/src/Libraries/NewNRefactory/ICSharpCode.NRefactory.CSharp/Parser/mcs/ecore.cs

Large files files are truncated, but you can click here to view the full file

//
// ecore.cs: Core of the Expression representation for the intermediate tree.
//
// Author:
//   Miguel de Icaza (miguel@ximian.com)
//   Marek Safar (marek.safar@seznam.cz)
//
// Copyright 2001, 2002, 2003 Ximian, Inc.
// Copyright 2003-2008 Novell, Inc.
// Copyright 2011 Xamarin Inc.
//
//

using System;
using System.Collections.Generic;
using System.Text;
using SLE = System.Linq.Expressions;
using System.Linq;

#if STATIC
using IKVM.Reflection;
using IKVM.Reflection.Emit;
#else
using System.Reflection;
using System.Reflection.Emit;
#endif

namespace Mono.CSharp {

	/// <remarks>
	///   The ExprClass class contains the is used to pass the 
	///   classification of an expression (value, variable, namespace,
	///   type, method group, property access, event access, indexer access,
	///   nothing).
	/// </remarks>
	public enum ExprClass : byte {
		Unresolved	= 0,
		
		Value,
		Variable,
		Namespace,
		Type,
		TypeParameter,
		MethodGroup,
		PropertyAccess,
		EventAccess,
		IndexerAccess,
		Nothing, 
	}

	/// <remarks>
	///   This is used to tell Resolve in which types of expressions we're
	///   interested.
	/// </remarks>
	[Flags]
	public enum ResolveFlags {
		// Returns Value, Variable, PropertyAccess, EventAccess or IndexerAccess.
		VariableOrValue		= 1,

		// Returns a type expression.
		Type			= 1 << 1,

		// Returns a method group.
		MethodGroup		= 1 << 2,

		TypeParameter	= 1 << 3,

		// Mask of all the expression class flags.
		MaskExprClass = VariableOrValue | Type | MethodGroup | TypeParameter,
	}

	//
	// This is just as a hint to AddressOf of what will be done with the
	// address.
	[Flags]
	public enum AddressOp {
		Store = 1,
		Load  = 2,
		LoadStore = 3
	};
	
	/// <summary>
	///   This interface is implemented by variables
	/// </summary>
	public interface IMemoryLocation {
		/// <summary>
		///   The AddressOf method should generate code that loads
		///   the address of the object and leaves it on the stack.
		///
		///   The `mode' argument is used to notify the expression
		///   of whether this will be used to read from the address or
		///   write to the address.
		///
		///   This is just a hint that can be used to provide good error
		///   reporting, and should have no other side effects. 
		/// </summary>
		void AddressOf (EmitContext ec, AddressOp mode);
	}

	//
	// An expressions resolved as a direct variable reference
	//
	public interface IVariableReference : IFixedExpression
	{
		bool IsHoisted { get; }
		string Name { get; }
		VariableInfo VariableInfo { get; }

		void SetHasAddressTaken ();
	}

	//
	// Implemented by an expression which could be or is always
	// fixed
	//
	public interface IFixedExpression
	{
		bool IsFixed { get; }
	}

	public interface IExpressionCleanup
	{
		void EmitCleanup (EmitContext ec);
	}

	/// <remarks>
	///   Base class for expressions
	/// </remarks>
	public abstract class Expression {
		public ExprClass eclass;
		protected TypeSpec type;
		protected Location loc;
		
		public TypeSpec Type {
			get { return type; }
			set { type = value; }
		}

		public virtual bool IsSideEffectFree {
			get {
				return false;
			}
		}

		public Location Location {
			get { return loc; }
		}

		public virtual bool IsNull {
			get {
				return false;
			}
		}

		//
		// Returns true when the expression during Emit phase breaks stack
		// by using await expression
		//
		public virtual bool ContainsEmitWithAwait ()
		{
			return false;
		}

		/// <summary>
		///   Performs semantic analysis on the Expression
		/// </summary>
		///
		/// <remarks>
		///   The Resolve method is invoked to perform the semantic analysis
		///   on the node.
		///
		///   The return value is an expression (it can be the
		///   same expression in some cases) or a new
		///   expression that better represents this node.
		///   
		///   For example, optimizations of Unary (LiteralInt)
		///   would return a new LiteralInt with a negated
		///   value.
		///   
		///   If there is an error during semantic analysis,
		///   then an error should be reported (using Report)
		///   and a null value should be returned.
		///   
		///   There are two side effects expected from calling
		///   Resolve(): the the field variable "eclass" should
		///   be set to any value of the enumeration
		///   `ExprClass' and the type variable should be set
		///   to a valid type (this is the type of the
		///   expression).
		/// </remarks>
		protected abstract Expression DoResolve (ResolveContext rc);

		public virtual Expression DoResolveLValue (ResolveContext rc, Expression right_side)
		{
			return null;
		}

		//
		// This is used if the expression should be resolved as a type or namespace name.
		// the default implementation fails.   
		//
		public virtual TypeSpec ResolveAsType (IMemberContext mc)
		{
			ResolveContext ec = new ResolveContext (mc);
			Expression e = Resolve (ec);
			if (e != null)
				e.Error_UnexpectedKind (ec, ResolveFlags.Type, loc);

			return null;
		}

		public static void ErrorIsInaccesible (IMemberContext rc, string member, Location loc)
		{
			rc.Module.Compiler.Report.Error (122, loc, "`{0}' is inaccessible due to its protection level", member);
		}

		public void Error_ExpressionMustBeConstant (ResolveContext rc, Location loc, string e_name)
		{
			rc.Report.Error (133, loc, "The expression being assigned to `{0}' must be constant", e_name);
		}

		public void Error_ConstantCanBeInitializedWithNullOnly (ResolveContext rc, TypeSpec type, Location loc, string name)
		{
			rc.Report.Error (134, loc, "A constant `{0}' of reference type `{1}' can only be initialized with null",
				name, TypeManager.CSharpName (type));
		}

		public static void Error_InvalidExpressionStatement (Report Report, Location loc)
		{
			Report.Error (201, loc, "Only assignment, call, increment, decrement, await, and new object expressions can be used as a statement");
		}
		
		public void Error_InvalidExpressionStatement (BlockContext ec)
		{
			Error_InvalidExpressionStatement (ec.Report, loc);
		}

		public static void Error_VoidInvalidInTheContext (Location loc, Report Report)
		{
			Report.Error (1547, loc, "Keyword `void' cannot be used in this context");
		}

		public virtual void Error_ValueCannotBeConverted (ResolveContext ec, TypeSpec target, bool expl)
		{
			Error_ValueCannotBeConvertedCore (ec, loc, target, expl);
		}

		protected void Error_ValueCannotBeConvertedCore (ResolveContext ec, Location loc, TypeSpec target, bool expl)
		{
			// The error was already reported as CS1660
			if (type == InternalType.AnonymousMethod || type == InternalType.ErrorType)
				return;

			string from_type = type.GetSignatureForError ();
			string to_type = target.GetSignatureForError ();
			if (from_type == to_type) {
				from_type = type.GetSignatureForErrorIncludingAssemblyName ();
				to_type = target.GetSignatureForErrorIncludingAssemblyName ();
			}

			if (expl) {
				ec.Report.Error (30, loc, "Cannot convert type `{0}' to `{1}'",
					from_type, to_type);
				return;
			}

			ec.Report.DisableReporting ();
			bool expl_exists = Convert.ExplicitConversion (ec, this, target, Location.Null) != null;
			ec.Report.EnableReporting ();

			if (expl_exists) {
				ec.Report.Error (266, loc,
					"Cannot implicitly convert type `{0}' to `{1}'. An explicit conversion exists (are you missing a cast?)",
					from_type, to_type);
			} else {
				ec.Report.Error (29, loc, "Cannot implicitly convert type `{0}' to `{1}'",
					from_type, to_type);
			}
		}

		public void Error_TypeArgumentsCannotBeUsed (IMemberContext context, MemberSpec member, int arity, Location loc)
		{
			// Better message for possible generic expressions
			if (member != null && (member.Kind & MemberKind.GenericMask) != 0) {
				var report = context.Module.Compiler.Report;
				report.SymbolRelatedToPreviousError (member);
				if (member is TypeSpec)
					member = ((TypeSpec) member).GetDefinition ();
				else
					member = ((MethodSpec) member).GetGenericMethodDefinition ();

				string name = member.Kind == MemberKind.Method ? "method" : "type";
				if (member.IsGeneric) {
					report.Error (305, loc, "Using the generic {0} `{1}' requires `{2}' type argument(s)",
						name, member.GetSignatureForError (), member.Arity.ToString ());
				} else {
					report.Error (308, loc, "The non-generic {0} `{1}' cannot be used with the type arguments",
						name, member.GetSignatureForError ());
				}
			} else {
				Error_TypeArgumentsCannotBeUsed (context, ExprClassName, GetSignatureForError (), loc);
			}
		}

		public void Error_TypeArgumentsCannotBeUsed (IMemberContext context, string exprType, string name, Location loc)
		{
			context.Module.Compiler.Report.Error (307, loc, "The {0} `{1}' cannot be used with type arguments",
				exprType, name);
		}

		protected virtual void Error_TypeDoesNotContainDefinition (ResolveContext ec, TypeSpec type, string name)
		{
			Error_TypeDoesNotContainDefinition (ec, loc, type, name);
		}

		public static void Error_TypeDoesNotContainDefinition (ResolveContext ec, Location loc, TypeSpec type, string name)
		{
			ec.Report.SymbolRelatedToPreviousError (type);
			ec.Report.Error (117, loc, "`{0}' does not contain a definition for `{1}'",
				TypeManager.CSharpName (type), name);
		}

		public virtual void Error_ValueAssignment (ResolveContext rc, Expression rhs)
		{
			if (rhs == EmptyExpression.LValueMemberAccess || rhs == EmptyExpression.LValueMemberOutAccess) {
				rc.Report.SymbolRelatedToPreviousError (type);
				if (rc.CurrentInitializerVariable != null) {
					rc.Report.Error (1918, loc, "Members of value type `{0}' cannot be assigned using a property `{1}' object initializer",
						type.GetSignatureForError (), GetSignatureForError ());
				} else {
					rc.Report.Error (1612, loc, "Cannot modify a value type return value of `{0}'. Consider storing the value in a temporary variable",
						GetSignatureForError ());
				}
			} else {
				rc.Report.Error (131, loc, "The left-hand side of an assignment must be a variable, a property or an indexer");
			}
		}

		protected void Error_VoidPointerOperation (ResolveContext rc)
		{
			rc.Report.Error (242, loc, "The operation in question is undefined on void pointers");
		}

		public ResolveFlags ExprClassToResolveFlags {
			get {
				switch (eclass) {
				case ExprClass.Type:
				case ExprClass.Namespace:
					return ResolveFlags.Type;
					
				case ExprClass.MethodGroup:
					return ResolveFlags.MethodGroup;
					
				case ExprClass.TypeParameter:
					return ResolveFlags.TypeParameter;
					
				case ExprClass.Value:
				case ExprClass.Variable:
				case ExprClass.PropertyAccess:
				case ExprClass.EventAccess:
				case ExprClass.IndexerAccess:
					return ResolveFlags.VariableOrValue;
					
				default:
					throw new InternalErrorException (loc.ToString () + " " +  GetType () + " ExprClass is Invalid after resolve");
				}
			}
		}

		public virtual string GetSignatureForError ()
		{
			return type.GetDefinition ().GetSignatureForError ();
		}
	       
		/// <summary>
		///   Resolves an expression and performs semantic analysis on it.
		/// </summary>
		///
		/// <remarks>
		///   Currently Resolve wraps DoResolve to perform sanity
		///   checking and assertion checking on what we expect from Resolve.
		/// </remarks>
		public Expression Resolve (ResolveContext ec, ResolveFlags flags)
		{
			if (eclass != ExprClass.Unresolved)
				return this;
			
			Expression e;
			try {
				e = DoResolve (ec);

				if (e == null)
					return null;

				if ((flags & e.ExprClassToResolveFlags) == 0) {
					e.Error_UnexpectedKind (ec, flags, loc);
					return null;
				}

				if (e.type == null)
					throw new InternalErrorException ("Expression `{0}' didn't set its type in DoResolve", e.GetType ());

				return e;
			} catch (Exception ex) {
				if (loc.IsNull || ec.Module.Compiler.Settings.DebugFlags > 0 || ex is CompletionResult || ec.Report.IsDisabled || ex is FatalException)
					throw;

				ec.Report.Error (584, loc, "Internal compiler error: {0}", ex.Message);
				return ErrorExpression.Instance;	// TODO: Add location
			}
		}

		/// <summary>
		///   Resolves an expression and performs semantic analysis on it.
		/// </summary>
		public Expression Resolve (ResolveContext rc)
		{
			return Resolve (rc, ResolveFlags.VariableOrValue | ResolveFlags.MethodGroup);
		}

		/// <summary>
		///   Resolves an expression for LValue assignment
		/// </summary>
		///
		/// <remarks>
		///   Currently ResolveLValue wraps DoResolveLValue to perform sanity
		///   checking and assertion checking on what we expect from Resolve
		/// </remarks>
		public Expression ResolveLValue (ResolveContext ec, Expression right_side)
		{
			int errors = ec.Report.Errors;
			bool out_access = right_side == EmptyExpression.OutAccess;

			Expression e = DoResolveLValue (ec, right_side);

			if (e != null && out_access && !(e is IMemoryLocation)) {
				// FIXME: There's no problem with correctness, the 'Expr = null' handles that.
				//        Enabling this 'throw' will "only" result in deleting useless code elsewhere,

				//throw new InternalErrorException ("ResolveLValue didn't return an IMemoryLocation: " +
				//				  e.GetType () + " " + e.GetSignatureForError ());
				e = null;
			}

			if (e == null) {
				if (errors == ec.Report.Errors) {
					if (out_access)
						ec.Report.Error (1510, loc, "A ref or out argument must be an assignable variable");
					else
						Error_ValueAssignment (ec, right_side);
				}
				return null;
			}

			if (e.eclass == ExprClass.Unresolved)
				throw new Exception ("Expression " + e + " ExprClass is Invalid after resolve");

			if ((e.type == null) && !(e is GenericTypeExpr))
				throw new Exception ("Expression " + e + " did not set its type after Resolve");

			return e;
		}

		public virtual void EncodeAttributeValue (IMemberContext rc, AttributeEncoder enc, TypeSpec targetType)
		{
			rc.Module.Compiler.Report.Error (182, loc,
				"An attribute argument must be a constant expression, typeof expression or array creation expression");
		}

		/// <summary>
		///   Emits the code for the expression
		/// </summary>
		///
		/// <remarks>
		///   The Emit method is invoked to generate the code
		///   for the expression.  
		/// </remarks>
		public abstract void Emit (EmitContext ec);


		// Emit code to branch to @target if this expression is equivalent to @on_true.
		// The default implementation is to emit the value, and then emit a brtrue or brfalse.
		// Subclasses can provide more efficient implementations, but those MUST be equivalent,
		// including the use of conditional branches.  Note also that a branch MUST be emitted
		public virtual void EmitBranchable (EmitContext ec, Label target, bool on_true)
		{
			Emit (ec);
			ec.Emit (on_true ? OpCodes.Brtrue : OpCodes.Brfalse, target);
		}

		// Emit this expression for its side effects, not for its value.
		// The default implementation is to emit the value, and then throw it away.
		// Subclasses can provide more efficient implementations, but those MUST be equivalent
		public virtual void EmitSideEffect (EmitContext ec)
		{
			Emit (ec);
			ec.Emit (OpCodes.Pop);
		}

		//
		// Emits the expression into temporary field variable. The method
		// should be used for await expressions only
		//
		public virtual Expression EmitToField (EmitContext ec)
		{
			//
			// This is the await prepare Emit method. When emitting code like
			// a + b we emit code like
			//
			// a.Emit ()
			// b.Emit ()
			// Opcodes.Add
			//
			// For await a + await b we have to interfere the flow to keep the
			// stack clean because await yields from the expression. The emit
			// then changes to
			//
			// a = a.EmitToField ()	// a is changed to temporary field access
			// b = b.EmitToField ()
			// a.Emit ()
			// b.Emit ()
			// Opcodes.Add
			//
			//
			// The idea is to emit expression and leave the stack empty with
			// result value still available.
			//
			// Expressions should override this default implementation when
			// optimized version can be provided (e.g. FieldExpr)
			//
			//
			// We can optimize for side-effect free expressions, they can be
			// emitted out of order
			//
			if (IsSideEffectFree)
				return this;

			bool needs_temporary = ContainsEmitWithAwait ();
			if (!needs_temporary)
				ec.EmitThis ();

			// Emit original code
			var field = EmitToFieldSource (ec);
			if (field == null) {
				//
				// Store the result to temporary field when we
				// cannot load `this' directly
				//
				field = ec.GetTemporaryField (type);
				if (needs_temporary) {
					//
					// Create temporary local (we cannot load `this' before Emit)
					//
					var temp = ec.GetTemporaryLocal (type);
					ec.Emit (OpCodes.Stloc, temp);

					ec.EmitThis ();
					ec.Emit (OpCodes.Ldloc, temp);
					field.EmitAssignFromStack (ec);

					ec.FreeTemporaryLocal (temp, type);
				} else {
					field.EmitAssignFromStack (ec);
				}
			}

			return field;
		}

		protected virtual FieldExpr EmitToFieldSource (EmitContext ec)
		{
			//
			// Default implementation calls Emit method
			//
			Emit (ec);
			return null;
		}

		protected static void EmitExpressionsList (EmitContext ec, List<Expression> expressions)
		{
			if (ec.HasSet (BuilderContext.Options.AsyncBody)) {
				bool contains_await = false;

				for (int i = 1; i < expressions.Count; ++i) {
					if (expressions[i].ContainsEmitWithAwait ()) {
						contains_await = true;
						break;
					}
				}

				if (contains_await) {
					for (int i = 0; i < expressions.Count; ++i) {
						expressions[i] = expressions[i].EmitToField (ec);
					}
				}
			}

			for (int i = 0; i < expressions.Count; ++i) {
				expressions[i].Emit (ec);
			}
		}

		/// <summary>
		///   Protected constructor.  Only derivate types should
		///   be able to be created
		/// </summary>

		protected Expression ()
		{
		}

		/// <summary>
		///   Returns a fully formed expression after a MemberLookup
		/// </summary>
		/// 
		static Expression ExprClassFromMemberInfo (MemberSpec spec, Location loc)
		{
			if (spec is EventSpec)
				return new EventExpr ((EventSpec) spec, loc);
			if (spec is ConstSpec)
				return new ConstantExpr ((ConstSpec) spec, loc);
			if (spec is FieldSpec)
				return new FieldExpr ((FieldSpec) spec, loc);
			if (spec is PropertySpec)
				return new PropertyExpr ((PropertySpec) spec, loc);
			if (spec is TypeSpec)
				return new TypeExpression (((TypeSpec) spec), loc);

			return null;
		}

		public static MethodSpec ConstructorLookup (ResolveContext rc, TypeSpec type, ref Arguments args, Location loc)
		{
			var ctors = MemberCache.FindMembers (type, Constructor.ConstructorName, true);
			if (ctors == null) {
				rc.Report.SymbolRelatedToPreviousError (type);
				if (type.IsStruct) {
					// Report meaningful error for struct as they always have default ctor in C# context
					OverloadResolver.Error_ConstructorMismatch (rc, type, args == null ? 0 : args.Count, loc);
				} else {
					rc.Report.Error (143, loc, "The class `{0}' has no constructors defined",
						type.GetSignatureForError ());
				}

				return null;
			}

			var r = new OverloadResolver (ctors, OverloadResolver.Restrictions.NoBaseMembers, loc);
			if (!rc.HasSet (ResolveContext.Options.BaseInitializer)) {
				r.InstanceQualifier = new ConstructorInstanceQualifier (type);
			}

			return r.ResolveMember<MethodSpec> (rc, ref args);
		}

		[Flags]
		public enum MemberLookupRestrictions
		{
			None = 0,
			InvocableOnly = 1,
			ExactArity = 1 << 2,
			ReadAccess = 1 << 3
		}

		//
		// Lookup type `queried_type' for code in class `container_type' with a qualifier of
		// `qualifier_type' or null to lookup members in the current class.
		//
		public static Expression MemberLookup (IMemberContext rc, bool errorMode, TypeSpec queried_type, string name, int arity, MemberLookupRestrictions restrictions, Location loc)
		{
			var members = MemberCache.FindMembers (queried_type, name, false);
			if (members == null)
				return null;

			MemberSpec non_method = null;
			MemberSpec ambig_non_method = null;
			do {
				for (int i = 0; i < members.Count; ++i) {
					var member = members[i];

					// HACK: for events because +=/-= can appear at same class only, should use OverrideToBase there
					if ((member.Modifiers & Modifiers.OVERRIDE) != 0 && member.Kind != MemberKind.Event)
						continue;

					if ((member.Modifiers & Modifiers.BACKING_FIELD) != 0)
						continue;

					if ((arity > 0 || (restrictions & MemberLookupRestrictions.ExactArity) != 0) && member.Arity != arity)
						continue;

					if (!errorMode) {
						if (!member.IsAccessible (rc))
							continue;

						//
						// With runtime binder we can have a situation where queried type is inaccessible
						// because it came via dynamic object, the check about inconsisted accessibility
						// had no effect as the type was unknown during compilation
						//
						// class A {
						//		private class N { }
						//
						//		public dynamic Foo ()
						//		{
						//			return new N ();
						//		}
						//	}
						//
						if (rc.Module.Compiler.IsRuntimeBinder && !member.DeclaringType.IsAccessible (rc))
							continue;
					}

					if ((restrictions & MemberLookupRestrictions.InvocableOnly) != 0) {
						if (member is MethodSpec)
							return new MethodGroupExpr (members, queried_type, loc);

						if (!Invocation.IsMemberInvocable (member))
							continue;
					}

					if (non_method == null || member is MethodSpec || non_method.IsNotCSharpCompatible) {
						non_method = member;
					} else if (!errorMode && !member.IsNotCSharpCompatible) {
						ambig_non_method = member;
					}
				}

				if (non_method != null) {
					if (ambig_non_method != null && rc != null) {
						var report = rc.Module.Compiler.Report;
						report.SymbolRelatedToPreviousError (non_method);
						report.SymbolRelatedToPreviousError (ambig_non_method);
						report.Error (229, loc, "Ambiguity between `{0}' and `{1}'",
							non_method.GetSignatureForError (), ambig_non_method.GetSignatureForError ());
					}

					if (non_method is MethodSpec)
						return new MethodGroupExpr (members, queried_type, loc);

					return ExprClassFromMemberInfo (non_method, loc);
				}

				if (members[0].DeclaringType.BaseType == null)
					members = null;
				else
					members = MemberCache.FindMembers (members[0].DeclaringType.BaseType, name, false);

			} while (members != null);

			return null;
		}

		protected virtual void Error_NegativeArrayIndex (ResolveContext ec, Location loc)
		{
			throw new NotImplementedException ();
		}

		public virtual void Error_OperatorCannotBeApplied (ResolveContext rc, Location loc, string oper, TypeSpec t)
		{
			if (t == InternalType.ErrorType)
				return;

			rc.Report.Error (23, loc, "The `{0}' operator cannot be applied to operand of type `{1}'",
				oper, t.GetSignatureForError ());
		}

		protected void Error_PointerInsideExpressionTree (ResolveContext ec)
		{
			ec.Report.Error (1944, loc, "An expression tree cannot contain an unsafe pointer operation");
		}

		/// <summary>
		///   Returns an expression that can be used to invoke operator true
		///   on the expression if it exists.
		/// </summary>
		protected static Expression GetOperatorTrue (ResolveContext ec, Expression e, Location loc)
		{
			return GetOperatorTrueOrFalse (ec, e, true, loc);
		}

		/// <summary>
		///   Returns an expression that can be used to invoke operator false
		///   on the expression if it exists.
		/// </summary>
		protected static Expression GetOperatorFalse (ResolveContext ec, Expression e, Location loc)
		{
			return GetOperatorTrueOrFalse (ec, e, false, loc);
		}

		static Expression GetOperatorTrueOrFalse (ResolveContext ec, Expression e, bool is_true, Location loc)
		{
			var op = is_true ? Operator.OpType.True : Operator.OpType.False;
			var methods = MemberCache.GetUserOperator (e.type, op, false);
			if (methods == null)
				return null;

			Arguments arguments = new Arguments (1);
			arguments.Add (new Argument (e));

			var res = new OverloadResolver (methods, OverloadResolver.Restrictions.BaseMembersIncluded | OverloadResolver.Restrictions.NoBaseMembers, loc);
			var oper = res.ResolveOperator (ec, ref arguments);

			if (oper == null)
				return null;

			return new UserOperatorCall (oper, arguments, null, loc);
		}
		
		public virtual string ExprClassName
		{
			get {
				switch (eclass){
				case ExprClass.Unresolved:
					return "Unresolved";
				case ExprClass.Value:
					return "value";
				case ExprClass.Variable:
					return "variable";
				case ExprClass.Namespace:
					return "namespace";
				case ExprClass.Type:
					return "type";
				case ExprClass.MethodGroup:
					return "method group";
				case ExprClass.PropertyAccess:
					return "property access";
				case ExprClass.EventAccess:
					return "event access";
				case ExprClass.IndexerAccess:
					return "indexer access";
				case ExprClass.Nothing:
					return "null";
				case ExprClass.TypeParameter:
					return "type parameter";
				}
				throw new Exception ("Should not happen");
			}
		}
		
		/// <summary>
		///   Reports that we were expecting `expr' to be of class `expected'
		/// </summary>
		public void Error_UnexpectedKind (IMemberContext ctx, Expression memberExpr, string expected, string was, Location loc)
		{
			var name = memberExpr.GetSignatureForError ();

			ctx.Module.Compiler.Report.Error (118, loc, "`{0}' is a `{1}' but a `{2}' was expected", name, was, expected);
		}

		public virtual void Error_UnexpectedKind (ResolveContext ec, ResolveFlags flags, Location loc)
		{
			string [] valid = new string [4];
			int count = 0;

			if ((flags & ResolveFlags.VariableOrValue) != 0) {
				valid [count++] = "variable";
				valid [count++] = "value";
			}

			if ((flags & ResolveFlags.Type) != 0)
				valid [count++] = "type";

			if ((flags & ResolveFlags.MethodGroup) != 0)
				valid [count++] = "method group";

			if (count == 0)
				valid [count++] = "unknown";

			StringBuilder sb = new StringBuilder (valid [0]);
			for (int i = 1; i < count - 1; i++) {
				sb.Append ("', `");
				sb.Append (valid [i]);
			}
			if (count > 1) {
				sb.Append ("' or `");
				sb.Append (valid [count - 1]);
			}

			ec.Report.Error (119, loc, 
				"Expression denotes a `{0}', where a `{1}' was expected", ExprClassName, sb.ToString ());
		}
		
		public static void UnsafeError (ResolveContext ec, Location loc)
		{
			UnsafeError (ec.Report, loc);
		}

		public static void UnsafeError (Report Report, Location loc)
		{
			Report.Error (214, loc, "Pointers and fixed size buffers may only be used in an unsafe context");
		}

		//
		// Converts `source' to an int, uint, long or ulong.
		//
		protected Expression ConvertExpressionToArrayIndex (ResolveContext ec, Expression source)
		{
			var btypes = ec.BuiltinTypes;

			if (source.type.BuiltinType == BuiltinTypeSpec.Type.Dynamic) {
				Arguments args = new Arguments (1);
				args.Add (new Argument (source));
				return new DynamicConversion (btypes.Int, CSharpBinderFlags.ConvertArrayIndex, args, loc).Resolve (ec);
			}

			Expression converted;
			
			using (ec.Set (ResolveContext.Options.CheckedScope)) {
				converted = Convert.ImplicitConversion (ec, source, btypes.Int, source.loc);
				if (converted == null)
					converted = Convert.ImplicitConversion (ec, source, btypes.UInt, source.loc);
				if (converted == null)
					converted = Convert.ImplicitConversion (ec, source, btypes.Long, source.loc);
				if (converted == null)
					converted = Convert.ImplicitConversion (ec, source, btypes.ULong, source.loc);

				if (converted == null) {
					source.Error_ValueCannotBeConverted (ec, btypes.Int, false);
					return null;
				}
			}

			//
			// Only positive constants are allowed at compile time
			//
			Constant c = converted as Constant;
			if (c != null && c.IsNegative)
				Error_NegativeArrayIndex (ec, source.loc);

			// No conversion needed to array index
			if (converted.Type.BuiltinType == BuiltinTypeSpec.Type.Int)
				return converted;

			return new ArrayIndexCast (converted, btypes.Int).Resolve (ec);
		}

		//
		// Derived classes implement this method by cloning the fields that
		// could become altered during the Resolve stage
		//
		// Only expressions that are created for the parser need to implement
		// this.
		//
		protected virtual void CloneTo (CloneContext clonectx, Expression target)
		{
			throw new NotImplementedException (
				String.Format (
					"CloneTo not implemented for expression {0}", this.GetType ()));
		}

		//
		// Clones an expression created by the parser.
		//
		// We only support expressions created by the parser so far, not
		// expressions that have been resolved (many more classes would need
		// to implement CloneTo).
		//
		// This infrastructure is here merely for Lambda expressions which
		// compile the same code using different type values for the same
		// arguments to find the correct overload
		//
		public virtual Expression Clone (CloneContext clonectx)
		{
			Expression cloned = (Expression) MemberwiseClone ();
			CloneTo (clonectx, cloned);

			return cloned;
		}

		//
		// Implementation of expression to expression tree conversion
		//
		public abstract Expression CreateExpressionTree (ResolveContext ec);

		protected Expression CreateExpressionFactoryCall (ResolveContext ec, string name, Arguments args)
		{
			return CreateExpressionFactoryCall (ec, name, null, args, loc);
		}

		protected Expression CreateExpressionFactoryCall (ResolveContext ec, string name, TypeArguments typeArguments, Arguments args)
		{
			return CreateExpressionFactoryCall (ec, name, typeArguments, args, loc);
		}

		public static Expression CreateExpressionFactoryCall (ResolveContext ec, string name, TypeArguments typeArguments, Arguments args, Location loc)
		{
			return new Invocation (new MemberAccess (CreateExpressionTypeExpression (ec, loc), name, typeArguments, loc), args);
		}

		protected static TypeExpr CreateExpressionTypeExpression (ResolveContext ec, Location loc)
		{
			var t = ec.Module.PredefinedTypes.Expression.Resolve ();
			if (t == null)
				return null;

			return new TypeExpression (t, loc);
		}

		//
		// Implemented by all expressions which support conversion from
		// compiler expression to invokable runtime expression. Used by
		// dynamic C# binder.
		//
		public virtual SLE.Expression MakeExpression (BuilderContext ctx)
		{
			throw new NotImplementedException ("MakeExpression for " + GetType ());
		}
			
		public virtual object Accept (StructuralVisitor visitor)
		{
			return visitor.Visit (this);
		}
	}

	/// <summary>
	///   This is just a base class for expressions that can
	///   appear on statements (invocations, object creation,
	///   assignments, post/pre increment and decrement).  The idea
	///   being that they would support an extra Emition interface that
	///   does not leave a result on the stack.
	/// </summary>
	public abstract class ExpressionStatement : Expression {

		public ExpressionStatement ResolveStatement (BlockContext ec)
		{
			Expression e = Resolve (ec);
			if (e == null)
				return null;

			ExpressionStatement es = e as ExpressionStatement;
			if (es == null)
				Error_InvalidExpressionStatement (ec);

			if (ec.CurrentAnonymousMethod is AsyncInitializer && !(e is Assign) &&
				(e.Type.IsGenericTask || e.Type == ec.Module.PredefinedTypes.Task.TypeSpec)) {
				ec.Report.Warning (4014, 1, e.Location,
					"The statement is not awaited and execution of current method continues before the call is completed. Consider using `await' operator");
			}

			return es;
		}

		/// <summary>
		///   Requests the expression to be emitted in a `statement'
		///   context.  This means that no new value is left on the
		///   stack after invoking this method (constrasted with
		///   Emit that will always leave a value on the stack).
		/// </summary>
		public abstract void EmitStatement (EmitContext ec);

		public override void EmitSideEffect (EmitContext ec)
		{
			EmitStatement (ec);
		}
	}

	/// <summary>
	///   This kind of cast is used to encapsulate the child
	///   whose type is child.Type into an expression that is
	///   reported to return "return_type".  This is used to encapsulate
	///   expressions which have compatible types, but need to be dealt
	///   at higher levels with.
	///
	///   For example, a "byte" expression could be encapsulated in one
	///   of these as an "unsigned int".  The type for the expression
	///   would be "unsigned int".
	///
	/// </summary>
	public abstract class TypeCast : Expression
	{
		protected readonly Expression child;

		protected TypeCast (Expression child, TypeSpec return_type)
		{
			eclass = child.eclass;
			loc = child.Location;
			type = return_type;
			this.child = child;
		}

		public Expression Child {
			get {
				return child;
			}
		}

		public override bool ContainsEmitWithAwait ()
		{
			return child.ContainsEmitWithAwait ();
		}

		public override Expression CreateExpressionTree (ResolveContext ec)
		{
			Arguments args = new Arguments (2);
			args.Add (new Argument (child.CreateExpressionTree (ec)));
			args.Add (new Argument (new TypeOf (type, loc)));

			if (type.IsPointer || child.Type.IsPointer)
				Error_PointerInsideExpressionTree (ec);

			return CreateExpressionFactoryCall (ec, ec.HasSet (ResolveContext.Options.CheckedScope) ? "ConvertChecked" : "Convert", args);
		}

		protected override Expression DoResolve (ResolveContext ec)
		{
			// This should never be invoked, we are born in fully
			// initialized state.

			return this;
		}

		public override void Emit (EmitContext ec)
		{
			child.Emit (ec);
		}

		public override SLE.Expression MakeExpression (BuilderContext ctx)
		{
#if STATIC
			return base.MakeExpression (ctx);
#else
			return ctx.HasSet (BuilderContext.Options.CheckedScope) ?
				SLE.Expression.ConvertChecked (child.MakeExpression (ctx), type.GetMetaInfo ()) :
				SLE.Expression.Convert (child.MakeExpression (ctx), type.GetMetaInfo ());
#endif
		}

		protected override void CloneTo (CloneContext clonectx, Expression t)
		{
			// Nothing to clone
		}

		public override bool IsNull {
			get { return child.IsNull; }
		}
	}

	public class EmptyCast : TypeCast {
		EmptyCast (Expression child, TypeSpec target_type)
			: base (child, target_type)
		{
		}

		public static Expression Create (Expression child, TypeSpec type)
		{
			Constant c = child as Constant;
			if (c != null)
				return new EmptyConstantCast (c, type);

			EmptyCast e = child as EmptyCast;
			if (e != null)
				return new EmptyCast (e.child, type);

			return new EmptyCast (child, type);
		}

		public override void EmitBranchable (EmitContext ec, Label label, bool on_true)
		{
			child.EmitBranchable (ec, label, on_true);
		}

		public override void EmitSideEffect (EmitContext ec)
		{
			child.EmitSideEffect (ec);
		}
	}

	//
	// Used for predefined type user operator (no obsolete check, etc.)
	//
	public class OperatorCast : TypeCast
	{
		readonly MethodSpec conversion_operator;

		public OperatorCast (Expression expr, TypeSpec target_type)
			: this (expr, target_type, target_type, false)
		{
		}
		
		public OperatorCast (Expression expr, TypeSpec target_type, bool find_explicit)
			: this (expr, target_type, target_type, find_explicit)
		{
		}
		
		public OperatorCast (Expression expr, TypeSpec declaringType, TypeSpec returnType, bool isExplicit)
			: base (expr, returnType)
		{
			var op = isExplicit ? Operator.OpType.Explicit : Operator.OpType.Implicit;
			var mi = MemberCache.GetUserOperator (declaringType, op, true);

			if (mi != null) {
				foreach (MethodSpec oper in mi) {
					if (oper.ReturnType != returnType)
						continue;

					if (oper.Parameters.Types[0] == expr.Type) {
						conversion_operator = oper;
						return;
					}
				}
			}

			throw new InternalErrorException ("Missing predefined user operator between `{0}' and `{1}'",
				returnType.GetSignatureForError (), expr.Type.GetSignatureForError ());
		}

		public override void Emit (EmitContext ec)
		{
			child.Emit (ec);
			ec.Emit (OpCodes.Call, conversion_operator);
		}
	}
	
	//
	// Constant specialization of EmptyCast.
	// We need to special case this since an empty cast of
	// a constant is still a constant. 
	//
	public class EmptyConstantCast : Constant
	{
		public readonly Constant child;

		public EmptyConstantCast (Constant child, TypeSpec type)
			: base (child.Location)
		{
			if (child == null)
				throw new ArgumentNullException ("child");

			this.child = child;
			this.eclass = child.eclass;
			this.type = type;
		}

		public override Constant ConvertExplicitly (bool in_checked_context, TypeSpec target_type)
		{
			if (child.Type == target_type)
				return child;

			// FIXME: check that 'type' can be converted to 'target_type' first
			return child.ConvertExplicitly (in_checked_context, target_type);
		}

		public override Expression CreateExpressionTree (ResolveContext ec)
		{
			Arguments args = Arguments.CreateForExpressionTree (ec, null,
				child.CreateExpressionTree (ec),
				new TypeOf (type, loc));

			if (type.IsPointer)
				Error_PointerInsideExpressionTree (ec);

			return CreateExpressionFactoryCall (ec, "Convert", args);
		}

		public override bool IsDefaultValue {
			get { return child.IsDefaultValue; }
		}

		public override bool IsNegative {
			get { return child.IsNegative; }
		}

		public override bool IsNull {
			get { return child.IsNull; }
		}
		
		public override bool IsOneInteger {
			get { return child.IsOneInteger; }
		}

		public override bool IsSideEffectFree {
			get {
				return child.IsSideEffectFree;
			}
		}

		public override bool IsZeroInteger {
			get { return child.IsZeroInteger; }
		}

		public override void Emit (EmitContext ec)
		{
			child.Emit (ec);			
		}

		public override void EmitBranchable (EmitContext ec, Label label, bool on_true)
		{
			child.EmitBranchable (ec, label, on_true);

			// Only to make verifier happy
			if (TypeManager.IsGenericParameter (type) && child.IsNull)
				ec.Emit (OpCodes.Unbox_Any, type);
		}

		public override void EmitSideEffect (EmitContext ec)
		{
			child.EmitSideEffect (ec);
		}

		public override object GetValue ()
		{
			return child.GetValue ();
		}

		public override string GetValueAsLiteral ()
		{
			return child.GetValueAsLiteral ();
		}

		public override long GetValueAsLong ()
		{
			return child.GetValueAsLong ();
		}

		public override Constant ConvertImplicitly (TypeSpec target_type)
		{
			if (type == target_type)
				return this;

			// FIXME: Do we need to check user conversions?
			if (!Convert.ImplicitStandardConversionExists (this, target_type))
				return null;

			return child.ConvertImplicitly (target_type);
		}
	}

	/// <summary>
	///  This class is used to wrap literals which belong inside Enums
	/// </summary>
	public class EnumConstant : Constant
	{
		public Constant Child;

		public EnumConstant (Constant child, TypeSpec enum_type)
			: base (child.Location)
		{
			this.Child = child;

			this.eclass = ExprClass.Value;
			this.type = enum_type;
		}

		protected EnumConstant (Location loc)
			: base (loc)
		{
		}

		public override void Emit (EmitContext ec)
		{
			Child.Emit (ec);
		}

		public override void EncodeAttributeValue (IMemberContext rc, AttributeEncoder enc, TypeSpec targetType)
		{
			Child.EncodeAttributeValue (rc, enc, Child.Type);
		}

		public override void EmitBranchable (EmitContext ec, Label label, bool on_true)
		{
			Child.EmitBranchable (ec, label, on_true);
		}

		public override void EmitSideEffect (EmitContext ec)
		{
			Child.EmitSideEffect (ec);
		}

		public override string GetSignatureForError()
		{
			return TypeManager.CSharpName (Type);
		}

		public override object GetValue ()
		{
			return Child.GetValue ();
		}

#if !STATIC
		public override object GetTypedValue ()
		{
			//
			// The method can be used in dynamic context only (on closed types)
			//
			// System.Enum.ToObject cannot be called on dynamic types
			// EnumBuilder has to be used, but we cannot use EnumBuilder
			// because it does not properly support generics
			//
			return System.Enum.ToObject (type.GetMetaInfo (), Child.GetValue ());
		}
#endif

		public override string GetValueAsLiteral ()
		{
			return Child.GetValueAsLiteral ();
		}

		public override long GetValueAsLong ()
		{
			return Child.GetValueAsLong ();
		}

		public EnumConstant Increment()
		{
			return new EnumConstant (((IntegralConstant) Child).Increment (), type);
		}

		public override bool IsDefaultValue {
			get {
				return Child.IsDefaultValue;
			}
		}

		public override bool IsSideEffectFree {
			get {
				return Child.IsSideEffectFree;
			}
		}

		public override bool IsZeroInteger {
			get { return Child.IsZeroInteger; }
		}

		public override bool IsNegative {
			get {
				return Child.IsNegative;
			}
		}

		public override Constant ConvertExplicitly(bool in_checked_context, TypeSpec target_type)
		{
			if (Child.Type == target_type)
				return Child;

			return Child.ConvertExplicitly (in_checked_context, target_type);
		}

		public override Constant ConvertImplicitly (TypeSpec type)
		{
			if (this.type == type) {
				return this;
			}

			if (!Convert.ImplicitStandardConversionExists (this, type)){
				return null;
			}

			return Child.ConvertImplicitly (type);
		}
	}

	/// <summary>
	///   This kind of cast is used to encapsulate Value Types in objects.
	///
	///   The effect of it is to box the value type emitted by the previous
	///   operation.
	/// </summary>
	public class BoxedCast : TypeCast {

		public BoxedCast (Expression expr, TypeSpec target_type)
			: base (expr, target_type)
		{
			eclass = ExprClass.Value;
		}
		
		protected override Expression DoResolve (ResolveContext ec)
		{
			// This should never be invoked, we are born in fully
			// initialized state.

			return this;
		}

		public override void EncodeAttributeValue (IMemberContext rc, AttributeEncoder enc, TypeSpec targetType)
		{
			// Only boxing to object type is supported
			if (targetType.BuiltinType != BuiltinTypeSpec.Type.Object) {
				base.EncodeAttributeValue (rc, enc, targetType);
				return;
			}

			enc.Encode (child.Type);
			child.EncodeAttributeValue (rc, enc, child.Type);
		}

		public override void Emit (EmitContext ec)
		{
			base.Emit (ec);
			
			ec.Emit (OpCodes.Box, child.Type);
		}

		public override void EmitSideEffect (EmitContext ec)
		{
			// boxing is side-effectful, since it involves runtime checks, except when boxing to Object or ValueType
			// so, we need to emit the box+pop instructions in most cases
			if (child.Type.IsStruct &&
			    (type.BuiltinType == BuiltinTypeSpec.Type.Object || type.BuiltinType == BuiltinTypeSpec.Type.ValueType))
				child.EmitSideEffect (ec);
			else
				base.EmitSideEffect (ec);
		}
	}

	public class UnboxCast : TypeCast {
		public UnboxCast (Expression expr, TypeSpec return_type)
			: base (expr, return_type)
		{
		}

		protected override Expression DoResolve (ResolveContext ec)
		{
			// This should never be invoked, we are born in fully
			// initialized state.

			return this;
		}

		public override void Emit (EmitContext ec)
		{
			base.Emit (ec);

			ec.Emit (OpCodes.Unbox_Any, type);
		}
	}
	
	/// <summary>
	///   This is used to perform explicit numeric conversions.
	///
	///   Explicit numeric conversions might trigger exceptions in a checked
	///   context, so they should generate the conv.ovf opcodes instead of
	///   conv opcodes.
	/// </summary>
	public class ConvCast : TypeCast {
		public enum Mode : byte {
			I1_U1, I1_U2, I1_U4, I1_U8, I1_CH,
			U1_I1, U1_CH,
			I2_I1, I2_U1, I2_U2, I2_U4, I2_U8, I2_CH,
			U2_I1, U2_U1, U2_I2, U2_CH,
			I4_I1, I4_U1, I4_I2, I4_U2, I4_U4, I4_U8, I4_CH,
			U4_I1, U4_U1, U4_I2, U4_U2, U4_I4, U4_CH,
			I8_I1, I8_U1, I8_I2, I8_U2, I8_I4, I8_U4, I8_U8, I8_CH, I8_I,
			U8_I1, U8_U1, U8_I2, U8_U2, U8_I4, U8_U4, U8_I8, U8_CH, U8_I,
			CH_I1, CH_U1, CH_I2,
			R4_I1, R4_U1, R4_I2, R4_U2, R4_I4, R4_U4, R4_I8, R4_U8, R4_CH,
			R8_I1, R8_U1, R8_I2, R8_U2, R8_I4, R8_U4, R8_I8, R8_U8, R8_CH, R8_R4,
			I_I8,
		}

		Mode mode;
		
		public ConvCast (Expression child, TypeSpec return_type, Mode m)
			: base (child, return_type)
		{
			mode = m;
		}

		protected override Expression DoResolve (ResolveContext ec)
		{
			// This should never be invoked, we are born in fully
			// initialized state.

			return this;
		}

		public override string ToString ()
		{
			return String.Format ("ConvCast ({0}, {1})", mode, child);
		}
		
		public override void Emit (EmitContext ec)
		{
			base.Emit (ec);

			if (ec.HasSet (EmitContext.Options.CheckedScope)) {
				switch (mode){
				case Mode.I1_U1: ec.Emit (OpCodes.Conv_Ovf_U1); break;
				case Mode.I1_U2: ec.Emit (OpCodes.Conv_Ovf_U2); break;
				case Mode.I1_U4: ec.Emit (OpCodes.Conv_Ovf_U4); break;
				case Mode.I1_U8: ec.Emit (OpCodes.Conv_Ovf_U8); break;
				case Mode.I1_CH: ec.Emit (OpCodes.Conv_Ovf_U2); break;

				case Mode.U1_I1: ec.Emit (OpCodes.Conv_Ovf_I1_Un); break;
				case Mode.U1_CH: /* nothing */ break;

				case Mode.I2_I1: ec.Emit (OpCodes.Conv_Ovf_I1); break;
				case Mode.I2_U1: ec.Emit (OpCodes.Conv_Ovf_U1); break;
				case Mode.I2_U2: ec.Emit (OpCodes.Conv_Ovf_U2); break;
				case Mode.I2_U4: ec.Emit (OpCodes.Conv_Ovf_U4); break;
				case Mode.I2_U8: ec.Emit (OpCodes.Conv_Ovf_U8); break;
				case Mode.I2_CH: ec.Emit (OpCodes.Conv_Ovf_U2); break;

				case Mode.U2_I1: ec.Emit (OpCodes.Conv_Ovf_I1_Un); break;
				case Mode.U2_U1: ec.Emit (OpCodes.Conv_Ovf_U1_Un); break;
				case Mode.U2_I2: ec.Emit (OpCodes.Conv_Ovf_I2_Un); break;
				case Mode.U2_CH: /* nothing */ break;

				case Mode.I4_I1: ec.Emit (OpCodes.Conv_Ovf_I1); break;
				case Mode.I4_U1: ec.Emit (OpCodes.Conv_Ovf_U1); break;
				case Mode.I4_I2: ec.Emit (OpCodes.Conv_Ovf_I2); break;
				case Mode.I4_U4: ec.Emit (OpCodes.Conv_Ovf_U4); break;
				case Mode.I4_U2: ec.Emit (OpCodes.Conv_Ovf_U2); break;
				case Mode.I4_U8: ec.Emit (OpCodes.Conv_Ovf_U8); break;
				case Mode.I4_CH: ec.Emit (OpCodes.Conv_Ovf_U2); break;

				case Mode.U4_I1: ec.Emit (OpCodes.Conv_Ovf_I1_Un); break;
				case Mode.U4_U1: ec.Emit (OpCodes.Conv_Ovf_U1_Un); break;
				case Mode.U4_I2: ec.Emit (OpCodes.Conv_Ovf_I2_Un); break;
				case Mode.U4_U2: ec.Emit (OpCodes.Conv_Ovf_U2_Un); break;
				case Mode.U4_I4: ec.Emit (OpCodes.Conv_Ovf_I4_Un); break;
				case Mode.U4_CH: ec.Emit (OpCodes.Conv_Ovf_U2_Un); break;

				case Mode.I8_I1: ec.Emit (OpCodes.Conv_Ovf_I1); break;
				case Mode.I8_U1: ec.Emit (OpCodes.Conv_Ovf_U1); break;
				case Mode.I8_I2: ec.Emit (OpCodes.Conv_Ovf_I2); break;
				case Mode.I8_U2: ec.Emit (OpCodes.Conv_Ovf_U2); break;
				case Mode.I8_I4: ec.Emit (OpCodes.Conv_Ovf_I4); break;
				case Mode.I8_U4: ec.Emit (OpCodes.Conv_Ovf_U4); break;
				case Mode.I8_U8: ec.Emit (OpCodes.Conv_Ovf_U8); break;
				case Mode.I8_CH: ec.Emit (OpCodes.Conv_Ovf_U2); break;
				case Mode.I8_I: ec.Emit (OpCodes.Conv_Ovf_U); break;

				case Mode.U8_I1: ec.Emit (OpCodes.Conv_Ovf_I1_Un); break;
				case Mode.U8_U1: ec.Emit (OpCodes.Conv_Ovf_U1_Un); break;
				case Mode.U8_I2: ec.Emit (OpCodes.Conv_Ovf_I2_Un); break;
				case Mode.U8_U2: ec.Emit (OpCodes.Conv_Ovf_U2_Un); break;
				case Mode.U8_I4: ec.Emit (OpCodes.Conv_Ovf_I4_Un); break;
				case Mode.U8_U4: ec.Emit (OpCodes.Conv_Ovf_U4_Un); break;
				case Mode.U8_I8: ec.Emit (OpCodes.Conv_Ovf_I8_Un); break;
				case Mode.U8_CH: ec.Emit (OpCodes.Conv_Ovf_U2_Un); break;
				case Mode.U8_I: ec.Emit (OpCodes.Conv_Ovf_U_Un); break;

				case Mode.CH_I1: ec.Emit (OpCodes.Conv_Ovf_I1_Un); break;
				case Mode.CH_U1: ec.Emit (OpCodes.Conv_Ovf_U1_Un); break;
				case Mode.CH_I2: ec.Emit (OpCodes.Conv_Ovf_I2_Un); break;

				case Mode.R4_I1: ec.Emit (OpCodes.Conv_Ovf_I1); break;
				case Mode.R4_U1: ec.Emit (OpCodes.Conv_Ovf_U1); break;
				case Mode.R4_I2: ec.Emit (OpCodes.Conv_Ovf_I2); break;
				case Mode.R4_U2: ec.Emit (OpCodes.Conv_Ovf_U2); break;
				case Mode.R4_I4: ec.Emit (OpCodes.Conv_Ovf_I4); break;
				case Mode.R4_U4: ec.Emit (OpCodes.Conv_Ovf_U4); break;
				case Mode.R4_I8: ec.Emit (OpCodes.Conv_Ovf_I8); break;
				case Mode.R4_U8: ec.Emit (OpCodes.Conv_Ovf_U8); break;
				case Mode.R4_CH: ec.Emit (OpCodes.Conv_Ovf_U2); break;

				case Mode.R8_I1: ec.Emit (OpCodes.Conv_Ovf_I1); break;
				case Mode.R8_U1: ec.Emit (OpCodes.Conv_Ovf_U1); break;
				case Mode.R8_I2: ec.Emit (OpCodes.Conv_Ovf_I2); break;
				case Mode.R8_U2: ec.Emit (OpCodes.Conv_Ovf_U2); break;
				case Mode.R8_I4: ec.Emit (OpCodes.Conv_Ovf_I4); break;
				case Mode.R8_U4: ec.Emit (OpCodes.Conv_Ovf_U4); break;
				case Mode.R8_I8: ec.Emit (OpCodes.Conv_Ovf_I8); break;
				case Mode.R8_U8: ec.Emit (OpCodes.Conv_Ovf_U8); break;
				case Mode.R8_CH: ec.Emit (OpCodes.Conv_Ovf_U2); break;
				case Mode.R8_R4: ec.Emit (OpCodes.Conv_R4); break;

				case Mode.I_I8: ec.Emit (OpCodes.Conv_Ovf_I8_Un); break;
				}
			} else {
				switch (mode){
				case Mode.I1_U1: ec.Emit (OpCodes.Conv_U1); break;
				case Mode.I1_U2: ec.Emit (OpCodes.Conv_U2); break;
				case Mode.I1_U4: ec.Emit (OpCodes.Conv_U4); break;
				case Mode.I1_U8: ec.Emit (OpCodes.Conv_I8); break;
				case Mode.I1_CH: ec.Emit (OpCodes.Conv_U2); break;

				case Mode.U1_I1: ec.Emit (OpCodes.Conv_I1); break;
				case Mode.U1_CH: ec.Emit (OpCodes.Conv_U2); break;

				case Mode.I2_I1: ec.Emit (OpCodes.Conv_I1); break;
				case Mode.I2_U1: ec.Emit (OpCodes.Conv_U1); break;
				case Mode.I2_U2: ec.Emit (OpCodes.Conv_U2); break;
				case Mode.I2_U4: ec.Emit (OpCodes.Conv_U4); break;
				case Mode.I2_U8: ec.Emit (OpCodes.Conv_I8); break;
				case Mode.I2_CH: ec.Emit (OpCodes.Conv_U2); break;

				case Mode.U2_I1: ec.Emit (OpCodes.Conv_I1); break;
				case Mode.U2_U1: ec.Emit (OpCodes.Conv_U1); break;
				case Mode.U2_I2: ec.Emit (OpCodes.Conv_I2); break;
				case Mode.U2_CH: /* nothing */ break;

				case Mode.I4_I1: ec.Emit (OpCodes.Conv_I1); break;
				case Mode.I4_U1: ec.Emit (OpCodes.Conv_U1); break;
				case Mode.I4_I2: ec.Emit (OpCodes.Conv_I2); break;
	…