fix detecting closure env for nested asts (#14326)

Co-authored-by: b3liever <b3liever@yandex.com>

compiler/injectdestructors.nim

@@ -26,7 +26,7 @@ import
   strutils, options, dfa, lowerings, tables, modulegraphs, msgs,
   lineinfos, parampatterns, sighashes, liftdestructors
 
-from trees import exprStructuralEquivalent
+from trees import exprStructuralEquivalent, getRoot
 from algorithm import reverse
 
 const
@@ -383,8 +383,8 @@ proc sinkParamIsLastReadCheck(c: var Con, s: PNode) =
         "` is already consumed at " & toFileLineCol(c. graph.config, s.info))
 
 proc isCapturedVar(n: PNode): bool =
-  n.kind == nkDotExpr and n[0].kind == nkHiddenDeref and
-      n[0][0].kind == nkSym and n[0][0].sym.name.s[0] == ':'
+  let root = getRoot(n)
+  if root != nil: result = root.name.s[0] == ':'
 
 proc passCopyToSink(n: PNode; c: var Con): PNode =
   result = newNodeIT(nkStmtListExpr, n.info, n.typ)