Show the exact position of undefined variables

In particular, undefined variable errors in a "with" previously didn't
show *any* position information, so this should help a lot in those
cases.

1 files changed, 1 insertions, 1 deletions

diff --git a/src/libexpr/nixexpr.cc b/src/libexpr/nixexpr.cc
index c847e3baf832..03a14695f108 100644
--- a/src/libexpr/nixexpr.cc
+++ b/src/libexpr/nixexpr.cc
@@ -198,7 +198,7 @@ void ExprVar::bindVars(const StaticEnv & env)
     /* Otherwise, the variable must be obtained from the nearest
        enclosing `with'.  If there is no `with', then we can issue an
        "undefined variable" error now. */
-    if (withLevel == -1) throw EvalError(format("undefined variable `%1%'") % name);
+    if (withLevel == -1) throw ParseError(format("undefined variable `%1%' at %2%") % name % pos);
 
     fromWith = true;
     this->level = withLevel;