From 086efac49b746214c8d39347fa2d96f0f85413b2 Mon Sep 17 00:00:00 2001
From: flywind <43030857+xflywind@users.noreply.github.com>
Date: Tue, 14 Jul 2020 15:22:48 +0800
Subject: [PATCH] fix #6608 (#14963)

* fix #6608
---
 compiler/semexprs.nim   | 11 ++++++++++-
 tests/errmsgs/t6608.nim | 16 ++++++++++++++++
 2 files changed, 26 insertions(+), 1 deletion(-)
 create mode 100644 tests/errmsgs/t6608.nim

diff --git a/compiler/semexprs.nim b/compiler/semexprs.nim
index de9f2198a2..fd9203f342 100644
--- a/compiler/semexprs.nim
+++ b/compiler/semexprs.nim
@@ -955,8 +955,17 @@ proc semIndirectOp(c: PContext, n: PNode, flags: TExprFlags): PNode =
             hasErrorType = true
             break
         if not hasErrorType:
+          let typ = n[0].typ
           msg.add(">\nbut expected one of: \n" &
-              typeToString(n[0].typ))
+              typeToString(typ))
+          # prefer notin preferToResolveSymbols
+          # t.sym != nil
+          # sfAnon notin t.sym.flags
+          # t.kind != tySequence(It is tyProc)
+          if typ.sym != nil and sfAnon notin typ.sym.flags and 
+                                typ.kind == tyProc:
+            msg.add(" = " & 
+                typeToString(typ, preferDesc))
           localError(c.config, n.info, msg)
         return errorNode(c, n)
       result = nil
diff --git a/tests/errmsgs/t6608.nim b/tests/errmsgs/t6608.nim
new file mode 100644
index 0000000000..3d82f3cd89
--- /dev/null
+++ b/tests/errmsgs/t6608.nim
@@ -0,0 +1,16 @@
+discard """
+  cmd: "nim c --hints:off $file"
+  errormsg: "type mismatch: got <>"
+  nimout: '''t6608.nim(14, 4) Error: type mismatch: got <>
+but expected one of:
+AcceptCB = proc (s: string){.closure.}'''
+  line: 14
+"""
+
+type
+  AcceptCB = proc (s: string)
+
+proc x(x: AcceptCB) =
+  x()
+
+x()