From 27e32e0a7d0931503803b26c24783dfd4433b715 Mon Sep 17 00:00:00 2001
From: Andreas Rumpf <rumpf_a@web.de>
Date: Sun, 25 Feb 2018 17:43:28 +0100
Subject: [PATCH] improve the error message for #4659; closes #4659

---
 compiler/semcall.nim | 21 ++++++++++++---------
 1 file changed, 12 insertions(+), 9 deletions(-)

diff --git a/compiler/semcall.nim b/compiler/semcall.nim
index 5bdd817d5..6fef11c48 100644
--- a/compiler/semcall.nim
+++ b/compiler/semcall.nim
@@ -169,21 +169,24 @@ proc presentFailedCandidates(c: PContext, n: PNode, errors: CandidateErrors):
     else:
       add(candidates, err.sym.getProcHeader(prefer))
     add(candidates, "\n")
-    if err.firstMismatch != 0 and n.len > 2:
-      add(candidates, "  first type mismatch at position: " & $err.firstMismatch &
-        "\n  required type: ")
+    if err.firstMismatch != 0 and n.len > 1:
+      let cond = n.len > 2
+      if cond:
+        candidates.add("  first type mismatch at position: " & $err.firstMismatch &
+          "\n  required type: ")
       var wanted, got: PType = nil
       if err.firstMismatch < err.sym.typ.len:
         wanted = err.sym.typ.sons[err.firstMismatch]
-        candidates.add typeToString(wanted)
+        if cond: candidates.add typeToString(wanted)
       else:
-        candidates.add "none"
+        if cond: candidates.add "none"
       if err.firstMismatch < n.len:
-        candidates.add "\n  but expression '"
-        candidates.add renderTree(n[err.firstMismatch])
-        candidates.add "' is of type: "
+        if cond:
+          candidates.add "\n  but expression '"
+          candidates.add renderTree(n[err.firstMismatch])
+          candidates.add "' is of type: "
         got = n[err.firstMismatch].typ
-        candidates.add typeToString(got)
+        if cond: candidates.add typeToString(got)
       if wanted != nil and got != nil:
         effectProblem(wanted, got, candidates)
       candidates.add "\n"