1 use super::{AnonymousLifetimeMode, ImplTraitContext, LoweringContext, ParamMode};
2 use super::{GenericArgsCtor, ParenthesizedGenericArgs};
4 use rustc::lint::builtin::ELIDED_LIFETIMES_IN_PATHS;
6 use rustc_errors::{struct_span_err, Applicability};
8 use rustc_hir::def::{DefKind, PartialRes, Res};
9 use rustc_hir::def_id::DefId;
10 use rustc_hir::GenericArg;
11 use rustc_session::lint::BuiltinLintDiagnostics;
13 use syntax::ast::{self, *};
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::Method, _)
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.
168 "lower_qpath: no final extension segment in {}..{}",
174 crate fn lower_path_extra(
178 param_mode: ParamMode,
179 explicit_owner: Option<NodeId>,
180 ) -> &'hir hir::Path<'hir> {
181 self.arena.alloc(hir::Path {
183 segments: self.arena.alloc_from_iter(p.segments.iter().map(|segment| {
184 self.lower_path_segment(
189 ParenthesizedGenericArgs::Err,
190 ImplTraitContext::disallowed(),
202 param_mode: ParamMode,
203 ) -> &'hir hir::Path<'hir> {
204 let res = self.expect_full_res(id);
205 let res = self.lower_res(res);
206 self.lower_path_extra(res, p, param_mode, None)
209 crate fn lower_path_segment(
212 segment: &PathSegment,
213 param_mode: ParamMode,
214 expected_lifetimes: usize,
215 parenthesized_generic_args: ParenthesizedGenericArgs,
216 itctx: ImplTraitContext<'_, 'hir>,
217 explicit_owner: Option<NodeId>,
218 ) -> hir::PathSegment<'hir> {
219 let (mut generic_args, infer_args) = if let Some(ref generic_args) = segment.args {
220 let msg = "parenthesized type parameters may only be used with a `Fn` trait";
221 match **generic_args {
222 GenericArgs::AngleBracketed(ref data) => {
223 self.lower_angle_bracketed_parameter_data(data, param_mode, itctx)
225 GenericArgs::Parenthesized(ref data) => match parenthesized_generic_args {
226 ParenthesizedGenericArgs::Ok => self.lower_parenthesized_parameter_data(data),
227 ParenthesizedGenericArgs::Err => {
228 let mut err = struct_span_err!(self.sess, data.span, E0214, "{}", msg);
229 err.span_label(data.span, "only `Fn` traits may use parentheses");
230 if let Ok(snippet) = self.sess.source_map().span_to_snippet(data.span) {
231 // Do not suggest going from `Trait()` to `Trait<>`
232 if data.inputs.len() > 0 {
233 if let Some(split) = snippet.find('(') {
234 let trait_name = &snippet[0..split];
235 let args = &snippet[split + 1..snippet.len() - 1];
238 "use angle brackets instead",
239 format!("{}<{}>", trait_name, args),
240 Applicability::MaybeIncorrect,
247 self.lower_angle_bracketed_parameter_data(
248 &data.as_angle_bracketed_args(),
259 self.lower_angle_bracketed_parameter_data(&Default::default(), param_mode, itctx)
262 let has_lifetimes = generic_args.args.iter().any(|arg| match arg {
263 GenericArg::Lifetime(_) => true,
266 let first_generic_span = generic_args
270 .chain(generic_args.bindings.iter().map(|b| b.span))
272 if !generic_args.parenthesized && !has_lifetimes {
273 generic_args.args = self
274 .elided_path_lifetimes(path_span, expected_lifetimes)
275 .map(|lt| GenericArg::Lifetime(lt))
276 .chain(generic_args.args.into_iter())
278 if expected_lifetimes > 0 && param_mode == ParamMode::Explicit {
279 let anon_lt_suggestion = vec!["'_"; expected_lifetimes].join(", ");
280 let no_non_lt_args = generic_args.args.len() == expected_lifetimes;
281 let no_bindings = generic_args.bindings.is_empty();
282 let (incl_angl_brckt, insertion_sp, suggestion) = if no_non_lt_args && no_bindings {
283 // If there are no (non-implicit) generic args or associated type
284 // bindings, our suggestion includes the angle brackets.
285 (true, path_span.shrink_to_hi(), format!("<{}>", anon_lt_suggestion))
287 // Otherwise (sorry, this is kind of gross) we need to infer the
288 // place to splice in the `'_, ` from the generics that do exist.
289 let first_generic_span = first_generic_span
290 .expect("already checked that non-lifetime args or bindings exist");
291 (false, first_generic_span.shrink_to_lo(), format!("{}, ", anon_lt_suggestion))
293 match self.anonymous_lifetime_mode {
294 // In create-parameter mode we error here because we don't want to support
295 // deprecated impl elision in new features like impl elision and `async fn`,
296 // both of which work using the `CreateParameter` mode:
298 // impl Foo for std::cell::Ref<u32> // note lack of '_
299 // async fn foo(_: std::cell::Ref<u32>) { ... }
300 AnonymousLifetimeMode::CreateParameter => {
301 let mut err = struct_span_err!(
305 "implicit elided lifetime not allowed here"
307 rustc::lint::add_elided_lifetime_in_path_suggestion(
318 AnonymousLifetimeMode::PassThrough | AnonymousLifetimeMode::ReportError => {
319 self.resolver.lint_buffer().buffer_lint_with_diagnostic(
320 ELIDED_LIFETIMES_IN_PATHS,
323 "hidden lifetime parameters in types are deprecated",
324 BuiltinLintDiagnostics::ElidedLifetimesInPaths(
337 let res = self.expect_full_res(segment.id);
338 let id = if let Some(owner) = explicit_owner {
339 self.lower_node_id_with_owner(segment.id, owner)
341 self.lower_node_id(segment.id)
344 "lower_path_segment: ident={:?} original-id={:?} new-id={:?}",
345 segment.ident, segment.id, id,
349 ident: segment.ident,
351 res: Some(self.lower_res(res)),
353 args: if generic_args.is_empty() {
356 Some(self.arena.alloc(generic_args.into_generic_args(self.arena)))
361 fn lower_angle_bracketed_parameter_data(
363 data: &AngleBracketedArgs,
364 param_mode: ParamMode,
365 mut itctx: ImplTraitContext<'_, 'hir>,
366 ) -> (GenericArgsCtor<'hir>, bool) {
367 let &AngleBracketedArgs { ref args, ref constraints, .. } = data;
368 let has_non_lt_args = args.iter().any(|arg| match arg {
369 ast::GenericArg::Lifetime(_) => false,
370 ast::GenericArg::Type(_) => true,
371 ast::GenericArg::Const(_) => true,
375 args: args.iter().map(|a| self.lower_generic_arg(a, itctx.reborrow())).collect(),
376 bindings: self.arena.alloc_from_iter(
377 constraints.iter().map(|b| self.lower_assoc_ty_constraint(b, itctx.reborrow())),
379 parenthesized: false,
381 !has_non_lt_args && param_mode == ParamMode::Optional,
385 fn lower_parenthesized_parameter_data(
387 data: &ParenthesizedArgs,
388 ) -> (GenericArgsCtor<'hir>, bool) {
389 // Switch to `PassThrough` mode for anonymous lifetimes; this
390 // means that we permit things like `&Ref<T>`, where `Ref` has
391 // a hidden lifetime parameter. This is needed for backwards
392 // compatibility, even in contexts like an impl header where
393 // we generally don't permit such things (see #51008).
394 self.with_anonymous_lifetime_mode(AnonymousLifetimeMode::PassThrough, |this| {
395 let &ParenthesizedArgs { ref inputs, ref output, span } = data;
396 let inputs = this.arena.alloc_from_iter(
397 inputs.iter().map(|ty| this.lower_ty_direct(ty, ImplTraitContext::disallowed())),
399 let output_ty = match output {
400 FunctionRetTy::Ty(ty) => this.lower_ty(&ty, ImplTraitContext::disallowed()),
401 FunctionRetTy::Default(_) => this.arena.alloc(this.ty_tup(span, &[])),
403 let args = smallvec![GenericArg::Type(this.ty_tup(span, inputs))];
404 let binding = this.output_ty_binding(output_ty.span, output_ty);
406 GenericArgsCtor { args, bindings: arena_vec![this; binding], parenthesized: true },
412 /// An associated type binding `Output = $ty`.
413 crate fn output_ty_binding(
416 ty: &'hir hir::Ty<'hir>,
417 ) -> hir::TypeBinding<'hir> {
418 let ident = Ident::with_dummy_span(hir::FN_OUTPUT_NAME);
419 let kind = hir::TypeBindingKind::Equality { ty };
420 hir::TypeBinding { hir_id: self.next_id(), span, ident, kind }