rustc_hir_analysis/hir_ty_lowering/errors.rs
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use rustc_data_structures::fx::{FxIndexMap, FxIndexSet};
use rustc_data_structures::sorted_map::SortedMap;
use rustc_data_structures::unord::UnordMap;
use rustc_errors::codes::*;
use rustc_errors::{
Applicability, Diag, ErrorGuaranteed, MultiSpan, pluralize, struct_span_code_err,
};
use rustc_hir as hir;
use rustc_hir::def::{DefKind, Res};
use rustc_hir::def_id::DefId;
use rustc_middle::bug;
use rustc_middle::ty::print::{PrintPolyTraitRefExt as _, PrintTraitRefExt as _};
use rustc_middle::ty::{
self, AdtDef, Binder, GenericParamDefKind, TraitRef, Ty, TyCtxt, TypeVisitableExt,
suggest_constraining_type_param,
};
use rustc_session::parse::feature_err;
use rustc_span::edit_distance::find_best_match_for_name;
use rustc_span::{BytePos, DUMMY_SP, Ident, Span, Symbol, kw, sym};
use rustc_trait_selection::error_reporting::traits::report_dyn_incompatibility;
use rustc_trait_selection::traits::{
FulfillmentError, TraitAliasExpansionInfo, dyn_compatibility_violations_for_assoc_item,
};
use crate::errors::{
self, AssocItemConstraintsNotAllowedHere, ManualImplementation, MissingTypeParams,
ParenthesizedFnTraitExpansion, TraitObjectDeclaredWithNoTraits,
};
use crate::fluent_generated as fluent;
use crate::hir_ty_lowering::{AssocItemQSelf, HirTyLowerer};
impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
/// On missing type parameters, emit an E0393 error and provide a structured suggestion using
/// the type parameter's name as a placeholder.
pub(crate) fn complain_about_missing_type_params(
&self,
missing_type_params: Vec<Symbol>,
def_id: DefId,
span: Span,
empty_generic_args: bool,
) {
if missing_type_params.is_empty() {
return;
}
self.dcx().emit_err(MissingTypeParams {
span,
def_span: self.tcx().def_span(def_id),
span_snippet: self.tcx().sess.source_map().span_to_snippet(span).ok(),
missing_type_params,
empty_generic_args,
});
}
/// When the code is using the `Fn` traits directly, instead of the `Fn(A) -> B` syntax, emit
/// an error and attempt to build a reasonable structured suggestion.
pub(crate) fn complain_about_internal_fn_trait(
&self,
span: Span,
trait_def_id: DefId,
trait_segment: &'_ hir::PathSegment<'_>,
is_impl: bool,
) {
if self.tcx().features().unboxed_closures() {
return;
}
let trait_def = self.tcx().trait_def(trait_def_id);
if !trait_def.paren_sugar {
if trait_segment.args().parenthesized == hir::GenericArgsParentheses::ParenSugar {
// For now, require that parenthetical notation be used only with `Fn()` etc.
feature_err(
&self.tcx().sess,
sym::unboxed_closures,
span,
"parenthetical notation is only stable when used with `Fn`-family traits",
)
.emit();
}
return;
}
let sess = self.tcx().sess;
if trait_segment.args().parenthesized != hir::GenericArgsParentheses::ParenSugar {
// For now, require that parenthetical notation be used only with `Fn()` etc.
let mut err = feature_err(
sess,
sym::unboxed_closures,
span,
"the precise format of `Fn`-family traits' type parameters is subject to change",
);
// Do not suggest the other syntax if we are in trait impl:
// the desugaring would contain an associated type constraint.
if !is_impl {
err.span_suggestion(
span,
"use parenthetical notation instead",
fn_trait_to_string(self.tcx(), trait_segment, true),
Applicability::MaybeIncorrect,
);
}
err.emit();
}
if is_impl {
let trait_name = self.tcx().def_path_str(trait_def_id);
self.dcx().emit_err(ManualImplementation { span, trait_name });
}
}
pub(super) fn complain_about_assoc_item_not_found<I>(
&self,
all_candidates: impl Fn() -> I,
qself: AssocItemQSelf,
assoc_kind: ty::AssocKind,
assoc_name: Ident,
span: Span,
constraint: Option<&hir::AssocItemConstraint<'tcx>>,
) -> ErrorGuaranteed
where
I: Iterator<Item = ty::PolyTraitRef<'tcx>>,
{
let tcx = self.tcx();
// First and foremost, provide a more user-friendly & “intuitive” error on kind mismatches.
if let Some(assoc_item) = all_candidates().find_map(|r| {
tcx.associated_items(r.def_id())
.filter_by_name_unhygienic(assoc_name.name)
.find(|item| tcx.hygienic_eq(assoc_name, item.ident(tcx), r.def_id()))
}) {
return self.complain_about_assoc_kind_mismatch(
assoc_item, assoc_kind, assoc_name, span, constraint,
);
}
let assoc_kind_str = assoc_kind_str(assoc_kind);
let qself_str = qself.to_string(tcx);
// The fallback span is needed because `assoc_name` might be an `Fn()`'s `Output` without a
// valid span, so we point at the whole path segment instead.
let is_dummy = assoc_name.span == DUMMY_SP;
let mut err = errors::AssocItemNotFound {
span: if is_dummy { span } else { assoc_name.span },
assoc_name,
assoc_kind: assoc_kind_str,
qself: &qself_str,
label: None,
sugg: None,
};
if is_dummy {
err.label = Some(errors::AssocItemNotFoundLabel::NotFound { span });
return self.dcx().emit_err(err);
}
let all_candidate_names: Vec<_> = all_candidates()
.flat_map(|r| tcx.associated_items(r.def_id()).in_definition_order())
.filter_map(|item| {
(!item.is_impl_trait_in_trait() && item.kind == assoc_kind).then_some(item.name)
})
.collect();
if let Some(suggested_name) =
find_best_match_for_name(&all_candidate_names, assoc_name.name, None)
{
err.sugg = Some(errors::AssocItemNotFoundSugg::Similar {
span: assoc_name.span,
assoc_kind: assoc_kind_str,
suggested_name,
});
return self.dcx().emit_err(err);
}
// If we didn't find a good item in the supertraits (or couldn't get
// the supertraits), like in ItemCtxt, then look more generally from
// all visible traits. If there's one clear winner, just suggest that.
let visible_traits: Vec<_> = tcx
.all_traits()
.filter(|trait_def_id| {
let viz = tcx.visibility(*trait_def_id);
let def_id = self.item_def_id();
viz.is_accessible_from(def_id, tcx)
})
.collect();
let wider_candidate_names: Vec<_> = visible_traits
.iter()
.flat_map(|trait_def_id| tcx.associated_items(*trait_def_id).in_definition_order())
.filter_map(|item| {
(!item.is_impl_trait_in_trait() && item.kind == assoc_kind).then_some(item.name)
})
.collect();
if let Some(suggested_name) =
find_best_match_for_name(&wider_candidate_names, assoc_name.name, None)
{
if let [best_trait] = visible_traits
.iter()
.copied()
.filter(|trait_def_id| {
tcx.associated_items(trait_def_id)
.filter_by_name_unhygienic(suggested_name)
.any(|item| item.kind == assoc_kind)
})
.collect::<Vec<_>>()[..]
{
let trait_name = tcx.def_path_str(best_trait);
err.label = Some(errors::AssocItemNotFoundLabel::FoundInOtherTrait {
span: assoc_name.span,
assoc_kind: assoc_kind_str,
trait_name: &trait_name,
suggested_name,
identically_named: suggested_name == assoc_name.name,
});
if let AssocItemQSelf::TyParam(ty_param_def_id, ty_param_span) = qself
// Not using `self.item_def_id()` here as that would yield the opaque type itself if we're
// inside an opaque type while we're interested in the overarching type alias (TAIT).
// FIXME: However, for trait aliases, this incorrectly returns the enclosing module...
&& let item_def_id =
tcx.hir().get_parent_item(tcx.local_def_id_to_hir_id(ty_param_def_id))
// FIXME: ...which obviously won't have any generics.
&& let Some(generics) = tcx.hir().get_generics(item_def_id.def_id)
{
// FIXME: Suggest adding supertrait bounds if we have a `Self` type param.
// FIXME(trait_alias): Suggest adding `Self: Trait` to
// `trait Alias = where Self::Proj:;` with `trait Trait { type Proj; }`.
if generics
.bounds_for_param(ty_param_def_id)
.flat_map(|pred| pred.bounds.iter())
.any(|b| match b {
hir::GenericBound::Trait(t, ..) => {
t.trait_ref.trait_def_id() == Some(best_trait)
}
_ => false,
})
{
// The type param already has a bound for `trait_name`, we just need to
// change the associated item.
err.sugg = Some(errors::AssocItemNotFoundSugg::SimilarInOtherTrait {
span: assoc_name.span,
assoc_kind: assoc_kind_str,
suggested_name,
});
return self.dcx().emit_err(err);
}
let trait_args = &ty::GenericArgs::identity_for_item(tcx, best_trait)[1..];
let mut trait_ref = trait_name.clone();
let applicability = if let [arg, args @ ..] = trait_args {
use std::fmt::Write;
write!(trait_ref, "</* {arg}").unwrap();
args.iter().try_for_each(|arg| write!(trait_ref, ", {arg}")).unwrap();
trait_ref += " */>";
Applicability::HasPlaceholders
} else {
Applicability::MaybeIncorrect
};
let identically_named = suggested_name == assoc_name.name;
if let DefKind::TyAlias = tcx.def_kind(item_def_id)
&& !tcx.type_alias_is_lazy(item_def_id)
{
err.sugg = Some(errors::AssocItemNotFoundSugg::SimilarInOtherTraitQPath {
lo: ty_param_span.shrink_to_lo(),
mi: ty_param_span.shrink_to_hi(),
hi: (!identically_named).then_some(assoc_name.span),
trait_ref,
identically_named,
suggested_name,
applicability,
});
} else {
let mut err = self.dcx().create_err(err);
if suggest_constraining_type_param(
tcx,
generics,
&mut err,
&qself_str,
&trait_ref,
Some(best_trait),
None,
) && !identically_named
{
// We suggested constraining a type parameter, but the associated item on it
// was also not an exact match, so we also suggest changing it.
err.span_suggestion_verbose(
assoc_name.span,
fluent::hir_analysis_assoc_item_not_found_similar_in_other_trait_with_bound_sugg,
suggested_name,
Applicability::MaybeIncorrect,
);
}
return err.emit();
}
}
return self.dcx().emit_err(err);
}
}
// If we still couldn't find any associated item, and only one associated item exists,
// suggest using it.
if let [candidate_name] = all_candidate_names.as_slice() {
err.sugg = Some(errors::AssocItemNotFoundSugg::Other {
span: assoc_name.span,
qself: &qself_str,
assoc_kind: assoc_kind_str,
suggested_name: *candidate_name,
});
} else {
err.label = Some(errors::AssocItemNotFoundLabel::NotFound { span: assoc_name.span });
}
self.dcx().emit_err(err)
}
fn complain_about_assoc_kind_mismatch(
&self,
assoc_item: &ty::AssocItem,
assoc_kind: ty::AssocKind,
ident: Ident,
span: Span,
constraint: Option<&hir::AssocItemConstraint<'tcx>>,
) -> ErrorGuaranteed {
let tcx = self.tcx();
let bound_on_assoc_const_label = if let ty::AssocKind::Const = assoc_item.kind
&& let Some(constraint) = constraint
&& let hir::AssocItemConstraintKind::Bound { .. } = constraint.kind
{
let lo = if constraint.gen_args.span_ext.is_dummy() {
ident.span
} else {
constraint.gen_args.span_ext
};
Some(lo.between(span.shrink_to_hi()))
} else {
None
};
// FIXME(associated_const_equality): This has quite a few false positives and negatives.
let wrap_in_braces_sugg = if let Some(constraint) = constraint
&& let Some(hir_ty) = constraint.ty()
&& let ty = self.lower_ty(hir_ty)
&& (ty.is_enum() || ty.references_error())
&& tcx.features().associated_const_equality()
{
Some(errors::AssocKindMismatchWrapInBracesSugg {
lo: hir_ty.span.shrink_to_lo(),
hi: hir_ty.span.shrink_to_hi(),
})
} else {
None
};
// For equality constraints, we want to blame the term (RHS) instead of the item (LHS) since
// one can argue that that's more “intuitive” to the user.
let (span, expected_because_label, expected, got) = if let Some(constraint) = constraint
&& let hir::AssocItemConstraintKind::Equality { term } = constraint.kind
{
let span = match term {
hir::Term::Ty(ty) => ty.span,
hir::Term::Const(ct) => ct.span(),
};
(span, Some(ident.span), assoc_item.kind, assoc_kind)
} else {
(ident.span, None, assoc_kind, assoc_item.kind)
};
self.dcx().emit_err(errors::AssocKindMismatch {
span,
expected: assoc_kind_str(expected),
got: assoc_kind_str(got),
expected_because_label,
assoc_kind: assoc_kind_str(assoc_item.kind),
def_span: tcx.def_span(assoc_item.def_id),
bound_on_assoc_const_label,
wrap_in_braces_sugg,
})
}
pub(super) fn report_ambiguous_assoc_ty(
&self,
span: Span,
types: &[String],
traits: &[String],
name: Symbol,
) -> ErrorGuaranteed {
let mut err = struct_span_code_err!(self.dcx(), span, E0223, "ambiguous associated type");
if self
.tcx()
.resolutions(())
.confused_type_with_std_module
.keys()
.any(|full_span| full_span.contains(span))
{
err.span_suggestion_verbose(
span.shrink_to_lo(),
"you are looking for the module in `std`, not the primitive type",
"std::",
Applicability::MachineApplicable,
);
} else {
let mut types = types.to_vec();
types.sort();
let mut traits = traits.to_vec();
traits.sort();
match (&types[..], &traits[..]) {
([], []) => {
err.span_suggestion_verbose(
span,
format!(
"if there were a type named `Type` that implements a trait named \
`Trait` with associated type `{name}`, you could use the \
fully-qualified path",
),
format!("<Type as Trait>::{name}"),
Applicability::HasPlaceholders,
);
}
([], [trait_str]) => {
err.span_suggestion_verbose(
span,
format!(
"if there were a type named `Example` that implemented `{trait_str}`, \
you could use the fully-qualified path",
),
format!("<Example as {trait_str}>::{name}"),
Applicability::HasPlaceholders,
);
}
([], traits) => {
err.span_suggestions(
span,
format!(
"if there were a type named `Example` that implemented one of the \
traits with associated type `{name}`, you could use the \
fully-qualified path",
),
traits.iter().map(|trait_str| format!("<Example as {trait_str}>::{name}")),
Applicability::HasPlaceholders,
);
}
([type_str], []) => {
err.span_suggestion_verbose(
span,
format!(
"if there were a trait named `Example` with associated type `{name}` \
implemented for `{type_str}`, you could use the fully-qualified path",
),
format!("<{type_str} as Example>::{name}"),
Applicability::HasPlaceholders,
);
}
(types, []) => {
err.span_suggestions(
span,
format!(
"if there were a trait named `Example` with associated type `{name}` \
implemented for one of the types, you could use the fully-qualified \
path",
),
types
.into_iter()
.map(|type_str| format!("<{type_str} as Example>::{name}")),
Applicability::HasPlaceholders,
);
}
(types, traits) => {
let mut suggestions = vec![];
for type_str in types {
for trait_str in traits {
suggestions.push(format!("<{type_str} as {trait_str}>::{name}"));
}
}
err.span_suggestions(
span,
"use fully-qualified syntax",
suggestions,
Applicability::MachineApplicable,
);
}
}
}
err.emit()
}
pub(crate) fn complain_about_ambiguous_inherent_assoc_ty(
&self,
name: Ident,
candidates: Vec<DefId>,
span: Span,
) -> ErrorGuaranteed {
let mut err = struct_span_code_err!(
self.dcx(),
name.span,
E0034,
"multiple applicable items in scope"
);
err.span_label(name.span, format!("multiple `{name}` found"));
self.note_ambiguous_inherent_assoc_ty(&mut err, candidates, span);
err.emit()
}
// FIXME(fmease): Heavily adapted from `rustc_hir_typeck::method::suggest`. Deduplicate.
fn note_ambiguous_inherent_assoc_ty(
&self,
err: &mut Diag<'_>,
candidates: Vec<DefId>,
span: Span,
) {
let tcx = self.tcx();
// Dynamic limit to avoid hiding just one candidate, which is silly.
let limit = if candidates.len() == 5 { 5 } else { 4 };
for (index, &item) in candidates.iter().take(limit).enumerate() {
let impl_ = tcx.impl_of_method(item).unwrap();
let note_span = if item.is_local() {
Some(tcx.def_span(item))
} else if impl_.is_local() {
Some(tcx.def_span(impl_))
} else {
None
};
let title = if candidates.len() > 1 {
format!("candidate #{}", index + 1)
} else {
"the candidate".into()
};
let impl_ty = tcx.at(span).type_of(impl_).instantiate_identity();
let note = format!("{title} is defined in an impl for the type `{impl_ty}`");
if let Some(span) = note_span {
err.span_note(span, note);
} else {
err.note(note);
}
}
if candidates.len() > limit {
err.note(format!("and {} others", candidates.len() - limit));
}
}
// FIXME(inherent_associated_types): Find similarly named associated types and suggest them.
pub(crate) fn complain_about_inherent_assoc_ty_not_found(
&self,
name: Ident,
self_ty: Ty<'tcx>,
candidates: Vec<(DefId, (DefId, DefId))>,
fulfillment_errors: Vec<FulfillmentError<'tcx>>,
span: Span,
) -> ErrorGuaranteed {
// FIXME(fmease): This was copied in parts from an old version of `rustc_hir_typeck::method::suggest`.
// Either
// * update this code by applying changes similar to #106702 or by taking a
// Vec<(DefId, (DefId, DefId), Option<Vec<FulfillmentError<'tcx>>>)> or
// * deduplicate this code across the two crates.
let tcx = self.tcx();
let adt_did = self_ty.ty_adt_def().map(|def| def.did());
let add_def_label = |err: &mut Diag<'_>| {
if let Some(did) = adt_did {
err.span_label(
tcx.def_span(did),
format!("associated item `{name}` not found for this {}", tcx.def_descr(did)),
);
}
};
if fulfillment_errors.is_empty() {
// FIXME(fmease): Copied from `rustc_hir_typeck::method::probe`. Deduplicate.
let limit = if candidates.len() == 5 { 5 } else { 4 };
let type_candidates = candidates
.iter()
.take(limit)
.map(|&(impl_, _)| {
format!("- `{}`", tcx.at(span).type_of(impl_).instantiate_identity())
})
.collect::<Vec<_>>()
.join("\n");
let additional_types = if candidates.len() > limit {
format!("\nand {} more types", candidates.len() - limit)
} else {
String::new()
};
let mut err = struct_span_code_err!(
self.dcx(),
name.span,
E0220,
"associated type `{name}` not found for `{self_ty}` in the current scope"
);
err.span_label(name.span, format!("associated item not found in `{self_ty}`"));
err.note(format!(
"the associated type was found for\n{type_candidates}{additional_types}",
));
add_def_label(&mut err);
return err.emit();
}
let mut bound_spans: SortedMap<Span, Vec<String>> = Default::default();
let mut bound_span_label = |self_ty: Ty<'_>, obligation: &str, quiet: &str| {
let msg = format!("`{}`", if obligation.len() > 50 { quiet } else { obligation });
match self_ty.kind() {
// Point at the type that couldn't satisfy the bound.
ty::Adt(def, _) => {
bound_spans.get_mut_or_insert_default(tcx.def_span(def.did())).push(msg)
}
// Point at the trait object that couldn't satisfy the bound.
ty::Dynamic(preds, _, _) => {
for pred in preds.iter() {
match pred.skip_binder() {
ty::ExistentialPredicate::Trait(tr) => {
bound_spans
.get_mut_or_insert_default(tcx.def_span(tr.def_id))
.push(msg.clone());
}
ty::ExistentialPredicate::Projection(_)
| ty::ExistentialPredicate::AutoTrait(_) => {}
}
}
}
// Point at the closure that couldn't satisfy the bound.
ty::Closure(def_id, _) => {
bound_spans
.get_mut_or_insert_default(tcx.def_span(*def_id))
.push(format!("`{quiet}`"));
}
_ => {}
}
};
let format_pred = |pred: ty::Predicate<'tcx>| {
let bound_predicate = pred.kind();
match bound_predicate.skip_binder() {
ty::PredicateKind::Clause(ty::ClauseKind::Projection(pred)) => {
// `<Foo as Iterator>::Item = String`.
let projection_term = pred.projection_term;
let quiet_projection_term =
projection_term.with_self_ty(tcx, Ty::new_var(tcx, ty::TyVid::ZERO));
let term = pred.term;
let obligation = format!("{projection_term} = {term}");
let quiet = format!("{quiet_projection_term} = {term}");
bound_span_label(projection_term.self_ty(), &obligation, &quiet);
Some((obligation, projection_term.self_ty()))
}
ty::PredicateKind::Clause(ty::ClauseKind::Trait(poly_trait_ref)) => {
let p = poly_trait_ref.trait_ref;
let self_ty = p.self_ty();
let path = p.print_only_trait_path();
let obligation = format!("{self_ty}: {path}");
let quiet = format!("_: {path}");
bound_span_label(self_ty, &obligation, &quiet);
Some((obligation, self_ty))
}
_ => None,
}
};
// FIXME(fmease): `rustc_hir_typeck::method::suggest` uses a `skip_list` to filter out some bounds.
// I would do the same here if it didn't mean more code duplication.
let mut bounds: Vec<_> = fulfillment_errors
.into_iter()
.map(|error| error.root_obligation.predicate)
.filter_map(format_pred)
.map(|(p, _)| format!("`{p}`"))
.collect();
bounds.sort();
bounds.dedup();
let mut err = self.dcx().struct_span_err(
name.span,
format!("the associated type `{name}` exists for `{self_ty}`, but its trait bounds were not satisfied")
);
if !bounds.is_empty() {
err.note(format!(
"the following trait bounds were not satisfied:\n{}",
bounds.join("\n")
));
}
err.span_label(
name.span,
format!("associated type cannot be referenced on `{self_ty}` due to unsatisfied trait bounds")
);
for (span, mut bounds) in bound_spans {
if !tcx.sess.source_map().is_span_accessible(span) {
continue;
}
bounds.sort();
bounds.dedup();
let msg = match &bounds[..] {
[bound] => format!("doesn't satisfy {bound}"),
bounds if bounds.len() > 4 => format!("doesn't satisfy {} bounds", bounds.len()),
[bounds @ .., last] => format!("doesn't satisfy {} or {last}", bounds.join(", ")),
[] => unreachable!(),
};
err.span_label(span, msg);
}
add_def_label(&mut err);
err.emit()
}
/// When there are any missing associated types, emit an E0191 error and attempt to supply a
/// reasonable suggestion on how to write it. For the case of multiple associated types in the
/// same trait bound have the same name (as they come from different supertraits), we instead
/// emit a generic note suggesting using a `where` clause to constraint instead.
pub(crate) fn check_for_required_assoc_tys(
&self,
principal_span: Span,
missing_assoc_types: FxIndexSet<(DefId, ty::PolyTraitRef<'tcx>)>,
potential_assoc_types: Vec<usize>,
trait_bounds: &[hir::PolyTraitRef<'_>],
) -> Result<(), ErrorGuaranteed> {
if missing_assoc_types.is_empty() {
return Ok(());
}
let tcx = self.tcx();
// FIXME: This logic needs some more care w.r.t handling of conflicts
let missing_assoc_types: Vec<_> = missing_assoc_types
.into_iter()
.map(|(def_id, trait_ref)| (tcx.associated_item(def_id), trait_ref))
.collect();
let mut names: FxIndexMap<_, Vec<Symbol>> = Default::default();
let mut names_len = 0;
// Account for things like `dyn Foo + 'a`, like in tests `issue-22434.rs` and
// `issue-22560.rs`.
let mut dyn_compatibility_violations = Ok(());
for (assoc_item, trait_ref) in &missing_assoc_types {
names.entry(trait_ref).or_default().push(assoc_item.name);
names_len += 1;
let violations =
dyn_compatibility_violations_for_assoc_item(tcx, trait_ref.def_id(), *assoc_item);
if !violations.is_empty() {
dyn_compatibility_violations = Err(report_dyn_incompatibility(
tcx,
principal_span,
None,
trait_ref.def_id(),
&violations,
)
.emit());
}
}
if let Err(guar) = dyn_compatibility_violations {
return Err(guar);
}
// related to issue #91997, turbofishes added only when in an expr or pat
let mut in_expr_or_pat = false;
if let ([], [bound]) = (&potential_assoc_types[..], &trait_bounds) {
let grandparent = tcx.parent_hir_node(tcx.parent_hir_id(bound.trait_ref.hir_ref_id));
in_expr_or_pat = match grandparent {
hir::Node::Expr(_) | hir::Node::Pat(_) => true,
_ => false,
};
}
// We get all the associated items that _are_ set,
// so that we can check if any of their names match one of the ones we are missing.
// This would mean that they are shadowing the associated type we are missing,
// and we can then use their span to indicate this to the user.
let bound_names = trait_bounds
.iter()
.filter_map(|poly_trait_ref| {
let path = poly_trait_ref.trait_ref.path.segments.last()?;
let args = path.args?;
Some(args.constraints.iter().filter_map(|constraint| {
let ident = constraint.ident;
let trait_def = path.res.def_id();
let assoc_item = tcx.associated_items(trait_def).find_by_name_and_kind(
tcx,
ident,
ty::AssocKind::Type,
trait_def,
);
Some((ident.name, assoc_item?))
}))
})
.flatten()
.collect::<UnordMap<Symbol, &ty::AssocItem>>();
let mut names = names
.into_iter()
.map(|(trait_, mut assocs)| {
assocs.sort();
let trait_ = trait_.print_trait_sugared();
format!("{} in `{trait_}`", match &assocs[..] {
[] => String::new(),
[only] => format!("`{only}`"),
[assocs @ .., last] => format!(
"{} and `{last}`",
assocs.iter().map(|a| format!("`{a}`")).collect::<Vec<_>>().join(", ")
),
})
})
.collect::<Vec<String>>();
names.sort();
let names = names.join(", ");
let mut err = struct_span_code_err!(
self.dcx(),
principal_span,
E0191,
"the value of the associated type{} {} must be specified",
pluralize!(names_len),
names,
);
let mut suggestions = vec![];
let mut types_count = 0;
let mut where_constraints = vec![];
let mut already_has_generics_args_suggestion = false;
let mut names: UnordMap<_, usize> = Default::default();
for (item, _) in &missing_assoc_types {
types_count += 1;
*names.entry(item.name).or_insert(0) += 1;
}
let mut dupes = false;
let mut shadows = false;
for (item, trait_ref) in &missing_assoc_types {
let prefix = if names[&item.name] > 1 {
let trait_def_id = trait_ref.def_id();
dupes = true;
format!("{}::", tcx.def_path_str(trait_def_id))
} else if bound_names.get(&item.name).is_some_and(|x| *x != item) {
let trait_def_id = trait_ref.def_id();
shadows = true;
format!("{}::", tcx.def_path_str(trait_def_id))
} else {
String::new()
};
let mut is_shadowed = false;
if let Some(assoc_item) = bound_names.get(&item.name)
&& *assoc_item != item
{
is_shadowed = true;
let rename_message =
if assoc_item.def_id.is_local() { ", consider renaming it" } else { "" };
err.span_label(
tcx.def_span(assoc_item.def_id),
format!("`{}{}` shadowed here{}", prefix, item.name, rename_message),
);
}
let rename_message = if is_shadowed { ", consider renaming it" } else { "" };
if let Some(sp) = tcx.hir().span_if_local(item.def_id) {
err.span_label(
sp,
format!("`{}{}` defined here{}", prefix, item.name, rename_message),
);
}
}
if potential_assoc_types.len() == missing_assoc_types.len() {
// When the amount of missing associated types equals the number of
// extra type arguments present. A suggesting to replace the generic args with
// associated types is already emitted.
already_has_generics_args_suggestion = true;
} else if let (Ok(snippet), false, false) =
(tcx.sess.source_map().span_to_snippet(principal_span), dupes, shadows)
{
let types: Vec<_> = missing_assoc_types
.iter()
.map(|(item, _)| format!("{} = Type", item.name))
.collect();
let code = if snippet.ends_with('>') {
// The user wrote `Trait<'a>` or similar and we don't have a type we can
// suggest, but at least we can clue them to the correct syntax
// `Trait<'a, Item = Type>` while accounting for the `<'a>` in the
// suggestion.
format!("{}, {}>", &snippet[..snippet.len() - 1], types.join(", "))
} else if in_expr_or_pat {
// The user wrote `Iterator`, so we don't have a type we can suggest, but at
// least we can clue them to the correct syntax `Iterator::<Item = Type>`.
format!("{}::<{}>", snippet, types.join(", "))
} else {
// The user wrote `Iterator`, so we don't have a type we can suggest, but at
// least we can clue them to the correct syntax `Iterator<Item = Type>`.
format!("{}<{}>", snippet, types.join(", "))
};
suggestions.push((principal_span, code));
} else if dupes {
where_constraints.push(principal_span);
}
let where_msg = "consider introducing a new type parameter, adding `where` constraints \
using the fully-qualified path to the associated types";
if !where_constraints.is_empty() && suggestions.is_empty() {
// If there are duplicates associated type names and a single trait bound do not
// use structured suggestion, it means that there are multiple supertraits with
// the same associated type name.
err.help(where_msg);
}
if suggestions.len() != 1 || already_has_generics_args_suggestion {
// We don't need this label if there's an inline suggestion, show otherwise.
let mut names: FxIndexMap<_, usize> = FxIndexMap::default();
for (item, _) in &missing_assoc_types {
types_count += 1;
*names.entry(item.name).or_insert(0) += 1;
}
let mut label = vec![];
for (item, trait_ref) in &missing_assoc_types {
let postfix = if names[&item.name] > 1 {
format!(" (from trait `{}`)", trait_ref.print_trait_sugared())
} else {
String::new()
};
label.push(format!("`{}`{}", item.name, postfix));
}
if !label.is_empty() {
err.span_label(
principal_span,
format!(
"associated type{} {} must be specified",
pluralize!(label.len()),
label.join(", "),
),
);
}
}
suggestions.sort_by_key(|&(span, _)| span);
// There are cases where one bound points to a span within another bound's span, like when
// you have code like the following (#115019), so we skip providing a suggestion in those
// cases to avoid having a malformed suggestion.
//
// pub struct Flatten<I> {
// inner: <IntoIterator<Item: IntoIterator<Item: >>::IntoIterator as Item>::core,
// ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
// | ^^^^^^^^^^^^^^^^^^^^^
// | |
// | associated types `Item`, `IntoIter` must be specified
// associated types `Item`, `IntoIter` must be specified
// }
let overlaps = suggestions.windows(2).any(|pair| pair[0].0.overlaps(pair[1].0));
if !suggestions.is_empty() && !overlaps {
err.multipart_suggestion(
format!("specify the associated type{}", pluralize!(types_count)),
suggestions,
Applicability::HasPlaceholders,
);
if !where_constraints.is_empty() {
err.span_help(where_constraints, where_msg);
}
}
Err(err.emit())
}
/// On ambiguous associated type, look for an associated function whose name matches the
/// extended path and, if found, emit an E0223 error with a structured suggestion.
/// e.g. for `String::from::utf8`, suggest `String::from_utf8` (#109195)
pub(crate) fn maybe_report_similar_assoc_fn(
&self,
span: Span,
qself_ty: Ty<'tcx>,
qself: &hir::Ty<'_>,
) -> Result<(), ErrorGuaranteed> {
let tcx = self.tcx();
if let Some((_, node)) = tcx.hir().parent_iter(qself.hir_id).skip(1).next()
&& let hir::Node::Expr(hir::Expr {
kind:
hir::ExprKind::Path(hir::QPath::TypeRelative(
hir::Ty {
kind:
hir::TyKind::Path(hir::QPath::TypeRelative(
_,
hir::PathSegment { ident: ident2, .. },
)),
..
},
hir::PathSegment { ident: ident3, .. },
)),
..
}) = node
&& let Some(adt_def) = qself_ty.ty_adt_def()
&& let [inherent_impl] = tcx.inherent_impls(adt_def.did())
&& let name = format!("{ident2}_{ident3}")
&& let Some(ty::AssocItem { kind: ty::AssocKind::Fn, .. }) = tcx
.associated_items(inherent_impl)
.filter_by_name_unhygienic(Symbol::intern(&name))
.next()
{
Err(struct_span_code_err!(self.dcx(), span, E0223, "ambiguous associated type")
.with_span_suggestion_verbose(
ident2.span.to(ident3.span),
format!("there is an associated function with a similar name: `{name}`"),
name,
Applicability::MaybeIncorrect,
)
.emit())
} else {
Ok(())
}
}
pub fn report_prohibit_generics_error<'a>(
&self,
segments: impl Iterator<Item = &'a hir::PathSegment<'a>> + Clone,
args_visitors: impl Iterator<Item = &'a hir::GenericArg<'a>> + Clone,
err_extend: GenericsArgsErrExtend<'_>,
) -> ErrorGuaranteed {
#[derive(PartialEq, Eq, Hash)]
enum ProhibitGenericsArg {
Lifetime,
Type,
Const,
Infer,
}
let mut prohibit_args = FxIndexSet::default();
args_visitors.for_each(|arg| {
match arg {
hir::GenericArg::Lifetime(_) => prohibit_args.insert(ProhibitGenericsArg::Lifetime),
hir::GenericArg::Type(_) => prohibit_args.insert(ProhibitGenericsArg::Type),
hir::GenericArg::Const(_) => prohibit_args.insert(ProhibitGenericsArg::Const),
hir::GenericArg::Infer(_) => prohibit_args.insert(ProhibitGenericsArg::Infer),
};
});
let types_and_spans: Vec<_> = segments
.clone()
.flat_map(|segment| {
if segment.args().args.is_empty() {
None
} else {
Some((
match segment.res {
hir::def::Res::PrimTy(ty) => {
format!("{} `{}`", segment.res.descr(), ty.name())
}
hir::def::Res::Def(_, def_id)
if let Some(name) = self.tcx().opt_item_name(def_id) =>
{
format!("{} `{name}`", segment.res.descr())
}
hir::def::Res::Err => "this type".to_string(),
_ => segment.res.descr().to_string(),
},
segment.ident.span,
))
}
})
.collect();
let this_type = match &types_and_spans[..] {
[.., _, (last, _)] => format!(
"{} and {last}",
types_and_spans[..types_and_spans.len() - 1]
.iter()
.map(|(x, _)| x.as_str())
.intersperse(", ")
.collect::<String>()
),
[(only, _)] => only.to_string(),
[] => bug!("expected one segment to deny"),
};
let arg_spans: Vec<Span> = segments
.clone()
.flat_map(|segment| segment.args().args)
.map(|arg| arg.span())
.collect();
let mut kinds = Vec::with_capacity(4);
prohibit_args.iter().for_each(|arg| match arg {
ProhibitGenericsArg::Lifetime => kinds.push("lifetime"),
ProhibitGenericsArg::Type => kinds.push("type"),
ProhibitGenericsArg::Const => kinds.push("const"),
ProhibitGenericsArg::Infer => kinds.push("generic"),
});
let (kind, s) = match kinds[..] {
[.., _, last] => (
format!(
"{} and {last}",
kinds[..kinds.len() - 1]
.iter()
.map(|&x| x)
.intersperse(", ")
.collect::<String>()
),
"s",
),
[only] => (only.to_string(), ""),
[] => bug!("expected at least one generic to prohibit"),
};
let last_span = *arg_spans.last().unwrap();
let span: MultiSpan = arg_spans.into();
let mut err = struct_span_code_err!(
self.dcx(),
span,
E0109,
"{kind} arguments are not allowed on {this_type}",
);
err.span_label(last_span, format!("{kind} argument{s} not allowed"));
for (what, span) in types_and_spans {
err.span_label(span, format!("not allowed on {what}"));
}
generics_args_err_extend(self.tcx(), segments, &mut err, err_extend);
err.emit()
}
pub fn report_trait_object_addition_traits_error(
&self,
regular_traits: &Vec<TraitAliasExpansionInfo<'_>>,
) -> ErrorGuaranteed {
let first_trait = ®ular_traits[0];
let additional_trait = ®ular_traits[1];
let mut err = struct_span_code_err!(
self.dcx(),
additional_trait.bottom().1,
E0225,
"only auto traits can be used as additional traits in a trait object"
);
additional_trait.label_with_exp_info(
&mut err,
"additional non-auto trait",
"additional use",
);
first_trait.label_with_exp_info(&mut err, "first non-auto trait", "first use");
err.help(format!(
"consider creating a new trait with all of these as supertraits and using that \
trait here instead: `trait NewTrait: {} {{}}`",
regular_traits
.iter()
// FIXME: This should `print_sugared`, but also needs to integrate projection bounds...
.map(|t| t.trait_ref().print_only_trait_path().to_string())
.collect::<Vec<_>>()
.join(" + "),
));
err.note(
"auto-traits like `Send` and `Sync` are traits that have special properties; \
for more information on them, visit \
<https://doc.rust-lang.org/reference/special-types-and-traits.html#auto-traits>",
);
err.emit()
}
pub fn report_trait_object_with_no_traits_error(
&self,
span: Span,
trait_bounds: &Vec<(Binder<'tcx, TraitRef<'tcx>>, Span)>,
) -> ErrorGuaranteed {
let tcx = self.tcx();
let trait_alias_span = trait_bounds
.iter()
.map(|&(trait_ref, _)| trait_ref.def_id())
.find(|&trait_ref| tcx.is_trait_alias(trait_ref))
.map(|trait_ref| tcx.def_span(trait_ref));
self.dcx().emit_err(TraitObjectDeclaredWithNoTraits { span, trait_alias_span })
}
}
/// Emit an error for the given associated item constraint.
pub fn prohibit_assoc_item_constraint(
cx: &dyn HirTyLowerer<'_>,
constraint: &hir::AssocItemConstraint<'_>,
segment: Option<(DefId, &hir::PathSegment<'_>, Span)>,
) -> ErrorGuaranteed {
let tcx = cx.tcx();
let mut err = cx.dcx().create_err(AssocItemConstraintsNotAllowedHere {
span: constraint.span,
fn_trait_expansion: if let Some((_, segment, span)) = segment
&& segment.args().parenthesized == hir::GenericArgsParentheses::ParenSugar
{
Some(ParenthesizedFnTraitExpansion {
span,
expanded_type: fn_trait_to_string(tcx, segment, false),
})
} else {
None
},
});
// Emit a suggestion to turn the assoc item binding into a generic arg
// if the relevant item has a generic param whose name matches the binding name;
// otherwise suggest the removal of the binding.
if let Some((def_id, segment, _)) = segment
&& segment.args().parenthesized == hir::GenericArgsParentheses::No
{
// Suggests removal of the offending binding
let suggest_removal = |e: &mut Diag<'_>| {
let constraints = segment.args().constraints;
let args = segment.args().args;
// Compute the span to remove based on the position
// of the binding. We do that as follows:
// 1. Find the index of the binding in the list of bindings
// 2. Locate the spans preceding and following the binding.
// If it's the first binding the preceding span would be
// that of the last arg
// 3. Using this information work out whether the span
// to remove will start from the end of the preceding span,
// the start of the next span or will simply be the
// span encomassing everything within the generics brackets
let Some(index) = constraints.iter().position(|b| b.hir_id == constraint.hir_id) else {
bug!("a type binding exists but its HIR ID not found in generics");
};
let preceding_span = if index > 0 {
Some(constraints[index - 1].span)
} else {
args.last().map(|a| a.span())
};
let next_span = constraints.get(index + 1).map(|constraint| constraint.span);
let removal_span = match (preceding_span, next_span) {
(Some(prec), _) => constraint.span.with_lo(prec.hi()),
(None, Some(next)) => constraint.span.with_hi(next.lo()),
(None, None) => {
let Some(generics_span) = segment.args().span_ext() else {
bug!("a type binding exists but generic span is empty");
};
generics_span
}
};
// Now emit the suggestion
e.span_suggestion_verbose(
removal_span,
format!("consider removing this associated item {}", constraint.kind.descr()),
"",
Applicability::MaybeIncorrect,
);
};
// Suggest replacing the associated item binding with a generic argument.
// i.e., replacing `<..., T = A, ...>` with `<..., A, ...>`.
let suggest_direct_use = |e: &mut Diag<'_>, sp: Span| {
if let Ok(snippet) = tcx.sess.source_map().span_to_snippet(sp) {
e.span_suggestion_verbose(
constraint.span,
format!("to use `{snippet}` as a generic argument specify it directly"),
snippet,
Applicability::MaybeIncorrect,
);
}
};
// Check if the type has a generic param with the same name
// as the assoc type name in the associated item binding.
let generics = tcx.generics_of(def_id);
let matching_param = generics.own_params.iter().find(|p| p.name == constraint.ident.name);
// Now emit the appropriate suggestion
if let Some(matching_param) = matching_param {
match (constraint.kind, &matching_param.kind) {
(
hir::AssocItemConstraintKind::Equality { term: hir::Term::Ty(ty) },
GenericParamDefKind::Type { .. },
) => suggest_direct_use(&mut err, ty.span),
(
hir::AssocItemConstraintKind::Equality { term: hir::Term::Const(c) },
GenericParamDefKind::Const { .. },
) => {
suggest_direct_use(&mut err, c.span());
}
(hir::AssocItemConstraintKind::Bound { bounds }, _) => {
// Suggest `impl<T: Bound> Trait<T> for Foo` when finding
// `impl Trait<T: Bound> for Foo`
// Get the parent impl block based on the binding we have
// and the trait DefId
let impl_block = tcx
.hir()
.parent_iter(constraint.hir_id)
.find_map(|(_, node)| node.impl_block_of_trait(def_id));
let type_with_constraints =
tcx.sess.source_map().span_to_snippet(constraint.span);
if let Some(impl_block) = impl_block
&& let Ok(type_with_constraints) = type_with_constraints
{
// Filter out the lifetime parameters because
// they should be declared before the type parameter
let lifetimes: String = bounds
.iter()
.filter_map(|bound| {
if let hir::GenericBound::Outlives(lifetime) = bound {
Some(format!("{lifetime}, "))
} else {
None
}
})
.collect();
// Figure out a span and suggestion string based on
// whether there are any existing parameters
let param_decl = if let Some(param_span) =
impl_block.generics.span_for_param_suggestion()
{
(param_span, format!(", {lifetimes}{type_with_constraints}"))
} else {
(
impl_block.generics.span.shrink_to_lo(),
format!("<{lifetimes}{type_with_constraints}>"),
)
};
let suggestions = vec![
param_decl,
(constraint.span.with_lo(constraint.ident.span.hi()), String::new()),
];
err.multipart_suggestion_verbose(
"declare the type parameter right after the `impl` keyword",
suggestions,
Applicability::MaybeIncorrect,
);
}
}
_ => suggest_removal(&mut err),
}
} else {
suggest_removal(&mut err);
}
}
err.emit()
}
pub(crate) fn fn_trait_to_string(
tcx: TyCtxt<'_>,
trait_segment: &hir::PathSegment<'_>,
parenthesized: bool,
) -> String {
let args = trait_segment
.args
.and_then(|args| args.args.first())
.and_then(|arg| match arg {
hir::GenericArg::Type(ty) => match ty.kind {
hir::TyKind::Tup(t) => t
.iter()
.map(|e| tcx.sess.source_map().span_to_snippet(e.span))
.collect::<Result<Vec<_>, _>>()
.map(|a| a.join(", ")),
_ => tcx.sess.source_map().span_to_snippet(ty.span),
}
.map(|s| {
// `is_empty()` checks to see if the type is the unit tuple, if so we don't want a comma
if parenthesized || s.is_empty() { format!("({s})") } else { format!("({s},)") }
})
.ok(),
_ => None,
})
.unwrap_or_else(|| "()".to_string());
let ret = trait_segment
.args()
.constraints
.iter()
.find_map(|c| {
if c.ident.name == sym::Output
&& let Some(ty) = c.ty()
&& ty.span != tcx.hir().span(trait_segment.hir_id)
{
tcx.sess.source_map().span_to_snippet(ty.span).ok()
} else {
None
}
})
.unwrap_or_else(|| "()".to_string());
if parenthesized {
format!("{}{} -> {}", trait_segment.ident, args, ret)
} else {
format!("{}<{}, Output={}>", trait_segment.ident, args, ret)
}
}
/// Used for generics args error extend.
pub enum GenericsArgsErrExtend<'tcx> {
EnumVariant {
qself: &'tcx hir::Ty<'tcx>,
assoc_segment: &'tcx hir::PathSegment<'tcx>,
adt_def: AdtDef<'tcx>,
},
OpaqueTy,
PrimTy(hir::PrimTy),
SelfTyAlias {
def_id: DefId,
span: Span,
},
SelfTyParam(Span),
Param(DefId),
DefVariant,
None,
}
fn generics_args_err_extend<'a>(
tcx: TyCtxt<'_>,
segments: impl Iterator<Item = &'a hir::PathSegment<'a>> + Clone,
err: &mut Diag<'_>,
err_extend: GenericsArgsErrExtend<'_>,
) {
match err_extend {
GenericsArgsErrExtend::EnumVariant { qself, assoc_segment, adt_def } => {
err.note("enum variants can't have type parameters");
let type_name = tcx.item_name(adt_def.did());
let msg = format!(
"you might have meant to specify type parameters on enum \
`{type_name}`"
);
let Some(args) = assoc_segment.args else {
return;
};
// Get the span of the generics args *including* the leading `::`.
// We do so by stretching args.span_ext to the left by 2. Earlier
// it was done based on the end of assoc segment but that sometimes
// led to impossible spans and caused issues like #116473
let args_span = args.span_ext.with_lo(args.span_ext.lo() - BytePos(2));
if tcx.generics_of(adt_def.did()).is_empty() {
// FIXME(estebank): we could also verify that the arguments being
// work for the `enum`, instead of just looking if it takes *any*.
err.span_suggestion_verbose(
args_span,
format!("{type_name} doesn't have generic parameters"),
"",
Applicability::MachineApplicable,
);
return;
}
let Ok(snippet) = tcx.sess.source_map().span_to_snippet(args_span) else {
err.note(msg);
return;
};
let (qself_sugg_span, is_self) =
if let hir::TyKind::Path(hir::QPath::Resolved(_, path)) = &qself.kind {
// If the path segment already has type params, we want to overwrite
// them.
match &path.segments {
// `segment` is the previous to last element on the path,
// which would normally be the `enum` itself, while the last
// `_` `PathSegment` corresponds to the variant.
[
..,
hir::PathSegment {
ident, args, res: Res::Def(DefKind::Enum, _), ..
},
_,
] => (
// We need to include the `::` in `Type::Variant::<Args>`
// to point the span to `::<Args>`, not just `<Args>`.
ident
.span
.shrink_to_hi()
.to(args.map_or(ident.span.shrink_to_hi(), |a| a.span_ext)),
false,
),
[segment] => {
(
// We need to include the `::` in `Type::Variant::<Args>`
// to point the span to `::<Args>`, not just `<Args>`.
segment.ident.span.shrink_to_hi().to(segment
.args
.map_or(segment.ident.span.shrink_to_hi(), |a| a.span_ext)),
kw::SelfUpper == segment.ident.name,
)
}
_ => {
err.note(msg);
return;
}
}
} else {
err.note(msg);
return;
};
let suggestion = vec![
if is_self {
// Account for people writing `Self::Variant::<Args>`, where
// `Self` is the enum, and suggest replacing `Self` with the
// appropriate type: `Type::<Args>::Variant`.
(qself.span, format!("{type_name}{snippet}"))
} else {
(qself_sugg_span, snippet)
},
(args_span, String::new()),
];
err.multipart_suggestion_verbose(msg, suggestion, Applicability::MaybeIncorrect);
}
GenericsArgsErrExtend::PrimTy(prim_ty) => {
let name = prim_ty.name_str();
for segment in segments {
if let Some(args) = segment.args {
err.span_suggestion_verbose(
segment.ident.span.shrink_to_hi().to(args.span_ext),
format!("primitive type `{name}` doesn't have generic parameters"),
"",
Applicability::MaybeIncorrect,
);
}
}
}
GenericsArgsErrExtend::OpaqueTy => {
err.note("`impl Trait` types can't have type parameters");
}
GenericsArgsErrExtend::DefVariant => {
err.note("enum variants can't have type parameters");
}
GenericsArgsErrExtend::Param(def_id) => {
let span = tcx.def_ident_span(def_id).unwrap();
let kind = tcx.def_descr(def_id);
let name = tcx.item_name(def_id);
err.span_note(span, format!("{kind} `{name}` defined here"));
}
GenericsArgsErrExtend::SelfTyParam(span) => {
err.span_suggestion_verbose(
span,
"the `Self` type doesn't accept type parameters",
"",
Applicability::MaybeIncorrect,
);
}
GenericsArgsErrExtend::SelfTyAlias { def_id, span } => {
let ty = tcx.at(span).type_of(def_id).instantiate_identity();
let span_of_impl = tcx.span_of_impl(def_id);
let def_id = match *ty.kind() {
ty::Adt(self_def, _) => self_def.did(),
_ => return,
};
let type_name = tcx.item_name(def_id);
let span_of_ty = tcx.def_ident_span(def_id);
let generics = tcx.generics_of(def_id).count();
let msg = format!("`Self` is of type `{ty}`");
if let (Ok(i_sp), Some(t_sp)) = (span_of_impl, span_of_ty) {
let mut span: MultiSpan = vec![t_sp].into();
span.push_span_label(
i_sp,
format!("`Self` is on type `{type_name}` in this `impl`"),
);
let mut postfix = "";
if generics == 0 {
postfix = ", which doesn't have generic parameters";
}
span.push_span_label(t_sp, format!("`Self` corresponds to this type{postfix}"));
err.span_note(span, msg);
} else {
err.note(msg);
}
for segment in segments {
if let Some(args) = segment.args
&& segment.ident.name == kw::SelfUpper
{
if generics == 0 {
// FIXME(estebank): we could also verify that the arguments being
// work for the `enum`, instead of just looking if it takes *any*.
err.span_suggestion_verbose(
segment.ident.span.shrink_to_hi().to(args.span_ext),
"the `Self` type doesn't accept type parameters",
"",
Applicability::MachineApplicable,
);
return;
} else {
err.span_suggestion_verbose(
segment.ident.span,
format!(
"the `Self` type doesn't accept type parameters, use the \
concrete type's name `{type_name}` instead if you want to \
specify its type parameters"
),
type_name,
Applicability::MaybeIncorrect,
);
}
}
}
}
_ => {}
}
}
pub(super) fn assoc_kind_str(kind: ty::AssocKind) -> &'static str {
match kind {
ty::AssocKind::Fn => "function",
ty::AssocKind::Const => "constant",
ty::AssocKind::Type => "type",
}
}