Don't know why I got sniped into this on a friday night, but here's clang-tidy with only cppcoreguideline checks enabled, against every example:

First example: https://godbolt.org/z/898rorEqG

Second example: https://godbolt.org/z/K6aceesG9

Third example: https://godbolt.org/z/KcbqzMzdK

and I can't get the fourth example to compile without fixing the problems.