1 use super::{AnonymousLifetimeMode, ImplTraitContext, LoweringContext, ParamMode};
2 use super::{GenericArgsCtor, ParenthesizedGenericArgs};
4 use rustc_ast::{self as ast, *};
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;
15 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 path_span_lo = p.span.shrink_to_lo();
34 let proj_start = p.segments.len() - partial_res.unresolved_segments();
35 let path = self.arena.alloc(hir::Path {
36 res: self.lower_res(partial_res.base_res()),
37 segments: self.arena.alloc_from_iter(p.segments[..proj_start].iter().enumerate().map(
39 let param_mode = match (qself_position, param_mode) {
40 (Some(j), ParamMode::Optional) if i < j => {
41 // This segment is part of the trait path in a
42 // qualified path - one of `a`, `b` or `Trait`
43 // in `<X as a::b::Trait>::T::U::method`.
49 // Figure out if this is a type/trait segment,
50 // which may need lifetime elision performed.
51 let parent_def_id = |this: &mut Self, def_id: DefId| DefId {
53 index: this.resolver.def_key(def_id).parent.expect("missing parent"),
55 let type_def_id = match partial_res.base_res() {
56 Res::Def(DefKind::AssocTy, def_id) if i + 2 == proj_start => {
57 Some(parent_def_id(self, def_id))
59 Res::Def(DefKind::Variant, def_id) if i + 1 == proj_start => {
60 Some(parent_def_id(self, def_id))
62 Res::Def(DefKind::Struct, def_id)
63 | Res::Def(DefKind::Union, def_id)
64 | Res::Def(DefKind::Enum, def_id)
65 | Res::Def(DefKind::TyAlias, def_id)
66 | Res::Def(DefKind::Trait, def_id)
67 if i + 1 == proj_start =>
73 let parenthesized_generic_args = match partial_res.base_res() {
74 // `a::b::Trait(Args)`
75 Res::Def(DefKind::Trait, _) if i + 1 == proj_start => {
76 ParenthesizedGenericArgs::Ok
78 // `a::b::Trait(Args)::TraitItem`
79 Res::Def(DefKind::AssocFn, _)
80 | Res::Def(DefKind::AssocConst, _)
81 | Res::Def(DefKind::AssocTy, _)
82 if i + 2 == proj_start =>
84 ParenthesizedGenericArgs::Ok
86 // Avoid duplicated errors.
87 Res::Err => ParenthesizedGenericArgs::Ok,
89 _ => ParenthesizedGenericArgs::Err,
92 let num_lifetimes = type_def_id.map_or(0, |def_id| {
93 if let Some(&n) = self.type_def_lifetime_params.get(&def_id) {
96 assert!(!def_id.is_local());
97 let n = self.resolver.item_generics_num_lifetimes(def_id, self.sess);
98 self.type_def_lifetime_params.insert(def_id, n);
101 self.lower_path_segment(
106 parenthesized_generic_args,
112 span: p.segments[..proj_start]
114 .map_or(path_span_lo, |segment| path_span_lo.to(segment.span())),
117 // Simple case, either no projections, or only fully-qualified.
118 // E.g., `std::mem::size_of` or `<I as Iterator>::Item`.
119 if partial_res.unresolved_segments() == 0 {
120 return hir::QPath::Resolved(qself, path);
123 // Create the innermost type that we're projecting from.
124 let mut ty = if path.segments.is_empty() {
125 // If the base path is empty that means there exists a
126 // syntactical `Self`, e.g., `&i32` in `<&i32>::clone`.
127 qself.expect("missing QSelf for <T>::...")
129 // Otherwise, the base path is an implicit `Self` type path,
130 // e.g., `Vec` in `Vec::new` or `<I as Iterator>::Item` in
131 // `<I as Iterator>::Item::default`.
132 let new_id = self.next_id();
133 self.arena.alloc(self.ty_path(new_id, path.span, hir::QPath::Resolved(qself, path)))
136 // Anything after the base path are associated "extensions",
137 // out of which all but the last one are associated types,
138 // e.g., for `std::vec::Vec::<T>::IntoIter::Item::clone`:
139 // * base path is `std::vec::Vec<T>`
140 // * "extensions" are `IntoIter`, `Item` and `clone`
142 // 1. `std::vec::Vec<T>` (created above)
143 // 2. `<std::vec::Vec<T>>::IntoIter`
144 // 3. `<<std::vec::Vec<T>>::IntoIter>::Item`
145 // * final path is `<<<std::vec::Vec<T>>::IntoIter>::Item>::clone`
146 for (i, segment) in p.segments.iter().enumerate().skip(proj_start) {
147 let hir_segment = self.arena.alloc(self.lower_path_segment(
152 ParenthesizedGenericArgs::Err,
156 let qpath = hir::QPath::TypeRelative(ty, hir_segment);
158 // It's finished, return the extension of the right node type.
159 if i == p.segments.len() - 1 {
163 // Wrap the associated extension in another type node.
164 let new_id = self.next_id();
165 ty = self.arena.alloc(self.ty_path(new_id, path_span_lo.to(segment.span()), qpath));
168 // We should've returned in the for loop above.
170 self.sess.diagnostic().span_bug(
173 "lower_qpath: no final extension segment in {}..{}",
180 crate fn lower_path_extra(
184 param_mode: ParamMode,
185 explicit_owner: Option<NodeId>,
186 ) -> &'hir hir::Path<'hir> {
187 self.arena.alloc(hir::Path {
189 segments: self.arena.alloc_from_iter(p.segments.iter().map(|segment| {
190 self.lower_path_segment(
195 ParenthesizedGenericArgs::Err,
196 ImplTraitContext::disallowed(),
208 param_mode: ParamMode,
209 ) -> &'hir hir::Path<'hir> {
210 let res = self.expect_full_res(id);
211 let res = self.lower_res(res);
212 self.lower_path_extra(res, p, param_mode, None)
215 crate fn lower_path_segment(
218 segment: &PathSegment,
219 param_mode: ParamMode,
220 expected_lifetimes: usize,
221 parenthesized_generic_args: ParenthesizedGenericArgs,
222 itctx: ImplTraitContext<'_, 'hir>,
223 explicit_owner: Option<NodeId>,
224 ) -> hir::PathSegment<'hir> {
225 let (mut generic_args, infer_args) = if let Some(ref generic_args) = segment.args {
226 let msg = "parenthesized type parameters may only be used with a `Fn` trait";
227 match **generic_args {
228 GenericArgs::AngleBracketed(ref data) => {
229 self.lower_angle_bracketed_parameter_data(data, param_mode, itctx)
231 GenericArgs::Parenthesized(ref data) => match parenthesized_generic_args {
232 ParenthesizedGenericArgs::Ok => self.lower_parenthesized_parameter_data(data),
233 ParenthesizedGenericArgs::Err => {
234 let mut err = struct_span_err!(self.sess, data.span, E0214, "{}", msg);
235 err.span_label(data.span, "only `Fn` traits may use parentheses");
236 if let Ok(snippet) = self.sess.source_map().span_to_snippet(data.span) {
237 // Do not suggest going from `Trait()` to `Trait<>`
238 if !data.inputs.is_empty() {
239 if let Some(split) = snippet.find('(') {
240 let trait_name = &snippet[0..split];
241 let args = &snippet[split + 1..snippet.len() - 1];
244 "use angle brackets instead",
245 format!("{}<{}>", trait_name, args),
246 Applicability::MaybeIncorrect,
253 self.lower_angle_bracketed_parameter_data(
254 &data.as_angle_bracketed_args(),
265 self.lower_angle_bracketed_parameter_data(&Default::default(), param_mode, itctx)
269 generic_args.args.iter().any(|arg| matches!(arg, GenericArg::Lifetime(_)));
270 let first_generic_span = generic_args
274 .chain(generic_args.bindings.iter().map(|b| b.span))
276 if !generic_args.parenthesized && !has_lifetimes {
277 generic_args.args = self
278 .elided_path_lifetimes(
279 first_generic_span.map_or(segment.ident.span, |s| s.shrink_to_lo()),
282 .map(GenericArg::Lifetime)
283 .chain(generic_args.args.into_iter())
285 if expected_lifetimes > 0 && param_mode == ParamMode::Explicit {
286 let anon_lt_suggestion = vec!["'_"; expected_lifetimes].join(", ");
287 let no_non_lt_args = generic_args.args.len() == expected_lifetimes;
288 let no_bindings = generic_args.bindings.is_empty();
289 let (incl_angl_brckt, insertion_sp, suggestion) = if no_non_lt_args && no_bindings {
290 // If there are no (non-implicit) generic args or associated type
291 // bindings, our suggestion includes the angle brackets.
292 (true, path_span.shrink_to_hi(), format!("<{}>", anon_lt_suggestion))
294 // Otherwise (sorry, this is kind of gross) we need to infer the
295 // place to splice in the `'_, ` from the generics that do exist.
296 let first_generic_span = first_generic_span
297 .expect("already checked that non-lifetime args or bindings exist");
298 (false, first_generic_span.shrink_to_lo(), format!("{}, ", anon_lt_suggestion))
300 match self.anonymous_lifetime_mode {
301 // In create-parameter mode we error here because we don't want to support
302 // deprecated impl elision in new features like impl elision and `async fn`,
303 // both of which work using the `CreateParameter` mode:
305 // impl Foo for std::cell::Ref<u32> // note lack of '_
306 // async fn foo(_: std::cell::Ref<u32>) { ... }
307 AnonymousLifetimeMode::CreateParameter => {
308 let mut err = struct_span_err!(
312 "implicit elided lifetime not allowed here"
314 rustc_errors::add_elided_lifetime_in_path_suggestion(
315 &self.sess.source_map(),
325 AnonymousLifetimeMode::PassThrough | AnonymousLifetimeMode::ReportError => {
326 self.resolver.lint_buffer().buffer_lint_with_diagnostic(
327 ELIDED_LIFETIMES_IN_PATHS,
330 "hidden lifetime parameters in types are deprecated",
331 BuiltinLintDiagnostics::ElidedLifetimesInPaths(
344 let res = self.expect_full_res(segment.id);
345 let id = if let Some(owner) = explicit_owner {
346 self.lower_node_id_with_owner(segment.id, owner)
348 self.lower_node_id(segment.id)
351 "lower_path_segment: ident={:?} original-id={:?} new-id={:?}",
352 segment.ident, segment.id, id,
356 ident: segment.ident,
358 res: Some(self.lower_res(res)),
360 args: if generic_args.is_empty() {
363 Some(self.arena.alloc(generic_args.into_generic_args(self.arena)))
368 pub(crate) fn lower_angle_bracketed_parameter_data(
370 data: &AngleBracketedArgs,
371 param_mode: ParamMode,
372 mut itctx: ImplTraitContext<'_, 'hir>,
373 ) -> (GenericArgsCtor<'hir>, bool) {
374 let has_non_lt_args = data.args.iter().any(|arg| match arg {
375 AngleBracketedArg::Arg(ast::GenericArg::Lifetime(_))
376 | AngleBracketedArg::Constraint(_) => false,
377 AngleBracketedArg::Arg(ast::GenericArg::Type(_) | ast::GenericArg::Const(_)) => true,
382 .filter_map(|arg| match arg {
383 AngleBracketedArg::Arg(arg) => Some(self.lower_generic_arg(arg, itctx.reborrow())),
384 AngleBracketedArg::Constraint(_) => None,
387 let bindings = self.arena.alloc_from_iter(data.args.iter().filter_map(|arg| match arg {
388 AngleBracketedArg::Constraint(c) => {
389 Some(self.lower_assoc_ty_constraint(c, itctx.reborrow()))
391 AngleBracketedArg::Arg(_) => None,
393 let ctor = GenericArgsCtor { args, bindings, parenthesized: false };
394 (ctor, !has_non_lt_args && param_mode == ParamMode::Optional)
397 fn lower_parenthesized_parameter_data(
399 data: &ParenthesizedArgs,
400 ) -> (GenericArgsCtor<'hir>, bool) {
401 // Switch to `PassThrough` mode for anonymous lifetimes; this
402 // means that we permit things like `&Ref<T>`, where `Ref` has
403 // a hidden lifetime parameter. This is needed for backwards
404 // compatibility, even in contexts like an impl header where
405 // we generally don't permit such things (see #51008).
406 self.with_anonymous_lifetime_mode(AnonymousLifetimeMode::PassThrough, |this| {
407 let ParenthesizedArgs { span, inputs, inputs_span, output } = data;
408 let inputs = this.arena.alloc_from_iter(
409 inputs.iter().map(|ty| this.lower_ty_direct(ty, ImplTraitContext::disallowed())),
411 let output_ty = match output {
412 FnRetTy::Ty(ty) => this.lower_ty(&ty, ImplTraitContext::disallowed()),
413 FnRetTy::Default(_) => this.arena.alloc(this.ty_tup(*span, &[])),
415 let args = smallvec![GenericArg::Type(this.ty_tup(*inputs_span, inputs))];
416 let binding = this.output_ty_binding(output_ty.span, output_ty);
418 GenericArgsCtor { args, bindings: arena_vec![this; binding], parenthesized: true },
424 /// An associated type binding `Output = $ty`.
425 crate fn output_ty_binding(
428 ty: &'hir hir::Ty<'hir>,
429 ) -> hir::TypeBinding<'hir> {
430 let ident = Ident::with_dummy_span(hir::FN_OUTPUT_NAME);
431 let kind = hir::TypeBindingKind::Equality { ty };
432 let args = arena_vec![self;];
433 let bindings = arena_vec![self;];
434 let gen_args = self.arena.alloc(hir::GenericArgs { args, bindings, parenthesized: false });
435 hir::TypeBinding { hir_id: self.next_id(), gen_args, span, ident, kind }