From 79f5a74408fab60c21e3905b72fe7dcdcb34eb52 Mon Sep 17 00:00:00 2001
From: ringabout <43030857+ringabout@users.noreply.github.com>
Date: Thu, 22 Aug 2024 13:21:13 +0800
Subject: [PATCH] fixes #23454; IndexDefect thrown when destructuring a lent
 tuple (#23993)

fixes #23454
---
 compiler/transf.nim           |  5 ++++-
 tests/lent/tlent_from_var.nim | 36 +++++++++++++++++++++++++++++++++++
 2 files changed, 40 insertions(+), 1 deletion(-)

diff --git a/compiler/transf.nim b/compiler/transf.nim
index 7ab4ccae234c..4061a407cba5 100644
--- a/compiler/transf.nim
+++ b/compiler/transf.nim
@@ -496,7 +496,10 @@ proc transformAddrDeref(c: PTransf, n: PNode, kinds: TNodeKinds): PNode =
       elif n.typ.skipTypes(abstractInst).kind in {tyVar}:
         result.typ = toVar(result.typ, n.typ.skipTypes(abstractInst).kind, c.idgen)
   else:
-    if n[0].kind in kinds:
+    if n[0].kind in kinds and
+        not (n[0][0].kind == nkSym and n[0][0].sym.kind == skForVar and
+          n[0][0].typ.skipTypes(abstractVar).kind == tyTuple
+        ): # elimination is harmful to `for tuple unpack` because of newTupleAccess
       # addr ( deref ( x )) --> x
       result = n[0][0]
       if n.typ.skipTypes(abstractVar).kind != tyOpenArray:
diff --git a/tests/lent/tlent_from_var.nim b/tests/lent/tlent_from_var.nim
index d61ff6dc009a..8cf65e2860ad 100644
--- a/tests/lent/tlent_from_var.nim
+++ b/tests/lent/tlent_from_var.nim
@@ -50,3 +50,39 @@ template get*[T: not void](self: Opt[T]): T = self.value()
 method connect*(
   self: Opt[(int, int)]) =
   discard self.get()[0]
+
+block: # bug #23454
+  type
+    Letter = enum
+      A
+
+    LetterPairs = object
+      values: seq[(Letter, string)]
+
+  iterator items(list: var LetterPairs): lent (Letter, string) =
+    for item in list.values:
+      yield item
+
+  var instance = LetterPairs(values: @[(A, "foo")])
+
+  for (a, _) in instance:
+    case a
+    of A: discard
+
+block: # bug #23454
+  type
+    Letter = enum
+      A
+
+    LetterPairs = object
+      values: seq[(Letter, string)]
+
+  iterator items(list: var LetterPairs): var (Letter, string) =
+    for item in list.values.mItems:
+      yield item
+
+  var instance = LetterPairs(values: @[(A, "foo")])
+
+  for (a, _) in instance:
+    case a
+    of A: discard