fixes #5405

compiler/sem.nim

@@ -168,16 +168,6 @@ proc commonType*(x, y: PType): PType =
 proc newSymS(kind: TSymKind, n: PNode, c: PContext): PSym =
   result = newSym(kind, considerQuotedIdent(n), getCurrOwner(), n.info)
 
-proc getGenSym(c: PContext; s: PSym): PSym =
-  var it = c.p
-  while it != nil:
-    result = get(it, s)
-    if result != nil:
-      #echo "got from table ", result.name.s, " ", result.info
-      return result
-    it = it.next
-  result = s
-
 proc newSymG*(kind: TSymKind, n: PNode, c: PContext): PSym =
   proc `$`(kind: TSymKind): string = substr(system.`$`(kind), 2).toLowerAscii
 

compiler/semdata.nim

@@ -157,6 +157,26 @@ proc get*(p: PProcCon; key: PSym): PSym =
   if p.mapping.data == nil: return nil
   result = PSym(p.mapping.idTableGet(key))
 
+proc getGenSym*(c: PContext; s: PSym): PSym =
+  if sfGenSym notin s.flags: return s
+  var it = c.p
+  while it != nil:
+    result = get(it, s)
+    if result != nil:
+      #echo "got from table ", result.name.s, " ", result.info
+      return result
+    it = it.next
+  result = s
+
+proc considerGenSyms*(c: PContext; n: PNode) =
+  if n.kind == nkSym:
+    let s = getGenSym(c, n.sym)
+    if n.sym != s:
+      n.sym = s
+  else:
+    for i in 0..<n.safeLen:
+      considerGenSyms(c, n.sons[i])
+
 proc newOptionEntry*(): POptionEntry =
   new(result)
   result.options = gOptions

compiler/sigmatch.nim

@@ -1583,12 +1583,14 @@ proc prepareOperand(c: PContext; formal: PType; a: PNode): PNode =
     result = c.semOperand(c, a, flags)
   else:
     result = a
+    considerGenSyms(c, result)
 
 proc prepareOperand(c: PContext; a: PNode): PNode =
   if a.typ.isNil:
     result = c.semOperand(c, a, {efDetermineType})
   else:
     result = a
+    considerGenSyms(c, result)
 
 proc prepareNamedParam(a: PNode) =
   if a.sons[0].kind != nkIdent:

tests/template/tgensymregression.nim

@@ -1,3 +1,10 @@
+discard """
+  output: '''[0.0, 0.0, 0.0]
+
+[0.0, 0.0, 0.0, 0.0]
+
+5050'''
+"""
 
 template mathPerComponent(op: untyped): untyped =
   proc op*[N,T](v,u: array[N,T]): array[N,T] {.inline.} =
@@ -32,3 +39,11 @@ proc main =
   discard zipWithIndex(@[true, false])
 
 main()
+
+# bug #5405
+
+proc main2() =
+  let s = toSeq(1..100).foldL(a + b)
+  echo s
+
+main2()