Enable using patterns in place of catch clauses.

NRefactory/ICSharpCode.NRefactory/CSharp/Ast/PatternMatching/Match.cs

@@ -12,6 +12,8 @@ namespace ICSharpCode.NRefactory.CSharp.PatternMatching
 	/// </summary>
 	public sealed class Match
 	{
+		// TODO: maybe we should add an implicit Match->bool conversion? (operator implicit bool(Match m) { return m != null; })
+		
 		List<KeyValuePair<string, AstNode>> results = new List<KeyValuePair<string, AstNode>>();
 		
 		internal int CheckPoint()

NRefactory/ICSharpCode.NRefactory/CSharp/Ast/PatternMatching/Pattern.cs

@@ -79,6 +79,11 @@ namespace ICSharpCode.NRefactory.CSharp.PatternMatching
 			return p != null ? new SwitchSectionPlaceholder(p) : null;
 		}
 		
+		public static implicit operator CatchClause(Pattern p)
+		{
+			return p != null ? new CatchClausePlaceholder(p) : null;
+		}
+		
 		// Make debugging easier by giving Patterns a ToString() implementation
 		public override string ToString()
 		{

NRefactory/ICSharpCode.NRefactory/CSharp/Ast/PatternMatching/Placeholder.cs

@@ -210,4 +210,33 @@ namespace ICSharpCode.NRefactory.CSharp.PatternMatching
 			return child.DoMatchCollection(role, pos, match, backtrackingStack);
 		}
 	}
+	
+	sealed class CatchClausePlaceholder : CatchClause
+	{
+		readonly AstNode child;
+		
+		public CatchClausePlaceholder(AstNode child)
+		{
+			this.child = child;
+		}
+		
+		public override NodeType NodeType {
+			get { return NodeType.Placeholder; }
+		}
+		
+		public override S AcceptVisitor<T, S>(IAstVisitor<T, S> visitor, T data)
+		{
+			return ((IPatternAstVisitor<T, S>)visitor).VisitPlaceholder(this, child, data);
+		}
+		
+		protected internal override bool DoMatch(AstNode other, Match match)
+		{
+			return child.DoMatch(other, match);
+		}
+		
+		internal override bool DoMatchCollection(Role role, AstNode pos, Match match, Stack<Pattern.PossibleMatch> backtrackingStack)
+		{
+			return child.DoMatchCollection(role, pos, match, backtrackingStack);
+		}
+	}
 }