolKind {
 			get { return SymbolKind.Field; }

ICSharpCode.Decompiler/CSharp/Syntax/TypeMembers/EventDeclaration.cs

@@ -79,8 +79,6 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 		public static readonly TokenRole AddKeywordRole = new TokenRole("add");
 		public static readonly TokenRole RemoveKeywordRole = new TokenRole("remove");
 
-		public static readonly Role<Accessor> AddAccessorRole = new Role<Accessor>("AddAccessor", null);
-		public static readonly Role<Accessor> RemoveAccessorRole = new Role<Accessor>("RemoveAccessor", null);
 
 		public override SymbolKind SymbolKind {
 			get { return SymbolKind.Event; }

ICSharpCode.Decompiler/CSharp/Syntax/TypeMembers/FixedFieldDeclaration.cs

@@ -34,7 +34,6 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 	public partial class FixedFieldDeclaration : EntityDeclaration
 	{
 		public static readonly TokenRole FixedKeywordRole = new TokenRole("fixed");
-		public static readonly Role<FixedVariableInitializer> VariableRole = new Role<FixedVariableInitializer>("FixedVariable", null);
 
 		public override SymbolKind SymbolKind {
 			get { return SymbolKind.Field; }

ICSharpCode.Decompiler/CSharp/Syntax/TypeMembers/IndexerDeclaration.cs

@@ -45,9 +45,6 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 	public partial class IndexerDeclaration : EntityDeclaration
 	{
 		public static readonly TokenRole ThisKeywordRole = new TokenRole("this");
-		public static readonly Role<Accessor> GetterRole = PropertyDeclaration.GetterRole;
-		public static readonly Role<Accessor> SetterRole = PropertyDeclaration.SetterRole;
-		public static readonly Role<Expression> ExpressionBodyRole = new Role<Expression>("ExpressionBody", null);
 
 		public override SymbolKind SymbolKind {
 			get { return SymbolKind.Indexer; }

ICSharpCode.Decompiler/CSharp/Syntax/TypeMembers/MethodDeclaration.cs

@@ -72,7 +72,7 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 
 		public bool IsExtensionMethod {
 			get {
-				ParameterDeclaration pd = (ParameterDeclaration)GetChildByRole(Roles.Parameter);
+				ParameterDeclaration pd = (ParameterDeclaration)GetChildByRole<ParameterDeclaration>(SlotKind.Parameter);
 				return pd != null && pd.HasThisModifier;
 			}
 		}

ICSharpCode.Decompiler/CSharp/Syntax/TypeMembers/ParameterDeclaration.cs

@@ -37,7 +37,6 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 	[DecompilerAstNode(hasNullNode: false, hasPatternPlaceholder: true)]
 	public partial class ParameterDeclaration : AstNode
 	{
-		public static readonly Role<AttributeSection> AttributeRole = EntityDeclaration.AttributeRole;
 		public static readonly TokenRole ThisModifierRole = new TokenRole("this");
 		public static readonly TokenRole ScopedRefRole = new TokenRole("scoped");
 		public static readonly TokenRole RefModifierRole = new TokenRole("ref");

ICSharpCode.Decompiler/CSharp/Syntax/TypeMembers/PropertyDeclaration.cs

@@ -44,9 +44,6 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 		public static readonly TokenRole GetKeywordRole = new TokenRole("get");
 		public static readonly TokenRole SetKeywordRole = new TokenRole("set");
 		public static readonly TokenRole InitKeywordRole = new TokenRole("init");
-		public static readonly Role<Accessor> GetterRole = new Role<Accessor>("Getter", null);
-		public static readonly Role<Accessor> SetterRole = new Role<Accessor>("Setter", null);
-		public static readonly Role<Expression> ExpressionBodyRole = new Role<Expression>("ExpressionBody", null);
 
 		public override SymbolKind SymbolKind {
 			get { return SymbolKind.Property; }

ICSharpCode.Decompiler/CSharp/Syntax/TypeSystemAstBuilder.cs

@@ -633,11 +633,11 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 			{
 				if (ConvertUnboundTypeArguments && typeArguments[i].Kind == TypeKind.UnboundTypeArgument)
 				{
-					result.AddChild(MakeSimpleType(typeParameters[i].Name), Roles.TypeArgument);
+					result.AddChild(MakeSimpleType(typeParameters[i].Name), SlotKind.TypeArgument);
 				}
 				else
 				{
-					result.AddChild(ConvertType(typeArguments[i]), Roles.TypeArgument);
+					result.AddChild(ConvertType(typeArguments[i]), SlotKind.TypeArgument);
 				}
 			}
 		}

ICSharpCode.Decompiler/CSharp/Transforms/AddCheckedBlocks.cs

@@ -393,7 +393,7 @@ namespace ICSharpCode.Decompiler.CSharp.Transforms
 				{
 					// We cannot use checked/unchecked for top-level-expressions.
 				}
-				else if (expr.Role is Role<Expression> || expr.Role is Role<AstNode>)
+				else if (expr.Slot?.ChildType is Type ct && ct.IsAssignableFrom(typeof(Expression)))
 				{
 					// We use '<' so that expressions are introduced on the deepest level possible (goal 3)
 					var costIfWrapWithChecked = result.CostInCheckedContext.WrapInCheckedExpr();

ICSharpCode.Decompiler/CSharp/Transforms/DeclareVariables.cs

@@ -725,14 +725,14 @@ namespace ICSharpCode.Decompiler.CSharp.Transforms
 										}
 									}
 								},
-								BlockStatement.StatementRole);
+								SlotKind.Statement);
 						}
 						else
 						{
 							insertionParent.InsertChildBefore(
 								v.InsertionPoint.nextNode,
 								vds,
-								BlockStatement.StatementRole);
+								SlotKind.Statement);
 							insertionParent.InsertChildBefore(
 								v.InsertionPoint.nextNode,
 								new ExpressionStatement {
@@ -750,7 +750,7 @@ namespace ICSharpCode.Decompiler.CSharp.Transforms
 										}
 									}
 								},
-								BlockStatement.StatementRole);
+								SlotKind.Statement);
 						}
 					}
 					else
@@ -758,7 +758,7 @@ namespace ICSharpCode.Decompiler.CSharp.Transforms
 						insertionParent.InsertChildBefore(
 							v.InsertionPoint.nextNode,
 							vds,
-							BlockStatement.StatementRole);
+							SlotKind.Statement);
 					}
 				}
 			}

ICSharpCode.Decompiler/CSharp/Transforms/FixNameCollisions.cs

@@ -42,7 +42,7 @@ namespace ICSharpCode.Decompiler.CSharp.Transforms
 			foreach (var typeDecl in rootNode.DescendantsAndSelf.OfType<TypeDeclaration>())
 			{
 				var memberNames = typeDecl.Members.Select(m => {
-					var type = m.GetChildByRole(EntityDeclaration.PrivateImplementationTypeRole);
+					var type = m.GetChildByRole<AstType>(SlotKind.PrivateImplementationType);
 					return type is null ? m.Name : type + "." + m.Name;
 				}).ToHashSet();
 				// memberNames does not include fields or non-custom events because those
@@ -72,7 +72,7 @@ namespace ICSharpCode.Decompiler.CSharp.Transforms
 					ISymbol symbol = node.GetSymbol();
 					if (symbol != null && renamedSymbols.TryGetValue(symbol, out string? newName))
 					{
-						node.GetChildByRole(Roles.Identifier).Name = newName;
+						node.GetChildByRole<Identifier>(SlotKind.Identifier).Name = newName;
 					}
 				}
 			}

ICSharpCode.Decompiler/CSharp/Transforms/IntroduceUsingDeclarations.cs

@@ -73,7 +73,7 @@ namespace ICSharpCode.Decompiler.CSharp.Transforms
 					{
 						resolvedNamespaces.Add(resolvedNamespace);
 					}
-					rootNode.InsertChildAfter(insertionPoint, new UsingDeclaration { Import = nsType }, SyntaxTree.MemberRole);
+					rootNode.InsertChildAfter(insertionPoint, new UsingDeclaration { Import = nsType }, SlotKind.Member);
 				}
 			}
 

ICSharpCode.Decompiler/CSharp/Transforms/PatternStatementTransform.cs

@@ -192,7 +192,7 @@ namespace ICSharpCode.Decompiler.CSharp.Transforms
 			if (next is ForStatement forStatement && ForStatementUsesVariable(forStatement, variable))
 			{
 				node.Remove();
-				next.InsertChildAfter(null, node, ForStatement.InitializerRole);
+				next.InsertChildAfter(null, node, SlotKind.Initializer);
 				return (ForStatement)next;
 			}
 			Match m3 = forPattern.Match(next);

ICSharpCode.Decompiler/CSharp/Transforms/TransformFieldAndConstructorInitializers.cs

@@ -482,7 +482,7 @@ namespace ICSharpCode.Decompiler.CSharp.Transforms
 				var ci = new ConstructorInitializer { ConstructorInitializerType = type };
 
 				// Move arguments from invocation to initializer:
-				invocation.GetChildrenByRole(Roles.Argument).MoveTo(ci.Arguments);
+				invocation.GetChildrenByRole<Expression>(SlotKind.Argument).MoveTo(ci.Arguments);
 				// Add the initializer: (unless it is the default 'base()')
 				if (!(ci.ConstructorInitializerType == ConstructorInitializerType.Base && ci.Arguments.Count == 0))
 					constructorDeclaration.Initializer = ci.CopyAnnotationsFrom(invocation);
@@ -619,7 +619,7 @@ namespace ICSharpCode.Decompiler.CSharp.Transforms
 						foreach (var param in PrimaryConstructorDecl.Parameters)
 						{
 							param.Remove();
-							this.TypeDeclaration.InsertChildAfter(insertionPoint, param, Roles.Parameter);
+							this.TypeDeclaration.InsertChildAfter(insertionPoint, param, SlotKind.Parameter);
 							insertionPoint = param;
 						}
 					}

ICSharpCode.Decompiler/ICSharpCode.Decompiler.csproj

@@ -264,7 +264,6 @@
     <Compile Include="CSharp\Syntax\PatternMatching\Pattern.cs" />
     <Compile Include="CSharp\Syntax\PatternMatching\Repeat.cs" />
     <Compile Include="CSharp\Syntax\PrimitiveType.cs" />
-    <Compile Include="CSharp\Syntax\Role.cs" />
     <Compile Include="CSharp\Syntax\Roles.cs" />
     <Compile Include="CSharp\Syntax\SimpleType.cs" />
     <Compile Include="CSharp\Syntax\Statements\BlockStatement.cs" />

ICSharpCode.Decompiler/Output/TextTokenWriter.cs

@@ -300,7 +300,7 @@ namespace ICSharpCode.Decompiler
 					// Attach member reference to token only if there's no identifier in the current node.
 					var member = GetCurrentMemberReference();
 					var node = nodeStack.Peek();
-					if (member != null && node.GetChildByRole(Roles.Identifier) is null)
+					if (member != null && node.GetChildByRole<Identifier>(SlotKind.Identifier) is null)
 					{
 						switch (member)
 						{

ILSpy/Languages/CSharpHighlightingTokenWriter.cs

@@ -350,7 +350,7 @@ namespace ICSharpCode.ILSpy.Languages
 				{
 					if (identifier.Name == "value"
 						&& identifier.Ancestors.OfType<Accessor>().FirstOrDefault() is { } accessor
-						&& accessor.Role != PropertyDeclaration.GetterRole)
+						&& accessor.Slot?.Kind != SlotKind.Getter)
 					{
 						color = valueKeywordColor;
 					}
@@ -476,17 +476,17 @@ namespace ICSharpCode.ILSpy.Languages
 
 			AstNode node = nodeStack.Peek();
 			var symbol = node.GetSymbol();
-			if (symbol == null && node.Role == Roles.TargetExpression && node.Parent is InvocationExpression)
+			if (symbol == null && node.Slot?.Kind == SlotKind.TargetExpression && node.Parent is InvocationExpression)
 			{
 				symbol = node.Parent.GetSymbol();
 			}
-			if (symbol != null && node.Role == Roles.Type && node.Parent is ObjectCreateExpression)
+			if (symbol != null && node.Slot?.Kind == SlotKind.Type && node.Parent is ObjectCreateExpression)
 			{
 				var ctorSymbol = node.Parent.GetSymbol();
 				if (ctorSymbol != null)
 					symbol = ctorSymbol;
 			}
-			if (node is IdentifierExpression && node.Role == Roles.TargetExpression && node.Parent is InvocationExpression && symbol is IMember member)
+			if (node is IdentifierExpression && node.Slot?.Kind == SlotKind.TargetExpression && node.Parent is InvocationExpression && symbol is IMember member)
 			{
 				var declaringType = member.DeclaringType;
 				if (declaringType != null && declaringType.Kind == TypeKind.Delegate)