ide_db/
path_transform.rs

1//! See [`PathTransform`].
2
3use crate::helpers::mod_path_to_ast;
4use either::Either;
5use hir::{
6    AsAssocItem, HirDisplay, HirFileId, ImportPathConfig, ModuleDef, SemanticsScope,
7    prettify_macro_expansion,
8};
9use itertools::Itertools;
10use rustc_hash::FxHashMap;
11use span::Edition;
12use syntax::{
13    NodeOrToken, SyntaxNode,
14    ast::{self, AstNode, HasGenericArgs, HasName, make},
15    syntax_editor::{self, SyntaxEditor},
16};
17
18#[derive(Default, Debug)]
19struct AstSubsts {
20    types_and_consts: Vec<TypeOrConst>,
21    lifetimes: Vec<ast::LifetimeArg>,
22}
23
24#[derive(Debug)]
25enum TypeOrConst {
26    Either(ast::TypeArg), // indistinguishable type or const param
27    Const(ast::ConstArg),
28}
29
30type LifetimeName = String;
31type DefaultedParam = Either<hir::TypeParam, hir::ConstParam>;
32
33/// `PathTransform` substitutes path in SyntaxNodes in bulk.
34///
35/// This is mostly useful for IDE code generation. If you paste some existing
36/// code into a new context (for example, to add method overrides to an `impl`
37/// block), you generally want to appropriately qualify the names, and sometimes
38/// you might want to substitute generic parameters as well:
39///
40/// ```ignore
41/// mod x {
42///   pub struct A<V>;
43///   pub trait T<U> { fn foo(&self, _: U) -> A<U>; }
44/// }
45///
46/// mod y {
47///   use x::T;
48///
49///   impl T<()> for () {
50///      // If we invoke **Add Missing Members** here, we want to copy-paste `foo`.
51///      // But we want a slightly-modified version of it:
52///      fn foo(&self, _: ()) -> x::A<()> {}
53///   }
54/// }
55/// ```
56pub struct PathTransform<'a> {
57    generic_def: Option<hir::GenericDef>,
58    substs: AstSubsts,
59    target_scope: &'a SemanticsScope<'a>,
60    source_scope: &'a SemanticsScope<'a>,
61}
62
63impl<'a> PathTransform<'a> {
64    pub fn trait_impl(
65        target_scope: &'a SemanticsScope<'a>,
66        source_scope: &'a SemanticsScope<'a>,
67        trait_: hir::Trait,
68        impl_: ast::Impl,
69    ) -> PathTransform<'a> {
70        PathTransform {
71            source_scope,
72            target_scope,
73            generic_def: Some(trait_.into()),
74            substs: get_syntactic_substs(impl_).unwrap_or_default(),
75        }
76    }
77
78    pub fn function_call(
79        target_scope: &'a SemanticsScope<'a>,
80        source_scope: &'a SemanticsScope<'a>,
81        function: hir::Function,
82        generic_arg_list: ast::GenericArgList,
83    ) -> PathTransform<'a> {
84        PathTransform {
85            source_scope,
86            target_scope,
87            generic_def: Some(function.into()),
88            substs: get_type_args_from_arg_list(generic_arg_list).unwrap_or_default(),
89        }
90    }
91
92    pub fn impl_transformation(
93        target_scope: &'a SemanticsScope<'a>,
94        source_scope: &'a SemanticsScope<'a>,
95        impl_: hir::Impl,
96        generic_arg_list: ast::GenericArgList,
97    ) -> PathTransform<'a> {
98        PathTransform {
99            source_scope,
100            target_scope,
101            generic_def: Some(impl_.into()),
102            substs: get_type_args_from_arg_list(generic_arg_list).unwrap_or_default(),
103        }
104    }
105
106    pub fn adt_transformation(
107        target_scope: &'a SemanticsScope<'a>,
108        source_scope: &'a SemanticsScope<'a>,
109        adt: hir::Adt,
110        generic_arg_list: ast::GenericArgList,
111    ) -> PathTransform<'a> {
112        PathTransform {
113            source_scope,
114            target_scope,
115            generic_def: Some(adt.into()),
116            substs: get_type_args_from_arg_list(generic_arg_list).unwrap_or_default(),
117        }
118    }
119
120    pub fn generic_transformation(
121        target_scope: &'a SemanticsScope<'a>,
122        source_scope: &'a SemanticsScope<'a>,
123    ) -> PathTransform<'a> {
124        PathTransform {
125            source_scope,
126            target_scope,
127            generic_def: None,
128            substs: AstSubsts::default(),
129        }
130    }
131
132    #[must_use]
133    pub fn apply(&self, syntax: &SyntaxNode) -> SyntaxNode {
134        self.build_ctx().apply(syntax)
135    }
136
137    #[must_use]
138    pub fn apply_all<'b>(
139        &self,
140        nodes: impl IntoIterator<Item = &'b SyntaxNode>,
141    ) -> Vec<SyntaxNode> {
142        let ctx = self.build_ctx();
143        nodes.into_iter().map(|node| ctx.apply(&node.clone())).collect()
144    }
145
146    fn prettify_target_node(&self, node: SyntaxNode) -> SyntaxNode {
147        match self.target_scope.file_id() {
148            HirFileId::FileId(_) => node,
149            HirFileId::MacroFile(file_id) => {
150                let db = self.target_scope.db;
151                prettify_macro_expansion(
152                    db,
153                    node,
154                    &db.expansion_span_map(file_id),
155                    self.target_scope.module().krate().into(),
156                )
157            }
158        }
159    }
160
161    fn prettify_target_ast<N: AstNode>(&self, node: N) -> N {
162        N::cast(self.prettify_target_node(node.syntax().clone())).unwrap()
163    }
164
165    fn build_ctx(&self) -> Ctx<'a> {
166        let db = self.source_scope.db;
167        let target_module = self.target_scope.module();
168        let source_module = self.source_scope.module();
169        let skip = match self.generic_def {
170            // this is a trait impl, so we need to skip the first type parameter (i.e. Self) -- this is a bit hacky
171            Some(hir::GenericDef::Trait(_)) => 1,
172            _ => 0,
173        };
174        let mut type_substs: FxHashMap<hir::TypeParam, ast::Type> = Default::default();
175        let mut const_substs: FxHashMap<hir::ConstParam, SyntaxNode> = Default::default();
176        let mut defaulted_params: Vec<DefaultedParam> = Default::default();
177        let target_edition = target_module.krate().edition(self.source_scope.db);
178        self.generic_def
179            .into_iter()
180            .flat_map(|it| it.type_or_const_params(db))
181            .skip(skip)
182            // The actual list of trait type parameters may be longer than the one
183            // used in the `impl` block due to trailing default type parameters.
184            // For that case we extend the `substs` with an empty iterator so we
185            // can still hit those trailing values and check if they actually have
186            // a default type. If they do, go for that type from `hir` to `ast` so
187            // the resulting change can be applied correctly.
188            .zip(self.substs.types_and_consts.iter().map(Some).chain(std::iter::repeat(None)))
189            .for_each(|(k, v)| match (k.split(db), v) {
190                (Either::Right(k), Some(TypeOrConst::Either(v))) => {
191                    if let Some(ty) = v.ty() {
192                        type_substs.insert(k, self.prettify_target_ast(ty));
193                    }
194                }
195                (Either::Right(k), None) => {
196                    if let Some(default) = k.default(db)
197                        && let Some(default) =
198                            &default.display_source_code(db, source_module.into(), false).ok()
199                    {
200                        type_substs.insert(k, make::ty(default).clone_for_update());
201                        defaulted_params.push(Either::Left(k));
202                    }
203                }
204                (Either::Left(k), Some(TypeOrConst::Either(v))) => {
205                    if let Some(ty) = v.ty() {
206                        const_substs.insert(k, self.prettify_target_node(ty.syntax().clone()));
207                    }
208                }
209                (Either::Left(k), Some(TypeOrConst::Const(v))) => {
210                    if let Some(expr) = v.expr() {
211                        // FIXME: expressions in curly brackets can cause ambiguity after insertion
212                        // (e.g. `N * 2` -> `{1 + 1} * 2`; it's unclear whether `{1 + 1}`
213                        // is a standalone statement or a part of another expression)
214                        // and sometimes require slight modifications; see
215                        // https://doc.rust-lang.org/reference/statements.html#expression-statements
216                        // (default values in curly brackets can cause the same problem)
217                        const_substs.insert(k, self.prettify_target_node(expr.syntax().clone()));
218                    }
219                }
220                (Either::Left(k), None) => {
221                    if let Some(default) =
222                        k.default(db, target_module.krate().to_display_target(db))
223                        && let Some(default) = default.expr()
224                    {
225                        const_substs.insert(k, default.syntax().clone_for_update());
226                        defaulted_params.push(Either::Right(k));
227                    }
228                }
229                _ => (), // ignore mismatching params
230            });
231        // No need to prettify lifetimes, there's nothing to prettify.
232        let lifetime_substs: FxHashMap<_, _> = self
233            .generic_def
234            .into_iter()
235            .flat_map(|it| it.lifetime_params(db))
236            .zip(self.substs.lifetimes.clone())
237            .filter_map(|(k, v)| {
238                Some((k.name(db).display(db, target_edition).to_string(), v.lifetime()?))
239            })
240            .collect();
241        let mut ctx = Ctx {
242            type_substs,
243            const_substs,
244            lifetime_substs,
245            target_module,
246            source_scope: self.source_scope,
247            same_self_type: self.target_scope.has_same_self_type(self.source_scope),
248            target_edition,
249        };
250        ctx.transform_default_values(defaulted_params);
251        ctx
252    }
253}
254
255struct Ctx<'a> {
256    type_substs: FxHashMap<hir::TypeParam, ast::Type>,
257    const_substs: FxHashMap<hir::ConstParam, SyntaxNode>,
258    lifetime_substs: FxHashMap<LifetimeName, ast::Lifetime>,
259    target_module: hir::Module,
260    source_scope: &'a SemanticsScope<'a>,
261    same_self_type: bool,
262    target_edition: Edition,
263}
264
265fn preorder_rev(item: &SyntaxNode) -> impl Iterator<Item = SyntaxNode> {
266    let x = item
267        .preorder()
268        .filter_map(|event| match event {
269            syntax::WalkEvent::Enter(node) => Some(node),
270            syntax::WalkEvent::Leave(_) => None,
271        })
272        .collect_vec();
273    x.into_iter().rev()
274}
275
276impl Ctx<'_> {
277    fn apply(&self, item: &SyntaxNode) -> SyntaxNode {
278        // `transform_path` may update a node's parent and that would break the
279        // tree traversal. Thus all paths in the tree are collected into a vec
280        // so that such operation is safe.
281        let item = self.transform_path(item).clone_subtree();
282        let mut editor = SyntaxEditor::new(item.clone());
283        preorder_rev(&item).filter_map(ast::Lifetime::cast).for_each(|lifetime| {
284            if let Some(subst) = self.lifetime_substs.get(&lifetime.syntax().text().to_string()) {
285                editor
286                    .replace(lifetime.syntax(), subst.clone_subtree().clone_for_update().syntax());
287            }
288        });
289
290        editor.finish().new_root().clone()
291    }
292
293    fn transform_default_values(&mut self, defaulted_params: Vec<DefaultedParam>) {
294        // By now the default values are simply copied from where they are declared
295        // and should be transformed. As any value is allowed to refer to previous
296        // generic (both type and const) parameters, they should be all iterated left-to-right.
297        for param in defaulted_params {
298            let value = match &param {
299                Either::Left(k) => self.type_substs.get(k).unwrap().syntax(),
300                Either::Right(k) => self.const_substs.get(k).unwrap(),
301            };
302            // `transform_path` may update a node's parent and that would break the
303            // tree traversal. Thus all paths in the tree are collected into a vec
304            // so that such operation is safe.
305            let new_value = self.transform_path(value);
306            match param {
307                Either::Left(k) => {
308                    self.type_substs.insert(k, ast::Type::cast(new_value.clone()).unwrap());
309                }
310                Either::Right(k) => {
311                    self.const_substs.insert(k, new_value.clone());
312                }
313            }
314        }
315    }
316
317    fn transform_path(&self, path: &SyntaxNode) -> SyntaxNode {
318        fn find_child_paths_and_ident_pats(
319            root_path: &SyntaxNode,
320        ) -> Vec<Either<ast::Path, ast::IdentPat>> {
321            let mut result: Vec<Either<ast::Path, ast::IdentPat>> = Vec::new();
322            for child in root_path.children() {
323                if let Some(child_path) = ast::Path::cast(child.clone()) {
324                    result.push(either::Left(child_path));
325                } else if let Some(child_ident_pat) = ast::IdentPat::cast(child.clone()) {
326                    result.push(either::Right(child_ident_pat));
327                } else {
328                    result.extend(find_child_paths_and_ident_pats(&child));
329                }
330            }
331            result
332        }
333
334        let root_path = path.clone_subtree();
335
336        let result = find_child_paths_and_ident_pats(&root_path);
337        let mut editor = SyntaxEditor::new(root_path.clone());
338        for sub_path in result {
339            let new = self.transform_path(sub_path.syntax());
340            editor.replace(sub_path.syntax(), new);
341        }
342
343        let update_sub_item = editor.finish().new_root().clone().clone_subtree();
344        let item = find_child_paths_and_ident_pats(&update_sub_item);
345        let mut editor = SyntaxEditor::new(update_sub_item);
346        for sub_path in item {
347            self.transform_path_or_ident_pat(&mut editor, &sub_path);
348        }
349        editor.finish().new_root().clone()
350    }
351    fn transform_path_or_ident_pat(
352        &self,
353        editor: &mut SyntaxEditor,
354        item: &Either<ast::Path, ast::IdentPat>,
355    ) -> Option<()> {
356        match item {
357            Either::Left(path) => self.transform_path_(editor, path),
358            Either::Right(ident_pat) => self.transform_ident_pat(editor, ident_pat),
359        }
360    }
361
362    fn transform_path_(&self, editor: &mut SyntaxEditor, path: &ast::Path) -> Option<()> {
363        if path.qualifier().is_some() {
364            return None;
365        }
366        if path.segment().is_some_and(|s| {
367            s.parenthesized_arg_list().is_some()
368                || (s.self_token().is_some() && path.parent_path().is_none())
369        }) {
370            // don't try to qualify `Fn(Foo) -> Bar` paths, they are in prelude anyway
371            // don't try to qualify sole `self` either, they are usually locals, but are returned as modules due to namespace clashing
372            return None;
373        }
374        let resolution = self.source_scope.speculative_resolve(path)?;
375
376        match resolution {
377            hir::PathResolution::TypeParam(tp) => {
378                if let Some(subst) = self.type_substs.get(&tp) {
379                    let parent = path.syntax().parent()?;
380                    if let Some(parent) = ast::Path::cast(parent.clone()) {
381                        // Path inside path means that there is an associated
382                        // type/constant on the type parameter. It is necessary
383                        // to fully qualify the type with `as Trait`. Even
384                        // though it might be unnecessary if `subst` is generic
385                        // type, always fully qualifying the path is safer
386                        // because of potential clash of associated types from
387                        // multiple traits
388
389                        let trait_ref = find_trait_for_assoc_item(
390                            self.source_scope,
391                            tp,
392                            parent.segment()?.name_ref()?,
393                        )
394                        .and_then(|trait_ref| {
395                            let cfg = ImportPathConfig {
396                                prefer_no_std: false,
397                                prefer_prelude: true,
398                                prefer_absolute: false,
399                                allow_unstable: true,
400                            };
401                            let found_path = self.target_module.find_path(
402                                self.source_scope.db,
403                                hir::ModuleDef::Trait(trait_ref),
404                                cfg,
405                            )?;
406                            match make::ty_path(mod_path_to_ast(&found_path, self.target_edition)) {
407                                ast::Type::PathType(path_ty) => Some(path_ty),
408                                _ => None,
409                            }
410                        });
411
412                        let segment = make::path_segment_ty(subst.clone(), trait_ref);
413                        let qualified = make::path_from_segments(std::iter::once(segment), false);
414                        editor.replace(path.syntax(), qualified.clone_for_update().syntax());
415                    } else if let Some(path_ty) = ast::PathType::cast(parent) {
416                        let old = path_ty.syntax();
417
418                        if old.parent().is_some() {
419                            editor.replace(old, subst.clone_subtree().clone_for_update().syntax());
420                        } else {
421                            // Some `path_ty` has no parent, especially ones made for default value
422                            // of type parameters.
423                            // In this case, `ted` cannot replace `path_ty` with `subst` directly.
424                            // So, just replace its children as long as the `subst` is the same type.
425                            let new = subst.clone_subtree().clone_for_update();
426                            if !matches!(new, ast::Type::PathType(..)) {
427                                return None;
428                            }
429                            let start = path_ty.syntax().first_child().map(NodeOrToken::Node)?;
430                            let end = path_ty.syntax().last_child().map(NodeOrToken::Node)?;
431                            editor.replace_all(
432                                start..=end,
433                                new.syntax().children().map(NodeOrToken::Node).collect::<Vec<_>>(),
434                            );
435                        }
436                    } else {
437                        editor.replace(
438                            path.syntax(),
439                            subst.clone_subtree().clone_for_update().syntax(),
440                        );
441                    }
442                }
443            }
444            hir::PathResolution::Def(def) if def.as_assoc_item(self.source_scope.db).is_none() => {
445                if let hir::ModuleDef::Trait(_) = def
446                    && matches!(path.segment()?.kind()?, ast::PathSegmentKind::Type { .. })
447                {
448                    // `speculative_resolve` resolves segments like `<T as
449                    // Trait>` into `Trait`, but just the trait name should
450                    // not be used as the replacement of the original
451                    // segment.
452                    return None;
453                }
454
455                let cfg = ImportPathConfig {
456                    prefer_no_std: false,
457                    prefer_prelude: true,
458                    prefer_absolute: false,
459                    allow_unstable: true,
460                };
461                let found_path = self.target_module.find_path(self.source_scope.db, def, cfg)?;
462                let res = mod_path_to_ast(&found_path, self.target_edition).clone_for_update();
463                let mut res_editor = SyntaxEditor::new(res.syntax().clone_subtree());
464                if let Some(args) = path.segment().and_then(|it| it.generic_arg_list())
465                    && let Some(segment) = res.segment()
466                {
467                    if let Some(old) = segment.generic_arg_list() {
468                        res_editor
469                            .replace(old.syntax(), args.clone_subtree().syntax().clone_for_update())
470                    } else {
471                        res_editor.insert(
472                            syntax_editor::Position::last_child_of(segment.syntax()),
473                            args.clone_subtree().syntax().clone_for_update(),
474                        );
475                    }
476                }
477                let res = res_editor.finish().new_root().clone();
478                editor.replace(path.syntax().clone(), res);
479            }
480            hir::PathResolution::ConstParam(cp) => {
481                if let Some(subst) = self.const_substs.get(&cp) {
482                    editor.replace(path.syntax(), subst.clone_subtree().clone_for_update());
483                }
484            }
485            hir::PathResolution::SelfType(imp) => {
486                // keep Self type if it does not need to be replaced
487                if self.same_self_type {
488                    return None;
489                }
490
491                let ty = imp.self_ty(self.source_scope.db);
492                let ty_str = &ty
493                    .display_source_code(
494                        self.source_scope.db,
495                        self.source_scope.module().into(),
496                        true,
497                    )
498                    .ok()?;
499                let ast_ty = make::ty(ty_str).clone_for_update();
500
501                if let Some(adt) = ty.as_adt()
502                    && let ast::Type::PathType(path_ty) = &ast_ty
503                {
504                    let cfg = ImportPathConfig {
505                        prefer_no_std: false,
506                        prefer_prelude: true,
507                        prefer_absolute: false,
508                        allow_unstable: true,
509                    };
510                    let found_path = self.target_module.find_path(
511                        self.source_scope.db,
512                        ModuleDef::from(adt),
513                        cfg,
514                    )?;
515
516                    if let Some(qual) =
517                        mod_path_to_ast(&found_path, self.target_edition).qualifier()
518                    {
519                        let res = make::path_concat(qual, path_ty.path()?).clone_for_update();
520                        editor.replace(path.syntax(), res.syntax());
521                        return Some(());
522                    }
523                }
524
525                editor.replace(path.syntax(), ast_ty.syntax());
526            }
527            hir::PathResolution::Local(_)
528            | hir::PathResolution::Def(_)
529            | hir::PathResolution::BuiltinAttr(_)
530            | hir::PathResolution::ToolModule(_)
531            | hir::PathResolution::DeriveHelper(_) => (),
532        }
533        Some(())
534    }
535
536    fn transform_ident_pat(
537        &self,
538        editor: &mut SyntaxEditor,
539        ident_pat: &ast::IdentPat,
540    ) -> Option<()> {
541        let name = ident_pat.name()?;
542
543        let temp_path = make::path_from_text(&name.text());
544
545        let resolution = self.source_scope.speculative_resolve(&temp_path)?;
546
547        match resolution {
548            hir::PathResolution::Def(def) if def.as_assoc_item(self.source_scope.db).is_none() => {
549                let cfg = ImportPathConfig {
550                    prefer_no_std: false,
551                    prefer_prelude: true,
552                    prefer_absolute: false,
553                    allow_unstable: true,
554                };
555                let found_path = self.target_module.find_path(self.source_scope.db, def, cfg)?;
556                let res = mod_path_to_ast(&found_path, self.target_edition).clone_for_update();
557                editor.replace(ident_pat.syntax(), res.syntax());
558                Some(())
559            }
560            _ => None,
561        }
562    }
563}
564
565// FIXME: It would probably be nicer if we could get this via HIR (i.e. get the
566// trait ref, and then go from the types in the substs back to the syntax).
567fn get_syntactic_substs(impl_def: ast::Impl) -> Option<AstSubsts> {
568    let target_trait = impl_def.trait_()?;
569    let path_type = match target_trait {
570        ast::Type::PathType(path) => path,
571        _ => return None,
572    };
573    let generic_arg_list = path_type.path()?.segment()?.generic_arg_list()?;
574
575    get_type_args_from_arg_list(generic_arg_list)
576}
577
578fn get_type_args_from_arg_list(generic_arg_list: ast::GenericArgList) -> Option<AstSubsts> {
579    let mut result = AstSubsts::default();
580    generic_arg_list.generic_args().for_each(|generic_arg| match generic_arg {
581        // Const params are marked as consts on definition only,
582        // being passed to the trait they are indistguishable from type params;
583        // anyway, we don't really need to distinguish them here.
584        ast::GenericArg::TypeArg(type_arg) => {
585            result.types_and_consts.push(TypeOrConst::Either(type_arg))
586        }
587        // Some const values are recognized correctly.
588        ast::GenericArg::ConstArg(const_arg) => {
589            result.types_and_consts.push(TypeOrConst::Const(const_arg));
590        }
591        ast::GenericArg::LifetimeArg(l_arg) => result.lifetimes.push(l_arg),
592        _ => (),
593    });
594
595    Some(result)
596}
597
598fn find_trait_for_assoc_item(
599    scope: &SemanticsScope<'_>,
600    type_param: hir::TypeParam,
601    assoc_item: ast::NameRef,
602) -> Option<hir::Trait> {
603    let db = scope.db;
604    let trait_bounds = type_param.trait_bounds(db);
605
606    let assoc_item_name = assoc_item.text();
607
608    for trait_ in trait_bounds {
609        let names = trait_.items(db).into_iter().filter_map(|item| match item {
610            hir::AssocItem::TypeAlias(ta) => Some(ta.name(db)),
611            hir::AssocItem::Const(cst) => cst.name(db),
612            _ => None,
613        });
614
615        for name in names {
616            if assoc_item_name.as_str() == name.as_str() {
617                // It is fine to return the first match because in case of
618                // multiple possibilities, the exact trait must be disambiguated
619                // in the definition of trait being implemented, so this search
620                // should not be needed.
621                return Some(trait_);
622            }
623        }
624    }
625
626    None
627}
ide_db/path_transform.rs

ide_db/
path_transform.rs
