1 //! An algorithm to find a path to refer to a certain item.
5 use hir_expand::name::{known, AsName, Name};
6 use rustc_hash::FxHashSet;
9 use crate::nameres::DefMap;
13 path::{ModPath, PathKind},
14 visibility::Visibility,
15 ModuleDefId, ModuleId,
18 /// Find a path that can be used to refer to a certain item. This can depend on
19 /// *from where* you're referring to the item, hence the `from` parameter.
20 pub fn find_path(db: &dyn DefDatabase, item: ItemInNs, from: ModuleId) -> Option<ModPath> {
21 let _p = profile::span("find_path");
22 find_path_inner(db, item, from, MAX_PATH_LEN, None)
25 pub fn find_path_prefixed(
29 prefix_kind: PrefixKind,
30 ) -> Option<ModPath> {
31 let _p = profile::span("find_path_prefixed");
32 find_path_inner(db, item, from, MAX_PATH_LEN, Some(prefix_kind))
35 const MAX_PATH_LEN: usize = 15;
38 fn starts_with_std(&self) -> bool {
39 self.segments().first() == Some(&known::std)
42 // When std library is present, paths starting with `std::`
43 // should be preferred over paths starting with `core::` and `alloc::`
44 fn can_start_with_std(&self) -> bool {
45 let first_segment = self.segments().first();
46 first_segment == Some(&known::alloc) || first_segment == Some(&known::core)
50 fn check_self_super(def_map: &DefMap, item: ItemInNs, from: ModuleId) -> Option<ModPath> {
51 if item == ItemInNs::Types(from.into()) {
52 // - if the item is the module we're in, use `self`
53 Some(ModPath::from_segments(PathKind::Super(0), Vec::new()))
54 } else if let Some(parent_id) = def_map[from.local_id].parent {
55 // - if the item is the parent module, use `super` (this is not used recursively, since `super::super` is ugly)
56 let parent_id = def_map.module_id(parent_id);
57 if item == ItemInNs::Types(ModuleDefId::ModuleId(parent_id)) {
58 Some(ModPath::from_segments(PathKind::Super(1), Vec::new()))
67 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
69 /// Causes paths to always start with either `self`, `super`, `crate` or a crate-name.
70 /// This is the same as plain, just that paths will start with `self` iprepended f the path
71 /// starts with an identifier that is not a crate.
73 /// Causes paths to ignore imports in the local module.
75 /// Causes paths to start with `crate` where applicable, effectively forcing paths to be absolute.
81 fn prefix(self) -> PathKind {
83 PrefixKind::BySelf => PathKind::Super(0),
84 PrefixKind::Plain => PathKind::Plain,
85 PrefixKind::ByCrate => PathKind::Crate,
90 fn is_absolute(&self) -> bool {
91 self == &PrefixKind::ByCrate
100 mut prefixed: Option<PrefixKind>,
101 ) -> Option<ModPath> {
108 // - if the item is already in scope, return the name under which it is
109 let def_map = from.def_map(db);
110 let scope_name = def_map.with_ancestor_maps(db, from.local_id, &mut |def_map, local_id| {
111 def_map[local_id].scope.name_of(item).map(|(name, _)| name.clone())
113 if prefixed.is_none() && scope_name.is_some() {
115 .map(|scope_name| ModPath::from_segments(PathKind::Plain, vec![scope_name]));
118 // - if the item is the crate root, return `crate`
119 let root = def_map.crate_root(db);
120 if item == ItemInNs::Types(ModuleDefId::ModuleId(root)) && def_map.block_id().is_none() {
121 // FIXME: the `block_id()` check should be unnecessary, but affects the result
122 return Some(ModPath::from_segments(PathKind::Crate, Vec::new()));
125 if prefixed.filter(PrefixKind::is_absolute).is_none() {
126 if let modpath @ Some(_) = check_self_super(&def_map, item, from) {
131 // - if the item is the crate root of a dependency crate, return the name from the extern prelude
132 for (name, def_id) in def_map.extern_prelude() {
133 if item == ItemInNs::Types(*def_id) {
134 let name = scope_name.unwrap_or_else(|| name.clone());
135 return Some(ModPath::from_segments(PathKind::Plain, vec![name]));
139 // - if the item is in the prelude, return the name from there
140 if let Some(prelude_module) = def_map.prelude() {
141 let prelude_def_map = prelude_module.def_map(db);
142 let prelude_scope: &crate::item_scope::ItemScope =
143 &prelude_def_map[prelude_module.local_id].scope;
144 if let Some((name, vis)) = prelude_scope.name_of(item) {
145 if vis.is_visible_from(db, from) {
146 return Some(ModPath::from_segments(PathKind::Plain, vec![name.clone()]));
151 // - if the item is a builtin, it's in scope
152 if let ItemInNs::Types(ModuleDefId::BuiltinType(builtin)) = item {
153 return Some(ModPath::from_segments(PathKind::Plain, vec![builtin.as_name()]));
157 // - if the item is an enum variant, refer to it via the enum
158 if let Some(ModuleDefId::EnumVariantId(variant)) = item.as_module_def_id() {
159 if let Some(mut path) = find_path(db, ItemInNs::Types(variant.parent.into()), from) {
160 let data = db.enum_data(variant.parent);
161 path.push_segment(data.variants[variant.local_id].name.clone());
164 // If this doesn't work, it seems we have no way of referring to the
165 // enum; that's very weird, but there might still be a reexport of the
169 // - otherwise, look for modules containing (reexporting) it and import it from one of those
171 let crate_root = def_map.crate_root(db);
172 let crate_attrs = db.attrs(crate_root.into());
173 let prefer_no_std = crate_attrs.by_key("no_std").exists();
174 let mut best_path = None;
175 let mut best_path_len = max_len;
177 if item.krate(db) == Some(from.krate) {
178 // Item was defined in the same crate that wants to import it. It cannot be found in any
179 // dependency in this case.
181 let local_imports = find_local_import_locations(db, item, from);
182 for (module_id, name) in local_imports {
183 if let Some(mut path) = find_path_inner(
185 ItemInNs::Types(ModuleDefId::ModuleId(module_id)),
190 path.push_segment(name);
192 let new_path = if let Some(best_path) = best_path {
193 select_best_path(best_path, path, prefer_no_std)
197 best_path_len = new_path.len();
198 best_path = Some(new_path);
202 // Item was defined in some upstream crate. This means that it must be exported from one,
203 // too (unless we can't name it at all). It could *also* be (re)exported by the same crate
204 // that wants to import it here, but we always prefer to use the external path here.
206 let crate_graph = db.crate_graph();
207 let extern_paths = crate_graph[from.krate].dependencies.iter().filter_map(|dep| {
208 let import_map = db.import_map(dep.crate_id);
209 import_map.import_info_for(item).and_then(|info| {
210 // Determine best path for containing module and append last segment from `info`.
211 let mut path = find_path_inner(
213 ItemInNs::Types(ModuleDefId::ModuleId(info.container)),
218 mark::hit!(partially_imported);
219 path.push_segment(info.path.segments.last().unwrap().clone());
224 for path in extern_paths {
225 let new_path = if let Some(best_path) = best_path {
226 select_best_path(best_path, path, prefer_no_std)
230 best_path = Some(new_path);
234 // If the item is declared inside a block expression, don't use a prefix, as we don't handle
235 // that correctly (FIXME).
236 if let Some(item_module) = item.as_module_def_id().and_then(|did| did.module(db)) {
237 if item_module.def_map(db).block_id().is_some() && prefixed.is_some() {
238 mark::hit!(prefixed_in_block_expression);
239 prefixed = Some(PrefixKind::Plain);
243 if let Some(prefix) = prefixed.map(PrefixKind::prefix) {
244 best_path.or_else(|| {
245 scope_name.map(|scope_name| ModPath::from_segments(prefix, vec![scope_name]))
252 fn select_best_path(old_path: ModPath, new_path: ModPath, prefer_no_std: bool) -> ModPath {
253 if old_path.starts_with_std() && new_path.can_start_with_std() {
255 mark::hit!(prefer_no_std_paths);
258 mark::hit!(prefer_std_paths);
261 } else if new_path.starts_with_std() && old_path.can_start_with_std() {
263 mark::hit!(prefer_no_std_paths);
266 mark::hit!(prefer_std_paths);
269 } else if new_path.len() < old_path.len() {
276 /// Finds locations in `from.krate` from which `item` can be imported by `from`.
277 fn find_local_import_locations(
278 db: &dyn DefDatabase,
281 ) -> Vec<(ModuleId, Name)> {
282 let _p = profile::span("find_local_import_locations");
284 // `from` can import anything below `from` with visibility of at least `from`, and anything
285 // above `from` with any visibility. That means we do not need to descend into private siblings
286 // of `from` (and similar).
288 let def_map = from.def_map(db);
290 // Compute the initial worklist. We start with all direct child modules of `from` as well as all
291 // of its (recursive) parent modules.
292 let data = &def_map[from.local_id];
294 data.children.values().map(|child| def_map.module_id(*child)).collect::<Vec<_>>();
295 for ancestor in iter::successors(from.containing_module(db), |m| m.containing_module(db)) {
296 worklist.push(ancestor);
299 let def_map = def_map.crate_root(db).def_map(db);
301 let mut seen: FxHashSet<_> = FxHashSet::default();
303 let mut locations = Vec::new();
304 while let Some(module) = worklist.pop() {
305 if !seen.insert(module) {
306 continue; // already processed this module
310 let data = if module.krate == from.krate {
311 if module.block.is_some() {
312 // Re-query the block's DefMap
313 ext_def_map = module.def_map(db);
314 &ext_def_map[module.local_id]
316 // Reuse the root DefMap
317 &def_map[module.local_id]
320 // The crate might reexport a module defined in another crate.
321 ext_def_map = module.def_map(db);
322 &ext_def_map[module.local_id]
325 if let Some((name, vis)) = data.scope.name_of(item) {
326 if vis.is_visible_from(db, from) {
327 let is_private = if let Visibility::Module(private_to) = vis {
328 private_to.local_id == module.local_id
332 let is_original_def = if let Some(module_def_id) = item.as_module_def_id() {
333 data.scope.declarations().any(|it| it == module_def_id)
338 // Ignore private imports. these could be used if we are
339 // in a submodule of this module, but that's usually not
340 // what the user wants; and if this module can import
341 // the item and we're a submodule of it, so can we.
342 // Also this keeps the cached data smaller.
343 if !is_private || is_original_def {
344 locations.push((module, name.clone()));
349 // Descend into all modules visible from `from`.
350 for (_, per_ns) in data.scope.entries() {
351 if let Some((ModuleDefId::ModuleId(module), vis)) = per_ns.take_types_vis() {
352 if vis.is_visible_from(db, from) {
353 worklist.push(module);
364 use base_db::fixture::WithFixture;
365 use hir_expand::hygiene::Hygiene;
366 use syntax::ast::AstNode;
367 use test_utils::mark;
369 use crate::test_db::TestDB;
373 /// `code` needs to contain a cursor marker; checks that `find_path` for the
374 /// item the `path` refers to returns that same path when called from the
375 /// module the cursor is in.
376 fn check_found_path_(ra_fixture: &str, path: &str, prefix_kind: Option<PrefixKind>) {
377 let (db, pos) = TestDB::with_position(ra_fixture);
378 let module = db.module_at_position(pos);
379 let parsed_path_file = syntax::SourceFile::parse(&format!("use {};", path));
381 parsed_path_file.syntax_node().descendants().find_map(syntax::ast::Path::cast).unwrap();
382 let mod_path = ModPath::from_src(ast_path, &Hygiene::new_unhygienic()).unwrap();
384 let def_map = module.def_map(&db);
385 let resolved = def_map
390 crate::item_scope::BuiltinShadowMode::Module,
397 find_path_inner(&db, ItemInNs::Types(resolved), module, MAX_PATH_LEN, prefix_kind);
398 assert_eq!(found_path, Some(mod_path), "{:?}", prefix_kind);
408 check_found_path_(ra_fixture, unprefixed, None);
409 check_found_path_(ra_fixture, prefixed, Some(PrefixKind::Plain));
410 check_found_path_(ra_fixture, absolute, Some(PrefixKind::ByCrate));
411 check_found_path_(ra_fixture, self_prefixed, Some(PrefixKind::BySelf));
421 check_found_path(code, "S", "S", "crate::S", "self::S");
431 check_found_path(code, "E::A", "E::A", "E::A", "E::A");
443 check_found_path(code, "foo::S", "foo::S", "crate::foo::S", "self::foo::S");
457 check_found_path(code, "super::S", "super::S", "crate::foo::S", "super::S");
468 check_found_path(code, "self", "self", "crate::foo", "self");
479 check_found_path(code, "crate", "crate", "crate", "crate");
491 check_found_path(code, "crate::S", "crate::S", "crate::S", "crate::S");
495 fn different_crate() {
497 //- /main.rs crate:main deps:std
499 //- /std.rs crate:std
502 check_found_path(code, "std::S", "std::S", "std::S", "std::S");
506 fn different_crate_renamed() {
508 //- /main.rs crate:main deps:std
509 extern crate std as std_renamed;
511 //- /std.rs crate:std
524 fn partially_imported() {
525 mark::check!(partially_imported);
526 // Tests that short paths are used even for external items, when parts of the path are
529 //- /main.rs crate:main deps:syntax
534 //- /lib.rs crate:syntax
536 pub enum ModuleItem {
544 "syntax::ast::ModuleItem",
545 "syntax::ast::ModuleItem",
546 "syntax::ast::ModuleItem",
550 //- /main.rs crate:main deps:syntax
554 //- /lib.rs crate:syntax
556 pub enum ModuleItem {
563 "syntax::ast::ModuleItem",
564 "syntax::ast::ModuleItem",
565 "syntax::ast::ModuleItem",
566 "syntax::ast::ModuleItem",
571 fn same_crate_reexport() {
575 mod foo { pub(super) struct S; }
576 pub(crate) use foo::*;
580 check_found_path(code, "bar::S", "bar::S", "crate::bar::S", "self::bar::S");
584 fn same_crate_reexport_rename() {
588 mod foo { pub(super) struct S; }
589 pub(crate) use foo::S as U;
593 check_found_path(code, "bar::U", "bar::U", "crate::bar::U", "self::bar::U");
597 fn different_crate_reexport() {
599 //- /main.rs crate:main deps:std
601 //- /std.rs crate:std deps:core
603 //- /core.rs crate:core
606 check_found_path(code, "std::S", "std::S", "std::S", "std::S");
612 //- /main.rs crate:main deps:std
614 //- /std.rs crate:std
615 pub mod prelude { pub struct S; }
619 check_found_path(code, "S", "S", "S", "S");
623 fn enum_variant_from_prelude() {
625 //- /main.rs crate:main deps:std
627 //- /std.rs crate:std
629 pub enum Option<T> { Some(T), None }
635 check_found_path(code, "None", "None", "None", "None");
636 check_found_path(code, "Some", "Some", "Some", "Some");
648 pub mod bar { pub struct S; }
650 pub use crate::foo::bar::S;
652 check_found_path(code, "baz::S", "baz::S", "crate::baz::S", "self::baz::S");
656 fn discount_private_imports() {
660 pub mod bar { pub struct S; }
665 // crate::S would be shorter, but using private imports seems wrong
666 check_found_path(code, "crate::bar::S", "crate::bar::S", "crate::bar::S", "crate::bar::S");
684 check_found_path(code, "crate::foo::S", "crate::foo::S", "crate::foo::S", "crate::foo::S");
688 fn prefer_std_paths_over_alloc() {
689 mark::check!(prefer_std_paths);
691 //- /main.rs crate:main deps:alloc,std
694 //- /std.rs crate:std deps:alloc
696 pub use alloc::sync::Arc;
699 //- /zzz.rs crate:alloc
714 fn prefer_core_paths_over_std() {
715 mark::check!(prefer_no_std_paths);
717 //- /main.rs crate:main deps:core,std
722 //- /std.rs crate:std deps:core
725 pub use core::fmt::Error;
728 //- /zzz.rs crate:core
744 fn prefer_alloc_paths_over_std() {
746 //- /main.rs crate:main deps:alloc,std
751 //- /std.rs crate:std deps:alloc
754 pub use alloc::sync::Arc;
757 //- /zzz.rs crate:alloc
773 fn prefer_shorter_paths_if_not_alloc() {
775 //- /main.rs crate:main deps:megaalloc,std
778 //- /std.rs crate:std deps:megaalloc
780 pub use megaalloc::sync::Arc;
783 //- /zzz.rs crate:megaalloc
796 fn builtins_are_in_scope() {
805 check_found_path(code, "u8", "u8", "u8", "u8");
806 check_found_path(code, "u16", "u16", "u16", "u16");
826 fn inner_items_from_outer_scope() {
844 fn inner_items_from_inner_module() {
845 mark::check!(prefixed_in_block_expression);
865 fn outer_items_with_inner_items_present() {
869 pub struct CompleteMe;
877 "module::CompleteMe",
878 "module::CompleteMe",
879 "crate::module::CompleteMe",
880 "self::module::CompleteMe",