[nim check]fix #17460 (#17569)

compiler/semstmts.nim

@@ -726,6 +726,8 @@ proc semForVars(c: PContext, n: PNode; flags: TExprFlags): PNode =
       if n[0].kind == nkVarTuple:
         if n[0].len-1 != iterAfterVarLent.len:
           localError(c.config, n[0].info, errWrongNumberOfVariables)
+          return errorNode(c, n)
+
         for i in 0..<n[0].len-1:
           var v = symForVar(c, n[0][i])
           if getCurrOwner(c).kind == skModule: incl(v.flags, sfGlobal)

tests/errmsgs/t17460.nim

@@ -0,0 +1,19 @@
+discard """
+  cmd: "nim check $options $file"
+  errormsg: "wrong number of variables"
+"""
+
+iterator xclusters*[T](a: openarray[T]; s: static[int]): array[s, T] {.inline.} =
+  var result: array[s, T] # iterators have no default result variable
+  var i = 0
+  while i < len(a):
+    for j, x in mpairs(result):
+      x = a[(i + j) mod len(a)]
+    yield result
+    inc(i)
+
+proc m =
+  for (i, j, k) in xclusters([1, 2, 3, 4, 5], 3):
+    echo i, j, k
+
+m()