From 3bd6b7ddc7e7cd8f1551b79f3dbd74c539db14d1 Mon Sep 17 00:00:00 2001
From: Araq <rumpf_a@web.de>
Date: Sun, 5 Nov 2017 02:51:20 +0100
Subject: [PATCH] improve the error messages for bug #6692

---
 compiler/msgs.nim     | 4 ++--
 compiler/semexprs.nim | 9 +++++----
 2 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/compiler/msgs.nim b/compiler/msgs.nim
index 8d43103dbe..2668c72ae0 100644
--- a/compiler/msgs.nim
+++ b/compiler/msgs.nim
@@ -61,7 +61,7 @@ type
     errBaseTypeMustBeOrdinal, errInheritanceOnlyWithNonFinalObjects,
     errInheritanceOnlyWithEnums, errIllegalRecursionInTypeX,
     errCannotInstantiateX, errExprHasNoAddress, errXStackEscape,
-    errVarForOutParamNeeded,
+    errVarForOutParamNeededX,
     errPureTypeMismatch, errTypeMismatch, errButExpected, errButExpectedX,
     errAmbiguousCallXYZ, errWrongNumberOfArguments,
     errWrongNumberOfArgumentsInCall,
@@ -268,7 +268,7 @@ const
     errCannotInstantiateX: "cannot instantiate: \'$1\'",
     errExprHasNoAddress: "expression has no address",
     errXStackEscape: "address of '$1' may not escape its stack frame",
-    errVarForOutParamNeeded: "for a \'var\' type a variable needs to be passed",
+    errVarForOutParamNeededX: "for a \'var\' type a variable needs to be passed; but '$1' is immutable",
     errPureTypeMismatch: "type mismatch",
     errTypeMismatch: "type mismatch: got (",
     errButExpected: "but expected one of: ",
diff --git a/compiler/semexprs.nim b/compiler/semexprs.nim
index 7a16f495a7..d600b1c486 100644
--- a/compiler/semexprs.nim
+++ b/compiler/semexprs.nim
@@ -465,7 +465,7 @@ proc newHiddenAddrTaken(c: PContext, n: PNode): PNode =
     result = newNodeIT(nkHiddenAddr, n.info, makeVarType(c, n.typ))
     addSon(result, n)
     if isAssignable(c, n) notin {arLValue, arLocalLValue}:
-      localError(n.info, errVarForOutParamNeeded)
+      localError(n.info, errVarForOutParamNeededX, $n)
 
 proc analyseIfAddressTaken(c: PContext, n: PNode): PNode =
   result = n
@@ -509,9 +509,10 @@ proc analyseIfAddressTakenInCall(c: PContext, n: PNode) =
     for i in countup(1, sonsLen(n) - 1):
       if i < sonsLen(t) and t.sons[i] != nil and
           skipTypes(t.sons[i], abstractInst-{tyTypeDesc}).kind == tyVar:
-        if isAssignable(c, n.sons[i]) notin {arLValue, arLocalLValue}:
-          if n.sons[i].kind != nkHiddenAddr:
-            localError(n.sons[i].info, errVarForOutParamNeeded)
+        let it = n[i]
+        if isAssignable(c, it) notin {arLValue, arLocalLValue}:
+          if it.kind != nkHiddenAddr:
+            localError(it.info, errVarForOutParamNeededX, $it)
     return
   for i in countup(1, sonsLen(n) - 1):
     if n.sons[i].kind == nkHiddenCallConv: