Unclear error message when a function is passed to with

[domenkozar]

This often happens due to careless usage of with (import lib) where lib file is a function.

Current behaviour

$ cat foo.nix 
with (a: a);

a

$ nix-build foo.nix 
error: value is a function while a set was expected

Expected behaviour

I'd expect the error message to be:

error: value is a function while a set was expected in with statement, at /home/ielectric/dev/nixpkgs/foo.nix:1:5

[domenkozar]

cc @edolstra

[domenkozar]

value is %1% while a set was expected needs to always have Pos attached as per #3505

[stale]

I marked this as stale due to inactivity. → More info

[SuperSandro2000]

bump

[stale]

I marked this as stale due to inactivity. → More info

[roberth]

Still bad, at least in the repl

nix-repl> with (a: a); b   
error:
       … <borked>

         at «none»:0: (source not available)

       error: value is a function while a set was expected

It literally says <borked>

[nixos-discourse]

This issue has been mentioned on NixOS Discourse. There might be relevant details there:

https://discourse.nixos.org/t/2023-06-22-nix-team-meeting-minutes-65/29643/1