fixes #25637; nim ic with destructors (#25723)

fixes #25637

This pull request refactors the way the `sfInjectDestructors` flag is
set on symbols during lambda lifting in the Nim compiler. The main
change is the introduction of a helper procedure to encapsulate the
logic for marking symbols that require destructor injection, improving
code clarity and maintainability.

Refactoring and code quality improvements:

* Introduced the `markInjectDestructors` procedure to encapsulate the
logic for marking a symbol with the `sfInjectDestructors` flag, ensuring
that `backendEnsureMutable` is always called before modifying the
symbol's flags.
* Replaced direct flag manipulation (`owner.incl sfInjectDestructors`
and `prc.incl sfInjectDestructors`) with calls to the new
`markInjectDestructors` procedure in multiple locations, including
`makeClosure`, `createTypeBoundOpsLL`, and `rawClosureCreation`.
[[1]](diffhunk://#diff-19193904ba011a2bcc1e1a9768a7eb57cac57a274cad73d388149776ec2901e6L231-R235)
[[2]](diffhunk://#diff-19193904ba011a2bcc1e1a9768a7eb57cac57a274cad73d388149776ec2901e6L243-R247)
[[3]](diffhunk://#diff-19193904ba011a2bcc1e1a9768a7eb57cac57a274cad73d388149776ec2901e6L639-R643)

compiler/lambdalifting.nim

@@ -216,6 +216,10 @@ proc newAsgnStmt(le, ri: PNode, info: TLineInfo): PNode =
   result[0] = le
   result[1] = ri
 
+proc markInjectDestructors(s: PSym) {.inline.} =
+  backendEnsureMutable s
+  s.flagsImpl.incl sfInjectDestructors
+
 proc makeClosure*(g: ModuleGraph; idgen: IdGenerator; prc: PSym; env: PNode; info: TLineInfo): PNode =
   result = newNodeIT(nkClosure, info, prc.typ)
   result.add(newSymNode(prc))
@@ -228,7 +232,7 @@ proc makeClosure*(g: ModuleGraph; idgen: IdGenerator; prc: PSym; env: PNode; inf
   #if isClosureIterator(result.typ):
   createTypeBoundOps(g, nil, result.typ, info, idgen)
   if tfHasAsgn in result.typ.flags or optSeqDestructors in g.config.globalOptions:
-    prc.incl sfInjectDestructors
+    markInjectDestructors(prc)
 
 template liftingHarmful(conf: ConfigRef; owner: PSym): bool =
   ## lambda lifting can be harmful for JS-like code generators.
@@ -240,7 +244,7 @@ proc createTypeBoundOpsLL(g: ModuleGraph; refType: PType; info: TLineInfo; idgen
     createTypeBoundOps(g, nil, refType.elementType, info, idgen)
     createTypeBoundOps(g, nil, refType, info, idgen)
     if tfHasAsgn in refType.flags or optSeqDestructors in g.config.globalOptions:
-      owner.incl sfInjectDestructors
+      markInjectDestructors(owner)
 
 proc genCreateEnv(env: PNode): PNode =
   var c = newNodeIT(nkObjConstr, env.info, env.typ)
@@ -636,7 +640,7 @@ proc rawClosureCreation(owner: PSym;
         if owner.kind != skMacro:
           createTypeBoundOps(d.graph, nil, fieldAccess.typ, env.info, d.idgen)
         if tfHasAsgn in fieldAccess.typ.flags or optSeqDestructors in d.graph.config.globalOptions:
-          owner.incl sfInjectDestructors
+          markInjectDestructors(owner)
 
   let upField = lookupInRecord(env.typ.skipTypes({tyOwned, tyRef, tyPtr}).n, getIdent(d.graph.cache, upName))
   if upField != nil:

tests/ic/tmiscs.nim

@@ -7,6 +7,7 @@ discard """
 1.0
 2.0
 55
+@[1, 2]
 '''
 """
 
@@ -79,3 +80,14 @@ let x = compute:
 
 echo x
 
+# Crash: bridge.nim(206, 5) `allowEmpty` unexpected nkEmpty [AssertionDefect]
+# Bare closure iterator type alias
+type IntIter = iterator(): int {.closure.}
+proc run(it: IntIter): seq[int] =
+  result = @[]
+  for x in it():
+    result.add(x)
+let gen: IntIter = iterator(): int {.closure.} =
+  yield 1
+  yield 2
+echo run(gen)