1 // Copyright 2016 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
12 use rustc::ty::TyCtxt;
17 use rustc::hir::def_id::{DefId, LOCAL_CRATE};
18 use rustc::hir::itemlikevisit::ItemLikeVisitor;
19 use rustc::hir::print::visibility_qualified;
21 use rustc::util::nodemap::DefIdSet;
23 use rustc_data_structures::fx::FxHashMap;
25 pub fn check_crate<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>) {
26 let mut used_trait_imports = DefIdSet();
27 for &body_id in tcx.hir.krate().bodies.keys() {
28 let item_def_id = tcx.hir.body_owner_def_id(body_id);
29 let imports = tcx.used_trait_imports(item_def_id);
30 debug!("GatherVisitor: item_def_id={:?} with imports {:#?}", item_def_id, imports);
31 used_trait_imports.extend(imports.iter());
34 let mut visitor = CheckVisitor { tcx, used_trait_imports };
35 tcx.hir.krate().visit_all_item_likes(&mut visitor);
37 unused_crates_lint(tcx);
40 impl<'a, 'tcx, 'v> ItemLikeVisitor<'v> for CheckVisitor<'a, 'tcx> {
41 fn visit_item(&mut self, item: &hir::Item) {
42 if item.vis.node.is_pub() || item.span.is_dummy() {
45 if let hir::ItemKind::Use(ref path, _) = item.node {
46 self.check_import(item.id, path.span);
50 fn visit_trait_item(&mut self, _trait_item: &hir::TraitItem) {
53 fn visit_impl_item(&mut self, _impl_item: &hir::ImplItem) {
57 struct CheckVisitor<'a, 'tcx: 'a> {
58 tcx: TyCtxt<'a, 'tcx, 'tcx>,
59 used_trait_imports: DefIdSet,
62 impl<'a, 'tcx> CheckVisitor<'a, 'tcx> {
63 fn check_import(&self, id: ast::NodeId, span: Span) {
64 let def_id = self.tcx.hir.local_def_id(id);
65 if !self.tcx.maybe_unused_trait_import(def_id) {
69 let import_def_id = self.tcx.hir.local_def_id(id);
70 if self.used_trait_imports.contains(&import_def_id) {
74 let msg = if let Ok(snippet) = self.tcx.sess.codemap().span_to_snippet(span) {
75 format!("unused import: `{}`", snippet)
77 "unused import".to_string()
79 self.tcx.lint_node(lint::builtin::UNUSED_IMPORTS, id, span, &msg);
83 fn unused_crates_lint<'tcx>(tcx: TyCtxt<'_, 'tcx, 'tcx>) {
84 let lint = lint::builtin::UNUSED_EXTERN_CRATES;
86 // Collect first the crates that are completely unused. These we
87 // can always suggest removing (no matter which edition we are
89 let unused_extern_crates: FxHashMap<DefId, Span> =
90 tcx.maybe_unused_extern_crates(LOCAL_CRATE)
92 .filter(|&&(def_id, _)| {
93 // The `def_id` here actually was calculated during resolution (at least
94 // at the time of this writing) and is being shipped to us via a side
95 // channel of the tcx. There may have been extra expansion phases,
96 // however, which ended up removing the `def_id` *after* expansion such
97 // as the `ReplaceBodyWithLoop` pass (which is a bit of a hack, but hey)
99 // As a result we need to verify that `def_id` is indeed still valid for
100 // our AST and actually present in the HIR map. If it's not there then
101 // there's safely nothing to warn about, and otherwise we carry on with
104 // Note that if we carry through to the `extern_mod_stmt_cnum` query
105 // below it'll cause a panic because `def_id` is actually bogus at this
106 // point in time otherwise.
107 if let Some(id) = tcx.hir.as_local_node_id(def_id) {
108 if tcx.hir.find(id).is_none() {
114 .filter(|&&(def_id, _)| {
115 let cnum = tcx.extern_mod_stmt_cnum(def_id).unwrap();
116 !tcx.is_compiler_builtins(cnum)
117 && !tcx.is_panic_runtime(cnum)
118 && !tcx.has_global_allocator(cnum)
123 // Collect all the extern crates (in a reliable order).
124 let mut crates_to_lint = vec![];
125 tcx.hir.krate().visit_all_item_likes(&mut CollectExternCrateVisitor {
127 crates_to_lint: &mut crates_to_lint,
130 for extern_crate in &crates_to_lint {
131 assert!(extern_crate.def_id.is_local());
133 // If the crate is fully unused, we suggest removing it altogether.
134 // We do this in any edition.
135 if let Some(&span) = unused_extern_crates.get(&extern_crate.def_id) {
136 assert_eq!(extern_crate.def_id.krate, LOCAL_CRATE);
137 let hir_id = tcx.hir.definitions().def_index_to_hir_id(extern_crate.def_id.index);
138 let id = tcx.hir.hir_to_node_id(hir_id);
139 let msg = "unused extern crate";
140 tcx.struct_span_lint_node(lint, id, span, msg)
141 .span_suggestion_short(span, "remove it", "".to_string())
146 // If we are not in Rust 2018 edition, then we don't make any further
148 if !tcx.sess.rust_2018() {
152 // If the extern crate has any attributes, they may have funky
153 // semantics we can't faithfully represent using `use` (most
154 // notably `#[macro_use]`). Ignore it.
155 if !tcx.get_attrs(extern_crate.def_id).is_empty() {
159 // Otherwise, we can convert it into a `use` of some kind.
160 let hir_id = tcx.hir.definitions().def_index_to_hir_id(extern_crate.def_id.index);
161 let id = tcx.hir.hir_to_node_id(hir_id);
162 let item = tcx.hir.expect_item(id);
163 let msg = "`extern crate` is not idiomatic in the new edition";
165 "convert it to a `{}`",
166 visibility_qualified(&item.vis, "use")
168 let base_replacement = match extern_crate.orig_name {
169 Some(orig_name) => format!("use {} as {};", orig_name, item.name),
170 None => format!("use {};", item.name),
172 let replacement = visibility_qualified(&item.vis, &base_replacement);
173 tcx.struct_span_lint_node(lint, id, extern_crate.span, msg)
174 .span_suggestion_short(extern_crate.span, &help, replacement)
179 struct CollectExternCrateVisitor<'a, 'tcx: 'a> {
180 tcx: TyCtxt<'a, 'tcx, 'tcx>,
181 crates_to_lint: &'a mut Vec<ExternCrateToLint>,
184 struct ExternCrateToLint {
185 /// def-id of the extern crate
188 /// span from the item
191 /// if `Some`, then this is renamed (`extern crate orig_name as
192 /// crate_name`), and -- perhaps surprisingly -- this stores the
193 /// *original* name (`item.name` will contain the new name)
194 orig_name: Option<ast::Name>,
197 impl<'a, 'tcx, 'v> ItemLikeVisitor<'v> for CollectExternCrateVisitor<'a, 'tcx> {
198 fn visit_item(&mut self, item: &hir::Item) {
199 if let hir::ItemKind::ExternCrate(orig_name) = item.node {
200 let extern_crate_def_id = self.tcx.hir.local_def_id(item.id);
201 self.crates_to_lint.push(
203 def_id: extern_crate_def_id,
211 fn visit_trait_item(&mut self, _trait_item: &hir::TraitItem) {
214 fn visit_impl_item(&mut self, _impl_item: &hir::ImplItem) {