rustc_lint: Stop creating a fake ast::Crate for running early lints

Add a trait generalizing over the crate root and freshly loaded modules instead
This also makes node IDs used for pre-expansion linting more precise

Author: petrochenkov

compiler/rustc_expand/src/base.rs

@@ -959,8 +959,9 @@ pub struct ExpansionData {
     pub is_trailing_mac: bool,
 }
 
-type OnExternModLoaded<'a> =
-    Option<&'a dyn Fn(Ident, Vec<Attribute>, Vec<P<Item>>, Span) -> (Vec<Attribute>, Vec<P<Item>>)>;
+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()

compiler/rustc_expand/src/expand.rs

@@ -1108,7 +1108,12 @@ impl InvocationCollectorNode for P<ast::Item> {
                     );
 
                 if let Some(extern_mod_loaded) = ecx.extern_mod_loaded {
-                    (attrs, items) = extern_mod_loaded(ident, attrs, items, inner_span);
+                    (attrs, items) = extern_mod_loaded(
+                        ecx.current_expansion.lint_node_id,
+                        attrs,
+                        items,
+                        ident.name,
+                    );
                 }
 
                 *mod_kind = ModKind::Loaded(items, Inline::No, inner_span);

compiler/rustc_interface/src/passes.rs

@@ -3,7 +3,7 @@ use crate::proc_macro_decls;
 use crate::util;
 
 use rustc_ast::mut_visit::MutVisitor;
-use rustc_ast::{self as ast, visit, DUMMY_NODE_ID};
+use rustc_ast::{self as ast, visit};
 use rustc_borrowck as mir_borrowck;
 use rustc_codegen_ssa::back::link::emit_metadata;
 use rustc_codegen_ssa::traits::CodegenBackend;
@@ -14,7 +14,7 @@ use rustc_errors::{Applicability, ErrorReported, PResult};
 use rustc_expand::base::{ExtCtxt, ResolverExpand};
 use rustc_hir::def_id::{StableCrateId, LOCAL_CRATE};
 use rustc_hir::Crate;
-use rustc_lint::LintStore;
+use rustc_lint::{EarlyCheckNode, LintStore};
 use rustc_metadata::creader::CStore;
 use rustc_metadata::{encode_metadata, EncodedMetadata};
 use rustc_middle::arena::Arena;
@@ -34,7 +34,7 @@ use rustc_session::lint;
 use rustc_session::output::{filename_for_input, filename_for_metadata};
 use rustc_session::search_paths::PathKind;
 use rustc_session::{Limit, Session};
-use rustc_span::symbol::{sym, Ident, Symbol};
+use rustc_span::symbol::{sym, Symbol};
 use rustc_span::{FileName, MultiSpan};
 use rustc_trait_selection::traits;
 use rustc_typeck as typeck;
@@ -233,11 +233,11 @@ pub fn register_plugins<'a>(
     Ok((krate, lint_store))
 }
 
-fn pre_expansion_lint(
+fn pre_expansion_lint<'a>(
     sess: &Session,
     lint_store: &LintStore,
     registered_tools: &RegisteredTools,
-    check_node: &ast::Crate,
+    check_node: impl EarlyCheckNode<'a>,
     node_name: &str,
 ) {
     sess.prof.generic_activity_with_arg("pre_AST_expansion_lint_checks", node_name).run(|| {
@@ -322,10 +322,15 @@ pub fn configure_and_expand(
         };
 
         let registered_tools = resolver.registered_tools().clone();
-        let extern_mod_loaded = |ident: Ident, attrs, items, span| {
-            let krate = ast::Crate { attrs, items, span, id: DUMMY_NODE_ID, is_placeholder: false };
-            pre_expansion_lint(sess, lint_store, &registered_tools, &krate, ident.name.as_str());
-            (krate.attrs, krate.items)
+        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));
 
@@ -507,7 +512,7 @@ pub fn lower_to_hir<'res, 'tcx>(
             resolver.registered_tools(),
             lint_buffer,
             rustc_lint::BuiltinCombinedEarlyLintPass::new(),
-            &krate,
+            &*krate,
         )
     });
 

compiler/rustc_lint/src/early.rs

@@ -16,9 +16,10 @@
 
 use crate::context::{EarlyContext, LintContext, LintStore};
 use crate::passes::{EarlyLintPass, EarlyLintPassObject};
-use rustc_ast as ast;
-use rustc_ast::visit as ast_visit;
+use rustc_ast::ptr::P;
+use rustc_ast::visit::{self as ast_visit, Visitor};
 use rustc_ast::AstLike;
+use rustc_ast::{self as ast, walk_list};
 use rustc_middle::ty::RegisteredTools;
 use rustc_session::lint::{BufferedEarlyLint, LintBuffer, LintPass};
 use rustc_session::Session;
@@ -32,7 +33,7 @@ macro_rules! run_early_pass { ($cx:expr, $f:ident, $($args:expr),*) => ({
     $cx.pass.$f(&$cx.context, $($args),*);
 }) }
 
-struct EarlyContextAndPass<'a, T: EarlyLintPass> {
+pub struct EarlyContextAndPass<'a, T: EarlyLintPass> {
     context: EarlyContext<'a>,
     pass: T,
 }
@@ -326,14 +327,65 @@ macro_rules! early_lint_pass_impl {
 
 crate::early_lint_methods!(early_lint_pass_impl, []);
 
-fn early_lint_node(
+/// Early lints work on different nodes - either on the crate root, or on freshly loaded modules.
+/// This trait generalizes over those nodes.
+pub trait EarlyCheckNode<'a>: Copy {
+    fn id(self) -> ast::NodeId;
+    fn attrs<'b>(self) -> &'b [ast::Attribute]
+    where
+        'a: 'b;
+    fn check<'b>(self, cx: &mut EarlyContextAndPass<'b, impl EarlyLintPass>)
+    where
+        'a: 'b;
+}
+
+impl<'a> EarlyCheckNode<'a> for &'a ast::Crate {
+    fn id(self) -> ast::NodeId {
+        ast::CRATE_NODE_ID
+    }
+    fn attrs<'b>(self) -> &'b [ast::Attribute]
+    where
+        'a: 'b,
+    {
+        &self.attrs
+    }
+    fn check<'b>(self, cx: &mut EarlyContextAndPass<'b, impl EarlyLintPass>)
+    where
+        'a: 'b,
+    {
+        run_early_pass!(cx, check_crate, self);
+        ast_visit::walk_crate(cx, self);
+        run_early_pass!(cx, check_crate_post, self);
+    }
+}
+
+impl<'a> EarlyCheckNode<'a> for (ast::NodeId, &'a [ast::Attribute], &'a [P<ast::Item>]) {
+    fn id(self) -> ast::NodeId {
+        self.0
+    }
+    fn attrs<'b>(self) -> &'b [ast::Attribute]
+    where
+        'a: 'b,
+    {
+        self.1
+    }
+    fn check<'b>(self, cx: &mut EarlyContextAndPass<'b, impl EarlyLintPass>)
+    where
+        'a: 'b,
+    {
+        walk_list!(cx, visit_attribute, self.1);
+        walk_list!(cx, visit_item, self.2);
+    }
+}
+
+fn early_lint_node<'a>(
     sess: &Session,
     warn_about_weird_lints: bool,
     lint_store: &LintStore,
     registered_tools: &RegisteredTools,
     buffered: LintBuffer,
     pass: impl EarlyLintPass,
-    check_node: &ast::Crate,
+    check_node: impl EarlyCheckNode<'a>,
 ) -> LintBuffer {
     let mut cx = EarlyContextAndPass {
         context: EarlyContext::new(
@@ -346,22 +398,18 @@ fn early_lint_node(
         pass,
     };
 
-    cx.with_lint_attrs(ast::CRATE_NODE_ID, &check_node.attrs, |cx| {
-        run_early_pass!(cx, check_crate, check_node);
-        ast_visit::walk_crate(cx, check_node);
-        run_early_pass!(cx, check_crate_post, check_node);
-    });
+    cx.with_lint_attrs(check_node.id(), check_node.attrs(), |cx| check_node.check(cx));
     cx.context.buffered
 }
 
-pub fn check_ast_node(
+pub fn check_ast_node<'a>(
     sess: &Session,
     pre_expansion: bool,
     lint_store: &LintStore,
     registered_tools: &RegisteredTools,
     lint_buffer: Option<LintBuffer>,
     builtin_lints: impl EarlyLintPass,
-    check_node: &ast::Crate,
+    check_node: impl EarlyCheckNode<'a>,
 ) {
     let passes =
         if pre_expansion { &lint_store.pre_expansion_passes } else { &lint_store.early_passes };

compiler/rustc_lint/src/levels.rs

@@ -5,7 +5,7 @@ use rustc_ast_pretty::pprust;
 use rustc_data_structures::fx::FxHashMap;
 use rustc_errors::{struct_span_err, Applicability, DiagnosticBuilder};
 use rustc_hir as hir;
-use rustc_hir::{intravisit, HirId, CRATE_HIR_ID};
+use rustc_hir::{intravisit, HirId};
 use rustc_middle::hir::nested_filter;
 use rustc_middle::lint::LevelAndSource;
 use rustc_middle::lint::LintDiagnosticBuilder;