Parse unsafe attributes

compiler/rustc_ast_lowering/src/expr.rs

@@ -1801,6 +1801,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
         let attr = attr::mk_attr_nested_word(
             &self.tcx.sess.psess.attr_id_generator,
             AttrStyle::Outer,
+            Unsafe::No,
             sym::allow,
             sym::unreachable_code,
             self.lower_span(span),

compiler/rustc_ast_lowering/src/lib.rs

@@ -911,6 +911,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         let kind = match attr.kind {
             AttrKind::Normal(ref normal) => AttrKind::Normal(P(NormalAttr {
                 item: AttrItem {
+                    unsafety: normal.item.unsafety,
                     path: normal.item.path.clone(),
                     args: self.lower_attr_args(&normal.item.args),
                     tokens: None,