Refactor ParameterModifier.This to allow 'this ref' parameters.

ICSharpCode.Decompiler/CSharp/OutputVisitor/CSharpOutputVisitor.cs

@@ -2173,6 +2173,9 @@ namespace ICSharpCode.Decompiler.CSharp.OutputVisitor
 		{
 			StartNode(parameterDeclaration);
 			WriteAttributes(parameterDeclaration.Attributes);
+			if (parameterDeclaration.HasThisModifier) {
+				WriteKeyword(ParameterDeclaration.ThisModifierRole);
+			}
 			switch (parameterDeclaration.ParameterModifier) {
 				case ParameterModifier.Ref:
 					WriteKeyword(ParameterDeclaration.RefModifierRole);
@@ -2183,9 +2186,6 @@ namespace ICSharpCode.Decompiler.CSharp.OutputVisitor
 				case ParameterModifier.Params:
 					WriteKeyword(ParameterDeclaration.ParamsModifierRole);
 					break;
-				case ParameterModifier.This:
-					WriteKeyword(ParameterDeclaration.ThisModifierRole);
-					break;
 				case ParameterModifier.In:
 					WriteKeyword(ParameterDeclaration.InModifierRole);
 					break;

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

@@ -71,7 +71,7 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 		public bool IsExtensionMethod {
 			get {
 				ParameterDeclaration pd = (ParameterDeclaration)GetChildByRole (Roles.Parameter);
-				return pd != null && pd.ParameterModifier == ParameterModifier.This;
+				return pd != null && pd.HasThisModifier;
 			}
 		}
 		

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

@@ -27,12 +27,12 @@
 
 namespace ICSharpCode.Decompiler.CSharp.Syntax
 {
-	public enum ParameterModifier {
+	public enum ParameterModifier
+	{
 		None,
 		Ref,
 		Out,
 		Params,
-		This,
 		In
 	}
 
@@ -98,7 +98,26 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 		}
 
 		public AstNodeCollection<AttributeSection> Attributes {
-			get { return GetChildrenByRole (AttributeRole); }
+			get { return GetChildrenByRole(AttributeRole); }
+		}
+
+		bool hasThisModifier;
+
+		public CSharpTokenNode ThisKeyword {
+			get {
+				if (hasThisModifier) {
+					return GetChildByRole(ThisModifierRole);
+				}
+				return CSharpTokenNode.Null;
+			}
+		}
+
+		public bool HasThisModifier {
+			get { return hasThisModifier; }
+			set {
+				ThrowIfFrozen();
+				hasThisModifier = value;
+			}
 		}
 
 		ParameterModifier parameterModifier;

ICSharpCode.Decompiler/CSharp/Syntax/TypeSystemAstBuilder.cs

@@ -1633,8 +1633,8 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 			foreach (IParameter p in method.Parameters) {
 				decl.Parameters.Add(ConvertParameter(p));
 			}
-			if (method.IsExtensionMethod && method.ReducedFrom == null && decl.Parameters.Any() && decl.Parameters.First().ParameterModifier == ParameterModifier.None)
-				decl.Parameters.First().ParameterModifier = ParameterModifier.This;
+			if (method.IsExtensionMethod && method.ReducedFrom == null && decl.Parameters.Any())
+				decl.Parameters.First().HasThisModifier = true;
 			
 			if (this.ShowTypeParameters && this.ShowTypeParameterConstraints && !method.IsOverride && !method.IsExplicitInterfaceImplementation) {
 				foreach (ITypeParameter tp in method.TypeParameters) {