From 6eef0cc2d5108f51ae3e0e46cee3d59d489df645 Mon Sep 17 00:00:00 2001
From: ringabout <43030857+ringabout@users.noreply.github.com>
Date: Tue, 23 Jun 2026 18:22:29 +0800
Subject: [PATCH] fixes #25908; resolves lent enum disambiguation (#25929)

fixes #25908

When an enum identifier is resolved as an `nkSymChoice`, one of the
candidates may come from a loop-local view and carry `tyVar` or
`tyLent`.

Enum disambiguation should compare the underlying enum type only.
Otherwise a pure-enum field can win incorrectly even though the intended
symbol is already present in the choice set.

Keep the `includePureEnum` lookup path for enum-typed expectations so
#23976 still works, but normalize `var`/`lent` only at the symchoice
selection point.
---
 compiler/sem.nim                 |  5 ++++-
 testament/important_packages.nim |  1 +
 tests/enum/tenum.nim             | 10 ++++++++++
 3 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/compiler/sem.nim b/compiler/sem.nim
index ba9190f572..54042d3fb2 100644
--- a/compiler/sem.nim
+++ b/compiler/sem.nim
@@ -105,9 +105,12 @@ proc fitNode(c: PContext, formal: PType, arg: PNode; info: TLineInfo): PNode =
     result.typ = formal
   elif arg.kind in nkSymChoices and formal.skipTypes(abstractInst).kind == tyEnum:
     # Pick the right 'sym' from the sym choice by looking at 'formal' type:
+    # The choice candidates may be wrapped in `var`/`lent` when they come from
+    # a loop-local view, but for enum disambiguation only the underlying enum
+    # type matters.
     result = nil
     for ch in arg:
-      if sameType(ch.typ, formal):
+      if sameType(ch.typ.skipTypes({tyVar, tyLent}), formal):
         return ch
     typeMismatch(c.config, info, formal, arg.typ, arg)
   else:
diff --git a/testament/important_packages.nim b/testament/important_packages.nim
index d05b9385e9..9ba4a24035 100644
--- a/testament/important_packages.nim
+++ b/testament/important_packages.nim
@@ -158,6 +158,7 @@ pkg "sim"
 pkg "smtp", "nimble compileExample"
 pkg "snip", "nimble test", "https://github.com/genotrance/snip"
 pkg "ssostrings", "nim c -r tests/tssostrings.nim"
+pkg "ssz_serialization", "nim c -r tests/test_all.nim"
 pkg "stew"
 pkg "stint", "nimble test_internal"
 pkg "strslice"
diff --git a/tests/enum/tenum.nim b/tests/enum/tenum.nim
index 7fd89ca0fa..92ee8a523b 100644
--- a/tests/enum/tenum.nim
+++ b/tests/enum/tenum.nim
@@ -283,3 +283,13 @@ block: # bug #23952
       doAssert s1 != s2
     static: foo()
     foo()
+
+# bug #25908
+type S {.pure.} = enum a, b
+
+iterator foo(x: array[1, S]): lent S =
+  yield x[0]
+
+iterator f(_: int | int): S =
+  for a in foo([S.b]): yield a
+for v in f(0): doAssert v == S.b
\ No newline at end of file