nixos-option: fix expression position calculation

This was causing null pointer dereferences. Pattern copied from Nix
source code.

1 files changed, 1 insertions, 1 deletions

diff --git a/pkgs/tools/nix/nixos-option/nixos-option.cc b/pkgs/tools/nix/nixos-option/nixos-option.cc
index e4f7bff3c662d..e2a73866d0ed3 100644
--- a/pkgs/tools/nix/nixos-option/nixos-option.cc
+++ b/pkgs/tools/nix/nixos-option/nixos-option.cc
@@ -119,7 +119,7 @@ Out::Out(Out & o, const std::string & start, const std::string & end, LinePolicy
 
 Value evaluateValue(Context & ctx, Value & v)
 {
-    ctx.state.forceValue(v, v.attrs->pos);
+    ctx.state.forceValue(v, [&]() { return v.determinePos(nix::noPos); });
     if (ctx.autoArgs.empty()) {
         return v;
     }