1 use crate::dep_graph::DepKind;
2 use rustc_data_structures::fx::FxHashSet;
3 use rustc_errors::{pluralize, struct_span_err, Applicability, MultiSpan};
5 use rustc_hir::def::DefKind;
6 use rustc_middle::ty::Representability;
7 use rustc_middle::ty::{self, DefIdTree, Ty, TyCtxt};
8 use rustc_query_system::query::QueryInfo;
9 use rustc_query_system::Value;
10 use rustc_span::def_id::LocalDefId;
15 impl<'tcx> Value<TyCtxt<'tcx>, DepKind> for Ty<'_> {
16 fn from_cycle_error(tcx: TyCtxt<'tcx>, _: &[QueryInfo<DepKind>]) -> Self {
17 // SAFETY: This is never called when `Self` is not `Ty<'tcx>`.
18 // FIXME: Represent the above fact in the trait system somehow.
19 unsafe { std::mem::transmute::<Ty<'tcx>, Ty<'_>>(tcx.ty_error()) }
23 impl<'tcx> Value<TyCtxt<'tcx>, DepKind> for ty::SymbolName<'_> {
24 fn from_cycle_error(tcx: TyCtxt<'tcx>, _: &[QueryInfo<DepKind>]) -> Self {
25 // SAFETY: This is never called when `Self` is not `SymbolName<'tcx>`.
26 // FIXME: Represent the above fact in the trait system somehow.
28 std::mem::transmute::<ty::SymbolName<'tcx>, ty::SymbolName<'_>>(ty::SymbolName::new(
35 impl<'tcx> Value<TyCtxt<'tcx>, DepKind> for ty::Binder<'_, ty::FnSig<'_>> {
36 fn from_cycle_error(tcx: TyCtxt<'tcx>, stack: &[QueryInfo<DepKind>]) -> Self {
37 let err = tcx.ty_error();
39 let arity = if let Some(frame) = stack.get(0)
40 && frame.query.dep_kind == DepKind::fn_sig
41 && let Some(def_id) = frame.query.def_id
42 && let Some(node) = tcx.hir().get_if_local(def_id)
43 && let Some(sig) = node.fn_sig()
45 sig.decl.inputs.len() + sig.decl.implicit_self.has_implicit_self() as usize
47 tcx.sess.abort_if_errors();
51 let fn_sig = ty::Binder::dummy(tcx.mk_fn_sig(
52 std::iter::repeat(err).take(arity),
55 rustc_hir::Unsafety::Normal,
56 rustc_target::spec::abi::Abi::Rust,
59 // SAFETY: This is never called when `Self` is not `ty::Binder<'tcx, ty::FnSig<'tcx>>`.
60 // FIXME: Represent the above fact in the trait system somehow.
61 unsafe { std::mem::transmute::<ty::PolyFnSig<'tcx>, ty::Binder<'_, ty::FnSig<'_>>>(fn_sig) }
65 impl<'tcx> Value<TyCtxt<'tcx>, DepKind> for Representability {
66 fn from_cycle_error(tcx: TyCtxt<'tcx>, cycle: &[QueryInfo<DepKind>]) -> Self {
67 let mut item_and_field_ids = Vec::new();
68 let mut representable_ids = FxHashSet::default();
70 if info.query.dep_kind == DepKind::representability
71 && let Some(field_id) = info.query.def_id
72 && let Some(field_id) = field_id.as_local()
73 && let Some(DefKind::Field) = info.query.def_kind
75 let parent_id = tcx.parent(field_id.to_def_id());
76 let item_id = match tcx.def_kind(parent_id) {
77 DefKind::Variant => tcx.parent(parent_id),
80 item_and_field_ids.push((item_id.expect_local(), field_id));
84 if info.query.dep_kind == DepKind::representability_adt_ty
85 && let Some(def_id) = info.query.ty_adt_id
86 && let Some(def_id) = def_id.as_local()
87 && !item_and_field_ids.iter().any(|&(id, _)| id == def_id)
89 representable_ids.insert(def_id);
92 recursive_type_error(tcx, item_and_field_ids, &representable_ids);
93 Representability::Infinite
97 impl<'tcx> Value<TyCtxt<'tcx>, DepKind> for ty::EarlyBinder<Ty<'_>> {
98 fn from_cycle_error(tcx: TyCtxt<'tcx>, cycle: &[QueryInfo<DepKind>]) -> Self {
99 ty::EarlyBinder(Ty::from_cycle_error(tcx, cycle))
103 impl<'tcx> Value<TyCtxt<'tcx>, DepKind> for ty::EarlyBinder<ty::Binder<'_, ty::FnSig<'_>>> {
104 fn from_cycle_error(tcx: TyCtxt<'tcx>, cycle: &[QueryInfo<DepKind>]) -> Self {
105 ty::EarlyBinder(ty::Binder::from_cycle_error(tcx, cycle))
109 // item_and_field_ids should form a cycle where each field contains the
110 // type in the next element in the list
111 pub fn recursive_type_error(
113 mut item_and_field_ids: Vec<(LocalDefId, LocalDefId)>,
114 representable_ids: &FxHashSet<LocalDefId>,
116 const ITEM_LIMIT: usize = 5;
118 // Rotate the cycle so that the item with the lowest span is first
119 let start_index = item_and_field_ids
122 .min_by_key(|&(_, &(id, _))| tcx.def_span(id))
125 item_and_field_ids.rotate_left(start_index);
127 let cycle_len = item_and_field_ids.len();
128 let show_cycle_len = cycle_len.min(ITEM_LIMIT);
130 let mut err_span = MultiSpan::from_spans(
131 item_and_field_ids[..show_cycle_len]
133 .map(|(id, _)| tcx.def_span(id.to_def_id()))
136 let mut suggestion = Vec::with_capacity(show_cycle_len * 2);
137 for i in 0..show_cycle_len {
138 let (_, field_id) = item_and_field_ids[i];
139 let (next_item_id, _) = item_and_field_ids[(i + 1) % cycle_len];
140 // Find the span(s) that contain the next item in the cycle
141 let hir_id = tcx.hir().local_def_id_to_hir_id(field_id);
142 let hir::Node::Field(field) = tcx.hir().get(hir_id) else { bug!("expected field") };
143 let mut found = Vec::new();
144 find_item_ty_spans(tcx, field.ty, next_item_id, &mut found, representable_ids);
146 // Couldn't find the type. Maybe it's behind a type alias?
147 // In any case, we'll just suggest boxing the whole field.
148 if found.is_empty() {
149 found.push(field.ty.span);
153 err_span.push_span_label(span, "recursive without indirection");
154 // FIXME(compiler-errors): This suggestion might be erroneous if Box is shadowed
155 suggestion.push((span.shrink_to_lo(), "Box<".to_string()));
156 suggestion.push((span.shrink_to_hi(), ">".to_string()));
160 let mut s = String::new();
161 for (i, (item_id, _)) in item_and_field_ids.iter().enumerate() {
162 let path = tcx.def_path_str(item_id.to_def_id());
163 write!(&mut s, "`{path}`").unwrap();
164 if i == (ITEM_LIMIT - 1) && cycle_len > ITEM_LIMIT {
165 write!(&mut s, " and {} more", cycle_len - 5).unwrap();
168 if cycle_len > 1 && i < cycle_len - 2 {
170 } else if cycle_len > 1 && i == cycle_len - 2 {
176 let mut err = struct_span_err!(
180 "recursive type{} {} {} infinite size",
181 pluralize!(cycle_len),
183 pluralize!("has", cycle_len),
185 err.multipart_suggestion(
186 "insert some indirection (e.g., a `Box`, `Rc`, or `&`) to break the cycle",
188 Applicability::HasPlaceholders,
193 fn find_item_ty_spans(
197 spans: &mut Vec<Span>,
198 seen_representable: &FxHashSet<LocalDefId>,
201 hir::TyKind::Path(hir::QPath::Resolved(_, path)) => {
202 if let Some(def_id) = path.res.opt_def_id() {
203 let check_params = def_id.as_local().map_or(true, |def_id| {
204 if def_id == needle {
207 seen_representable.contains(&def_id)
209 if check_params && let Some(args) = path.segments.last().unwrap().args {
210 let params_in_repr = tcx.params_in_repr(def_id);
211 // the domain size check is needed because the HIR may not be well-formed at this point
212 for (i, arg) in args.args.iter().enumerate().take(params_in_repr.domain_size()) {
213 if let hir::GenericArg::Type(ty) = arg && params_in_repr.contains(i as u32) {
214 find_item_ty_spans(tcx, ty, needle, spans, seen_representable);
220 hir::TyKind::Array(ty, _) => find_item_ty_spans(tcx, ty, needle, spans, seen_representable),
221 hir::TyKind::Tup(tys) => {
222 tys.iter().for_each(|ty| find_item_ty_spans(tcx, ty, needle, spans, seen_representable))