fixes #12899 (#12921)

* fixes #12899

* fixes regression: destroy global variables in reverse declaration order, closureleak test relies on it

tests/destructor/tnewruntime_strutils.nim

@@ -1,7 +1,9 @@
 discard """
   valgrind: true
   cmd: '''nim c --newruntime -d:useMalloc $file'''
-  output: '''422 422'''
+  output: '''
+@[(input: @["KXSC", "BGMC"]), (input: @["PXFX"]), (input: @["WXRQ", "ZSCZD"])]
+461 461'''
 """
 
 import strutils, os, std / wordwrap
@@ -13,6 +15,28 @@ import system / ansi_c
 proc retTuple(): (seq[int], int) =
   return (@[1], 1)
 
+# bug #12899
+
+import sequtils, strmisc
+
+const input = ["KXSC, BGMC => 7 PTHL", "PXFX => LBZJ", "WXRQ, ZSCZD => HLQM"]
+
+type
+  Reaction = object
+    input: seq[string]
+
+proc bug12899 =
+  var reactions: seq[Reaction] = @[]
+  for l in input:
+    let x = l.partition(" => ")
+    reactions.add Reaction(input: @(x[0].split(", ")))
+
+  let x = $reactions
+  echo x
+
+bug12899()
+
+
 proc nonStaticTests =
   doAssert formatBiggestFloat(1234.567, ffDecimal, -1) == "1234.567000"
   doAssert formatBiggestFloat(1234.567, ffDecimal, 0) == "1235" # bugs 8242, 12586