+++ /dev/null
-use crate::errors::{ExternCrateNotIdiomatic, UnusedExternCrate};
-use rustc_data_structures::fx::{FxHashMap, FxHashSet};
-use rustc_hir as hir;
-use rustc_hir::def::DefKind;
-use rustc_hir::def_id::{DefId, LocalDefId};
-use rustc_middle::ty::TyCtxt;
-use rustc_session::lint;
-use rustc_span::{Span, Symbol};
-
-pub fn check_crate(tcx: TyCtxt<'_>) {
- let mut used_trait_imports: FxHashSet<LocalDefId> = FxHashSet::default();
-
- for item_def_id in tcx.hir().body_owners() {
- let imports = tcx.used_trait_imports(item_def_id);
- debug!("GatherVisitor: item_def_id={:?} with imports {:#?}", item_def_id, imports);
- used_trait_imports.extend(imports.iter());
- }
-
- for &id in tcx.maybe_unused_trait_imports(()) {
- debug_assert_eq!(tcx.def_kind(id), DefKind::Use);
- if tcx.visibility(id).is_public() {
- continue;
- }
- if used_trait_imports.contains(&id) {
- continue;
- }
- let item = tcx.hir().expect_item(id);
- if item.span.is_dummy() {
- continue;
- }
- let hir::ItemKind::Use(path, _) = item.kind else { unreachable!() };
- tcx.struct_span_lint_hir(lint::builtin::UNUSED_IMPORTS, item.hir_id(), path.span, |lint| {
- let msg = if let Ok(snippet) = tcx.sess.source_map().span_to_snippet(path.span) {
- format!("unused import: `{}`", snippet)
- } else {
- "unused import".to_owned()
- };
- lint.build(&msg).emit();
- });
- }
-
- unused_crates_lint(tcx);
-}
-
-fn unused_crates_lint(tcx: TyCtxt<'_>) {
- let lint = lint::builtin::UNUSED_EXTERN_CRATES;
-
- // Collect first the crates that are completely unused. These we
- // can always suggest removing (no matter which edition we are
- // in).
- let unused_extern_crates: FxHashMap<LocalDefId, Span> = tcx
- .maybe_unused_extern_crates(())
- .iter()
- .filter(|&&(def_id, _)| {
- // The `def_id` here actually was calculated during resolution (at least
- // at the time of this writing) and is being shipped to us via a side
- // channel of the tcx. There may have been extra expansion phases,
- // however, which ended up removing the `def_id` *after* expansion.
- //
- // As a result we need to verify that `def_id` is indeed still valid for
- // our AST and actually present in the HIR map. If it's not there then
- // there's safely nothing to warn about, and otherwise we carry on with
- // our execution.
- //
- // Note that if we carry through to the `extern_mod_stmt_cnum` query
- // below it'll cause a panic because `def_id` is actually bogus at this
- // point in time otherwise.
- if tcx.hir().find(tcx.hir().local_def_id_to_hir_id(def_id)).is_none() {
- return false;
- }
- true
- })
- .filter(|&&(def_id, _)| {
- tcx.extern_mod_stmt_cnum(def_id).map_or(true, |cnum| {
- !tcx.is_compiler_builtins(cnum)
- && !tcx.is_panic_runtime(cnum)
- && !tcx.has_global_allocator(cnum)
- && !tcx.has_panic_handler(cnum)
- })
- })
- .cloned()
- .collect();
-
- // Collect all the extern crates (in a reliable order).
- let mut crates_to_lint = vec![];
-
- for id in tcx.hir().items() {
- if matches!(tcx.def_kind(id.def_id), DefKind::ExternCrate) {
- let item = tcx.hir().item(id);
- if let hir::ItemKind::ExternCrate(orig_name) = item.kind {
- crates_to_lint.push(ExternCrateToLint {
- def_id: item.def_id.to_def_id(),
- span: item.span,
- orig_name,
- warn_if_unused: !item.ident.as_str().starts_with('_'),
- });
- }
- }
- }
-
- let extern_prelude = &tcx.resolutions(()).extern_prelude;
-
- for extern_crate in &crates_to_lint {
- let def_id = extern_crate.def_id.expect_local();
- let item = tcx.hir().expect_item(def_id);
-
- // If the crate is fully unused, we suggest removing it altogether.
- // We do this in any edition.
- if extern_crate.warn_if_unused {
- if let Some(&span) = unused_extern_crates.get(&def_id) {
- // Removal suggestion span needs to include attributes (Issue #54400)
- let id = tcx.hir().local_def_id_to_hir_id(def_id);
- let span_with_attrs = tcx
- .hir()
- .attrs(id)
- .iter()
- .map(|attr| attr.span)
- .fold(span, |acc, attr_span| acc.to(attr_span));
-
- tcx.emit_spanned_lint(lint, id, span, UnusedExternCrate { span: span_with_attrs });
- continue;
- }
- }
-
- // If we are not in Rust 2018 edition, then we don't make any further
- // suggestions.
- if !tcx.sess.rust_2018() {
- continue;
- }
-
- // If the extern crate isn't in the extern prelude,
- // there is no way it can be written as a `use`.
- let orig_name = extern_crate.orig_name.unwrap_or(item.ident.name);
- if !extern_prelude.get(&orig_name).map_or(false, |from_item| !from_item) {
- 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.orig_name.is_some() {
- continue;
- }
-
- let id = tcx.hir().local_def_id_to_hir_id(def_id);
- // 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 !tcx.hir().attrs(id).is_empty() {
- continue;
- }
-
- let base_replacement = match extern_crate.orig_name {
- Some(orig_name) => format!("use {} as {};", orig_name, item.ident.name),
- None => format!("use {};", item.ident.name),
- };
- let vis = tcx.sess.source_map().span_to_snippet(item.vis_span).unwrap_or_default();
- let add_vis = |to| if vis.is_empty() { to } else { format!("{} {}", vis, to) };
- tcx.emit_spanned_lint(
- lint,
- id,
- extern_crate.span,
- ExternCrateNotIdiomatic {
- span: extern_crate.span,
- msg_code: add_vis("use".to_string()),
- suggestion_code: add_vis(base_replacement),
- },
- );
- }
-}
-
-struct ExternCrateToLint {
- /// `DefId` of the extern crate
- def_id: DefId,
-
- /// span from the item
- span: Span,
-
- /// if `Some`, then this is renamed (`extern crate orig_name as
- /// crate_name`), and -- perhaps surprisingly -- this stores the
- /// *original* name (`item.name` will contain the new name)
- orig_name: Option<Symbol>,
-
- /// if `false`, the original name started with `_`, so we shouldn't lint
- /// about it going unused (but we should still emit idiom lints).
- warn_if_unused: bool,
-}
projects / rustc.git / blobdiff