/// <summary>
/// Checks whether the specified type is a packed tuple.
/// </summary>
/// <param name="type">Type to check.</param>
/// <returns>true if the specified type is a tuple; otherwise, false.</returns>
public static bool IsTuple(Type type)
{
if (type == null)
{
throw new ArgumentNullException(nameof(type));
}
if (!type.IsGenericType() || type.IsGenericTypeDefinition())
{
return(false);
}
var genDef = type.GetGenericTypeDefinition();
if (!TupleTypes.Contains(genDef))
{
return(false);
}
if (genDef == TupleTypes[TupleTypeCount - 1])
{
return(IsTuple(type.GetGenericArguments().Last()));
}
return(true);
}
private bool IsTupleAccessor(MemberExpression node, out int position)
{
var decl = node.Member.DeclaringType;
if (decl.IsGenericType() && TupleTypes.Contains(decl.GetGenericTypeDefinition()))
{
var n = 0;
#if USE_SLIM
var name = ((PropertyInfoSlim)node.Member).Name;
#else
var name = node.Member.Name;
#endif
if (name == "Rest")
{
n = TupleTypeCount - 2;
}
else
{
n = name[4 /* "Item".Length */] - '0';
}
if (node.Expression is MemberExpression lhs && IsTupleAccessor(lhs, out position))
{
position += n;
return(true);
}
if (ReferenceEquals(node.Expression, _tupleParameter))
{
position = n;
return(true);
}
}
position = 0;
return(false);
}
private static IEnumerable <Expression> UnpackImplIterator(Expression expression)
{
var maxTupleType = TupleTypes[TupleTypeCount - 1];
var tuple = expression;
while (tuple != null)
{
if (tuple is not NewExpression newExpr)
{
throw new InvalidOperationException("Only NewExpression nodes can be used to unpack tuples.");
}
var type = newExpr.Type;
var tupleType = default(Type);
if (type.IsGenericType())
{
tupleType = type.GetGenericTypeDefinition();
}
if (tupleType == null || !TupleTypes.Contains(tupleType))
{
throw new InvalidOperationException("Specified type is not a tuple type.");
}
var hasRest = tupleType == maxTupleType;
#if USE_SLIM
var n = newExpr.ArgumentCount - (hasRest ? 1 : 0);
for (var i = 0; i < n; i++)
{
var arg = newExpr.GetArgument(i);
yield return(arg);
}
if (hasRest)
{
tuple = newExpr.GetArgument(n);
}
#else
var n = newExpr.Arguments.Count - (hasRest ? 1 : 0);
for (var i = 0; i < n; i++)
{
var arg = newExpr.Arguments[i];
yield return(arg);
}
if (hasRest)
{
tuple = newExpr.Arguments[n];
}
#endif
else
{
tuple = null;
}
}
}