From bf25b5eb823c3cbbacc06d33a3ff539de325be6a Mon Sep 17 00:00:00 2001
From: Tommy Ip <hkmp7tommy@gmail.com>
Date: Wed, 24 May 2017 17:30:27 +0100
Subject: [PATCH] Explain why a closure is `FnOnce` in closure errors

---
 src/librustc_borrowck/borrowck/mod.rs | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/librustc_borrowck/borrowck/mod.rs b/src/librustc_borrowck/borrowck/mod.rs
index f7c20542cbf2..297df4978a59 100644
--- a/src/librustc_borrowck/borrowck/mod.rs
+++ b/src/librustc_borrowck/borrowck/mod.rs
@@ -597,6 +597,9 @@ impl<'a, 'tcx> BorrowckCtxt<'a, 'tcx> {
                         if let Ok(ty::ClosureKind::FnOnce) =
                            ty::queries::closure_kind::try_get(self.tcx, DUMMY_SP, id) {
                             err.help("closure was moved because it only implements `FnOnce`");
+                            if let Some(&(_kind, Some(span))) = self.tables.closure_kinds.get( ) {
+                                err.span_label(span, "move occured here");
+                            }
                             false
                         } else {
                             true