fix #16384 and #17144

[ringabout]

fix #16384
fix #17144

[Araq]

Why backport? This is not a regression and risky in itself.

[ringabout]

the codes from #16384 works for Nim 1.4.0 but failed at Nim 1.4.2. This PR fix the issue?

[timotheecour]

LGTM after removing the TODO fixme since it now works.

also note for other reviewers that to view the diff, it's best to do it locally after diffing against a file where you indent the whole test inside a template main, then the resulting diff is tiny:

diff --git a/Users/timothee/git_clone//nim//Nim_devel//tests/stdlib/tlists.nim b/tests/stdlib/tlists.nim
index bbce444d5..91afcf4b6 100644
--- a/Users/timothee/git_clone//nim//Nim_devel//tests/stdlib/tlists.nim
+++ b/tests/stdlib/tlists.nim
@@ -2,11 +2,12 @@ discard """
   targets: "c js"
 """

-import lists, sequtils
+import std/[lists, sequtils]

 const
   data = [1, 2, 3, 4, 5, 6]

+
 template main =
   block SinglyLinkedListTest1:
     var L: SinglyLinkedList[int]
@@ -184,7 +185,10 @@ template main =
         doAssert l3.toSeq == [4, 5, 6]
         doAssert l2.toSeq == [1, 2, 3]
         l3.prepend l0
-        doAssert l3.toSeq == [4, 5, 6]
+        when nimvm:
+          # discard # TODO fixme
+        else:
+          doAssert l3.toSeq == [4, 5, 6]
       block:
         var c = [0, 1].toList
         c.prependMoved c

[timotheecour]

I'd be fine with backporting this in its current state, but can be decided later.