From d0919b6df8872f472fe02f7c4e7474ef49dfa9c4 Mon Sep 17 00:00:00 2001
From: Andreas Rumpf <rumpf_a@web.de>
Date: Mon, 16 Mar 2026 16:56:18 +0100
Subject: [PATCH] fixes #25596 (#25609)

---
 compiler/closureiters.nim  | 34 +++++++++++++++++++++++++---------
 tests/iter/tyieldintry.nim | 24 ++++++++++++++----------
 2 files changed, 39 insertions(+), 19 deletions(-)

diff --git a/compiler/closureiters.nim b/compiler/closureiters.nim
index 52f0bed2bb..96734ca8fa 100644
--- a/compiler/closureiters.nim
+++ b/compiler/closureiters.nim
@@ -139,7 +139,7 @@
 
 import
   ast, msgs, idents,
-  renderer, magicsys, lowerings, lambdalifting, modulegraphs, lineinfos
+  renderer, magicsys, lowerings, lambdalifting, modulegraphs, lineinfos, trees
 
 import std/tables
 
@@ -1390,18 +1390,34 @@ proc optimizeStates(ctx: var Ctx) =
   for i in 0 .. ctx.states.high:
     ctx.states[i].label.intVal = i
 
+proc detectCapturedSym(c: var Ctx, s: PSym, stateIdx: int) =
+  if s.kind in {skResult, skVar, skLet, skForVar, skTemp} and sfGlobal notin s.flags and s.owner == c.fn and s != c.externExcSym:
+    let vs = c.varStates.getOrDefault(s.itemId, localNotSeen)
+    if vs == localNotSeen: # First seing this variable
+      c.varStates[s.itemId] = stateIdx
+    elif vs == localRequiresLifting:
+      discard # Sym already marked
+    elif vs != stateIdx:
+      c.captureVar(s)
+
+proc isClosureIterLocal(c: Ctx, s: PSym): bool =
+  s.kind in {skResult, skVar, skLet, skForVar, skTemp} and
+  sfGlobal notin s.flags and s.owner == c.fn and s != c.externExcSym
+
 proc detectCapturedVars(c: var Ctx, n: PNode, stateIdx: int) =
   case n.kind
   of nkSym:
     let s = n.sym
-    if s.kind in {skResult, skVar, skLet, skForVar, skTemp} and sfGlobal notin s.flags and s.owner == c.fn and s != c.externExcSym:
-      let vs = c.varStates.getOrDefault(s.itemId, localNotSeen)
-      if vs == localNotSeen: # First seing this variable
-        c.varStates[s.itemId] = stateIdx
-      elif vs == localRequiresLifting:
-        discard # Sym already marked
-      elif vs != stateIdx:
-        c.captureVar(s)
+    detectCapturedSym(c, s, stateIdx)
+  of nkAddr, nkHiddenAddr:
+    let s = getRoot(n)
+    if s != nil and isClosureIterLocal(c, s):
+      detectCapturedSym(c, s, stateIdx)
+      # bug #25596; lifetime extension for `addr`-taken locals as
+      # we claim ARC/ORC do destruction based on scopes, not on last-usages.
+      c.captureVar(s)
+    for i in 0 ..< n.safeLen:
+      detectCapturedVars(c, n[i], stateIdx)
   of nkReturnStmt:
     if n[0].kind in {nkAsgn, nkFastAsgn, nkSinkAsgn}:
       # we have a `result = result` expression produced by the closure
diff --git a/tests/iter/tyieldintry.nim b/tests/iter/tyieldintry.nim
index 983cae5408..da0d0b0996 100644
--- a/tests/iter/tyieldintry.nim
+++ b/tests/iter/tyieldintry.nim
@@ -559,17 +559,21 @@ block: # void iterator
       discard
   var a = it
 
-block: # Locals present in only 1 state should be on the stack
+block:
+  # Locals present in only 1 state should be on the stack
   proc checkOnStack(a: pointer, shouldBeOnStack: bool) =
-    # Quick and dirty way to check if a points to stack
-    var dummy = 0
-    let dummyAddr = addr dummy
-    let distance = abs(cast[int](dummyAddr) - cast[int](a))
-    const requiredDistance = 300
-    if shouldBeOnStack:
-      doAssert(distance <= requiredDistance, "a is not on stack, but should")
-    else:
-      doAssert(distance > requiredDistance, "a is on stack, but should not")
+    # bug #25596: the very fact we take the address prevents the local
+    # from being on the stack
+    when false:
+      # Quick and dirty way to check if a points to stack
+      var dummy = 0
+      let dummyAddr = addr dummy
+      let distance = abs(cast[int](dummyAddr) - cast[int](a))
+      const requiredDistance = 300
+      if shouldBeOnStack:
+        doAssert(distance <= requiredDistance, "a is not on stack, but should")
+      else:
+        doAssert(distance > requiredDistance, "a is on stack, but should not")
 
   iterator it(): int {.closure.} =
     var a = 1