From d738ed9c927a881e6ffc7d21c4a87197f6689283 Mon Sep 17 00:00:00 2001
From: Araq <rumpf_a@web.de>
Date: Mon, 19 Mar 2018 19:39:44 +0100
Subject: [PATCH] better error messages for illegal captures

---
 compiler/lambdalifting.nim | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/compiler/lambdalifting.nim b/compiler/lambdalifting.nim
index fca5ef52eb..bc05ec80c7 100644
--- a/compiler/lambdalifting.nim
+++ b/compiler/lambdalifting.nim
@@ -275,8 +275,12 @@ proc freshVarForClosureIter*(s, owner: PSym): PNode =
 
 proc markAsClosure(owner: PSym; n: PNode) =
   let s = n.sym
-  if illegalCapture(s) or owner.typ.callConv notin {ccClosure, ccDefault}:
-    localError(n.info, errIllegalCaptureX, s.name.s)
+  if illegalCapture(s):
+    localError(n.info, "illegal capture '$1' of type <$2> which is declared here: $3" %
+      [s.name.s, typeToString(s.typ), $s.info])
+  elif owner.typ.callConv notin {ccClosure, ccDefault}:
+    localError(n.info, "illegal capture '$1' because '$2' has the calling convention: <$3>" %
+      [s.name.s, owner.name.s, CallingConvToStr[owner.typ.callConv]])
   incl(owner.typ.flags, tfCapturesEnv)
   owner.typ.callConv = ccClosure