a function has long-term write access to all of its in-out parameters.
he write access for an in-out parameter starts after all of the non-in-out parameters have been evaluated and lasts for the entire duration of that function call. If there are multiple in-out parameters, the write accesses start in the same order as the parameters appear.
One consequence of this long-term write access is that you can't access the original variable that was passed as in-out, even if scoping rules and access control would otherwise permit it—any access to the original creates a conflict. For example:
var stepSize = 1
func increment(_ number: inout Int) {
number += stepSize
}
increment(&stepSize)
// Error: conflicting accesses to stepSize
In the code above, stepSize is a global variable, and it is normally accessible from within increment(_:). However, the read access to stepSize overlaps with the write access to number. As shown in the figure below, both number and stepSize refer to the same location in memory. The read and write accesses refer to the same memory and they overlap, producing a conflict.
