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

// Copyright (c) 2010-2013 AlphaSierraPapa for the SharpDevelop Team
// 
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// to whom the Software is furnished to do so, subject to the following conditions:
// 
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// substantial portions of the Software.
// 
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// 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
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using System;
using System.Collections.Generic;

namespace ICSharpCode.Decompiler.CSharp.Syntax
{
	/// <summary>
	/// Base class for expressions.
	/// </summary>
	/// <remarks>
	/// 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>
	public abstract class Expression : AstNode
	{
		#region Null
		public new static readonly Expression Null = new NullExpression();

		sealed class NullExpression : Expression
		{
			public override bool IsNull {
				get {
					return true;
				}
			}

			public override void AcceptVisitor(IAstVisitor visitor)
			{
				visitor.VisitNullNode(this);
			}

			public override T AcceptVisitor<T>(IAstVisitor<T> visitor)
			{
				return visitor.VisitNullNode(this);
			}

			public override S AcceptVisitor<T, S>(IAstVisitor<T, S> visitor, T data)
			{
				return visitor.VisitNullNode(this, data);
			}

			protected internal override bool DoMatch(AstNode other, PatternMatching.Match match)
			{
				return other == null || other.IsNull;
			}
		}
		#endregion

		#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;
			}
		}

		public new Expression Clone()
		{
			return (Expression)base.Clone();
		}

		public Expression ReplaceWith(Func<Expression, Expression> replaceFunction)
		{
			if (replaceFunction == null)
				throw new ArgumentNullException(nameof(replaceFunction));
			return (Expression)base.ReplaceWith(node => replaceFunction((Expression)node));
		}
	}
}