* Turn build errors during evaluation into EvalErrors.

src/libexpr/nixexpr.hh

@@ -15,6 +15,7 @@ MakeError(AssertionError, EvalError)
 MakeError(ThrownError, AssertionError)
 MakeError(Abort, EvalError)
 MakeError(TypeError, EvalError)
+MakeError(ImportError, EvalError) // error building an imported derivation
 
 
 /* Position objects. */

src/libexpr/primops.cc

@@ -37,7 +37,11 @@ static void prim_import(EvalState & state, Value * * args, Value & v)
             throw EvalError(format("cannot import `%1%', since path `%2%' is not valid")
                 % path % *i);
         if (isDerivation(*i))
-            store->buildDerivations(singleton<PathSet>(*i));
+            try {
+                store->buildDerivations(singleton<PathSet>(*i));
+            } catch (Error & e) {
+                throw ImportError(e.msg());
+            }
     }
 
     state.evalFile(path, v);

src/libstore/build.cc

@@ -267,7 +267,7 @@ public:
 
 
 MakeError(SubstError, Error)
-MakeError(BuildError, Error) /* denoted a permanent build failure */
+MakeError(BuildError, Error) /* denotes a permanent build failure */
 
 
 //////////////////////////////////////////////////////////////////////

src/libstore/store-api.hh

@@ -16,8 +16,6 @@ namespace nix {
 typedef std::map<Path, Path> Roots;
 
 
-
-
 struct GCOptions
 {
     /* Garbage collector operation: