From 17c71334e16f6c65a549d95312d3f03e3c51ed98 Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <eelco.dolstra@logicblox.com>
Date: Fri, 6 Mar 2015 15:10:12 +0100
Subject: [PATCH] forceValueDeep: Add to error prefix

---
 src/libexpr/eval.cc | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 4404e04eb..7d1c3c2b9 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -1226,8 +1226,13 @@ void EvalState::forceValueDeep(Value & v)
         forceValue(v);
 
         if (v.type == tAttrs) {
-            foreach (Bindings::iterator, i, *v.attrs)
-                recurse(*i->value);
+            for (auto & i : *v.attrs)
+                try {
+                    recurse(*i.value);
+                } catch (Error & e) {
+                    addErrorPrefix(e, "while evaluating the attribute ‘%1%’ at %2%:\n", i.name, *i.pos);
+                    throw;
+                }
         }
 
         else if (v.type == tList) {