From d1229859c2612587bfd04111bae6584c0c9df051 Mon Sep 17 00:00:00 2001
From: Maximilian Bosch <maximilian@mbosch.me>
Date: Wed, 29 Apr 2020 22:48:29 +0200
Subject: [PATCH] Fix displaying error-position in
 `builtins.fetch{Tree,Tarball}`

Without dereferencing this pointer, you'd get an error like this:

```
error: unsupported argument 'abc' to 'fetchTarball', at 0x13627e8
```
---
 src/libexpr/primops/fetchTree.cc | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/libexpr/primops/fetchTree.cc b/src/libexpr/primops/fetchTree.cc
index 43c58485a..c5a0d9886 100644
--- a/src/libexpr/primops/fetchTree.cc
+++ b/src/libexpr/primops/fetchTree.cc
@@ -108,7 +108,7 @@ static void fetch(EvalState & state, const Pos & pos, Value * * args, Value & v,
                 name = state.forceStringNoCtx(*attr.value, *attr.pos);
             else
                 throw EvalError("unsupported argument '%s' to '%s', at %s",
-                    attr.name, who, attr.pos);
+                    attr.name, who, *attr.pos);
         }
 
         if (!url)