Name the field in Expander.

For code clarity.

Author: nnethercote

compiler/rustc_builtin_macros/src/derive.rs

@@ -10,7 +10,9 @@ use rustc_session::Session;
 use rustc_span::symbol::{sym, Ident};
 use rustc_span::{ErrorGuaranteed, Span};
 
-pub(crate) struct Expander(pub bool);
+pub(crate) struct Expander {
+    pub is_const: bool,
+}
 
 impl MultiItemModifier for Expander {
     fn expand(
@@ -58,7 +60,7 @@ impl MultiItemModifier for Expander {
                                 report_path_args(sess, meta);
                                 meta.path.clone()
                             })
-                            .map(|path| (path, dummy_annotatable(), None, self.0))
+                            .map(|path| (path, dummy_annotatable(), None, self.is_const))
                             .collect()
                     }
                     _ => vec![],

compiler/rustc_builtin_macros/src/lib.rs

@@ -109,8 +109,8 @@ pub fn register_builtin_macros(resolver: &mut dyn ResolverExpand) {
         bench: test::expand_bench,
         cfg_accessible: cfg_accessible::Expander,
         cfg_eval: cfg_eval::expand,
-        derive: derive::Expander(false),
-        derive_const: derive::Expander(true),
+        derive: derive::Expander { is_const: false },
+        derive_const: derive::Expander { is_const: true },
         global_allocator: global_allocator::expand,
         test: test::expand_test,
         test_case: test::expand_test_case,