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Resolve associated item bindings by namespace #118668

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Dec 8, 2023
Merged

Resolve associated item bindings by namespace #118668

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31 changes: 22 additions & 9 deletions compiler/rustc_hir_analysis/messages.ftl
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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
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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)
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Huh, how does this differ from find_by_name_and_kind?

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@fmease fmease Dec 7, 2023 •
edited
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find_by_name_and_kind is semantically identical to the code above but this version is slightly faster in theory since we only normalize the LHS above instead of normalizing both sides (which is what hygienic_eq does). assoc_ident has already been normalized above in adjust_ident_and_get_scope, so no need to do it again (adjust_ident_and_get_scope also returns the def_scope which is used later in is_accessible_from).

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pls note this

.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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