1 use crate::ImplTraitPosition;
3 use super::errors::{GenericTypeWithParentheses, UseAngleBrackets};
4 use super::ResolverAstLoweringExt;
5 use super::{GenericArgsCtor, LifetimeRes, ParenthesizedGenericArgs};
6 use super::{ImplTraitContext, LoweringContext, ParamMode};
8 use rustc_ast::{self as ast, *};
10 use rustc_hir::def::{DefKind, PartialRes, Res};
11 use rustc_hir::GenericArg;
12 use rustc_span::symbol::{kw, Ident};
13 use rustc_span::{BytePos, Span, DUMMY_SP};
15 use smallvec::smallvec;
17 impl<'a, 'hir> LoweringContext<'a, 'hir> {
18 #[instrument(level = "trace", skip(self))]
19 pub(crate) fn lower_qpath(
22 qself: &Option<QSelf>,
24 param_mode: ParamMode,
25 itctx: &mut ImplTraitContext,
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));
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 let parenthesized_generic_args = match partial_res.base_res() {
50 // `a::b::Trait(Args)`
51 Res::Def(DefKind::Trait, _) if i + 1 == proj_start => {
52 ParenthesizedGenericArgs::Ok
54 // `a::b::Trait(Args)::TraitItem`
55 Res::Def(DefKind::AssocFn, _)
56 | Res::Def(DefKind::AssocConst, _)
57 | Res::Def(DefKind::AssocTy, _)
58 if i + 2 == proj_start =>
60 ParenthesizedGenericArgs::Ok
62 // Avoid duplicated errors.
63 Res::Err => ParenthesizedGenericArgs::Ok,
65 _ => ParenthesizedGenericArgs::Err,
68 self.lower_path_segment(
72 parenthesized_generic_args,
77 span: self.lower_span(
78 p.segments[..proj_start]
80 .map_or(path_span_lo, |segment| path_span_lo.to(segment.span())),
84 // Simple case, either no projections, or only fully-qualified.
85 // E.g., `std::mem::size_of` or `<I as Iterator>::Item`.
86 if partial_res.unresolved_segments() == 0 {
87 return hir::QPath::Resolved(qself, path);
90 // Create the innermost type that we're projecting from.
91 let mut ty = if path.segments.is_empty() {
92 // If the base path is empty that means there exists a
93 // syntactical `Self`, e.g., `&i32` in `<&i32>::clone`.
94 qself.expect("missing QSelf for <T>::...")
96 // Otherwise, the base path is an implicit `Self` type path,
97 // e.g., `Vec` in `Vec::new` or `<I as Iterator>::Item` in
98 // `<I as Iterator>::Item::default`.
99 let new_id = self.next_id();
100 self.arena.alloc(self.ty_path(new_id, path.span, hir::QPath::Resolved(qself, path)))
103 // Anything after the base path are associated "extensions",
104 // out of which all but the last one are associated types,
105 // e.g., for `std::vec::Vec::<T>::IntoIter::Item::clone`:
106 // * base path is `std::vec::Vec<T>`
107 // * "extensions" are `IntoIter`, `Item` and `clone`
109 // 1. `std::vec::Vec<T>` (created above)
110 // 2. `<std::vec::Vec<T>>::IntoIter`
111 // 3. `<<std::vec::Vec<T>>::IntoIter>::Item`
112 // * final path is `<<<std::vec::Vec<T>>::IntoIter>::Item>::clone`
113 for (i, segment) in p.segments.iter().enumerate().skip(proj_start) {
114 let hir_segment = self.arena.alloc(self.lower_path_segment(
118 ParenthesizedGenericArgs::Err,
121 let qpath = hir::QPath::TypeRelative(ty, hir_segment);
123 // It's finished, return the extension of the right node type.
124 if i == p.segments.len() - 1 {
128 // Wrap the associated extension in another type node.
129 let new_id = self.next_id();
130 ty = self.arena.alloc(self.ty_path(new_id, path_span_lo.to(segment.span()), qpath));
133 // We should've returned in the for loop above.
135 self.diagnostic().span_bug(
138 "lower_qpath: no final extension segment in {}..{}",
145 pub(crate) fn lower_path_extra(
149 param_mode: ParamMode,
150 ) -> &'hir hir::Path<'hir> {
151 self.arena.alloc(hir::Path {
153 segments: self.arena.alloc_from_iter(p.segments.iter().map(|segment| {
154 self.lower_path_segment(
158 ParenthesizedGenericArgs::Err,
159 &mut ImplTraitContext::Disallowed(ImplTraitPosition::Path),
162 span: self.lower_span(p.span),
166 pub(crate) fn lower_path(
170 param_mode: ParamMode,
171 ) -> &'hir hir::Path<'hir> {
172 let res = self.expect_full_res(id);
173 let res = self.lower_res(res);
174 self.lower_path_extra(res, p, param_mode)
177 pub(crate) fn lower_path_segment(
180 segment: &PathSegment,
181 param_mode: ParamMode,
182 parenthesized_generic_args: ParenthesizedGenericArgs,
183 itctx: &mut ImplTraitContext,
184 ) -> hir::PathSegment<'hir> {
185 debug!("path_span: {:?}, lower_path_segment(segment: {:?})", path_span, segment,);
186 let (mut generic_args, infer_args) = if let Some(ref generic_args) = segment.args {
187 match **generic_args {
188 GenericArgs::AngleBracketed(ref data) => {
189 self.lower_angle_bracketed_parameter_data(data, param_mode, itctx)
191 GenericArgs::Parenthesized(ref data) => match parenthesized_generic_args {
192 ParenthesizedGenericArgs::Ok => self.lower_parenthesized_parameter_data(data),
193 ParenthesizedGenericArgs::Err => {
194 // Suggest replacing parentheses with angle brackets `Trait(params...)` to `Trait<params...>`
195 let sub = if !data.inputs.is_empty() {
196 // Start of the span to the 1st character of 1st argument
197 let open_param = data.inputs_span.shrink_to_lo().to(data
203 // Last character position of last argument to the end of the span
204 let close_param = data
210 .to(data.inputs_span.shrink_to_hi());
212 Some(UseAngleBrackets { open_param, close_param })
216 self.tcx.sess.emit_err(GenericTypeWithParentheses { span: data.span, sub });
218 self.lower_angle_bracketed_parameter_data(
219 &data.as_angle_bracketed_args(),
232 args: Default::default(),
234 parenthesized: false,
235 span: path_span.shrink_to_hi(),
237 param_mode == ParamMode::Optional,
242 generic_args.args.iter().any(|arg| matches!(arg, GenericArg::Lifetime(_)));
243 if !generic_args.parenthesized && !has_lifetimes {
244 self.maybe_insert_elided_lifetimes_in_path(
252 let res = self.expect_full_res(segment.id);
253 let hir_id = self.lower_node_id(segment.id);
255 "lower_path_segment: ident={:?} original-id={:?} new-id={:?}",
256 segment.ident, segment.id, hir_id,
260 ident: self.lower_ident(segment.ident),
262 res: self.lower_res(res),
264 args: if generic_args.is_empty() && generic_args.span.is_empty() {
267 Some(generic_args.into_generic_args(self))
272 fn maybe_insert_elided_lifetimes_in_path(
276 segment_ident_span: Span,
277 generic_args: &mut GenericArgsCtor<'hir>,
279 let (start, end) = match self.resolver.get_lifetime_res(segment_id) {
280 Some(LifetimeRes::ElidedAnchor { start, end }) => (start, end),
284 let expected_lifetimes = end.as_usize() - start.as_usize();
285 debug!(expected_lifetimes);
287 // Note: these spans are used for diagnostics when they can't be inferred.
288 // See rustc_resolve::late::lifetimes::LifetimeContext::add_missing_lifetime_specifiers_label
289 let elided_lifetime_span = if generic_args.span.is_empty() {
290 // If there are no brackets, use the identifier span.
291 // HACK: we use find_ancestor_inside to properly suggest elided spans in paths
292 // originating from macros, since the segment's span might be from a macro arg.
293 segment_ident_span.find_ancestor_inside(path_span).unwrap_or(path_span)
294 } else if generic_args.is_empty() {
295 // If there are brackets, but not generic arguments, then use the opening bracket
296 generic_args.span.with_hi(generic_args.span.lo() + BytePos(1))
298 // Else use an empty span right after the opening bracket.
299 generic_args.span.with_lo(generic_args.span.lo() + BytePos(1)).shrink_to_lo()
302 generic_args.args.insert_many(
304 (start.as_u32()..end.as_u32()).map(|i| {
305 let id = NodeId::from_u32(i);
306 let l = self.lower_lifetime(&Lifetime {
308 ident: Ident::new(kw::UnderscoreLifetime, elided_lifetime_span),
310 GenericArg::Lifetime(l)
315 pub(crate) fn lower_angle_bracketed_parameter_data(
317 data: &AngleBracketedArgs,
318 param_mode: ParamMode,
319 itctx: &mut ImplTraitContext,
320 ) -> (GenericArgsCtor<'hir>, bool) {
321 let has_non_lt_args = data.args.iter().any(|arg| match arg {
322 AngleBracketedArg::Arg(ast::GenericArg::Lifetime(_))
323 | AngleBracketedArg::Constraint(_) => false,
324 AngleBracketedArg::Arg(ast::GenericArg::Type(_) | ast::GenericArg::Const(_)) => true,
329 .filter_map(|arg| match arg {
330 AngleBracketedArg::Arg(arg) => Some(self.lower_generic_arg(arg, itctx)),
331 AngleBracketedArg::Constraint(_) => None,
334 let bindings = self.arena.alloc_from_iter(data.args.iter().filter_map(|arg| match arg {
335 AngleBracketedArg::Constraint(c) => Some(self.lower_assoc_ty_constraint(c, itctx)),
336 AngleBracketedArg::Arg(_) => None,
338 let ctor = GenericArgsCtor { args, bindings, parenthesized: false, span: data.span };
339 (ctor, !has_non_lt_args && param_mode == ParamMode::Optional)
342 fn lower_parenthesized_parameter_data(
344 data: &ParenthesizedArgs,
345 ) -> (GenericArgsCtor<'hir>, bool) {
346 // Switch to `PassThrough` mode for anonymous lifetimes; this
347 // means that we permit things like `&Ref<T>`, where `Ref` has
348 // a hidden lifetime parameter. This is needed for backwards
349 // compatibility, even in contexts like an impl header where
350 // we generally don't permit such things (see #51008).
351 let ParenthesizedArgs { span, inputs, inputs_span, output } = data;
352 let inputs = self.arena.alloc_from_iter(inputs.iter().map(|ty| {
353 self.lower_ty_direct(
355 &mut ImplTraitContext::Disallowed(ImplTraitPosition::FnTraitParam),
358 let output_ty = match output {
359 FnRetTy::Ty(ty) => self
360 .lower_ty(&ty, &mut ImplTraitContext::Disallowed(ImplTraitPosition::FnTraitReturn)),
361 FnRetTy::Default(_) => self.arena.alloc(self.ty_tup(*span, &[])),
363 let args = smallvec![GenericArg::Type(self.arena.alloc(self.ty_tup(*inputs_span, inputs)))];
364 let binding = self.output_ty_binding(output_ty.span, output_ty);
368 bindings: arena_vec![self; binding],
370 span: data.inputs_span,
376 /// An associated type binding `Output = $ty`.
377 pub(crate) fn output_ty_binding(
380 ty: &'hir hir::Ty<'hir>,
381 ) -> hir::TypeBinding<'hir> {
382 let ident = Ident::with_dummy_span(hir::FN_OUTPUT_NAME);
383 let kind = hir::TypeBindingKind::Equality { term: ty.into() };
384 let args = arena_vec![self;];
385 let bindings = arena_vec![self;];
386 let gen_args = self.arena.alloc(hir::GenericArgs {
389 parenthesized: false,
393 hir_id: self.next_id(),
395 span: self.lower_span(span),