1 use crate::ImplTraitPosition;
3 use super::ResolverAstLoweringExt;
4 use super::{GenericArgsCtor, LifetimeRes, ParenthesizedGenericArgs};
5 use super::{ImplTraitContext, LoweringContext, ParamMode};
7 use rustc_ast::{self as ast, *};
8 use rustc_errors::{struct_span_err, Applicability};
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;
18 impl<'a, 'hir> LoweringContext<'a, 'hir> {
19 #[instrument(level = "trace", skip(self))]
20 pub(crate) fn lower_qpath(
23 qself: &Option<QSelf>,
25 param_mode: ParamMode,
26 itctx: ImplTraitContext,
27 ) -> hir::QPath<'hir> {
28 let qself_position = qself.as_ref().map(|q| q.position);
29 let qself = qself.as_ref().map(|q| self.lower_ty(&q.ty, itctx));
32 self.resolver.get_partial_res(id).unwrap_or_else(|| PartialRes::new(Res::Err));
34 let path_span_lo = p.span.shrink_to_lo();
35 let proj_start = p.segments.len() - partial_res.unresolved_segments();
36 let path = self.arena.alloc(hir::Path {
37 res: self.lower_res(partial_res.base_res()),
38 segments: self.arena.alloc_from_iter(p.segments[..proj_start].iter().enumerate().map(
40 let param_mode = match (qself_position, param_mode) {
41 (Some(j), ParamMode::Optional) if i < j => {
42 // This segment is part of the trait path in a
43 // qualified path - one of `a`, `b` or `Trait`
44 // in `<X as a::b::Trait>::T::U::method`.
50 let parenthesized_generic_args = match partial_res.base_res() {
51 // `a::b::Trait(Args)`
52 Res::Def(DefKind::Trait, _) if i + 1 == proj_start => {
53 ParenthesizedGenericArgs::Ok
55 // `a::b::Trait(Args)::TraitItem`
56 Res::Def(DefKind::AssocFn, _)
57 | Res::Def(DefKind::AssocConst, _)
58 | Res::Def(DefKind::AssocTy, _)
59 if i + 2 == proj_start =>
61 ParenthesizedGenericArgs::Ok
63 // Avoid duplicated errors.
64 Res::Err => ParenthesizedGenericArgs::Ok,
66 _ => ParenthesizedGenericArgs::Err,
69 self.lower_path_segment(
73 parenthesized_generic_args,
78 span: self.lower_span(
79 p.segments[..proj_start]
81 .map_or(path_span_lo, |segment| path_span_lo.to(segment.span())),
85 // Simple case, either no projections, or only fully-qualified.
86 // E.g., `std::mem::size_of` or `<I as Iterator>::Item`.
87 if partial_res.unresolved_segments() == 0 {
88 return hir::QPath::Resolved(qself, path);
91 // Create the innermost type that we're projecting from.
92 let mut ty = if path.segments.is_empty() {
93 // If the base path is empty that means there exists a
94 // syntactical `Self`, e.g., `&i32` in `<&i32>::clone`.
95 qself.expect("missing QSelf for <T>::...")
97 // Otherwise, the base path is an implicit `Self` type path,
98 // e.g., `Vec` in `Vec::new` or `<I as Iterator>::Item` in
99 // `<I as Iterator>::Item::default`.
100 let new_id = self.next_id();
101 self.arena.alloc(self.ty_path(new_id, path.span, hir::QPath::Resolved(qself, path)))
104 // Anything after the base path are associated "extensions",
105 // out of which all but the last one are associated types,
106 // e.g., for `std::vec::Vec::<T>::IntoIter::Item::clone`:
107 // * base path is `std::vec::Vec<T>`
108 // * "extensions" are `IntoIter`, `Item` and `clone`
110 // 1. `std::vec::Vec<T>` (created above)
111 // 2. `<std::vec::Vec<T>>::IntoIter`
112 // 3. `<<std::vec::Vec<T>>::IntoIter>::Item`
113 // * final path is `<<<std::vec::Vec<T>>::IntoIter>::Item>::clone`
114 for (i, segment) in p.segments.iter().enumerate().skip(proj_start) {
115 let hir_segment = self.arena.alloc(self.lower_path_segment(
119 ParenthesizedGenericArgs::Err,
122 let qpath = hir::QPath::TypeRelative(ty, hir_segment);
124 // It's finished, return the extension of the right node type.
125 if i == p.segments.len() - 1 {
129 // Wrap the associated extension in another type node.
130 let new_id = self.next_id();
131 ty = self.arena.alloc(self.ty_path(new_id, path_span_lo.to(segment.span()), qpath));
134 // We should've returned in the for loop above.
136 self.sess.diagnostic().span_bug(
139 "lower_qpath: no final extension segment in {}..{}",
146 pub(crate) fn lower_path_extra(
150 param_mode: ParamMode,
151 ) -> &'hir hir::Path<'hir> {
152 self.arena.alloc(hir::Path {
154 segments: self.arena.alloc_from_iter(p.segments.iter().map(|segment| {
155 self.lower_path_segment(
159 ParenthesizedGenericArgs::Err,
160 ImplTraitContext::Disallowed(ImplTraitPosition::Path),
163 span: self.lower_span(p.span),
167 pub(crate) fn lower_path(
171 param_mode: ParamMode,
172 ) -> &'hir hir::Path<'hir> {
173 let res = self.expect_full_res(id);
174 let res = self.lower_res(res);
175 self.lower_path_extra(res, p, param_mode)
178 pub(crate) fn lower_path_segment(
181 segment: &PathSegment,
182 param_mode: ParamMode,
183 parenthesized_generic_args: ParenthesizedGenericArgs,
184 itctx: ImplTraitContext,
185 ) -> hir::PathSegment<'hir> {
186 debug!("path_span: {:?}, lower_path_segment(segment: {:?})", path_span, segment,);
187 let (mut generic_args, infer_args) = if let Some(ref generic_args) = segment.args {
188 let msg = "parenthesized type parameters may only be used with a `Fn` trait";
189 match **generic_args {
190 GenericArgs::AngleBracketed(ref data) => {
191 self.lower_angle_bracketed_parameter_data(data, param_mode, itctx)
193 GenericArgs::Parenthesized(ref data) => match parenthesized_generic_args {
194 ParenthesizedGenericArgs::Ok => self.lower_parenthesized_parameter_data(data),
195 ParenthesizedGenericArgs::Err => {
196 let mut err = struct_span_err!(self.sess, data.span, E0214, "{}", msg);
197 err.span_label(data.span, "only `Fn` traits may use parentheses");
198 // Suggest replacing parentheses with angle brackets `Trait(params...)` to `Trait<params...>`
199 if !data.inputs.is_empty() {
200 // Start of the span to the 1st character of 1st argument
201 let open_param = data.inputs_span.shrink_to_lo().to(data
207 // Last character position of last argument to the end of the span
208 let close_param = data
214 .to(data.inputs_span.shrink_to_hi());
215 err.multipart_suggestion(
216 &format!("use angle brackets instead",),
218 (open_param, String::from("<")),
219 (close_param, String::from(">")),
221 Applicability::MaybeIncorrect,
226 self.lower_angle_bracketed_parameter_data(
227 &data.as_angle_bracketed_args(),
240 args: Default::default(),
242 parenthesized: false,
243 span: path_span.shrink_to_hi(),
245 param_mode == ParamMode::Optional,
250 generic_args.args.iter().any(|arg| matches!(arg, GenericArg::Lifetime(_)));
251 if !generic_args.parenthesized && !has_lifetimes {
252 self.maybe_insert_elided_lifetimes_in_path(
260 let res = self.expect_full_res(segment.id);
261 let id = self.lower_node_id(segment.id);
263 "lower_path_segment: ident={:?} original-id={:?} new-id={:?}",
264 segment.ident, segment.id, id,
268 ident: self.lower_ident(segment.ident),
270 res: Some(self.lower_res(res)),
272 args: if generic_args.is_empty() && generic_args.span.is_empty() {
275 Some(generic_args.into_generic_args(self))
280 fn maybe_insert_elided_lifetimes_in_path(
284 segment_ident_span: Span,
285 generic_args: &mut GenericArgsCtor<'hir>,
287 let (start, end) = match self.resolver.get_lifetime_res(segment_id) {
288 Some(LifetimeRes::ElidedAnchor { start, end }) => (start, end),
292 let expected_lifetimes = end.as_usize() - start.as_usize();
293 debug!(expected_lifetimes);
295 // Note: these spans are used for diagnostics when they can't be inferred.
296 // See rustc_resolve::late::lifetimes::LifetimeContext::add_missing_lifetime_specifiers_label
297 let elided_lifetime_span = if generic_args.span.is_empty() {
298 // If there are no brackets, use the identifier span.
299 // HACK: we use find_ancestor_inside to properly suggest elided spans in paths
300 // originating from macros, since the segment's span might be from a macro arg.
301 segment_ident_span.find_ancestor_inside(path_span).unwrap_or(path_span)
302 } else if generic_args.is_empty() {
303 // If there are brackets, but not generic arguments, then use the opening bracket
304 generic_args.span.with_hi(generic_args.span.lo() + BytePos(1))
306 // Else use an empty span right after the opening bracket.
307 generic_args.span.with_lo(generic_args.span.lo() + BytePos(1)).shrink_to_lo()
310 generic_args.args.insert_many(
312 (start.as_u32()..end.as_u32()).map(|i| {
313 let id = NodeId::from_u32(i);
314 let l = self.lower_lifetime(&Lifetime {
316 ident: Ident::new(kw::UnderscoreLifetime, elided_lifetime_span),
318 GenericArg::Lifetime(l)
323 pub(crate) fn lower_angle_bracketed_parameter_data(
325 data: &AngleBracketedArgs,
326 param_mode: ParamMode,
327 itctx: ImplTraitContext,
328 ) -> (GenericArgsCtor<'hir>, bool) {
329 let has_non_lt_args = data.args.iter().any(|arg| match arg {
330 AngleBracketedArg::Arg(ast::GenericArg::Lifetime(_))
331 | AngleBracketedArg::Constraint(_) => false,
332 AngleBracketedArg::Arg(ast::GenericArg::Type(_) | ast::GenericArg::Const(_)) => true,
337 .filter_map(|arg| match arg {
338 AngleBracketedArg::Arg(arg) => Some(self.lower_generic_arg(arg, itctx)),
339 AngleBracketedArg::Constraint(_) => None,
342 let bindings = self.arena.alloc_from_iter(data.args.iter().filter_map(|arg| match arg {
343 AngleBracketedArg::Constraint(c) => Some(self.lower_assoc_ty_constraint(c, itctx)),
344 AngleBracketedArg::Arg(_) => None,
346 let ctor = GenericArgsCtor { args, bindings, parenthesized: false, span: data.span };
347 (ctor, !has_non_lt_args && param_mode == ParamMode::Optional)
350 fn lower_parenthesized_parameter_data(
352 data: &ParenthesizedArgs,
353 ) -> (GenericArgsCtor<'hir>, bool) {
354 // Switch to `PassThrough` mode for anonymous lifetimes; this
355 // means that we permit things like `&Ref<T>`, where `Ref` has
356 // a hidden lifetime parameter. This is needed for backwards
357 // compatibility, even in contexts like an impl header where
358 // we generally don't permit such things (see #51008).
359 let ParenthesizedArgs { span, inputs, inputs_span, output } = data;
360 let inputs = self.arena.alloc_from_iter(inputs.iter().map(|ty| {
361 self.lower_ty_direct(ty, ImplTraitContext::Disallowed(ImplTraitPosition::FnTraitParam))
363 let output_ty = match output {
365 self.lower_ty(&ty, ImplTraitContext::Disallowed(ImplTraitPosition::FnTraitReturn))
367 FnRetTy::Default(_) => self.arena.alloc(self.ty_tup(*span, &[])),
369 let args = smallvec![GenericArg::Type(self.ty_tup(*inputs_span, inputs))];
370 let binding = self.output_ty_binding(output_ty.span, output_ty);
374 bindings: arena_vec![self; binding],
376 span: data.inputs_span,
382 /// An associated type binding `Output = $ty`.
383 pub(crate) fn output_ty_binding(
386 ty: &'hir hir::Ty<'hir>,
387 ) -> hir::TypeBinding<'hir> {
388 let ident = Ident::with_dummy_span(hir::FN_OUTPUT_NAME);
389 let kind = hir::TypeBindingKind::Equality { term: ty.into() };
390 let args = arena_vec![self;];
391 let bindings = arena_vec![self;];
392 let gen_args = self.arena.alloc(hir::GenericArgs {
395 parenthesized: false,
399 hir_id: self.next_id(),
401 span: self.lower_span(span),