/// <summary>
/// Defers the binding of the operation until later time when the runtime values of all dynamic operation arguments have been computed.
/// </summary>
/// <param name="args">An array of arguments of the dynamic operation.</param>
/// <returns>The <see cref="DynamicMetaObject"/> representing the result of the binding.</returns>
public DynamicMetaObject Defer(params DynamicMetaObject[] args)
{
return(MakeDeferred(BindingRestrictions.Combine(args), args));
}
/// <summary>
/// Performs the runtime binding of the dynamic operation on a set of arguments.
/// </summary>
/// <param name="args">An array of arguments to the dynamic operation.</param>
/// <param name="parameters">The array of <see cref="ParameterExpression"/> instances that represent the parameters of the call site in the binding process.</param>
/// <param name="returnLabel">A LabelTarget used to return the result of the dynamic binding.</param>
/// <returns>
/// An Expression that performs tests on the dynamic operation arguments, and
/// performs the dynamic operation if the tests are valid. If the tests fail on
/// subsequent occurrences of the dynamic operation, Bind will be called again
/// to produce a new <see cref="Expression"/> for the new argument types.
/// </returns>
public sealed override Expression Bind(object[] args, ReadOnlyCollection <ParameterExpression> parameters, LabelTarget returnLabel)
{
ContractUtils.RequiresNotNull(args, "args");
ContractUtils.RequiresNotNull(parameters, "parameters");
ContractUtils.RequiresNotNull(returnLabel, "returnLabel");
if (args.Length == 0)
{
throw Error.OutOfRange("args.Length", 1);
}
if (parameters.Count == 0)
{
throw Error.OutOfRange("parameters.Count", 1);
}
if (args.Length != parameters.Count)
{
throw new ArgumentOutOfRangeException("args");
}
// Ensure that the binder's ReturnType matches CallSite's return
// type. We do this so meta objects and language binders can
// compose trees together without needing to insert converts.
Type expectedResult;
if (IsStandardBinder)
{
expectedResult = ReturnType;
if (returnLabel.Type != typeof(void) &&
!TypeUtils.AreReferenceAssignable(returnLabel.Type, expectedResult))
{
throw Error.BinderNotCompatibleWithCallSite(expectedResult, this, returnLabel.Type);
}
}
else
{
// Even for non-standard binders, we have to at least make sure
// it works with the CallSite's type to build the return.
expectedResult = returnLabel.Type;
}
DynamicMetaObject target = DynamicMetaObject.Create(args[0], parameters[0]);
DynamicMetaObject[] metaArgs = CreateArgumentMetaObjects(args, parameters);
DynamicMetaObject binding = Bind(target, metaArgs);
if (binding == null)
{
throw Error.BindingCannotBeNull();
}
Expression body = binding.Expression;
BindingRestrictions restrictions = binding.Restrictions;
// Ensure the result matches the expected result type.
if (expectedResult != typeof(void) &&
!TypeUtils.AreReferenceAssignable(expectedResult, body.Type))
{
//
// Blame the last person that handled the result: assume it's
// the dynamic object (if any), otherwise blame the language.
//
if (target.Value is IDynamicMetaObjectProvider)
{
throw Error.DynamicObjectResultNotAssignable(body.Type, target.Value.GetType(), this, expectedResult);
}
else
{
throw Error.DynamicBinderResultNotAssignable(body.Type, this, expectedResult);
}
}
// if the target is IDO, standard binders ask it to bind the rule so we may have a target-specific binding.
// it makes sense to restrict on the target's type in such cases.
// ideally IDO metaobjects should do this, but they often miss that type of "this" is significant.
if (IsStandardBinder && args[0] as IDynamicMetaObjectProvider != null)
{
if (restrictions == BindingRestrictions.Empty)
{
throw Error.DynamicBindingNeedsRestrictions(target.Value.GetType(), this);
}
}
restrictions = AddRemoteObjectRestrictions(restrictions, args, parameters);
// Add the return
if (body.NodeType != ExpressionType.Goto)
{
body = Expression.Return(returnLabel, body);
}
// Finally, add restrictions
if (restrictions != BindingRestrictions.Empty)
{
body = Expression.IfThen(restrictions.ToExpression(), body);
}
return(body);
}
/// <summary>
/// Returns a Restrictions object which includes our current restrictions merged
/// with a restriction limiting our type
/// </summary>
private BindingRestrictions GetRestrictions()
{
Debug.Assert(Restrictions == BindingRestrictions.Empty, "We don't merge, restrictions are always empty");
return(BindingRestrictions.GetTypeRestriction(this));
}
