Generate PatternPlaceholder nodes

ICSharpCode.Decompiler.Generators.Attributes/DecompilerAstNodeAttribute.cs

@@ -4,7 +4,7 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 {
 	public sealed class DecompilerAstNodeAttribute : Attribute
 	{
-		public DecompilerAstNodeAttribute(bool hasNullNode) { }
+		public DecompilerAstNodeAttribute(bool hasNullNode = false, bool hasPatternPlaceholder = false) { }
 	}
 
 	public sealed class ExcludeFromMatchAttribute : Attribute

ICSharpCode.Decompiler.Generators/DecompilerSyntaxTreeGenerator.cs

@@ -14,7 +14,7 @@ namespace ICSharpCode.Decompiler.Generators;
 [Generator]
 internal class DecompilerSyntaxTreeGenerator : IIncrementalGenerator
 {
-	record AstNodeAdditions(string NodeName, bool NeedsAcceptImpls, bool NeedsVisitor, bool NeedsNullNode, int NullNodeBaseCtorParamCount, bool IsTypeNode, string VisitMethodName, string VisitMethodParamType, EquatableArray<(string Member, string TypeName, bool RecursiveMatch, bool MatchAny)>? MembersToMatch);
+	record AstNodeAdditions(string NodeName, bool NeedsAcceptImpls, bool NeedsVisitor, bool NeedsNullNode, bool NeedsPatternPlaceholder, int NullNodeBaseCtorParamCount, bool IsTypeNode, string VisitMethodName, string VisitMethodParamType, EquatableArray<(string Member, string TypeName, bool RecursiveMatch, bool MatchAny)>? MembersToMatch);
 
 	AstNodeAdditions GetAstNodeAdditions(GeneratorAttributeSyntaxContext context, CancellationToken ct)
 	{
@@ -63,6 +63,7 @@ internal class DecompilerSyntaxTreeGenerator : IIncrementalGenerator
 		return new(targetSymbol.Name, !targetSymbol.MemberNames.Contains("AcceptVisitor"),
 			NeedsVisitor: !targetSymbol.IsAbstract && targetSymbol.BaseType!.IsAbstract,
 			NeedsNullNode: (bool)attribute.ConstructorArguments[0].Value!,
+			NeedsPatternPlaceholder: (bool)attribute.ConstructorArguments[1].Value!,
 			NullNodeBaseCtorParamCount: targetSymbol.InstanceConstructors.Min(m => m.Parameters.Length),
 			IsTypeNode: targetSymbol.Name == "AstType" || targetSymbol.BaseType?.Name == "AstType",
 			visitMethodName, paramTypeName, membersToMatch?.ToEquatableArray());
@@ -75,6 +76,13 @@ internal class DecompilerSyntaxTreeGenerator : IIncrementalGenerator
 		builder.AppendLine("namespace ICSharpCode.Decompiler.CSharp.Syntax;");
 		builder.AppendLine();
 
+		if (source.NeedsPatternPlaceholder)
+		{
+			builder.AppendLine("using ICSharpCode.Decompiler.CSharp.Syntax.PatternMatching;");
+		}
+
+		builder.AppendLine();
+
 		builder.AppendLine("#nullable enable");
 		builder.AppendLine();
 
@@ -140,6 +148,63 @@ internal class DecompilerSyntaxTreeGenerator : IIncrementalGenerator
 
 		}
 
+		if (source.NeedsPatternPlaceholder)
+		{
+			const string toTypeReferenceCode = @"
+
+		public override Decompiler.TypeSystem.ITypeReference ToTypeReference(Resolver.NameLookupMode lookupMode, Decompiler.TypeSystem.InterningProvider? interningProvider = null)
+		{
+			throw new System.NotSupportedException();
+		}";
+
+			builder.Append(
+		$@"		public static implicit operator {source.NodeName}?(PatternMatching.Pattern? pattern)
+	{{
+		return pattern != null ? new PatternPlaceholder(pattern) : null;
+	}}
+
+	sealed class PatternPlaceholder : {source.NodeName}, INode
+	{{
+		readonly PatternMatching.Pattern child;
+
+		public PatternPlaceholder(PatternMatching.Pattern child)
+		{{
+			this.child = child;
+		}}
+
+		public override NodeType NodeType {{
+			get {{ return NodeType.Pattern; }}
+		}}
+
+		public override void AcceptVisitor(IAstVisitor visitor)
+		{{
+			visitor.VisitPatternPlaceholder(this, child);
+		}}
+
+		public override T AcceptVisitor<T>(IAstVisitor<T> visitor)
+		{{
+			return visitor.VisitPatternPlaceholder(this, child);
+		}}
+
+		public override S AcceptVisitor<T, S>(IAstVisitor<T, S> visitor, T data)
+		{{
+			return visitor.VisitPatternPlaceholder(this, child, data);
+		}}
+
+		protected internal override bool DoMatch(AstNode? other, PatternMatching.Match match)
+		{{
+			return child.DoMatch(other, match);
+		}}
+
+		bool PatternMatching.INode.DoMatchCollection(Role? role, PatternMatching.INode? pos, PatternMatching.Match match, PatternMatching.BacktrackingInfo backtrackingInfo)
+		{{
+			return child.DoMatchCollection(role, pos, match, backtrackingInfo);
+		}}{(source.NodeName == "AstType" ? toTypeReferenceCode : "")}
+	}}
+"
+			);
+		}
+
 		if (source.NeedsAcceptImpls && source.NeedsVisitor)
 		{
 			builder.Append($@"	public override void AcceptVisitor(IAstVisitor visitor)
@@ -202,7 +267,7 @@ internal class DecompilerSyntaxTreeGenerator : IIncrementalGenerator
 		builder.AppendLine("namespace ICSharpCode.Decompiler.CSharp.Syntax;");
 
 		source = source
-			.Concat([new("NullNode", false, true, false, 0, false, "NullNode", "AstNode", null), new("PatternPlaceholder", false, true, false, 0, false, "PatternPlaceholder", "AstNode", null)])
+			.Concat([new("NullNode", false, true, false, false, 0, false, "NullNode", "AstNode", null), new("PatternPlaceholder", false, true, false, false, 0, false, "PatternPlaceholder", "AstNode", null)])
 			.ToImmutableArray();
 
 		WriteInterface("IAstVisitor", "void", "");

ICSharpCode.Decompiler/CSharp/Syntax/AstNode.cs

@@ -37,58 +37,12 @@ using ICSharpCode.Decompiler.TypeSystem;
 
 namespace ICSharpCode.Decompiler.CSharp.Syntax
 {
-	[DecompilerAstNode(hasNullNode: true)]
+	[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);
 
-		#region PatternPlaceholder
-		public static implicit operator AstNode?(PatternMatching.Pattern? pattern)
-		{
-			return pattern != null ? new PatternPlaceholder(pattern) : null;
-		}
-
-		sealed class PatternPlaceholder : AstNode, INode
-		{
-			readonly PatternMatching.Pattern child;
-
-			public PatternPlaceholder(PatternMatching.Pattern child)
-			{
-				this.child = child;
-			}
-
-			public override NodeType NodeType {
-				get { return NodeType.Pattern; }
-			}
-
-			public override void AcceptVisitor(IAstVisitor visitor)
-			{
-				visitor.VisitPatternPlaceholder(this, child);
-			}
-
-			public override T AcceptVisitor<T>(IAstVisitor<T> visitor)
-			{
-				return visitor.VisitPatternPlaceholder(this, child);
-			}
-
-			public override S AcceptVisitor<T, S>(IAstVisitor<T, S> visitor, T data)
-			{
-				return visitor.VisitPatternPlaceholder(this, child, data);
-			}
-
-			protected internal override bool DoMatch(AstNode? other, PatternMatching.Match match)
-			{
-				return child.DoMatch(other, match);
-			}
-
-			bool PatternMatching.INode.DoMatchCollection(Role? role, PatternMatching.INode? pos, PatternMatching.Match match, PatternMatching.BacktrackingInfo backtrackingInfo)
-			{
-				return child.DoMatchCollection(role, pos, match, backtrackingInfo);
-			}
-		}
-		#endregion
-
 		AstNode? parent;
 		AstNode? prevSibling;
 		AstNode? nextSibling;

ICSharpCode.Decompiler/CSharp/Syntax/AstType.cs

@@ -16,11 +16,9 @@
 // OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 // DEALINGS IN THE SOFTWARE.
 
-using System;
 using System.Collections.Generic;
 
 using ICSharpCode.Decompiler.CSharp.Resolver;
-using ICSharpCode.Decompiler.CSharp.Syntax.PatternMatching;
 using ICSharpCode.Decompiler.TypeSystem;
 
 namespace ICSharpCode.Decompiler.CSharp.Syntax
@@ -28,60 +26,9 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 	/// <summary>
 	/// A type reference in the C# AST.
 	/// </summary>
-	[DecompilerAstNode(hasNullNode: true)]
+	[DecompilerAstNode(hasNullNode: true, hasPatternPlaceholder: true)]
 	public abstract partial class AstType : AstNode
 	{
-		#region PatternPlaceholder
-		public static implicit operator AstType(PatternMatching.Pattern pattern)
-		{
-			return pattern != null ? new PatternPlaceholder(pattern) : null;
-		}
-
-		sealed class PatternPlaceholder : AstType, INode
-		{
-			readonly PatternMatching.Pattern child;
-
-			public PatternPlaceholder(PatternMatching.Pattern child)
-			{
-				this.child = child;
-			}
-
-			public override NodeType NodeType {
-				get { return NodeType.Pattern; }
-			}
-
-			public override void AcceptVisitor(IAstVisitor visitor)
-			{
-				visitor.VisitPatternPlaceholder(this, child);
-			}
-
-			public override T AcceptVisitor<T>(IAstVisitor<T> visitor)
-			{
-				return visitor.VisitPatternPlaceholder(this, child);
-			}
-
-			public override S AcceptVisitor<T, S>(IAstVisitor<T, S> visitor, T data)
-			{
-				return visitor.VisitPatternPlaceholder(this, child, data);
-			}
-
-			public override ITypeReference ToTypeReference(NameLookupMode lookupMode, InterningProvider interningProvider)
-			{
-				throw new NotSupportedException();
-			}
-
-			protected internal override bool DoMatch(AstNode other, PatternMatching.Match match)
-			{
-				return child.DoMatch(other, match);
-			}
-
-			bool PatternMatching.INode.DoMatchCollection(Role role, PatternMatching.INode pos, PatternMatching.Match match, PatternMatching.BacktrackingInfo backtrackingInfo)
-			{
-				return child.DoMatchCollection(role, pos, match, backtrackingInfo);
-			}
-		}
-		#endregion
-
 		public override NodeType NodeType {
 			get { return NodeType.TypeReference; }
 		}

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

@@ -94,52 +94,6 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 			}
 
 		}
-
-		#region PatternPlaceholder
-		public static implicit operator ArrayInitializerExpression(PatternMatching.Pattern pattern)
-		{
-			return pattern != null ? new PatternPlaceholder(pattern) : null;
-		}
-
-		sealed class PatternPlaceholder : ArrayInitializerExpression, PatternMatching.INode
-		{
-			readonly PatternMatching.Pattern child;
-
-			public PatternPlaceholder(PatternMatching.Pattern child)
-			{
-				this.child = child;
-			}
-
-			public override NodeType NodeType {
-				get { return NodeType.Pattern; }
-			}
-
-			public override void AcceptVisitor(IAstVisitor visitor)
-			{
-				visitor.VisitPatternPlaceholder(this, child);
-			}
-
-			public override T AcceptVisitor<T>(IAstVisitor<T> visitor)
-			{
-				return visitor.VisitPatternPlaceholder(this, child);
-			}
-
-			public override S AcceptVisitor<T, S>(IAstVisitor<T, S> visitor, T data)
-			{
-				return visitor.VisitPatternPlaceholder(this, child, data);
-			}
-
-			protected internal override bool DoMatch(AstNode other, PatternMatching.Match match)
-			{
-				return child.DoMatch(other, match);
-			}
-
-			bool PatternMatching.INode.DoMatchCollection(Role role, PatternMatching.INode pos, PatternMatching.Match match, PatternMatching.BacktrackingInfo backtrackingInfo)
-			{
-				return child.DoMatchCollection(role, pos, match, backtrackingInfo);
-			}
-		}
-		#endregion
 	}
 }
 

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

@@ -27,55 +27,9 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 	/// This class is useful even though it doesn't provide any additional functionality:
 	/// It can be used to communicate more information in APIs, e.g. "this subnode will always be an expression"
 	/// </remarks>
-	[DecompilerAstNode(hasNullNode: true)]
+	[DecompilerAstNode(hasNullNode: true, hasPatternPlaceholder: true)]
 	public abstract partial class Expression : AstNode
 	{
-		#region PatternPlaceholder
-		public static implicit operator Expression(PatternMatching.Pattern pattern)
-		{
-			return pattern != null ? new PatternPlaceholder(pattern) : null;
-		}
-
-		sealed class PatternPlaceholder : Expression, PatternMatching.INode
-		{
-			readonly PatternMatching.Pattern child;
-
-			public PatternPlaceholder(PatternMatching.Pattern child)
-			{
-				this.child = child;
-			}
-
-			public override NodeType NodeType {
-				get { return NodeType.Pattern; }
-			}
-
-			public override void AcceptVisitor(IAstVisitor visitor)
-			{
-				visitor.VisitPatternPlaceholder(this, child);
-			}
-
-			public override T AcceptVisitor<T>(IAstVisitor<T> visitor)
-			{
-				return visitor.VisitPatternPlaceholder(this, child);
-			}
-
-			public override S AcceptVisitor<T, S>(IAstVisitor<T, S> visitor, T data)
-			{
-				return visitor.VisitPatternPlaceholder(this, child, data);
-			}
-
-			protected internal override bool DoMatch(AstNode other, PatternMatching.Match match)
-			{
-				return child.DoMatch(other, match);
-			}
-
-			bool PatternMatching.INode.DoMatchCollection(Role role, PatternMatching.INode pos, PatternMatching.Match match, PatternMatching.BacktrackingInfo backtrackingInfo)
-			{
-				return child.DoMatchCollection(role, pos, match, backtrackingInfo);
-			}
-		}
-		#endregion
-
 		public override NodeType NodeType {
 			get {
 				return NodeType.Expression;

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

@@ -30,55 +30,9 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 	/// <summary>
 	/// [AttributeTarget: Attributes]
 	/// </summary>
-	[DecompilerAstNode(hasNullNode: false)]
+	[DecompilerAstNode(hasNullNode: false, hasPatternPlaceholder: true)]
 	public partial class AttributeSection : AstNode
 	{
-		#region PatternPlaceholder
-		public static implicit operator AttributeSection(PatternMatching.Pattern pattern)
-		{
-			return pattern != null ? new PatternPlaceholder(pattern) : null;
-		}
-
-		sealed class PatternPlaceholder : AttributeSection, PatternMatching.INode
-		{
-			readonly PatternMatching.Pattern child;
-
-			public PatternPlaceholder(PatternMatching.Pattern child)
-			{
-				this.child = child;
-			}
-
-			public override NodeType NodeType {
-				get { return NodeType.Pattern; }
-			}
-
-			public override void AcceptVisitor(IAstVisitor visitor)
-			{
-				visitor.VisitPatternPlaceholder(this, child);
-			}
-
-			public override T AcceptVisitor<T>(IAstVisitor<T> visitor)
-			{
-				return visitor.VisitPatternPlaceholder(this, child);
-			}
-
-			public override S AcceptVisitor<T, S>(IAstVisitor<T, S> visitor, T data)
-			{
-				return visitor.VisitPatternPlaceholder(this, child, data);
-			}
-
-			protected internal override bool DoMatch(AstNode other, PatternMatching.Match match)
-			{
-				return child.DoMatch(other, match);
-			}
-
-			bool PatternMatching.INode.DoMatchCollection(Role role, PatternMatching.INode pos, PatternMatching.Match match, PatternMatching.BacktrackingInfo backtrackingInfo)
-			{
-				return child.DoMatchCollection(role, pos, match, backtrackingInfo);
-			}
-		}
-		#endregion
-
 		public override NodeType NodeType {
 			get {
 				return NodeType.Unknown;

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

@@ -31,57 +31,11 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 	/// <summary>
 	/// { Statements }
 	/// </summary>
-	[DecompilerAstNode(hasNullNode: true)]
+	[DecompilerAstNode(hasNullNode: true, hasPatternPlaceholder: true)]
 	public partial class BlockStatement : Statement, IEnumerable<Statement>
 	{
 		public static readonly Role<Statement> StatementRole = new Role<Statement>("Statement", Statement.Null);
 
-		#region PatternPlaceholder
-		public static implicit operator BlockStatement(PatternMatching.Pattern pattern)
-		{
-			return pattern != null ? new PatternPlaceholder(pattern) : null;
-		}
-
-		sealed class PatternPlaceholder : BlockStatement, PatternMatching.INode
-		{
-			readonly PatternMatching.Pattern child;
-
-			public PatternPlaceholder(PatternMatching.Pattern child)
-			{
-				this.child = child;
-			}
-
-			public override NodeType NodeType {
-				get { return NodeType.Pattern; }
-			}
-
-			public override void AcceptVisitor(IAstVisitor visitor)
-			{
-				visitor.VisitPatternPlaceholder(this, child);
-			}
-
-			public override T AcceptVisitor<T>(IAstVisitor<T> visitor)
-			{
-				return visitor.VisitPatternPlaceholder(this, child);
-			}
-
-			public override S AcceptVisitor<T, S>(IAstVisitor<T, S> visitor, T data)
-			{
-				return visitor.VisitPatternPlaceholder(this, child, data);
-			}
-
-			protected internal override bool DoMatch(AstNode other, PatternMatching.Match match)
-			{
-				return child.DoMatch(other, match);
-			}
-
-			bool PatternMatching.INode.DoMatchCollection(Role role, PatternMatching.INode pos, PatternMatching.Match match, PatternMatching.BacktrackingInfo backtrackingInfo)
-			{
-				return child.DoMatchCollection(role, pos, match, backtrackingInfo);
-			}
-		}
-		#endregion
-
 		public CSharpTokenNode LBraceToken {
 			get { return GetChildByRole(Roles.LBrace); }
 		}

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

@@ -27,55 +27,9 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 	/// This class is useful even though it doesn't provide any additional functionality:
 	/// It can be used to communicate more information in APIs, e.g. "this subnode will always be a statement"
 	/// </remarks>
-	[DecompilerAstNode(hasNullNode: true)]
+	[DecompilerAstNode(hasNullNode: true, hasPatternPlaceholder: true)]
 	public abstract partial class Statement : AstNode
 	{
-		#region PatternPlaceholder
-		public static implicit operator Statement(PatternMatching.Pattern pattern)
-		{
-			return pattern != null ? new PatternPlaceholder(pattern) : null;
-		}
-
-		sealed class PatternPlaceholder : Statement, PatternMatching.INode
-		{
-			readonly PatternMatching.Pattern child;
-
-			public PatternPlaceholder(PatternMatching.Pattern child)
-			{
-				this.child = child;
-			}
-
-			public override NodeType NodeType {
-				get { return NodeType.Pattern; }
-			}
-
-			public override void AcceptVisitor(IAstVisitor visitor)
-			{
-				visitor.VisitPatternPlaceholder(this, child);
-			}
-
-			public override T AcceptVisitor<T>(IAstVisitor<T> visitor)
-			{
-				return visitor.VisitPatternPlaceholder(this, child);
-			}
-
-			public override S AcceptVisitor<T, S>(IAstVisitor<T, S> visitor, T data)
-			{
-				return visitor.VisitPatternPlaceholder(this, child, data);
-			}
-
-			protected internal override bool DoMatch(AstNode other, PatternMatching.Match match)
-			{
-				return child.DoMatch(other, match);
-			}
-
-			bool PatternMatching.INode.DoMatchCollection(Role role, PatternMatching.INode pos, PatternMatching.Match match, PatternMatching.BacktrackingInfo backtrackingInfo)
-			{
-				return child.DoMatchCollection(role, pos, match, backtrackingInfo);
-			}
-		}
-		#endregion
-
 		public new Statement Clone()
 		{
 			return (Statement)base.Clone();

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

@@ -72,55 +72,9 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 		}
 	}
 
-	[DecompilerAstNode(hasNullNode: false)]
+	[DecompilerAstNode(hasNullNode: false, hasPatternPlaceholder: true)]
 	public partial class SwitchSection : AstNode
 	{
-		#region PatternPlaceholder
-		public static implicit operator SwitchSection(PatternMatching.Pattern pattern)
-		{
-			return pattern != null ? new PatternPlaceholder(pattern) : null;
-		}
-
-		sealed class PatternPlaceholder : SwitchSection, PatternMatching.INode
-		{
-			readonly PatternMatching.Pattern child;
-
-			public PatternPlaceholder(PatternMatching.Pattern child)
-			{
-				this.child = child;
-			}
-
-			public override NodeType NodeType {
-				get { return NodeType.Pattern; }
-			}
-
-			public override void AcceptVisitor(IAstVisitor visitor)
-			{
-				visitor.VisitPatternPlaceholder(this, child);
-			}
-
-			public override T AcceptVisitor<T>(IAstVisitor<T> visitor)
-			{
-				return visitor.VisitPatternPlaceholder(this, child);
-			}
-
-			public override S AcceptVisitor<T, S>(IAstVisitor<T, S> visitor, T data)
-			{
-				return visitor.VisitPatternPlaceholder(this, child, data);
-			}
-
-			protected internal override bool DoMatch(AstNode other, PatternMatching.Match match)
-			{
-				return child.DoMatch(other, match);
-			}
-
-			bool PatternMatching.INode.DoMatchCollection(Role role, PatternMatching.INode pos, PatternMatching.Match match, PatternMatching.BacktrackingInfo backtrackingInfo)
-			{
-				return child.DoMatchCollection(role, pos, match, backtrackingInfo);
-			}
-		}
-		#endregion
-
 		public static readonly Role<CaseLabel> CaseLabelRole = new Role<CaseLabel>("CaseLabel", null);
 
 		public override NodeType NodeType {

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

@@ -71,7 +71,7 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 	/// <summary>
 	/// catch (Type VariableName) { Body }
 	/// </summary>
-	[DecompilerAstNode(hasNullNode: true)]
+	[DecompilerAstNode(hasNullNode: true, hasPatternPlaceholder: true)]
 	public partial class CatchClause : AstNode
 	{
 		public static readonly TokenRole CatchKeywordRole = new TokenRole("catch");
@@ -80,52 +80,6 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 		public static readonly TokenRole CondLPar = new TokenRole("(");
 		public static readonly TokenRole CondRPar = new TokenRole(")");
 
-		#region PatternPlaceholder
-		public static implicit operator CatchClause(PatternMatching.Pattern pattern)
-		{
-			return pattern != null ? new PatternPlaceholder(pattern) : null;
-		}
-
-		sealed class PatternPlaceholder : CatchClause, PatternMatching.INode
-		{
-			readonly PatternMatching.Pattern child;
-
-			public PatternPlaceholder(PatternMatching.Pattern child)
-			{
-				this.child = child;
-			}
-
-			public override NodeType NodeType {
-				get { return NodeType.Pattern; }
-			}
-
-			public override void AcceptVisitor(IAstVisitor visitor)
-			{
-				visitor.VisitPatternPlaceholder(this, child);
-			}
-
-			public override T AcceptVisitor<T>(IAstVisitor<T> visitor)
-			{
-				return visitor.VisitPatternPlaceholder(this, child);
-			}
-
-			public override S AcceptVisitor<T, S>(IAstVisitor<T, S> visitor, T data)
-			{
-				return visitor.VisitPatternPlaceholder(this, child, data);
-			}
-
-			protected internal override bool DoMatch(AstNode other, PatternMatching.Match match)
-			{
-				return child.DoMatch(other, match);
-			}
-
-			bool PatternMatching.INode.DoMatchCollection(Role role, PatternMatching.INode pos, PatternMatching.Match match, PatternMatching.BacktrackingInfo backtrackingInfo)
-			{
-				return child.DoMatchCollection(role, pos, match, backtrackingInfo);
-			}
-		}
-		#endregion
-
 		public override NodeType NodeType {
 			get {
 				return NodeType.Unknown;

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

@@ -30,7 +30,7 @@ using ICSharpCode.Decompiler.TypeSystem;
 
 namespace ICSharpCode.Decompiler.CSharp.Syntax
 {
-	[DecompilerAstNode(hasNullNode: false)]
+	[DecompilerAstNode(hasNullNode: false, hasPatternPlaceholder: true)]
 	public partial class ParameterDeclaration : AstNode
 	{
 		public static readonly Role<AttributeSection> AttributeRole = EntityDeclaration.AttributeRole;
@@ -42,52 +42,6 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 		public static readonly TokenRole InModifierRole = new TokenRole("in");
 		public static readonly TokenRole ParamsModifierRole = new TokenRole("params");
 
-		#region PatternPlaceholder
-		public static implicit operator ParameterDeclaration?(PatternMatching.Pattern pattern)
-		{
-			return pattern != null ? new PatternPlaceholder(pattern) : null;
-		}
-
-		sealed class PatternPlaceholder : ParameterDeclaration, PatternMatching.INode
-		{
-			readonly PatternMatching.Pattern child;
-
-			public PatternPlaceholder(PatternMatching.Pattern child)
-			{
-				this.child = child;
-			}
-
-			public override NodeType NodeType {
-				get { return NodeType.Pattern; }
-			}
-
-			public override void AcceptVisitor(IAstVisitor visitor)
-			{
-				visitor.VisitPatternPlaceholder(this, child);
-			}
-
-			public override T AcceptVisitor<T>(IAstVisitor<T> visitor)
-			{
-				return visitor.VisitPatternPlaceholder(this, child);
-			}
-
-			public override S AcceptVisitor<T, S>(IAstVisitor<T, S> visitor, T data)
-			{
-				return visitor.VisitPatternPlaceholder(this, child, data);
-			}
-
-			protected internal override bool DoMatch(AstNode? other, PatternMatching.Match match)
-			{
-				return child.DoMatch(other, match);
-			}
-
-			bool PatternMatching.INode.DoMatchCollection(Role role, PatternMatching.INode pos, PatternMatching.Match match, PatternMatching.BacktrackingInfo backtrackingInfo)
-			{
-				return child.DoMatchCollection(role, pos, match, backtrackingInfo);
-			}
-		}
-		#endregion
-
 		public override NodeType NodeType => NodeType.Unknown;
 
 		public AstNodeCollection<AttributeSection> Attributes {

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

@@ -27,55 +27,9 @@
 
 namespace ICSharpCode.Decompiler.CSharp.Syntax
 {
-	[DecompilerAstNode(hasNullNode: true)]
+	[DecompilerAstNode(hasNullNode: true, hasPatternPlaceholder: true)]
 	public partial class VariableInitializer : AstNode
 	{
-		#region PatternPlaceholder
-		public static implicit operator VariableInitializer(PatternMatching.Pattern pattern)
-		{
-			return pattern != null ? new PatternPlaceholder(pattern) : null;
-		}
-
-		sealed class PatternPlaceholder : VariableInitializer, PatternMatching.INode
-		{
-			readonly PatternMatching.Pattern child;
-
-			public PatternPlaceholder(PatternMatching.Pattern child)
-			{
-				this.child = child;
-			}
-
-			public override NodeType NodeType {
-				get { return NodeType.Pattern; }
-			}
-
-			public override void AcceptVisitor(IAstVisitor visitor)
-			{
-				visitor.VisitPatternPlaceholder(this, child);
-			}
-
-			public override T AcceptVisitor<T>(IAstVisitor<T> visitor)
-			{
-				return visitor.VisitPatternPlaceholder(this, child);
-			}
-
-			public override S AcceptVisitor<T, S>(IAstVisitor<T, S> visitor, T data)
-			{
-				return visitor.VisitPatternPlaceholder(this, child, data);
-			}
-
-			protected internal override bool DoMatch(AstNode other, PatternMatching.Match match)
-			{
-				return child.DoMatch(other, match);
-			}
-
-			bool PatternMatching.INode.DoMatchCollection(Role role, PatternMatching.INode pos, PatternMatching.Match match, PatternMatching.BacktrackingInfo backtrackingInfo)
-			{
-				return child.DoMatchCollection(role, pos, match, backtrackingInfo);
-			}
-		}
-		#endregion
-
 		public override NodeType NodeType {
 			get {
 				return NodeType.Unknown;