lix/doc/manual/rl-next/source-positions-in-errors.md

synopsis	issues	prs	credits	category
Source locations are printed more consistently in errors	561	9555	9999years horrors	Improvements

Source location information is now included in error messages more consistently. Given this code:

let
  attr = {foo = "bar";};
  key = {};
in
  attr.${key}

Previously, Nix would show this unhelpful message when attempting to evaluate it:

error:
       … while evaluating an attribute name

       error: value is a set while a string was expected

Now, the error message displays where the problematic value was found:

error:
       … while evaluating an attribute name

         at bad.nix:4:11:

            3|   key = {};
            4| in attr.${key}
             |           ^
            5|

       error: expected a string but found a set: { }