From 39ce47828321d7adfa92ea3f7713d97f8660a4f1 Mon Sep 17 00:00:00 2001
From: Sizhe Zhao <prc.zhao@outlook.com>
Date: Wed, 26 Mar 2025 18:48:57 +0800
Subject: [PATCH] docs: document unsafeGetAttrPos

---
 src/libexpr/primops.cc | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index 54682ea31..61e948549 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -2775,7 +2775,13 @@ static void prim_unsafeGetAttrPos(EvalState & state, const PosIdx pos, Value * *
 
 static RegisterPrimOp primop_unsafeGetAttrPos(PrimOp {
     .name = "__unsafeGetAttrPos",
+    .args = {"s", "set"},
     .arity = 2,
+    .doc = R"(
+      `unsafeGetAttrPos` returns the position of the attribute named *s*
+      from *set*. This is used by Nixpkgs to provide location information
+      in error messages.
+    )",
     .fun = prim_unsafeGetAttrPos,
 });