mono/mcs/class/System.Core/System.Linq.Expressions/Extensions.cs

//
// Extensions.cs
//
// Author:
//   Jb Evain ([email protected])
//
// (C) 2008 Novell, Inc. (http://www.novell.com)
//
// 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.
//

using System;
using System.Collections.Generic;
using System.Reflection;
using System.Reflection.Emit;
using System.Runtime.CompilerServices;

namespace System.Linq.Expressions {

	static class Extensions {

		public static bool IsGenericInstanceOf (this Type self, Type type)
		{
			if (!self.IsGenericType)
				return false;

			return self.GetGenericTypeDefinition () == type;
		}

		public static bool IsNullable (this Type self)
		{
			return self.IsValueType && self.IsGenericInstanceOf (typeof (Nullable<>));
		}

		public static bool IsExpression (this Type self)
		{
			return self == typeof (Expression) || self.IsSubclassOf (typeof (Expression));
		}

		public static bool IsGenericImplementationOf (this Type self, Type type, out Type generic_iface)
		{
			foreach (var iface in self.GetInterfaces ()) {
				if (!iface.IsGenericInstanceOf (type))
					continue;

				generic_iface = iface;
				return true;
			}

			generic_iface = null;
			return false;
		}

		public static bool IsAssignableTo (this Type self, Type type)
		{
			return type.IsAssignableFrom (self)
				|| ArrayTypeAreAssignable (self, type)
				|| ArrayTypeIsAssignableToInterface (self, type);		
		}

		public static Type GetFirstGenericArgument (this Type self)
		{
			return self.GetGenericArguments () [0];
		}

		public static Type MakeGenericTypeFrom (this Type self, Type type)
		{
			return self.MakeGenericType (type.GetGenericArguments ());
		}

		public static Type MakeNullableType (this Type self)
		{
			return typeof (Nullable<>).MakeGenericType (self);
		}

		public static Type GetNotNullableType (this Type self)
		{
			return self.IsNullable () ? self.GetFirstGenericArgument () : self;
		}

		public static MethodInfo GetInvokeMethod (this Type self)
		{
			return self.GetMethod ("Invoke", BindingFlags.Public | BindingFlags.Instance);
		}

		public static MethodInfo MakeGenericMethodFrom (this MethodInfo self, MethodInfo method)
		{
			return self.MakeGenericMethod (method.GetGenericArguments ());
		}

		public static Type [] GetParameterTypes (this MethodBase self)
		{
			var parameters = self.GetParameters ();
			var types = new Type [parameters.Length];

			for (int i = 0; i < types.Length; i++)
				types [i] = parameters [i].ParameterType;

			return types;
		}

		static bool ArrayTypeAreAssignable (Type type, Type candidate)
		{
			if (!type.IsArray || !candidate.IsArray)
				return false;

			if (type.GetArrayRank () != candidate.GetArrayRank ())
				return false;

			return type.GetElementType ().IsAssignableTo (candidate.GetElementType ());
		}

		static bool ArrayTypeIsAssignableToInterface (Type type, Type candidate)
		{
			if (!type.IsArray)
				return false;

			if (!(candidate.IsGenericInstanceOf (typeof (IList<>)) || candidate.IsGenericInstanceOf (typeof (ICollection<>)) || candidate.IsGenericInstanceOf (typeof (IEnumerable<>))))
				return false;

			return type.GetElementType () == candidate.GetFirstGenericArgument ();
		}

		public static void OnFieldOrProperty (this MemberInfo self,
			Action<FieldInfo> onfield, Action<PropertyInfo> onprop)
		{
			switch (self.MemberType) {
			case MemberTypes.Field:
				onfield ((FieldInfo) self);
				return;
			case MemberTypes.Property:
				onprop ((PropertyInfo) self);
				return;
			default:
				throw new ArgumentException ();
			}
		}

		public static T OnFieldOrProperty<T> (this MemberInfo self,
			Func<FieldInfo, T> onfield, Func<PropertyInfo, T> onprop)
		{
			switch (self.MemberType) {
			case MemberTypes.Field:
				return onfield ((FieldInfo) self);
			case MemberTypes.Property:
				return onprop ((PropertyInfo) self);
			default:
				throw new ArgumentException ();
			}
		}

		public static Type MakeStrongBoxType (this Type self)
		{
			return typeof (StrongBox<>).MakeGenericType (self);
		}
	}
}