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use rustc_data_structures::fx::FxHashSet;
use rustc_errors::{pluralize, struct_span_err, Applicability, MultiSpan};
use rustc_hir as hir;
use rustc_hir::def::DefKind;
use rustc_middle::ty::Representability;
use rustc_middle::ty::{self, DefIdTree, Ty, TyCtxt};
use rustc_query_system::query::QueryInfo;
use rustc_query_system::Value;
use rustc_span::def_id::LocalDefId;
use rustc_span::Span;
use std::fmt::Write;
impl<'tcx> Value<TyCtxt<'tcx>> for Ty<'_> {
fn from_cycle_error(tcx: TyCtxt<'tcx>, _: &[QueryInfo]) -> Self {
// SAFETY: This is never called when `Self` is not `Ty<'tcx>`.
// FIXME: Represent the above fact in the trait system somehow.
unsafe { std::mem::transmute::<Ty<'tcx>, Ty<'_>>(tcx.ty_error()) }
}
}
impl<'tcx> Value<TyCtxt<'tcx>> for ty::SymbolName<'_> {
fn from_cycle_error(tcx: TyCtxt<'tcx>, _: &[QueryInfo]) -> Self {
// SAFETY: This is never called when `Self` is not `SymbolName<'tcx>`.
// FIXME: Represent the above fact in the trait system somehow.
unsafe {
std::mem::transmute::<ty::SymbolName<'tcx>, ty::SymbolName<'_>>(ty::SymbolName::new(
tcx, "<error>",
))
}
}
}
impl<'tcx> Value<TyCtxt<'tcx>> for ty::Binder<'_, ty::FnSig<'_>> {
fn from_cycle_error(tcx: TyCtxt<'tcx>, stack: &[QueryInfo]) -> Self {
let err = tcx.ty_error();
let arity = if let Some(frame) = stack.get(0)
&& frame.query.name == "fn_sig"
&& let Some(def_id) = frame.query.def_id
&& let Some(node) = tcx.hir().get_if_local(def_id)
&& let Some(sig) = node.fn_sig()
{
sig.decl.inputs.len() + sig.decl.implicit_self.has_implicit_self() as usize
} else {
tcx.sess.abort_if_errors();
unreachable!()
};
let fn_sig = ty::Binder::dummy(tcx.mk_fn_sig(
std::iter::repeat(err).take(arity),
err,
false,
rustc_hir::Unsafety::Normal,
rustc_target::spec::abi::Abi::Rust,
));
// SAFETY: This is never called when `Self` is not `ty::Binder<'tcx, ty::FnSig<'tcx>>`.
// FIXME: Represent the above fact in the trait system somehow.
unsafe { std::mem::transmute::<ty::PolyFnSig<'tcx>, ty::Binder<'_, ty::FnSig<'_>>>(fn_sig) }
}
}
impl<'tcx> Value<TyCtxt<'tcx>> for Representability {
fn from_cycle_error(tcx: TyCtxt<'tcx>, cycle: &[QueryInfo]) -> Self {
let mut item_and_field_ids = Vec::new();
let mut representable_ids = FxHashSet::default();
for info in cycle {
if info.query.name == "representability"
&& let Some(field_id) = info.query.def_id
&& let Some(field_id) = field_id.as_local()
&& let Some(DefKind::Field) = info.query.def_kind
{
let parent_id = tcx.parent(field_id.to_def_id());
let item_id = match tcx.def_kind(parent_id) {
DefKind::Variant => tcx.parent(parent_id),
_ => parent_id,
};
item_and_field_ids.push((item_id.expect_local(), field_id));
}
}
for info in cycle {
if info.query.name == "representability_adt_ty"
&& let Some(def_id) = info.query.ty_adt_id
&& let Some(def_id) = def_id.as_local()
&& !item_and_field_ids.iter().any(|&(id, _)| id == def_id)
{
representable_ids.insert(def_id);
}
}
recursive_type_error(tcx, item_and_field_ids, &representable_ids);
Representability::Infinite
}
}
// item_and_field_ids should form a cycle where each field contains the
// type in the next element in the list
pub fn recursive_type_error(
tcx: TyCtxt<'_>,
mut item_and_field_ids: Vec<(LocalDefId, LocalDefId)>,
representable_ids: &FxHashSet<LocalDefId>,
) {
const ITEM_LIMIT: usize = 5;
// Rotate the cycle so that the item with the lowest span is first
let start_index = item_and_field_ids
.iter()
.enumerate()
.min_by_key(|&(_, &(id, _))| tcx.def_span(id))
.unwrap()
.0;
item_and_field_ids.rotate_left(start_index);
let cycle_len = item_and_field_ids.len();
let show_cycle_len = cycle_len.min(ITEM_LIMIT);
let mut err_span = MultiSpan::from_spans(
item_and_field_ids[..show_cycle_len]
.iter()
.map(|(id, _)| tcx.def_span(id.to_def_id()))
.collect(),
);
let mut suggestion = Vec::with_capacity(show_cycle_len * 2);
for i in 0..show_cycle_len {
let (_, field_id) = item_and_field_ids[i];
let (next_item_id, _) = item_and_field_ids[(i + 1) % cycle_len];
// Find the span(s) that contain the next item in the cycle
let hir_id = tcx.hir().local_def_id_to_hir_id(field_id);
let hir::Node::Field(field) = tcx.hir().get(hir_id) else { bug!("expected field") };
let mut found = Vec::new();
find_item_ty_spans(tcx, field.ty, next_item_id, &mut found, representable_ids);
// Couldn't find the type. Maybe it's behind a type alias?
// In any case, we'll just suggest boxing the whole field.
if found.is_empty() {
found.push(field.ty.span);
}
for span in found {
err_span.push_span_label(span, "recursive without indirection");
// FIXME(compiler-errors): This suggestion might be erroneous if Box is shadowed
suggestion.push((span.shrink_to_lo(), "Box<".to_string()));
suggestion.push((span.shrink_to_hi(), ">".to_string()));
}
}
let items_list = {
let mut s = String::new();
for (i, (item_id, _)) in item_and_field_ids.iter().enumerate() {
let path = tcx.def_path_str(item_id.to_def_id());
write!(&mut s, "`{path}`").unwrap();
if i == (ITEM_LIMIT - 1) && cycle_len > ITEM_LIMIT {
write!(&mut s, " and {} more", cycle_len - 5).unwrap();
break;
}
if cycle_len > 1 && i < cycle_len - 2 {
s.push_str(", ");
} else if cycle_len > 1 && i == cycle_len - 2 {
s.push_str(" and ")
}
}
s
};
let mut err = struct_span_err!(
tcx.sess,
err_span,
E0072,
"recursive type{} {} {} infinite size",
pluralize!(cycle_len),
items_list,
pluralize!("has", cycle_len),
);
err.multipart_suggestion(
"insert some indirection (e.g., a `Box`, `Rc`, or `&`) to break the cycle",
suggestion,
Applicability::HasPlaceholders,
);
err.emit();
}
fn find_item_ty_spans(
tcx: TyCtxt<'_>,
ty: &hir::Ty<'_>,
needle: LocalDefId,
spans: &mut Vec<Span>,
seen_representable: &FxHashSet<LocalDefId>,
) {
match ty.kind {
hir::TyKind::Path(hir::QPath::Resolved(_, path)) => {
if let Some(def_id) = path.res.opt_def_id() {
let check_params = def_id.as_local().map_or(true, |def_id| {
if def_id == needle {
spans.push(ty.span);
}
seen_representable.contains(&def_id)
});
if check_params && let Some(args) = path.segments.last().unwrap().args {
let params_in_repr = tcx.params_in_repr(def_id);
// the domain size check is needed because the HIR may not be well-formed at this point
for (i, arg) in args.args.iter().enumerate().take(params_in_repr.domain_size()) {
if let hir::GenericArg::Type(ty) = arg && params_in_repr.contains(i as u32) {
find_item_ty_spans(tcx, ty, needle, spans, seen_representable);
}
}
}
}
}
hir::TyKind::Array(ty, _) => find_item_ty_spans(tcx, ty, needle, spans, seen_representable),
hir::TyKind::Tup(tys) => {
tys.iter().for_each(|ty| find_item_ty_spans(tcx, ty, needle, spans, seen_representable))
}
_ => {}
}
}
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