From fc14213d2da7302b237dfe5ca51f6f4d9af34e5c Mon Sep 17 00:00:00 2001
From: DavHau <42246742+DavHau@users.noreply.github.com>
Date: Wed, 25 Mar 2020 07:19:00 +0000
Subject: [PATCH] improve toFile error message when containing potential drv
 path

---
 src/libexpr/primops.cc | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index 8de234951..6d7622900 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -1021,7 +1021,9 @@ static void prim_toFile(EvalState & state, const Pos & pos, Value * * args, Valu
 
     for (auto path : context) {
         if (path.at(0) != '/')
-            throw EvalError(format("in 'toFile': the file '%1%' cannot refer to derivation outputs, at %2%") % name % pos);
+            throw EvalError(format(
+                "in 'toFile': the file named '%1%' must not contain a reference "
+                "to a derivation but contains (%2%), at %3%") % name % path % pos);
         refs.insert(state.store->parseStorePath(path));
     }