In particular, this is important since if you mess up your ObjC error domain/enum pair, then the catch statement will appear to be working when it will never catch anything.

I had:

extern NSErrorDomain const ODOErrorDomain;

typedef NS_ENUM(NSInteger, ODOError) {
    ...
    ODOUnableToFindObjectWithID,
    ...
};

and then `catch ODOError.unableToFindObjectWithID` would compile, but not actually catch anything.

Good motivation. @jckarter, @xedin, think this would be easy enough for a starter bug?

Yes, I think this should be easy enough!

Hi @tjw,

I've began looking into this one and was hoping you could tell me I'm on the right track.

My current line of thinking is that the change will have to occur around
here, specifically strengthening the pattern checks, but i'm honestly not too sure.

Any guidance or strategies to work with these kinds of issues would be much appreciated.

Cheers,
Christian

@Cbieniak, that looks reasonable to me, but I'm no expert. One strategy that might help is to track down where in the compiler an error is generated when attempting to throw a value of a type that doesn't conform to Error.

That could help in making sure that the logic for testing the type is the same between the two spots.

PR: #23217

Fixed on master