From 409900956bc2ca0ee470b7a0e65bbcc63dedaac7 Mon Sep 17 00:00:00 2001
From: "github-actions[bot]"
 <41898282+github-actions[bot]@users.noreply.github.com>
Date: Tue, 14 Apr 2026 13:27:06 +0000
Subject: [PATCH] Add regression test: #4473, extern function parameters not
 flagged as unused

Fixes https://github.com/dotnet/fsharp/issues/4473

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
---
 .../ErrorMessages/WarnExpressionTests.fs         | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/tests/FSharp.Compiler.ComponentTests/ErrorMessages/WarnExpressionTests.fs b/tests/FSharp.Compiler.ComponentTests/ErrorMessages/WarnExpressionTests.fs
index b5cf1bcbccb..bc68eb4d7d9 100644
--- a/tests/FSharp.Compiler.ComponentTests/ErrorMessages/WarnExpressionTests.fs
+++ b/tests/FSharp.Compiler.ComponentTests/ErrorMessages/WarnExpressionTests.fs
@@ -277,3 +277,19 @@ let main _argv =
         """
         |> typecheck
         |> shouldSucceed
+
+    // https://github.com/dotnet/fsharp/issues/4473
+    [<Fact>]
+    let ``Issue 4473 - extern function parameters not flagged as unused with warnon 1182``() =
+        FSharp """
+module Test4473
+
+open System.Runtime.InteropServices
+
+[<DllImport("kernel32.dll")>]
+extern bool Beep(int frequency, int duration)
+        """
+        |> withWarnOn 1182
+        |> asLibrary
+        |> typecheck
+        |> shouldSucceed