This is more of a marketing or teaching problem than an actual language design problem. It's not about the compiler overriding the programmer, it's just designe

This is more of a marketing or teaching problem than an actual language design problem. It's not about the compiler overriding the programmer, it's just designed for a different purpose. There were already a bunch of places in the language that required compile-time evaluation- array sizes, template args, static_assert, case expressions, etc. "Can be" is all about enabling existing APIs to be used in those contexts. You can't (and don't want to) force those APIs to run exclusively at compile time, because programs are already using them at runtime all over the place! This talk about compile time evaluation got some people thinking about all the other things they'd like to do at compile time. And there is a way to do that with just `constexpr`- `constexpr` variable initializers are a new "compile-time-only" context just like array sizes/etc, so you can decide at the leaves what to compute ahead of time, without forcing the callees to be exclusively compile time. But there seems to be some kind of disconnect in how people learn about constexpr, where they hear "compile time" and imagine a different design than what actually went into the language, then get even more confused when they hear "can be" and imagine it as something that happens at the compiler's whim rather than deterministically based on the calling context.