private static void UnpackImpl(LambdaExpression expression, Type voidType, out Expression body, out IEnumerable <ParameterExpression> parameters)
{
var count = expression.Parameters.Count;
if (count == 0)
{
body = expression.Body;
parameters = expression.Parameters;
return;
}
if (count != 1)
{
throw new InvalidOperationException(string.Format(CultureInfo.InvariantCulture, "Expression '{0}' has more than one parameter. In order to detupletize a lambda expression, it should have exactly one parameter of a tuple type.", expression));
}
var tupleParameter = expression.Parameters[0];
var parameterType = tupleParameter.Type;
if (parameterType == voidType)
{
#if USE_SLIM
if (FreeVariableScanner.Find(expression.Body).Contains(tupleParameter))
#else
if (FreeVariableScanner.Scan(expression.Body).Contains(tupleParameter))
#endif
{
throw new InvalidOperationException(string.Format(CultureInfo.InvariantCulture, "The 'void' parameter is bound in the body of lambda expression '{0}'. In order to detupletize a lambda expression with a 'void' parameter, the parameter should be unbound.", expression));
}
body = expression.Body;
parameters = Array.Empty <ParameterExpression>();
return;
}
if (!IsTuple(parameterType))
{
throw new InvalidOperationException(string.Format(CultureInfo.InvariantCulture, "The type of parameter '{0}' in '{1}' is not a valid tuple type: '{2}'.", tupleParameter, expression, parameterType));
}
var tupleType = tupleParameter.Type;
var newParameters = new List <ParameterExpression>();
const int max = TupleTypeCount - 1 /* T1..T7,TRest */;
var type = tupleType;
var i = 0;
while (true)
{
var args = type.GetGenericArguments();
var n = args.Length;
if (args.Length == max)
{
n--;
}
for (var j = 0; j < n; j++)
{
var arg = args[j];
newParameters.Add(Expression.Parameter(arg, "p" + i++));
}
if (args.Length == max)
{
type = args.Last();
}
else
{
break;
}
}
var subst = new ParameterBasedDetupletizer(tupleParameter, newParameters);
body = subst.Visit(expression.Body);
parameters = newParameters;
}