Auto merge of #26663 - Eljay:fix-repr-attribute, r=sanxiyn

Fixes #26646.

Loops over all `#[repr(..)]` attributes instead of stopping at the first one to make sure they are all marked as used. Previously it stopped after the first `#[repr(C)]` was found causing all other attributes to be skipped by the linter.

src/librustc_lint/builtin.rs

@@ -821,10 +821,12 @@ fn get_lints(&self) -> LintArray {
     }
 
     fn check_item(&mut self, cx: &Context, it: &ast::Item) {
-        let has_extern_repr = it.attrs.iter().any(|attr| {
+        let extern_repr_count = it.attrs.iter().filter(|attr| {
             attr::find_repr_attrs(cx.tcx.sess.diagnostic(), attr).iter()
                 .any(|r| r == &attr::ReprExtern)
-        });
+        }).count();
+        let has_extern_repr = extern_repr_count > 0;
+
         if has_extern_repr {
             return;
         }

src/test/run-pass/issue-26646.rs

@@ -0,0 +1,21 @@
+// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![deny(unused_attributes)]
+
+#[repr(C)]
+#[repr(packed)]
+pub struct Foo;
+
+#[repr(packed)]
+#[repr(C)]
+pub struct Bar;
+
+fn main() { }