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: &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));
32 let base_res = partial_res.base_res();
33 let unresolved_segments = partial_res.unresolved_segments();
35 let path_span_lo = p.span.shrink_to_lo();
36 let proj_start = p.segments.len() - unresolved_segments;
37 let path = self.arena.alloc(hir::Path {
38 res: self.lower_res(base_res),
39 segments: self.arena.alloc_from_iter(p.segments[..proj_start].iter().enumerate().map(
41 let param_mode = match (qself_position, param_mode) {
42 (Some(j), ParamMode::Optional) if i < j => {
43 // This segment is part of the trait path in a
44 // qualified path - one of `a`, `b` or `Trait`
45 // in `<X as a::b::Trait>::T::U::method`.
51 let parenthesized_generic_args = match base_res {
52 // `a::b::Trait(Args)`
53 Res::Def(DefKind::Trait, _) if i + 1 == proj_start => {
54 ParenthesizedGenericArgs::Ok
56 // `a::b::Trait(Args)::TraitItem`
57 Res::Def(DefKind::AssocFn, _)
58 | Res::Def(DefKind::AssocConst, _)
59 | Res::Def(DefKind::AssocTy, _)
60 if i + 2 == proj_start =>
62 ParenthesizedGenericArgs::Ok
64 // Avoid duplicated errors.
65 Res::Err => ParenthesizedGenericArgs::Ok,
67 _ => ParenthesizedGenericArgs::Err,
70 self.lower_path_segment(
74 parenthesized_generic_args,
79 span: self.lower_span(
80 p.segments[..proj_start]
82 .map_or(path_span_lo, |segment| path_span_lo.to(segment.span())),
86 // Simple case, either no projections, or only fully-qualified.
87 // E.g., `std::mem::size_of` or `<I as Iterator>::Item`.
88 if unresolved_segments == 0 {
89 return hir::QPath::Resolved(qself, path);
92 // Create the innermost type that we're projecting from.
93 let mut ty = if path.segments.is_empty() {
94 // If the base path is empty that means there exists a
95 // syntactical `Self`, e.g., `&i32` in `<&i32>::clone`.
96 qself.expect("missing QSelf for <T>::...")
98 // Otherwise, the base path is an implicit `Self` type path,
99 // e.g., `Vec` in `Vec::new` or `<I as Iterator>::Item` in
100 // `<I as Iterator>::Item::default`.
101 let new_id = self.next_id();
102 self.arena.alloc(self.ty_path(new_id, path.span, hir::QPath::Resolved(qself, path)))
105 // Anything after the base path are associated "extensions",
106 // out of which all but the last one are associated types,
107 // e.g., for `std::vec::Vec::<T>::IntoIter::Item::clone`:
108 // * base path is `std::vec::Vec<T>`
109 // * "extensions" are `IntoIter`, `Item` and `clone`
111 // 1. `std::vec::Vec<T>` (created above)
112 // 2. `<std::vec::Vec<T>>::IntoIter`
113 // 3. `<<std::vec::Vec<T>>::IntoIter>::Item`
114 // * final path is `<<<std::vec::Vec<T>>::IntoIter>::Item>::clone`
115 for (i, segment) in p.segments.iter().enumerate().skip(proj_start) {
116 let hir_segment = self.arena.alloc(self.lower_path_segment(
120 ParenthesizedGenericArgs::Err,
123 let qpath = hir::QPath::TypeRelative(ty, hir_segment);
125 // It's finished, return the extension of the right node type.
126 if i == p.segments.len() - 1 {
130 // Wrap the associated extension in another type node.
131 let new_id = self.next_id();
132 ty = self.arena.alloc(self.ty_path(new_id, path_span_lo.to(segment.span()), qpath));
135 // We should've returned in the for loop above.
137 self.diagnostic().span_bug(
140 "lower_qpath: no final extension segment in {}..{}",
147 pub(crate) fn lower_path_extra(
151 param_mode: ParamMode,
152 ) -> &'hir hir::Path<'hir> {
153 self.arena.alloc(hir::Path {
155 segments: self.arena.alloc_from_iter(p.segments.iter().map(|segment| {
156 self.lower_path_segment(
160 ParenthesizedGenericArgs::Err,
161 &ImplTraitContext::Disallowed(ImplTraitPosition::Path),
164 span: self.lower_span(p.span),
168 pub(crate) fn lower_path(
172 param_mode: ParamMode,
173 ) -> &'hir hir::Path<'hir> {
174 let res = self.expect_full_res(id);
175 let res = self.lower_res(res);
176 self.lower_path_extra(res, p, param_mode)
179 pub(crate) fn lower_path_segment(
182 segment: &PathSegment,
183 param_mode: ParamMode,
184 parenthesized_generic_args: ParenthesizedGenericArgs,
185 itctx: &ImplTraitContext,
186 ) -> hir::PathSegment<'hir> {
187 debug!("path_span: {:?}, lower_path_segment(segment: {:?})", path_span, segment,);
188 let (mut generic_args, infer_args) = if let Some(ref generic_args) = segment.args {
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 // Suggest replacing parentheses with angle brackets `Trait(params...)` to `Trait<params...>`
197 let sub = if !data.inputs.is_empty() {
198 // Start of the span to the 1st character of 1st argument
199 let open_param = data.inputs_span.shrink_to_lo().to(data
205 // Last character position of last argument to the end of the span
206 let close_param = data
212 .to(data.inputs_span.shrink_to_hi());
214 Some(UseAngleBrackets { open_param, close_param })
218 self.tcx.sess.emit_err(GenericTypeWithParentheses { span: data.span, sub });
220 self.lower_angle_bracketed_parameter_data(
221 &data.as_angle_bracketed_args(),
234 args: Default::default(),
236 parenthesized: false,
237 span: path_span.shrink_to_hi(),
239 param_mode == ParamMode::Optional,
244 generic_args.args.iter().any(|arg| matches!(arg, GenericArg::Lifetime(_)));
245 if !generic_args.parenthesized && !has_lifetimes {
246 self.maybe_insert_elided_lifetimes_in_path(
254 let res = self.expect_full_res(segment.id);
255 let hir_id = self.lower_node_id(segment.id);
257 "lower_path_segment: ident={:?} original-id={:?} new-id={:?}",
258 segment.ident, segment.id, hir_id,
262 ident: self.lower_ident(segment.ident),
264 res: self.lower_res(res),
266 args: if generic_args.is_empty() && generic_args.span.is_empty() {
269 Some(generic_args.into_generic_args(self))
274 fn maybe_insert_elided_lifetimes_in_path(
278 segment_ident_span: Span,
279 generic_args: &mut GenericArgsCtor<'hir>,
281 let (start, end) = match self.resolver.get_lifetime_res(segment_id) {
282 Some(LifetimeRes::ElidedAnchor { start, end }) => (start, end),
286 let expected_lifetimes = end.as_usize() - start.as_usize();
287 debug!(expected_lifetimes);
289 // Note: these spans are used for diagnostics when they can't be inferred.
290 // See rustc_resolve::late::lifetimes::LifetimeContext::add_missing_lifetime_specifiers_label
291 let elided_lifetime_span = if generic_args.span.is_empty() {
292 // If there are no brackets, use the identifier span.
293 // HACK: we use find_ancestor_inside to properly suggest elided spans in paths
294 // originating from macros, since the segment's span might be from a macro arg.
295 segment_ident_span.find_ancestor_inside(path_span).unwrap_or(path_span)
296 } else if generic_args.is_empty() {
297 // If there are brackets, but not generic arguments, then use the opening bracket
298 generic_args.span.with_hi(generic_args.span.lo() + BytePos(1))
300 // Else use an empty span right after the opening bracket.
301 generic_args.span.with_lo(generic_args.span.lo() + BytePos(1)).shrink_to_lo()
304 generic_args.args.insert_many(
306 (start.as_u32()..end.as_u32()).map(|i| {
307 let id = NodeId::from_u32(i);
308 let l = self.lower_lifetime(&Lifetime {
310 ident: Ident::new(kw::UnderscoreLifetime, elided_lifetime_span),
312 GenericArg::Lifetime(l)
317 pub(crate) fn lower_angle_bracketed_parameter_data(
319 data: &AngleBracketedArgs,
320 param_mode: ParamMode,
321 itctx: &ImplTraitContext,
322 ) -> (GenericArgsCtor<'hir>, bool) {
323 let has_non_lt_args = data.args.iter().any(|arg| match arg {
324 AngleBracketedArg::Arg(ast::GenericArg::Lifetime(_))
325 | AngleBracketedArg::Constraint(_) => false,
326 AngleBracketedArg::Arg(ast::GenericArg::Type(_) | ast::GenericArg::Const(_)) => true,
331 .filter_map(|arg| match arg {
332 AngleBracketedArg::Arg(arg) => Some(self.lower_generic_arg(arg, itctx)),
333 AngleBracketedArg::Constraint(_) => None,
336 let bindings = self.arena.alloc_from_iter(data.args.iter().filter_map(|arg| match arg {
337 AngleBracketedArg::Constraint(c) => Some(self.lower_assoc_ty_constraint(c, itctx)),
338 AngleBracketedArg::Arg(_) => None,
340 let ctor = GenericArgsCtor { args, bindings, parenthesized: false, span: data.span };
341 (ctor, !has_non_lt_args && param_mode == ParamMode::Optional)
344 fn lower_parenthesized_parameter_data(
346 data: &ParenthesizedArgs,
347 ) -> (GenericArgsCtor<'hir>, bool) {
348 // Switch to `PassThrough` mode for anonymous lifetimes; this
349 // means that we permit things like `&Ref<T>`, where `Ref` has
350 // a hidden lifetime parameter. This is needed for backwards
351 // compatibility, even in contexts like an impl header where
352 // we generally don't permit such things (see #51008).
353 let ParenthesizedArgs { span, inputs, inputs_span, output } = data;
354 let inputs = self.arena.alloc_from_iter(inputs.iter().map(|ty| {
355 self.lower_ty_direct(ty, &ImplTraitContext::Disallowed(ImplTraitPosition::FnTraitParam))
357 let output_ty = match output {
359 self.lower_ty(&ty, &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),