* Allow a default value in attribute selection by writing

    x.y.z or default

  (as originally proposed in
  https://mail.cs.uu.nl/pipermail/nix-dev/2009-September/002989.html).

  For instance, an expression like

    stdenv.lib.attrByPath ["features" "ckSched"] false args

  can now be written as

    args.features.ckSched or false

1 files changed, 3 insertions, 3 deletions

diff --git a/src/libexpr/nixexpr.hh b/src/libexpr/nixexpr.hh
index 725e30c6fa6d..166289b29851 100644
--- a/src/libexpr/nixexpr.hh
+++ b/src/libexpr/nixexpr.hh
@@ -121,10 +121,10 @@ struct ExprVar : Expr
 
 struct ExprSelect : Expr
 {
-    Expr * e;
+    Expr * e, * def;
     AttrPath attrPath;
-    ExprSelect(Expr * e, const AttrPath & attrPath) : e(e), attrPath(attrPath) { };
-    ExprSelect(Expr * e, const Symbol & name) : e(e) { attrPath.push_back(name); };
+    ExprSelect(Expr * e, const AttrPath & attrPath, Expr * def) : e(e), def(def), attrPath(attrPath) { };
+    ExprSelect(Expr * e, const Symbol & name) : e(e), def(0) { attrPath.push_back(name); };
     COMMON_METHODS
 };