This came up a bit yesterday in PSA: `lhs == error.Typo` is not a compilation error, as I was looking at the proposal to remove ErrorSet.errorname.
All Errors belong to the global set, and ErrorSet is only a subset of those errors. Subsets are not disjoint, in that different sets can contain the same error (think OutOfMemory.
That being said, I’d rather we keep the ability to use ErrorSet.name rather than force the use of error.name. I think the latter promotes the use of Anonymous Error Sets and implicit Error Unions.