give ExprInheritFrom a handle to what its standing in for

Change-Id: I12088e0b618407e5432523bbc97be63c8d6fce62

1 files changed, 5 insertions, 2 deletions

diff --git a/src/libexpr/nixexpr.hh b/src/libexpr/nixexpr.hh
index 418f888b3..703a32e8f 100644
--- a/src/libexpr/nixexpr.hh
+++ b/src/libexpr/nixexpr.hh
@@ -144,7 +144,10 @@ struct ExprVar : Expr
  */
 struct ExprInheritFrom : ExprVar
 {
-    ExprInheritFrom(PosIdx pos, Displacement displ): ExprVar(pos, {})
+    ref<Expr> fromExpr;
+
+    ExprInheritFrom(PosIdx pos, Displacement displ, ref<Expr> fromExpr)
+          : ExprVar(pos, {}), fromExpr(fromExpr)
     {
         this->level = 0;
         this->displ = displ;
@@ -222,7 +225,7 @@ struct ExprAttrs : Expr
     };
     typedef std::map<Symbol, AttrDef> AttrDefs;
     AttrDefs attrs;
-    std::unique_ptr<std::vector<std::unique_ptr<Expr>>> inheritFromExprs;
+    std::unique_ptr<std::vector<ref<Expr>>> inheritFromExprs;
     struct DynamicAttrDef {
         std::unique_ptr<Expr> nameExpr, valueExpr;
         PosIdx pos;