rustc_interface: Hide some hacky details of early linting from expand

compiler/rustc_expand/src/base.rs

@@ -5,7 +5,7 @@ use rustc_ast::ptr::P;
 use rustc_ast::token::{self, Nonterminal};
 use rustc_ast::tokenstream::{CanSynthesizeMissingTokens, LazyTokenStream, TokenStream};
 use rustc_ast::visit::{AssocCtxt, Visitor};
-use rustc_ast::{self as ast, AstLike, Attribute, NodeId, PatKind};
+use rustc_ast::{self as ast, AstLike, Attribute, Item, NodeId, PatKind};
 use rustc_attr::{self as attr, Deprecation, Stability};
 use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::sync::{self, Lrc};
@@ -925,6 +925,9 @@ pub struct ExpansionData {
     pub prior_type_ascription: Option<(Span, bool)>,
 }
 
+type OnExternModLoaded<'a> =
+    Option<&'a dyn Fn(Ident, Vec<Attribute>, Vec<P<Item>>, Span) -> (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.
@@ -942,7 +945,7 @@ pub struct ExtCtxt<'a> {
     /// Called directly after having parsed an external `mod foo;` in expansion.
     ///
     /// `Ident` is the module name.
-    pub(super) extern_mod_loaded: Option<&'a dyn Fn(&ast::Crate, Ident)>,
+    pub(super) extern_mod_loaded: OnExternModLoaded<'a>,
 }
 
 impl<'a> ExtCtxt<'a> {
@@ -950,7 +953,7 @@ impl<'a> ExtCtxt<'a> {
         sess: &'a Session,
         ecfg: expand::ExpansionConfig<'a>,
         resolver: &'a mut dyn ResolverExpand,
-        extern_mod_loaded: Option<&'a dyn Fn(&ast::Crate, Ident)>,
+        extern_mod_loaded: OnExternModLoaded<'a>,
     ) -> ExtCtxt<'a> {
         ExtCtxt {
             sess,

compiler/rustc_expand/src/expand.rs

@@ -1298,7 +1298,7 @@ impl<'a, 'b> MutVisitor for InvocationCollector<'a, 'b> {
                     ModKind::Unloaded => {
                         // We have an outline `mod foo;` so we need to parse the file.
                         let ParsedExternalMod {
-                            items,
+                            mut items,
                             inner_span,
                             file_path,
                             dir_path,
@@ -1312,14 +1312,12 @@ impl<'a, 'b> MutVisitor for InvocationCollector<'a, 'b> {
                             &mut attrs,
                         );
 
-                        let krate =
-                            ast::Crate { attrs, items, span: inner_span, proc_macros: vec![] };
                         if let Some(extern_mod_loaded) = self.cx.extern_mod_loaded {
-                            extern_mod_loaded(&krate, ident);
+                            (attrs, items) = extern_mod_loaded(ident, attrs, items, inner_span);
                         }
 
-                        *mod_kind = ModKind::Loaded(krate.items, Inline::No, inner_span);
-                        item.attrs = krate.attrs;
+                        *mod_kind = ModKind::Loaded(items, Inline::No, inner_span);
+                        item.attrs = attrs;
                         // File can have inline attributes, e.g., `#![cfg(...)]` & co. => Reconfigure.
                         item = configure!(self, item);
                         (Some(file_path), dir_path, dir_ownership)

compiler/rustc_expand/src/lib.rs

@@ -1,5 +1,6 @@
 #![feature(crate_visibility_modifier)]
 #![feature(decl_macro)]
+#![feature(destructuring_assignment)]
 #![feature(or_patterns)]
 #![feature(proc_macro_diagnostic)]
 #![feature(proc_macro_internals)]

compiler/rustc_interface/src/passes.rs

@@ -302,8 +302,10 @@ fn configure_and_expand_inner<'a>(
             ..rustc_expand::expand::ExpansionConfig::default(crate_name.to_string())
         };
 
-        let extern_mod_loaded = |k: &ast::Crate, ident: Ident| {
-            pre_expansion_lint(sess, lint_store, k, &*ident.name.as_str())
+        let extern_mod_loaded = |ident: Ident, attrs, items, span| {
+            let krate = ast::Crate { attrs, items, span, proc_macros: vec![] };
+            pre_expansion_lint(sess, lint_store, &krate, &ident.name.as_str());
+            (krate.attrs, krate.items)
         };
         let mut ecx = ExtCtxt::new(&sess, cfg, &mut resolver, Some(&extern_mod_loaded));