Fix redundant import errors for preload extern crate

2 files changed, 77 insertions, 71 deletions

diff --git a/compiler/rustc_resolve/src/check_unused.rs b/compiler/rustc_resolve/src/check_unused.rs
index 13fec70e0a7..bf1ea2e2709 100644
--- a/compiler/rustc_resolve/src/check_unused.rs
+++ b/compiler/rustc_resolve/src/check_unused.rs
@@ -137,6 +137,81 @@ impl<'a, 'b, 'tcx> UnusedImportCheckVisitor<'a, 'b, 'tcx> {
             self.check_import_as_underscore(item, *id);
         }
     }
+
+    fn report_unused_extern_crate_items(
+        &mut self,
+        maybe_unused_extern_crates: FxHashMap<ast::NodeId, Span>,
+    ) {
+        let tcx = self.r.tcx();
+        for extern_crate in &self.extern_crate_items {
+            let warn_if_unused = !extern_crate.ident.name.as_str().starts_with('_');
+
+            // If the crate is fully unused, we suggest removing it altogether.
+            // We do this in any edition.
+            if warn_if_unused {
+                if let Some(&span) = maybe_unused_extern_crates.get(&extern_crate.id) {
+                    self.r.lint_buffer.buffer_lint_with_diagnostic(
+                        UNUSED_EXTERN_CRATES,
+                        extern_crate.id,
+                        span,
+                        "unused extern crate",
+                        BuiltinLintDiag::UnusedExternCrate {
+                            removal_span: extern_crate.span_with_attributes,
+                        },
+                    );
+                    continue;
+                }
+            }
+
+            // If we are not in Rust 2018 edition, then we don't make any further
+            // suggestions.
+            if !tcx.sess.at_least_rust_2018() {
+                continue;
+            }
+
+            // If the extern crate has any attributes, they may have funky
+            // semantics we can't faithfully represent using `use` (most
+            // notably `#[macro_use]`). Ignore it.
+            if extern_crate.has_attrs {
+                continue;
+            }
+
+            // If the extern crate is renamed, then we cannot suggest replacing it with a use as this
+            // would not insert the new name into the prelude, where other imports in the crate may be
+            // expecting it.
+            if extern_crate.renames {
+                continue;
+            }
+
+            // If the extern crate isn't in the extern prelude,
+            // there is no way it can be written as a `use`.
+            if !self
+                .r
+                .extern_prelude
+                .get(&extern_crate.ident)
+                .is_some_and(|entry| !entry.introduced_by_item)
+            {
+                continue;
+            }
+
+            let vis_span = extern_crate
+                .vis_span
+                .find_ancestor_inside(extern_crate.span)
+                .unwrap_or(extern_crate.vis_span);
+            let ident_span = extern_crate
+                .ident
+                .span
+                .find_ancestor_inside(extern_crate.span)
+                .unwrap_or(extern_crate.ident.span);
+            self.r.lint_buffer.buffer_lint_with_diagnostic(
+                UNUSED_EXTERN_CRATES,
+                extern_crate.id,
+                extern_crate.span,
+                "`extern crate` is not idiomatic in the new edition",
+                BuiltinLintDiag::ExternCrateNotIdiomatic { vis_span, ident_span },
+            );
+        }
+    }
 }
 
 impl<'a, 'b, 'tcx> Visitor<'a> for UnusedImportCheckVisitor<'a, 'b, 'tcx> {
@@ -335,6 +410,8 @@ impl Resolver<'_, '_> {
         };
         visit::walk_crate(&mut visitor, krate);
 
+        visitor.report_unused_extern_crate_items(maybe_unused_extern_crates);
+
         for unused in visitor.unused_imports.values() {
             let mut fixes = Vec::new();
             let spans = match calc_unused_spans(unused, &unused.use_tree, unused.use_tree_id) {
@@ -416,75 +493,6 @@ impl Resolver<'_, '_> {
             );
         }
 
-        for extern_crate in visitor.extern_crate_items {
-            let warn_if_unused = !extern_crate.ident.name.as_str().starts_with('_');
-
-            // If the crate is fully unused, we suggest removing it altogether.
-            // We do this in any edition.
-            if warn_if_unused {
-                if let Some(&span) = maybe_unused_extern_crates.get(&extern_crate.id) {
-                    visitor.r.lint_buffer.buffer_lint_with_diagnostic(
-                        UNUSED_EXTERN_CRATES,
-                        extern_crate.id,
-                        span,
-                        "unused extern crate",
-                        BuiltinLintDiag::UnusedExternCrate {
-                            removal_span: extern_crate.span_with_attributes,
-                        },
-                    );
-                    continue;
-                }
-            }
-
-            // If we are not in Rust 2018 edition, then we don't make any further
-            // suggestions.
-            if !tcx.sess.at_least_rust_2018() {
-                continue;
-            }
-
-            // If the extern crate has any attributes, they may have funky
-            // semantics we can't faithfully represent using `use` (most
-            // notably `#[macro_use]`). Ignore it.
-            if extern_crate.has_attrs {
-                continue;
-            }
-
-            // If the extern crate is renamed, then we cannot suggest replacing it with a use as this
-            // would not insert the new name into the prelude, where other imports in the crate may be
-            // expecting it.
-            if extern_crate.renames {
-                continue;
-            }
-
-            // If the extern crate isn't in the extern prelude,
-            // there is no way it can be written as a `use`.
-            if !visitor
-                .r
-                .extern_prelude
-                .get(&extern_crate.ident)
-                .is_some_and(|entry| !entry.introduced_by_item)
-            {
-                continue;
-            }
-
-            let vis_span = extern_crate
-                .vis_span
-                .find_ancestor_inside(extern_crate.span)
-                .unwrap_or(extern_crate.vis_span);
-            let ident_span = extern_crate
-                .ident
-                .span
-                .find_ancestor_inside(extern_crate.span)
-                .unwrap_or(extern_crate.ident.span);
-            visitor.r.lint_buffer.buffer_lint_with_diagnostic(
-                UNUSED_EXTERN_CRATES,
-                extern_crate.id,
-                extern_crate.span,
-                "`extern crate` is not idiomatic in the new edition",
-                BuiltinLintDiag::ExternCrateNotIdiomatic { vis_span, ident_span },
-            );
-        }
-
         let unused_imports = visitor.unused_imports;
         let mut check_redundant_imports = FxIndexSet::default();
         for module in self.arenas.local_modules().iter() {
diff --git a/compiler/rustc_resolve/src/imports.rs b/compiler/rustc_resolve/src/imports.rs
index 6647a9a2792..80ec69ab318 100644
--- a/compiler/rustc_resolve/src/imports.rs
+++ b/compiler/rustc_resolve/src/imports.rs
@@ -1336,9 +1336,7 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
         }
 
         let mut is_redundant = true;
-
         let mut redundant_span = PerNS { value_ns: None, type_ns: None, macro_ns: None };
-
         self.per_ns(|this, ns| {
             if is_redundant && let Ok(binding) = source_bindings[ns].get() {
                 if binding.res() == Res::Err {