findAlongAttrPath(): Throw AttrPathNotFound

2 files changed, 4 insertions, 2 deletions

diff --git a/src/libexpr/attr-path.cc b/src/libexpr/attr-path.cc
index b0f80db32..832235cfd 100644
--- a/src/libexpr/attr-path.cc
+++ b/src/libexpr/attr-path.cc
@@ -70,7 +70,7 @@ Value * findAlongAttrPath(EvalState & state, const string & attrPath,
 
             Bindings::iterator a = v->attrs->find(state.symbols.create(attr));
             if (a == v->attrs->end())
-                throw Error(format("attribute '%1%' in selection path '%2%' not found") % attr % attrPath);
+                throw AttrPathNotFound("attribute '%1%' in selection path '%2%' not found", attr, attrPath);
             v = &*a->value;
         }
 
@@ -82,7 +82,7 @@ Value * findAlongAttrPath(EvalState & state, const string & attrPath,
                     % attrPath % showType(*v));
 
             if (attrIndex >= v->listSize())
-                throw Error(format("list index %1% in selection path '%2%' is out of range") % attrIndex % attrPath);
+                throw AttrPathNotFound("list index %1% in selection path '%2%' is out of range", attrIndex, attrPath);
 
             v = v->listElems()[attrIndex];
         }
diff --git a/src/libexpr/attr-path.hh b/src/libexpr/attr-path.hh
index 46a341950..1eae64625 100644
--- a/src/libexpr/attr-path.hh
+++ b/src/libexpr/attr-path.hh
@@ -7,6 +7,8 @@
 
 namespace nix {
 
+MakeError(AttrPathNotFound, Error);
+
 Value * findAlongAttrPath(EvalState & state, const string & attrPath,
     Bindings & autoArgs, Value & vIn);