Unwrapped variables alias the original

[BarabasGitHub]

In previous versions of Zig (pre 4.0) they used to be copies, but now they're an alias it seems.

My linked list code which previously worked fine is now broken.

https://github.com/BarabasGitHub/ZigZag/blob/f76697ddcfb10d25e35bc4594db4e605ce871be8/containers/single_linked_list.zig#L20

            pub fn next(self: *Iterator) ?*Value {
                if (self.node) |node| {
                    self.node = node.next;
                    return &node.value;
                } else {
                    return null;
                }
            }

https://github.com/BarabasGitHub/ZigZag/blob/f76697ddcfb10d25e35bc4594db4e605ce871be8/containers/single_linked_list.zig#L47

        pub fn count(self: Self) usize {
            var i = usize(0);
            var node = self.head;
            while (node) |n| {
                node = n.next;
                i += 1;
            }
            return i;
        }

https://github.com/BarabasGitHub/ZigZag/blob/f76697ddcfb10d25e35bc4594db4e605ce871be8/containers/single_linked_list.zig#L88

        pub fn clear(self: *Self) void {
            var node = self.head;
            while (node) |n| {
                node = n.next;
                self.allocator.destroy(n);
            }
            self.head = null;
        }

Maybe this is how it's supposed to work, but it's not very intuitive.

The fix was to make explicit copies, one way or another, see: BarabasGitHub/ZigZag@42148fd#diff-fe4c994cb2028068ff82d5e173fd2bf9

[mikdusan]

duplicate of #2915