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Auto merge of rust-lang#118668 - fmease:resolve-assoc-item-bindings-b…
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…y-namespace, r=compiler-errors

Resolve associated item bindings by namespace

This is the 3rd commit split off from rust-lang#118360 with tests reblessed (they no longer contain duplicated diags which were caused by 4c0addc) & slightly adapted (removed supertraits from a UI test, cc rust-lang#118040).

> * Resolve all assoc item bindings (type, const, fn (feature `return_type_notation`)) by namespace instead of trying to resolve a type first (in the non-RTN case) and falling back to consts afterwards. This is consistent with RTN. E.g., for `Tr<K = {…}>` we now always try to look up assoc consts (this extends to supertrait bounds). This gets rid of assoc tys shadowing assoc consts in assoc item bindings which is undesirable & inconsistent (types and consts live in different namespaces after all)
> * Consolidate the resolution of assoc {ty, const} bindings and RTN (dedup, better diags for RTN)
> * Fix assoc consts being labeled as assoc *types* in several diagnostics
> * Make a bunch of diagnostics translatable

Fixes rust-lang#112560 (error → pass).

As discussed
r? `@compiler-errors`

---

**Addendum**: What I call “associated item bindings” are commonly referred to as “type bindings” for historical reasons. Nowadays, “type bindings” include assoc type bindings, assoc const bindings and RTN (return type notation) which is why I prefer not to use this outdated term.
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bors committed Dec 8, 2023
2 parents 8043f62 + 55559d9 commit 5ea6256
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31 changes: 22 additions & 9 deletions compiler/rustc_hir_analysis/messages.ftl
View file
Original file line number Diff line number Diff line change
@@ -1,8 +1,28 @@
hir_analysis_ambiguous_assoc_item = ambiguous associated {$assoc_kind} `{$assoc_name}` in bounds of `{$ty_param_name}`
.label = ambiguous associated {$assoc_kind} `{$assoc_name}`
hir_analysis_ambiguous_lifetime_bound =
ambiguous lifetime bound, explicit lifetime bound required
hir_analysis_assoc_bound_on_const = expected associated type, found {$descr}
.note = trait bounds not allowed on {$descr}
hir_analysis_assoc_item_not_found = associated {$assoc_kind} `{$assoc_name}` not found for `{$ty_param_name}`
hir_analysis_assoc_item_not_found_found_in_other_trait_label = there is {$identically_named ->
[true] an
*[false] a similarly named
} associated {$assoc_kind} `{$suggested_name}` in the trait `{$trait_name}`
hir_analysis_assoc_item_not_found_label = associated {$assoc_kind} `{$assoc_name}` not found
hir_analysis_assoc_item_not_found_other_sugg = `{$ty_param_name}` has the following associated {$assoc_kind}
hir_analysis_assoc_item_not_found_similar_in_other_trait_sugg = change the associated {$assoc_kind} name to use `{$suggested_name}` from `{$trait_name}`
hir_analysis_assoc_item_not_found_similar_in_other_trait_with_bound_sugg = and also change the associated {$assoc_kind} name
hir_analysis_assoc_item_not_found_similar_sugg = there is an associated {$assoc_kind} with a similar name
hir_analysis_assoc_kind_mismatch = expected {$expected}, found {$got}
.label = unexpected {$got}
.expected_because_label = expected a {$expected} because of this associated {$expected}
.note = the associated {$assoc_kind} is defined here
.bound_on_assoc_const_label = bounds are not allowed on associated constants
hir_analysis_assoc_kind_mismatch_wrap_in_braces_sugg = consider adding braces here
hir_analysis_assoc_type_binding_not_allowed =
associated type bindings are not allowed here
Expand Down Expand Up @@ -280,10 +300,6 @@ hir_analysis_placeholder_not_allowed_item_signatures = the placeholder `_` is no
hir_analysis_requires_note = the `{$trait_name}` impl for `{$ty}` requires that `{$error_predicate}`
hir_analysis_return_type_notation_conflicting_bound =
ambiguous associated function `{$assoc_name}` for `{$ty_name}`
.note = `{$assoc_name}` is declared in two supertraits: `{$first_bound}` and `{$second_bound}`
hir_analysis_return_type_notation_equality_bound =
return type notation is not allowed to use type equality
Expand All @@ -294,9 +310,6 @@ hir_analysis_return_type_notation_illegal_param_type =
return type notation is not allowed for functions that have type parameters
.label = type parameter declared here
hir_analysis_return_type_notation_missing_method =
cannot find associated function `{$assoc_name}` for `{$ty_name}`
hir_analysis_return_type_notation_on_non_rpitit =
return type notation used on function that is not `async` and does not return `impl Trait`
.note = function returns `{$ty}`, which is not compatible with associated type return bounds
Expand Down
134 changes: 34 additions & 100 deletions compiler/rustc_hir_analysis/src/astconv/bounds.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -3,8 +3,7 @@ use rustc_errors::struct_span_err;
use rustc_hir as hir;
use rustc_hir::def::{DefKind, Res};
use rustc_hir::def_id::{DefId, LocalDefId};
use rustc_lint_defs::Applicability;
use rustc_middle::ty::{self as ty, Ty, TypeVisitableExt};
use rustc_middle::ty::{self as ty, Ty};
use rustc_span::symbol::Ident;
use rustc_span::{ErrorGuaranteed, Span};
use rustc_trait_selection::traits;
Expand Down Expand Up @@ -256,64 +255,49 @@ impl<'tcx> dyn AstConv<'tcx> + '_ {

let tcx = self.tcx();

let return_type_notation =
binding.gen_args.parenthesized == hir::GenericArgsParentheses::ReturnTypeNotation;

let candidate = if return_type_notation {
if self.trait_defines_associated_item_named(
trait_ref.def_id(),
ty::AssocKind::Fn,
binding.item_name,
) {
trait_ref
let assoc_kind =
if binding.gen_args.parenthesized == hir::GenericArgsParentheses::ReturnTypeNotation {
ty::AssocKind::Fn
} else if let ConvertedBindingKind::Equality(term) = binding.kind
&& let ty::TermKind::Const(_) = term.node.unpack()
{
ty::AssocKind::Const
} else {
self.one_bound_for_assoc_method(
traits::supertraits(tcx, trait_ref),
trait_ref.print_only_trait_path(),
binding.item_name,
path_span,
)?
}
} else if self.trait_defines_associated_item_named(
ty::AssocKind::Type
};

let candidate = if self.trait_defines_associated_item_named(
trait_ref.def_id(),
ty::AssocKind::Type,
assoc_kind,
binding.item_name,
) {
// Simple case: X is defined in the current trait.
// Simple case: The assoc item is defined in the current trait.
trait_ref
} else {
// Otherwise, we have to walk through the supertraits to find
// those that do.
self.one_bound_for_assoc_type(
// one that does define it.
self.one_bound_for_assoc_item(
|| traits::supertraits(tcx, trait_ref),
trait_ref.skip_binder().print_only_trait_name(),
None,
assoc_kind,
binding.item_name,
path_span,
match binding.kind {
ConvertedBindingKind::Equality(term) => Some(term),
_ => None,
},
Some(&binding),
)?
};

let (assoc_ident, def_scope) =
tcx.adjust_ident_and_get_scope(binding.item_name, candidate.def_id(), hir_ref_id);

// We have already adjusted the item name above, so compare with `ident.normalize_to_macros_2_0()` instead
// of calling `filter_by_name_and_kind`.
let find_item_of_kind = |kind| {
tcx.associated_items(candidate.def_id())
.filter_by_name_unhygienic(assoc_ident.name)
.find(|i| i.kind == kind && i.ident(tcx).normalize_to_macros_2_0() == assoc_ident)
};
let assoc_item = if return_type_notation {
find_item_of_kind(ty::AssocKind::Fn)
} else {
find_item_of_kind(ty::AssocKind::Type)
.or_else(|| find_item_of_kind(ty::AssocKind::Const))
}
.expect("missing associated type");
// We have already adjusted the item name above, so compare with `.normalize_to_macros_2_0()`
// instead of calling `filter_by_name_and_kind` which would needlessly normalize the
// `assoc_ident` again and again.
let assoc_item = tcx
.associated_items(candidate.def_id())
.filter_by_name_unhygienic(assoc_ident.name)
.find(|i| i.kind == assoc_kind && i.ident(tcx).normalize_to_macros_2_0() == assoc_ident)
.expect("missing associated item");

if !assoc_item.visibility(tcx).is_accessible_from(def_scope, tcx) {
tcx.sess
Expand All @@ -340,7 +324,7 @@ impl<'tcx> dyn AstConv<'tcx> + '_ {
.or_insert(binding.span);
}

let projection_ty = if return_type_notation {
let projection_ty = if let ty::AssocKind::Fn = assoc_kind {
let mut emitted_bad_param_err = false;
// If we have an method return type bound, then we need to substitute
// the method's early bound params with suitable late-bound params.
Expand Down Expand Up @@ -467,7 +451,7 @@ impl<'tcx> dyn AstConv<'tcx> + '_ {
let late_bound_in_trait_ref =
tcx.collect_constrained_late_bound_regions(&projection_ty);
let late_bound_in_ty =
tcx.collect_referenced_late_bound_regions(&trait_ref.rebind(ty));
tcx.collect_referenced_late_bound_regions(&trait_ref.rebind(ty.node));
debug!(?late_bound_in_trait_ref);
debug!(?late_bound_in_ty);

Expand All @@ -492,77 +476,27 @@ impl<'tcx> dyn AstConv<'tcx> + '_ {
}
}

let assoc_item_def_id = projection_ty.skip_binder().def_id;
let def_kind = tcx.def_kind(assoc_item_def_id);
match binding.kind {
ConvertedBindingKind::Equality(..) if return_type_notation => {
ConvertedBindingKind::Equality(..) if let ty::AssocKind::Fn = assoc_kind => {
return Err(self.tcx().sess.emit_err(
crate::errors::ReturnTypeNotationEqualityBound { span: binding.span },
));
}
ConvertedBindingKind::Equality(mut term) => {
ConvertedBindingKind::Equality(term) => {
// "Desugar" a constraint like `T: Iterator<Item = u32>` this to
// the "projection predicate" for:
//
// `<T as Iterator>::Item = u32`
match (def_kind, term.unpack()) {
(DefKind::AssocTy, ty::TermKind::Ty(_))
| (DefKind::AssocConst, ty::TermKind::Const(_)) => (),
(_, _) => {
let got = if let Some(_) = term.ty() { "type" } else { "constant" };
let expected = tcx.def_descr(assoc_item_def_id);
let mut err = tcx.sess.struct_span_err(
binding.span,
format!("expected {expected} bound, found {got}"),
);
err.span_note(
tcx.def_span(assoc_item_def_id),
format!("{expected} defined here"),
);

if let DefKind::AssocConst = def_kind
&& let Some(t) = term.ty()
&& (t.is_enum() || t.references_error())
&& tcx.features().associated_const_equality
{
err.span_suggestion(
binding.span,
"if equating a const, try wrapping with braces",
format!("{} = {{ const }}", binding.item_name),
Applicability::HasPlaceholders,
);
}
let reported = err.emit();
term = match def_kind {
DefKind::AssocTy => Ty::new_error(tcx, reported).into(),
DefKind::AssocConst => ty::Const::new_error(
tcx,
reported,
tcx.type_of(assoc_item_def_id)
.instantiate(tcx, projection_ty.skip_binder().args),
)
.into(),
_ => unreachable!(),
};
}
}
bounds.push_projection_bound(
tcx,
projection_ty
.map_bound(|projection_ty| ty::ProjectionPredicate { projection_ty, term }),
projection_ty.map_bound(|projection_ty| ty::ProjectionPredicate {
projection_ty,
term: term.node,
}),
binding.span,
);
}
ConvertedBindingKind::Constraint(ast_bounds) => {
match def_kind {
DefKind::AssocTy => {}
_ => {
return Err(tcx.sess.emit_err(errors::AssocBoundOnConst {
span: assoc_ident.span,
descr: tcx.def_descr(assoc_item_def_id),
}));
}
}
// "Desugar" a constraint like `T: Iterator<Item: Debug>` to
//
// `<T as Iterator>::Item: Debug`
Expand Down
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