Re: [boost] expected<T, E...> (Was: [outcome] High level summary of review feedback accepted so far)

Gottlob Frege wrote:

On Sun, Jun 4, 2017 at 12:35 PM, Peter Dimov via Boost

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Perhaps the heuristic could be, if the argument can be interpreted as both a value and an error, the conversion is ambiguous, regardless of which of the two is a better match. This will make the above return ambiguous, which is probably as it should be.

I think I might agree with that. There will definitely be cases where expected has T == int and E == int, and worse, sometimes those cases will be: - T is a template param, so you don't "see" that it is sometimes an int - E is a #define or platform-defined, etc, so it is only _sometimes_ an int

T == int, E == int is not a problem, because it will always be ambiguous. The thorny case is E == int, T == something convertible from int, such as double, long, unsigned.