From 1aed58ceb6fc2bdbd4d323fb18fd6d7c9ee21630 Mon Sep 17 00:00:00 2001
From: Noratrieb <48135649+Noratrieb@users.noreply.github.com>
Date: Sat, 22 Mar 2025 22:29:23 +0100
Subject: Emit `unused_attributes` for `#[inline]` on exported functions

I saw someone post a code sample that contained these two attributes,
which immediately made me suspicious.
My suspicions were confirmed when I did a small test and checked the
compiler source code to confirm that in these cases, `#[inline]` is
indeed ignored (because you can't exactly `LocalCopy`an unmangled symbol
since that would lead to duplicate symbols, and doing a mix of an
unmangled `GloballyShared` and mangled `LocalCopy` instantiation is too
complicated for our current instatiation mode logic, which I don't want
to change right now).

So instead, emit the usual unused attribute lint with a message saying
that the attribute is ignored in this position.

I think this is not 100% true, since I expect LLVM `inlinehint` to still
be applied to such a function, but that's not why people use this
attribute, they use it for the `LocalCopy` instantiation mode, where it
doesn't work.
---
 compiler/rustc_passes/src/errors.rs | 5 +++++
 1 file changed, 5 insertions(+)

(limited to 'compiler/rustc_passes/src/errors.rs')

diff --git a/compiler/rustc_passes/src/errors.rs b/compiler/rustc_passes/src/errors.rs
index 9bb9b2353dc..b282828a8ae 100644
--- a/compiler/rustc_passes/src/errors.rs
+++ b/compiler/rustc_passes/src/errors.rs
@@ -1435,6 +1435,11 @@ pub(crate) struct OnlyHasEffectOn {
     pub target_name: String,
 }
 
+#[derive(LintDiagnostic)]
+#[diag(passes_inline_ignored_for_exported)]
+#[help]
+pub(crate) struct InlineIgnoredForExported {}
+
 #[derive(Diagnostic)]
 #[diag(passes_object_lifetime_err)]
 pub(crate) struct ObjectLifetimeErr {
-- 
cgit 1.4.1-3-g733a5