fixes #21138; closure func used in the loop (#25196)

fixes #21138

Author: ringabout

compiler/transf.nim

@@ -329,7 +329,7 @@ proc introduceNewLocalVars(c: PTransf, n: PNode): PNode =
     if a.kind == nkSym:
       n[1] = transformSymAux(c, a)
     return n
-  of nkProcDef: # todo optimize nosideeffects?
+  of nkProcDef, nkFuncDef, nkMethodDef, nkConverterDef: # todo optimize nosideeffects?
     result = newTransNode(n)
     let x = newSymNode(copySym(n[namePos].sym, c.idgen))
     c.transCon.mapping[n[namePos].sym.itemId] = x

tests/iter/titer.nim

@@ -145,3 +145,18 @@ proc main123() =
     discard
 
 main123()
+
+# bug #21138
+iterator ubi(): int =
+  when nimvm:
+    yield 0
+  else:
+    yield 0
+
+block:
+  for k in ubi():
+    func e() {.closure.} = discard
+
+static:
+  for k in ubi():
+    func e() {.closure.} = discard