From e6261b91683fdb015644699a1b023ceb87531e37 Mon Sep 17 00:00:00 2001
From: ringabout <43030857+ringabout@users.noreply.github.com>
Date: Mon, 27 Oct 2025 22:58:10 +0800
Subject: [PATCH 1/2] fixes #25122 #15353 #15353; Invalid C code generation
 with iterator with when nimvm

---
 compiler/transf.nim         | 21 ++++++++++++++++++++-
 tests/iter/titer_issues.nim | 26 ++++++++++++++++++++++++++
 2 files changed, 46 insertions(+), 1 deletion(-)

diff --git a/compiler/transf.nim b/compiler/transf.nim
index 066be57f8763..d06fc136c532 100644
--- a/compiler/transf.nim
+++ b/compiler/transf.nim
@@ -321,6 +321,13 @@ proc introduceNewLocalVars(c: PTransf, n: PNode): PNode =
     result = n
   of nkVarSection, nkLetSection:
     result = transformVarSection(c, n)
+    for i in 0..<result.len:
+      result[i] = introduceNewLocalVars(c, result[i])
+  of nkIdentDefs, nkVarTuple:
+    result = newTransNode(n)
+    for i in 0..<n.len-1:
+      result[i] = n[i]
+    result[^1] = introduceNewLocalVars(c, n[^1])
   of nkClosure:
     # it can happen that for-loop-inlining produced a fresh
     # set of variables, including some computed environment
@@ -328,7 +335,13 @@ proc introduceNewLocalVars(c: PTransf, n: PNode): PNode =
     let a = n[1]
     if a.kind == nkSym:
       n[1] = transformSymAux(c, a)
-    return n
+    if n[0].kind == nkSym:
+      result = n
+    else:
+      # introduces local vars for the lambda closures
+      result = newTransNode(n)
+      result[0] = introduceNewLocalVars(c, n[0])
+      result[1] = n[1]
   of nkProcDef, nkFuncDef, nkMethodDef, nkConverterDef: # todo optimize nosideeffects?
     result = newTransNode(n)
     let x = newSymNode(copySym(n[namePos].sym, c.idgen))
@@ -337,6 +350,12 @@ proc introduceNewLocalVars(c: PTransf, n: PNode): PNode =
     for i in 1..<n.len:
       result[i] = introduceNewLocalVars(c, n[i])
     result[namePos].sym.ast = result
+  of nkLambda:
+    result = newTransNode(n)
+    result[namePos] = n[namePos]
+    for i in 1..<n.len:
+      result[i] = introduceNewLocalVars(c, n[i])
+    result[namePos].sym.ast = result
   else:
     result = newTransNode(n)
     for i in 0..<n.len:
diff --git a/tests/iter/titer_issues.nim b/tests/iter/titer_issues.nim
index ff0b8eb49fd0..a66d27f423aa 100644
--- a/tests/iter/titer_issues.nim
+++ b/tests/iter/titer_issues.nim
@@ -432,3 +432,29 @@ block:
   let x = cast[typeof(aaa)](aaa)   # not even var
   for _ in x[]:
     discard
+
+iterator v(): int =
+  when nimvm:
+    yield 0
+  else:
+    yield 0
+for _ in v():
+  for c in v():
+    (; let _: proc() = proc() = discard c)
+
+proc foo =
+  for _ in v():
+    for c in v():
+      (; let _: proc() = proc() = discard c)
+
+foo()
+
+import std/[os, sugar]
+
+for file in walkDirRec("./"):
+  let multiplier = 5
+  discard(toSeq(1..4).map(x => x * multiplier))
+
+for unused_var in walkDir("."):
+  let outside = "x"
+  let closure = proc(): string = outside

From 47f4e421d1755638078104614a7d469301515bcd Mon Sep 17 00:00:00 2001
From: ringabout <43030857+ringabout@users.noreply.github.com>
Date: Tue, 28 Oct 2025 12:43:06 +0800
Subject: [PATCH 2/2] Conditional import and directory walking for non-js

---
 tests/iter/titer_issues.nim | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/tests/iter/titer_issues.nim b/tests/iter/titer_issues.nim
index a66d27f423aa..29bfe637fca9 100644
--- a/tests/iter/titer_issues.nim
+++ b/tests/iter/titer_issues.nim
@@ -449,12 +449,14 @@ proc foo =
 
 foo()
 
-import std/[os, sugar]
 
-for file in walkDirRec("./"):
-  let multiplier = 5
-  discard(toSeq(1..4).map(x => x * multiplier))
-
-for unused_var in walkDir("."):
-  let outside = "x"
-  let closure = proc(): string = outside
+when not defined(js):
+  import std/[os, sugar]
+  
+  for file in walkDirRec("./"):
+    let multiplier = 5
+    discard(toSeq(1..4).map(x => x * multiplier))
+  
+  for unused_var in walkDir("."):
+    let outside = "x"
+    let closure = proc(): string = outside