From ba047d0af80711ddad03f86e30e5a983fb7e2ae1 Mon Sep 17 00:00:00 2001
From: Andreas Rumpf <rumpf_a@web.de>
Date: Fri, 29 May 2026 08:08:42 +0200
Subject: [PATCH] fixes #25693 (#25842)

(cherry picked from commit 7813bd8b92824cacec9cddb5152f8c9ed645e03c)
---
 compiler/sigmatch.nim                     |  4 +++
 tests/template/toverload_over_untyped.nim | 32 +++++++++++++++++++++++
 2 files changed, 36 insertions(+)
 create mode 100644 tests/template/toverload_over_untyped.nim

diff --git a/compiler/sigmatch.nim b/compiler/sigmatch.nim
index cfe3a5973f..6ae9fe7374 100644
--- a/compiler/sigmatch.nim
+++ b/compiler/sigmatch.nim
@@ -2474,6 +2474,10 @@ proc paramTypesMatchAux(m: var TCandidate, f, a: PType,
       return arg
     elif f.kind == tyStatic and arg.typ.n != nil:
       return arg.typ.n
+    elif f.kind == tyUntyped:
+      # bug #25693: a different overload candidate may have sem-checked the
+      # operand and left symbols behind; templates expect the pristine AST.
+      return argOrig
     else:
       return argSemantized # argOrig
 
diff --git a/tests/template/toverload_over_untyped.nim b/tests/template/toverload_over_untyped.nim
new file mode 100644
index 0000000000..0f734480d6
--- /dev/null
+++ b/tests/template/toverload_over_untyped.nim
@@ -0,0 +1,32 @@
+discard """
+  output: "ok"
+"""
+
+# bug #25693
+
+template g(b: untyped) {.dirty.} =
+  template t: untyped = b
+
+proc d() = discard @[0]
+proc g(_: int) = discard
+
+proc f(a: var seq[int], _: string) =
+  let p = @[0]
+  d()
+  a = p
+
+let q = "a"
+g:
+  var a: seq[int]
+  try:
+    f(a, q & "1")
+  except CatchableError:
+    discard
+  try:
+    f(a, q & "1")
+  except CatchableError:
+    discard
+block: t()
+block: t()
+echo "ok"
+