feat: multiple suggestions for malformed crate_type attribute

Author: Blindspot22

compiler/rustc_builtin_macros/src/cfg_accessible.rs

@@ -45,7 +45,8 @@ impl MultiItemModifier for Expander {
         item: Annotatable,
         _is_derive_const: bool,
     ) -> ExpandResult<Vec<Annotatable>, Annotatable> {
-        let template = AttributeTemplate { list: Some("path"), ..Default::default() };
+        let template = AttributeTemplate { list: Some(&["path"]), ..Default::default() };
+
         validate_attr::check_builtin_meta_item(
             &ecx.ecfg.features,
             &ecx.sess.psess,

compiler/rustc_builtin_macros/src/derive.rs

@@ -35,8 +35,10 @@ impl MultiItemModifier for Expander {
         let (sess, features) = (ecx.sess, ecx.ecfg.features);
         let result =
             ecx.resolver.resolve_derives(ecx.current_expansion.id, ecx.force_mode, &|| {
-                let template =
-                    AttributeTemplate { list: Some("Trait1, Trait2, ..."), ..Default::default() };
+                let template = AttributeTemplate {
+                    list: Some(&["Trait1", "Trait2", "..."]),
+                    ..Default::default()
+                };
                 validate_attr::check_builtin_meta_item(
                     features,
                     &sess.psess,