Print Predicate for Compile-time Assertions on Failure about ut HOT 5 CLOSED

Not sure whether I fully understand, isn't the following what you are asking for 🤔

expect(1_i == 2);

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If I understand correctly, constant is for evaluating an expression at compile time. Please correct me if I'm wrong. When using constant the output for a failure is either true or false instead of a more detailed message containing the assertion. This is most likely a rather niche concern and possible a terrible idea anyways, but if you want to let users do more at compile time it might make sense. Maybe. 😶

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Ah, I see, yeah, you are right, constant is to ensure that expression can be evaluated at compile-time. It actually shows the expression (instead of true/false) if NTTP is supported (only gcc ATM, though, clang doesn't have it yet 😞).

NTTP branch -> https://github.com/boost-experimental/ut/blob/master/include/boost/ut.hpp#L1880
Full example -> https://godbolt.org/z/GJqhsE (it shows the expression in gcc but in clang it only shows true/false)

For the time being, for clang, I'd stick with the run-time version to see the expression and check whether it's constant on top of that (that works for both: clang and gcc)

constexpr auto expr = 1_i == 2;
expect(expr and constant<expr>);

Full example here -> https://godbolt.org/z/Zd-Ni9

from ut.

Awesome! That's exactly what I was talking about. 😌

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👍

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