From b3113166efd0d017669317584da888d22dbbb113 Mon Sep 17 00:00:00 2001
From: Jameson Nash <vtjnash@gmail.com>
Date: Fri, 23 Sep 2016 17:55:23 -0400
Subject: [PATCH] throw actual error message for broken generated functions

ref #18605
---
 src/alloc.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/alloc.c b/src/alloc.c
index 9355ec503688ee..f06ef3447454bb 100644
--- a/src/alloc.c
+++ b/src/alloc.c
@@ -529,8 +529,11 @@ JL_DLLEXPORT jl_code_info_t *jl_code_for_staged(jl_method_instance_t *linfo)
         }
 
         func = (jl_code_info_t*)jl_expand((jl_value_t*)ex);
-        if (!jl_is_code_info(func))
+        if (!jl_is_code_info(func)) {
+            if (jl_is_expr(func) && ((jl_expr_t*)func)->head == error_sym)
+                jl_interpret_toplevel_expr((jl_value_t*)func);
             jl_error("generated function body is not pure. this likely means it contains a closure or comprehension.");
+        }
 
         jl_array_t *stmts = (jl_array_t*)func->code;
         for (i = 0, l = jl_array_len(stmts); i < l; i++) {