From 8af81e3d246f5272f56a22018ef9cb67d652810a Mon Sep 17 00:00:00 2001
From: ringabout <43030857+ringabout@users.noreply.github.com>
Date: Tue, 22 Oct 2024 21:51:19 +0800
Subject: [PATCH] redefining field variables is disabled

---
 compiler/semfields.nim | 16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/compiler/semfields.nim b/compiler/semfields.nim
index 6e1498a140..43f159343d 100644
--- a/compiler/semfields.nim
+++ b/compiler/semfields.nim
@@ -17,7 +17,7 @@ type
     field: PSym
     replaceByFieldName: bool
     c: PContext
-    leftPartOfAssign: bool
+    leftPartOfDefinition: bool
 
 proc instFieldLoopBody(c: var TFieldInstCtx, n: PNode, forLoop: PNode): PNode =
   if c.field != nil and isEmptyType(c.field.typ):
@@ -29,6 +29,9 @@ proc instFieldLoopBody(c: var TFieldInstCtx, n: PNode, forLoop: PNode): PNode =
     result = n
     let ident = considerQuotedIdent(c.c, n)
     if c.replaceByFieldName:
+      if c.leftPartOfDefinition:
+        localError(c.c.config, n.info,
+                  "redefine field variable '$1' in a 'fields' loop" % [ident.s])
       if ident.id == considerQuotedIdent(c.c, forLoop[0]).id:
         let fieldName = if c.tupleType.isNil: c.field.name.s
                         elif c.tupleType.n.isNil: "Field" & $c.tupleIndex
@@ -38,9 +41,9 @@ proc instFieldLoopBody(c: var TFieldInstCtx, n: PNode, forLoop: PNode): PNode =
     # other fields:
     for i in ord(c.replaceByFieldName)..<forLoop.len-2:
       if ident.id == considerQuotedIdent(c.c, forLoop[i]).id:
-        if c.leftPartOfAssign:
+        if c.leftPartOfDefinition:
           localError(c.c.config, n.info,
-                    "field variable '$1' is not allowed to be used as a lvalue in a 'fields' loop" % [ident.s])
+                    "redefine field variable '$1' in a 'fields' loop" % [ident.s])
         var call = forLoop[^2]
         var tupl = call[i+1-ord(c.replaceByFieldName)]
         if c.field.isNil:
@@ -52,12 +55,11 @@ proc instFieldLoopBody(c: var TFieldInstCtx, n: PNode, forLoop: PNode): PNode =
           result.add(tupl)
           result.add(newSymNode(c.field, n.info))
         break
-  of nkIdentDefs, nkVarTuple, nkConstDef,
-      nkAsgn, nkFastAsgn, nkSinkAsgn:
+  of nkIdentDefs, nkVarTuple, nkConstDef:
     result = shallowCopy(n)
-    c.leftPartOfAssign = true
+    c.leftPartOfDefinition = true
     result[0] = instFieldLoopBody(c, n[0], forLoop)
-    c.leftPartOfAssign = false
+    c.leftPartOfDefinition = false
     for i in 1..<n.len:
       result[i] = instFieldLoopBody(c, n[i], forLoop)
   else: