Compile error when using - in regex (sometimes)

[merisanualex]

Hi, I believe I found a bug in Pattern, I expect that all 3 of these would compile fine but 3rd one seems to give a compile time error saying "Regular Expression contains syntax error":

rfl::Pattern<R"(-)", "first"> first; // works
rfl::Pattern<R"([\-])", "second"> second; // works
rfl::Pattern<R"([-])", "third"> third; // error

[liuzicheng1987]

@merisanualex , we are using an external library for that, CTRE:

https://github.com/hanickadot/compile-time-regular-expressions

Could you maybe ask them about this issue?