fixes #14165, fixes #18739, fix the second example of #6269 (#18812)

compiler/transf.nim

@@ -738,7 +738,7 @@ proc transformFor(c: PTransf, n: PNode): PNode =
   pushInfoContext(c.graph.config, n.info)
   inc(c.inlining)
   stmtList.add(transform(c, body))
-  #findWrongOwners(c, stmtList.pnode)
+  #findWrongOwners(c, stmtList.PNode)
   dec(c.inlining)
   popInfoContext(c.graph.config)
   popTransCon(c)
@@ -1019,10 +1019,11 @@ proc transform(c: PTransf, n: PNode): PNode =
   of nkAsgn:
     result = transformAsgn(c, n)
   of nkIdentDefs, nkConstDef:
-    result = n
+    result = newTransNode(n)
     result[0] = transform(c, n[0])
     # Skip the second son since it only contains an unsemanticized copy of the
     # variable type used by docgen
+    result[1] = n[1]
     result[2] = transform(c, n[2])
     # XXX comment handling really sucks:
     if importantComments(c.graph.config):
@@ -1033,8 +1034,10 @@ proc transform(c: PTransf, n: PNode): PNode =
     # (bug #2604). We need to patch this environment here too:
     let a = n[1]
     if a.kind == nkSym:
-      n[1] = transformSymAux(c, a)
-    return n
+      result = copyTree(n)
+      result[1] = transformSymAux(c, a)
+    else:
+      result = n
   of nkExceptBranch:
     result = transformExceptBranch(c, n)
   of nkCheckedFieldExpr:

tests/iter/titer.nim

@@ -62,3 +62,53 @@ type Rule[T] = (int, T)
 var t: seq[Rule[int]]
 for (c, t) in t:
   discard
+
+
+
+import std/sugar
+
+# bug #14165
+iterator log_nodups_hamming(): int {.inline.} =
+  let lb3 = 1
+  let lb4 = 123
+  proc mul3(): int = lb3 + lb4
+  yield mul3()
+
+for h in log_nodups_hamming():
+  break
+for h in log_nodups_hamming():
+  break
+for h in log_nodups_hamming():
+  break
+
+# bug #18536
+iterator envPairs*(): int =
+  var foo: seq[int]
+  proc fun() =
+    foo = @[]
+  fun()
+  yield 3
+
+proc main() =
+  for a in envPairs():
+    discard
+  for a in envPairs():
+    discard
+static: main()
+main()
+
+# bug #6269
+iterator makeFn(outer_val: int): proc(a: int): int =
+  for i in 0..1:
+    yield proc(a:int): int =
+      return a + i.int
+
+let v1 = 42
+
+let res = collect:
+  for fn1 in makeFn(v1):
+    let v2 = fn1(v1)
+    for fn2 in makeFn(v2):
+      fn2(v2)
+
+doAssert res == @[42, 43, 43, 44]