If the macros only exist to get file and line information, you could do the same thing by using `#[track_caller]` functions combined with `std::panic::Location` to get that same info. For example, `stack_err!` could be replaced with

  impl StackError {
      #[track_caller]
      fn new_location(msg: impl Display) -> Self {
          let loc = std::panic::Location::caller();
          Self::new(format!("{}:{} {msg}", loc.file(), loc.line()))
      }
  }

such that you call `.map_err(StackError::new_location("data is not a list of strings"))`. A macro is nice if you need to process format strings with arguments (though someone can call `StackError::new_location(format_args!(…))` if they want), but all of your examples show static strings so it's nice to avoid the error in that case.

The use of `std::panic::Location` also means instead of baking that into a format string you could also just have that be an extra field on the error, which would let you expose accessors for it, and you can then print them in your Debug/Display impls.

Speaking of, the Display impl really should not include its source. Standard handling for errors expects that an error prints just itself with Display because it's very common to recurse through sources and print those, so if Display prints the source too then you're duplicating output. Go ahead and print it on Debug though, that's nice for errors returned from `main()`.