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Resolve assoc item bindings by namespace
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If a const is expected, resolve a const.
If a type is expected, resolve a type.
Don't try to resolve a type first falling back to consts.
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@fmease
fmease committed Dec 7, 2023
1 parent dd6126e commit d82e780
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Showing 27 changed files with 598 additions and 416 deletions.
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
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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