1 use super::{AnonymousLifetimeMode, ImplTraitContext, LoweringContext, ParamMode};
2 use super::{GenericArgsCtor, ParenthesizedGenericArgs};
4 use rustc_ast::ast::{self, *};
5 use rustc_errors::{struct_span_err, Applicability};
7 use rustc_hir::def::{DefKind, PartialRes, Res};
8 use rustc_hir::def_id::DefId;
9 use rustc_hir::GenericArg;
10 use rustc_session::lint::builtin::ELIDED_LIFETIMES_IN_PATHS;
11 use rustc_session::lint::BuiltinLintDiagnostics;
12 use rustc_span::symbol::Ident;
16 use smallvec::smallvec;
18 impl<'a, 'hir> LoweringContext<'a, 'hir> {
22 qself: &Option<QSelf>,
24 param_mode: ParamMode,
25 mut itctx: ImplTraitContext<'_, 'hir>,
26 ) -> hir::QPath<'hir> {
27 let qself_position = qself.as_ref().map(|q| q.position);
28 let qself = qself.as_ref().map(|q| self.lower_ty(&q.ty, itctx.reborrow()));
31 self.resolver.get_partial_res(id).unwrap_or_else(|| PartialRes::new(Res::Err));
33 let proj_start = p.segments.len() - partial_res.unresolved_segments();
34 let path = self.arena.alloc(hir::Path {
35 res: self.lower_res(partial_res.base_res()),
36 segments: self.arena.alloc_from_iter(p.segments[..proj_start].iter().enumerate().map(
38 let param_mode = match (qself_position, param_mode) {
39 (Some(j), ParamMode::Optional) if i < j => {
40 // This segment is part of the trait path in a
41 // qualified path - one of `a`, `b` or `Trait`
42 // in `<X as a::b::Trait>::T::U::method`.
48 // Figure out if this is a type/trait segment,
49 // which may need lifetime elision performed.
50 let parent_def_id = |this: &mut Self, def_id: DefId| DefId {
52 index: this.resolver.def_key(def_id).parent.expect("missing parent"),
54 let type_def_id = match partial_res.base_res() {
55 Res::Def(DefKind::AssocTy, def_id) if i + 2 == proj_start => {
56 Some(parent_def_id(self, def_id))
58 Res::Def(DefKind::Variant, def_id) if i + 1 == proj_start => {
59 Some(parent_def_id(self, def_id))
61 Res::Def(DefKind::Struct, def_id)
62 | Res::Def(DefKind::Union, def_id)
63 | Res::Def(DefKind::Enum, def_id)
64 | Res::Def(DefKind::TyAlias, def_id)
65 | Res::Def(DefKind::Trait, def_id)
66 if i + 1 == proj_start =>
72 let parenthesized_generic_args = match partial_res.base_res() {
73 // `a::b::Trait(Args)`
74 Res::Def(DefKind::Trait, _) if i + 1 == proj_start => {
75 ParenthesizedGenericArgs::Ok
77 // `a::b::Trait(Args)::TraitItem`
78 Res::Def(DefKind::AssocFn, _)
79 | Res::Def(DefKind::AssocConst, _)
80 | Res::Def(DefKind::AssocTy, _)
81 if i + 2 == proj_start =>
83 ParenthesizedGenericArgs::Ok
85 // Avoid duplicated errors.
86 Res::Err => ParenthesizedGenericArgs::Ok,
88 _ => ParenthesizedGenericArgs::Err,
91 let num_lifetimes = type_def_id.map_or(0, |def_id| {
92 if let Some(&n) = self.type_def_lifetime_params.get(&def_id) {
95 assert!(!def_id.is_local());
96 let n = self.resolver.item_generics_num_lifetimes(def_id, self.sess);
97 self.type_def_lifetime_params.insert(def_id, n);
100 self.lower_path_segment(
105 parenthesized_generic_args,
114 // Simple case, either no projections, or only fully-qualified.
115 // E.g., `std::mem::size_of` or `<I as Iterator>::Item`.
116 if partial_res.unresolved_segments() == 0 {
117 return hir::QPath::Resolved(qself, path);
120 // Create the innermost type that we're projecting from.
121 let mut ty = if path.segments.is_empty() {
122 // If the base path is empty that means there exists a
123 // syntactical `Self`, e.g., `&i32` in `<&i32>::clone`.
124 qself.expect("missing QSelf for <T>::...")
126 // Otherwise, the base path is an implicit `Self` type path,
127 // e.g., `Vec` in `Vec::new` or `<I as Iterator>::Item` in
128 // `<I as Iterator>::Item::default`.
129 let new_id = self.next_id();
130 self.arena.alloc(self.ty_path(new_id, p.span, hir::QPath::Resolved(qself, path)))
133 // Anything after the base path are associated "extensions",
134 // out of which all but the last one are associated types,
135 // e.g., for `std::vec::Vec::<T>::IntoIter::Item::clone`:
136 // * base path is `std::vec::Vec<T>`
137 // * "extensions" are `IntoIter`, `Item` and `clone`
139 // 1. `std::vec::Vec<T>` (created above)
140 // 2. `<std::vec::Vec<T>>::IntoIter`
141 // 3. `<<std::vec::Vec<T>>::IntoIter>::Item`
142 // * final path is `<<<std::vec::Vec<T>>::IntoIter>::Item>::clone`
143 for (i, segment) in p.segments.iter().enumerate().skip(proj_start) {
144 let segment = self.arena.alloc(self.lower_path_segment(
149 ParenthesizedGenericArgs::Err,
153 let qpath = hir::QPath::TypeRelative(ty, segment);
155 // It's finished, return the extension of the right node type.
156 if i == p.segments.len() - 1 {
160 // Wrap the associated extension in another type node.
161 let new_id = self.next_id();
162 ty = self.arena.alloc(self.ty_path(new_id, p.span, qpath));
165 // We should've returned in the for loop above.
167 self.sess.diagnostic().span_bug(
170 "lower_qpath: no final extension segment in {}..{}",
177 crate fn lower_path_extra(
181 param_mode: ParamMode,
182 explicit_owner: Option<NodeId>,
183 ) -> &'hir hir::Path<'hir> {
184 self.arena.alloc(hir::Path {
186 segments: self.arena.alloc_from_iter(p.segments.iter().map(|segment| {
187 self.lower_path_segment(
192 ParenthesizedGenericArgs::Err,
193 ImplTraitContext::disallowed(),
205 param_mode: ParamMode,
206 ) -> &'hir hir::Path<'hir> {
207 let res = self.expect_full_res(id);
208 let res = self.lower_res(res);
209 self.lower_path_extra(res, p, param_mode, None)
212 crate fn lower_path_segment(
215 segment: &PathSegment,
216 param_mode: ParamMode,
217 expected_lifetimes: usize,
218 parenthesized_generic_args: ParenthesizedGenericArgs,
219 itctx: ImplTraitContext<'_, 'hir>,
220 explicit_owner: Option<NodeId>,
221 ) -> hir::PathSegment<'hir> {
222 let (mut generic_args, infer_args) = if let Some(ref generic_args) = segment.args {
223 let msg = "parenthesized type parameters may only be used with a `Fn` trait";
224 match **generic_args {
225 GenericArgs::AngleBracketed(ref data) => {
226 self.lower_angle_bracketed_parameter_data(data, param_mode, itctx)
228 GenericArgs::Parenthesized(ref data) => match parenthesized_generic_args {
229 ParenthesizedGenericArgs::Ok => self.lower_parenthesized_parameter_data(data),
230 ParenthesizedGenericArgs::Err => {
231 let mut err = struct_span_err!(self.sess, data.span, E0214, "{}", msg);
232 err.span_label(data.span, "only `Fn` traits may use parentheses");
233 if let Ok(snippet) = self.sess.source_map().span_to_snippet(data.span) {
234 // Do not suggest going from `Trait()` to `Trait<>`
235 if !data.inputs.is_empty() {
236 if let Some(split) = snippet.find('(') {
237 let trait_name = &snippet[0..split];
238 let args = &snippet[split + 1..snippet.len() - 1];
241 "use angle brackets instead",
242 format!("{}<{}>", trait_name, args),
243 Applicability::MaybeIncorrect,
250 self.lower_angle_bracketed_parameter_data(
251 &data.as_angle_bracketed_args(),
262 self.lower_angle_bracketed_parameter_data(&Default::default(), param_mode, itctx)
265 let has_lifetimes = generic_args.args.iter().any(|arg| match arg {
266 GenericArg::Lifetime(_) => true,
269 let first_generic_span = generic_args
273 .chain(generic_args.bindings.iter().map(|b| b.span))
275 if !generic_args.parenthesized && !has_lifetimes {
276 generic_args.args = self
277 .elided_path_lifetimes(
278 first_generic_span.map(|s| s.shrink_to_lo()).unwrap_or(segment.ident.span),
281 .map(GenericArg::Lifetime)
282 .chain(generic_args.args.into_iter())
284 if expected_lifetimes > 0 && param_mode == ParamMode::Explicit {
285 let anon_lt_suggestion = vec!["'_"; expected_lifetimes].join(", ");
286 let no_non_lt_args = generic_args.args.len() == expected_lifetimes;
287 let no_bindings = generic_args.bindings.is_empty();
288 let (incl_angl_brckt, insertion_sp, suggestion) = if no_non_lt_args && no_bindings {
289 // If there are no (non-implicit) generic args or associated type
290 // bindings, our suggestion includes the angle brackets.
291 (true, path_span.shrink_to_hi(), format!("<{}>", anon_lt_suggestion))
293 // Otherwise (sorry, this is kind of gross) we need to infer the
294 // place to splice in the `'_, ` from the generics that do exist.
295 let first_generic_span = first_generic_span
296 .expect("already checked that non-lifetime args or bindings exist");
297 (false, first_generic_span.shrink_to_lo(), format!("{}, ", anon_lt_suggestion))
299 match self.anonymous_lifetime_mode {
300 // In create-parameter mode we error here because we don't want to support
301 // deprecated impl elision in new features like impl elision and `async fn`,
302 // both of which work using the `CreateParameter` mode:
304 // impl Foo for std::cell::Ref<u32> // note lack of '_
305 // async fn foo(_: std::cell::Ref<u32>) { ... }
306 AnonymousLifetimeMode::CreateParameter => {
307 let mut err = struct_span_err!(
311 "implicit elided lifetime not allowed here"
313 rustc_session::lint::add_elided_lifetime_in_path_suggestion(
324 AnonymousLifetimeMode::PassThrough | AnonymousLifetimeMode::ReportError => {
325 self.resolver.lint_buffer().buffer_lint_with_diagnostic(
326 ELIDED_LIFETIMES_IN_PATHS,
329 "hidden lifetime parameters in types are deprecated",
330 BuiltinLintDiagnostics::ElidedLifetimesInPaths(
343 let res = self.expect_full_res(segment.id);
344 let id = if let Some(owner) = explicit_owner {
345 self.lower_node_id_with_owner(segment.id, owner)
347 self.lower_node_id(segment.id)
350 "lower_path_segment: ident={:?} original-id={:?} new-id={:?}",
351 segment.ident, segment.id, id,
355 ident: segment.ident,
357 res: Some(self.lower_res(res)),
359 args: if generic_args.is_empty() {
362 Some(self.arena.alloc(generic_args.into_generic_args(self.arena)))
367 fn lower_angle_bracketed_parameter_data(
369 data: &AngleBracketedArgs,
370 param_mode: ParamMode,
371 mut itctx: ImplTraitContext<'_, 'hir>,
372 ) -> (GenericArgsCtor<'hir>, bool) {
373 let has_non_lt_args = data.args.iter().any(|arg| match arg {
374 AngleBracketedArg::Arg(ast::GenericArg::Lifetime(_))
375 | AngleBracketedArg::Constraint(_) => false,
376 AngleBracketedArg::Arg(ast::GenericArg::Type(_) | ast::GenericArg::Const(_)) => true,
381 .filter_map(|arg| match arg {
382 AngleBracketedArg::Arg(arg) => Some(self.lower_generic_arg(arg, itctx.reborrow())),
383 AngleBracketedArg::Constraint(_) => None,
386 let bindings = self.arena.alloc_from_iter(data.args.iter().filter_map(|arg| match arg {
387 AngleBracketedArg::Constraint(c) => {
388 Some(self.lower_assoc_ty_constraint(c, itctx.reborrow()))
390 AngleBracketedArg::Arg(_) => None,
392 let ctor = GenericArgsCtor { args, bindings, parenthesized: false };
393 (ctor, !has_non_lt_args && param_mode == ParamMode::Optional)
396 fn lower_parenthesized_parameter_data(
398 data: &ParenthesizedArgs,
399 ) -> (GenericArgsCtor<'hir>, bool) {
400 // Switch to `PassThrough` mode for anonymous lifetimes; this
401 // means that we permit things like `&Ref<T>`, where `Ref` has
402 // a hidden lifetime parameter. This is needed for backwards
403 // compatibility, even in contexts like an impl header where
404 // we generally don't permit such things (see #51008).
405 self.with_anonymous_lifetime_mode(AnonymousLifetimeMode::PassThrough, |this| {
406 let &ParenthesizedArgs { ref inputs, ref output, span } = data;
407 let inputs = this.arena.alloc_from_iter(
408 inputs.iter().map(|ty| this.lower_ty_direct(ty, ImplTraitContext::disallowed())),
410 let output_ty = match output {
411 FnRetTy::Ty(ty) => this.lower_ty(&ty, ImplTraitContext::disallowed()),
412 FnRetTy::Default(_) => this.arena.alloc(this.ty_tup(span, &[])),
414 let args = smallvec![GenericArg::Type(this.ty_tup(span, inputs))];
415 let binding = this.output_ty_binding(output_ty.span, output_ty);
417 GenericArgsCtor { args, bindings: arena_vec![this; binding], parenthesized: true },
423 /// An associated type binding `Output = $ty`.
424 crate fn output_ty_binding(
427 ty: &'hir hir::Ty<'hir>,
428 ) -> hir::TypeBinding<'hir> {
429 let ident = Ident::with_dummy_span(hir::FN_OUTPUT_NAME);
430 let kind = hir::TypeBindingKind::Equality { ty };
431 hir::TypeBinding { hir_id: self.next_id(), span, ident, kind }