* Simplify the implementation of `with'. This gives a 7% speedup in

  evaluating the NixOS system configuration.

1 files changed, 4 insertions, 4 deletions

diff --git a/src/libexpr/nixexpr.cc b/src/libexpr/nixexpr.cc
index 3dfbddf5b89f..a9c83108e950 100644
--- a/src/libexpr/nixexpr.cc
+++ b/src/libexpr/nixexpr.cc
@@ -278,12 +278,12 @@ void ExprLet::bindVars(const StaticEnv & env)
 void ExprWith::bindVars(const StaticEnv & env)
 {
     /* Does this `with' have an enclosing `with'?  If so, record its
-       level so that we can copy the attributes of the enclosing
-       `with'. */
+       level so that `lookupVar' can look up variables in the previous
+       `with' if this one doesn't contain the desired attribute. */
     const StaticEnv * curEnv;
     unsigned int level;
-    prevWith = -1;
-    for (curEnv = &env, level = 0; curEnv; curEnv = curEnv->up, level++)
+    prevWith = 0;
+    for (curEnv = &env, level = 1; curEnv; curEnv = curEnv->up, level++)
         if (curEnv->isWith) {
             prevWith = level;
             break;