// Creates a GeneratorLambda as a lambda containing a parameterless
// generator. In the case where we return an IEnumerator, it's a very
// simple, constant-time construction. However, if the result is
// IEnumerable, it will perform a full tree walk to ensure that each
// call to GetEnumerator() returns an IEnumerator with the same
// values for the parameters.
public static LambdaExpression GeneratorLambda(
Type delegateType,
LabelTarget label,
Expression body,
string name,
bool rewriteAssignments,
IEnumerable <ParameterExpression> parameters)
{
ContractUtils.RequiresNotNull(delegateType, "delegateType");
ContractUtils.Requires(delegateType.IsSubclassOf(typeof(MulticastDelegate)), "Lambda type parameter must be derived from System.Delegate");
Type generatorType = delegateType.GetMethod("Invoke").GetReturnType();
var paramList = parameters.ToReadOnly();
if (IsEnumerableType(generatorType))
{
// rewrite body
body = TransformEnumerable(body, paramList);
}
return(Expression.Lambda(
delegateType,
Utils.Generator(name, label, body, generatorType, rewriteAssignments),
name,
paramList
));
}
protected override Expression VisitChildren(ExpressionVisitor visitor)
{
Expression b = visitor.Visit(_body);
if (b == _body)
{
return(this);
}
return(Utils.Generator(_name, _target, b, Type));
}
