> I would argue that the main value proposition of constexpr is not what the compiler can figure out automatically but allowing the developer to express where he wants constexpr and afterwards allow the compiler to verify if that's possible.
If you want to look at it that way, it only applies to variable declarations at best. Not function declarations, which is the most common case of where it's used (and it completely clutters the code).
And honestly, if that was the value proposition, they could've just done it a million other ways. Like think even 'template<auto V> static const auto constant = V' would let you do constant<whatever> and verify it at compile time. Yeah it's C++20 but they could've still done it then or used a different approach, there are lots of ways to address this (attributes, etc.). No need to clutter every function prototype in the language for something that small.
Also I think you're thinking more of consteval than constexpr.
If you want to look at it that way, it only applies to variable declarations at best. Not function declarations, which is the most common case of where it's used (and it completely clutters the code).
And honestly, if that was the value proposition, they could've just done it a million other ways. Like think even 'template<auto V> static const auto constant = V' would let you do constant<whatever> and verify it at compile time. Yeah it's C++20 but they could've still done it then or used a different approach, there are lots of ways to address this (attributes, etc.). No need to clutter every function prototype in the language for something that small.
Also I think you're thinking more of consteval than constexpr.