expand: Pass everything by reference to pre-expansion lint callback

compiler/rustc_expand/src/base.rs

@@ -925,6 +925,20 @@ fn cfg_accessible(
     fn registered_tools(&self) -> &FxHashSet<Ident>;
 }
 
+pub trait LintStoreExpand {
+    fn pre_expansion_lint(
+        &self,
+        sess: &Session,
+        registered_tools: &FxHashSet<Ident>,
+        node_id: NodeId,
+        attrs: &[Attribute],
+        items: &[P<Item>],
+        name: &str,
+    );
+}
+
+type LintStoreExpandDyn<'a> = Option<&'a (dyn LintStoreExpand + 'a)>;
+
 #[derive(Clone, Default)]
 pub struct ModuleData {
     /// Path to the module starting from the crate name, like `my_crate::foo::bar`.
@@ -959,10 +973,6 @@ pub struct ExpansionData {
     pub is_trailing_mac: bool,
 }
 
-type OnExternModLoaded<'a> = Option<
-    &'a dyn Fn(NodeId, Vec<Attribute>, Vec<P<Item>>, Symbol) -> (Vec<Attribute>, Vec<P<Item>>),
->;
-
 /// One of these is made during expansion and incrementally updated as we go;
 /// when a macro expansion occurs, the resulting nodes have the `backtrace()
 /// -> expn_data` of their expansion context stored into their span.
@@ -977,10 +987,8 @@ pub struct ExtCtxt<'a> {
     /// (or during eager expansion, but that's a hack).
     pub force_mode: bool,
     pub expansions: FxHashMap<Span, Vec<String>>,
-    /// Called directly after having parsed an external `mod foo;` in expansion.
-    ///
-    /// `Ident` is the module name.
-    pub(super) extern_mod_loaded: OnExternModLoaded<'a>,
+    /// Used for running pre-expansion lints on freshly loaded modules.
+    pub(super) lint_store: LintStoreExpandDyn<'a>,
     /// When we 'expand' an inert attribute, we leave it
     /// in the AST, but insert it here so that we know
     /// not to expand it again.
@@ -992,14 +1000,14 @@ pub fn new(
         sess: &'a Session,
         ecfg: expand::ExpansionConfig<'a>,
         resolver: &'a mut dyn ResolverExpand,
-        extern_mod_loaded: OnExternModLoaded<'a>,
+        lint_store: LintStoreExpandDyn<'a>,
     ) -> ExtCtxt<'a> {
         ExtCtxt {
             sess,
             ecfg,
             reduced_recursion_limit: None,
             resolver,
-            extern_mod_loaded,
+            lint_store,
             root_path: PathBuf::new(),
             current_expansion: ExpansionData {
                 id: LocalExpnId::ROOT,

compiler/rustc_expand/src/expand.rs

@@ -1097,7 +1097,7 @@ fn wrap_flat_map_node_noop_flat_map(
             ModKind::Unloaded => {
                 // We have an outline `mod foo;` so we need to parse the file.
                 let old_attrs_len = attrs.len();
-                let ParsedExternalMod { mut items, inner_span, file_path, dir_path, dir_ownership } =
+                let ParsedExternalMod { items, inner_span, file_path, dir_path, dir_ownership } =
                     parse_external_mod(
                         &ecx.sess,
                         ident,
@@ -1107,12 +1107,14 @@ fn wrap_flat_map_node_noop_flat_map(
                         &mut attrs,
                     );
 
-                if let Some(extern_mod_loaded) = ecx.extern_mod_loaded {
-                    (attrs, items) = extern_mod_loaded(
+                if let Some(lint_store) = ecx.lint_store {
+                    lint_store.pre_expansion_lint(
+                        ecx.sess,
+                        ecx.resolver.registered_tools(),
                         ecx.current_expansion.lint_node_id,
-                        attrs,
-                        items,
-                        ident.name,
+                        &attrs,
+                        &items,
+                        ident.name.as_str(),
                     );
                 }
 

compiler/rustc_interface/src/passes.rs

@@ -11,7 +11,7 @@
 use rustc_data_structures::sync::{Lrc, OnceCell, WorkerLocal};
 use rustc_data_structures::temp_dir::MaybeTempDir;
 use rustc_errors::{Applicability, ErrorReported, PResult};
-use rustc_expand::base::{ExtCtxt, ResolverExpand};
+use rustc_expand::base::{ExtCtxt, LintStoreExpand, ResolverExpand};
 use rustc_hir::def_id::{StableCrateId, LOCAL_CRATE};
 use rustc_hir::Crate;
 use rustc_lint::{EarlyCheckNode, LintStore};
@@ -253,6 +253,23 @@ fn pre_expansion_lint<'a>(
     });
 }
 
+// Cannot implement directly for `LintStore` due to trait coherence.
+struct LintStoreExpandImpl<'a>(&'a LintStore);
+
+impl LintStoreExpand for LintStoreExpandImpl<'_> {
+    fn pre_expansion_lint(
+        &self,
+        sess: &Session,
+        registered_tools: &RegisteredTools,
+        node_id: ast::NodeId,
+        attrs: &[ast::Attribute],
+        items: &[rustc_ast::ptr::P<ast::Item>],
+        name: &str,
+    ) {
+        pre_expansion_lint(sess, self.0, registered_tools, (node_id, attrs, items), name);
+    }
+}
+
 /// Runs the "early phases" of the compiler: initial `cfg` processing, loading compiler plugins,
 /// syntax expansion, secondary `cfg` expansion, synthesis of a test
 /// harness if one is to be provided, injection of a dependency on the
@@ -321,18 +338,8 @@ pub fn configure_and_expand(
             ..rustc_expand::expand::ExpansionConfig::default(crate_name.to_string())
         };
 
-        let registered_tools = resolver.registered_tools().clone();
-        let extern_mod_loaded = |node_id, attrs: Vec<_>, items: Vec<_>, name: Symbol| {
-            pre_expansion_lint(
-                sess,
-                lint_store,
-                &registered_tools,
-                (node_id, &*attrs, &*items),
-                name.as_str(),
-            );
-            (attrs, items)
-        };
-        let mut ecx = ExtCtxt::new(sess, cfg, resolver, Some(&extern_mod_loaded));
+        let lint_store = LintStoreExpandImpl(lint_store);
+        let mut ecx = ExtCtxt::new(sess, cfg, resolver, Some(&lint_store));
 
         // Expand macros now!
         let krate = sess.time("expand_crate", || ecx.monotonic_expander().expand_crate(krate));