option-test.m

#import <Foundation/Foundation.h>

typedef NS_OPTIONS(uint32_t, SomeOption) {
    SomeOptionNone = 0,
    SomeOptionFoo = 1 << 0,
    SomeOptionBar = 1 << 1,
};

int main(int argc, char *argv[]) {
    @autoreleasepool {
        SomeOption o = SomeOptionFoo|SomeOptionBar;
        NSLog(@"o = %u", o);
    }
}

So it seems to be a definite this value doesn't exist in the enum list warning.

For example if we add to Simon's example:

typedef NS_OPTIONS(uint32_t, SomeOption) {
    SomeOptionNone = 0,
    SomeOptionFoo = 1 << 0,
    SomeOptionBar = 1 << 1,
    SomeOptionBaz = 1 << 2,
    SomeOptionAll = (SomeOptionBar | SomeOptionFoo | SomeOptionBaz)
};

doing:

SomeOption option = (SomeOptionBar | SomeOptionFoo | SomeOptionBaz);

is fine, while

SomeOption option = (SomeOptionBar | SomeOptionFoo);

yields the same warning as before.