Based on simple examples, this will showcase error reporting improvements implemented in the open https://github.com/NixOS/nix/pull/6204 PR. For some errors, nix reports an odd, seemingly unrelated position. Or no position at all. Usually, the same location is used for several potential errors inside a given scope. This PR makes the relation between the error and the location more explicit. For example using "in the second argument of the function call" when the only available location is the function call itself. In some occasion, it adds error messages with no location, and an intermediate "context" trace for the closest known location.