From 5aa29c4c823cbe02a2d84080eefe3eb1aecf0a06 Mon Sep 17 00:00:00 2001
From: bjorn3 <bjorn3@users.noreply.github.com>
Date: Wed, 21 Mar 2018 14:34:46 +0100
Subject: [PATCH] Fix test error

---
 src/librustc_mir/interpret/const_eval.rs | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/src/librustc_mir/interpret/const_eval.rs b/src/librustc_mir/interpret/const_eval.rs
index 82eb28287b0..47f6f61072e 100644
--- a/src/librustc_mir/interpret/const_eval.rs
+++ b/src/librustc_mir/interpret/const_eval.rs
@@ -339,6 +339,14 @@ impl<'mir, 'tcx> super::Machine<'mir, 'tcx> for CompileTimeEvaluator {
         ecx: &mut EvalContext<'a, 'mir, 'tcx, Self>,
         cid: GlobalId<'tcx>,
     ) -> EvalResult<'tcx, AllocId> {
+        let alloc = ecx
+                    .tcx
+                    .interpret_interner
+                    .get_cached(cid.instance.def_id());
+        // Don't evaluate when already cached to prevent cycles
+        if let Some(alloc) = alloc {
+            return Ok(alloc)
+        }
         // ensure the static is computed
         ecx.const_eval(cid)?;
         Ok(ecx