From 832c38d3cbefb53da73ecf61b1e391967c75ed42 Mon Sep 17 00:00:00 2001
From: Scott Morrison <scott.morrison@anu.edu.au>
Date: Sat, 29 Apr 2017 18:06:38 +1000
Subject: [PATCH] fix(library/vm/vm_environment) use is_structure rather than
 try to catch an assertion

---
 src/library/vm/vm_environment.cpp | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/library/vm/vm_environment.cpp b/src/library/vm/vm_environment.cpp
index 463c14b7c3..5e18e684c6 100644
--- a/src/library/vm/vm_environment.cpp
+++ b/src/library/vm/vm_environment.cpp
@@ -218,9 +218,9 @@ vm_obj environment_is_namespace(vm_obj const & env, vm_obj const & n) {
 }
 
 vm_obj environment_structure_fields(vm_obj const & env, vm_obj const & n) {
-    try {
+    if (is_structure(to_env(env), to_name(n))) {
         return mk_vm_some(to_obj(get_structure_fields(to_env(env), to_name(n))));
-    } catch (exception &) {
+    } else {
         return mk_vm_none();
     }
 }