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auto-impl: parser support #149335

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46 changes: 43 additions & 3 deletions compiler/rustc_ast/src/ast.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -3635,6 +3635,8 @@ impl Item {
| ItemKind::DelegationMac(_)
| ItemKind::MacroDef(..) => None,
ItemKind::Static(_) => None,
ItemKind::AutoImpl(ai) => Some(&ai.generics),
ItemKind::ExternImpl(ei) => Some(&ei.generics),
ItemKind::Const(i) => Some(&i.generics),
ItemKind::Fn(i) => Some(&i.generics),
ItemKind::TyAlias(i) => Some(&i.generics),
Expand Down Expand Up @@ -3778,6 +3780,20 @@ pub struct Impl {
pub items: ThinVec<Box<AssocItem>>,
}

#[derive(Clone, Encodable, Decodable, Debug)]
pub struct AutoImpl {
pub generics: Generics,
pub constness: Const,
pub of_trait: Box<TraitImplHeader>,
pub items: ThinVec<Box<AssocItem>>,
}

#[derive(Clone, Encodable, Decodable, Debug)]
pub struct ExternImpl {
pub generics: Generics,
pub of_trait: Box<TraitImplHeader>,
}

#[derive(Clone, Encodable, Decodable, Debug)]
pub struct TraitImplHeader {
pub defaultness: Defaultness,
Expand Down Expand Up @@ -3958,6 +3974,10 @@ pub enum ItemKind {
///
/// E.g., `impl<A> Foo<A> { .. }` or `impl<A> Trait for Foo<A> { .. }`.
Impl(Impl),
/// An `auto impl` implementation, such as a supertrait `auto impl`.
AutoImpl(Box<AutoImpl>),
/// An `extern impl` directive
ExternImpl(Box<ExternImpl>),
/// A macro invocation.
///
/// E.g., `foo!(..)`.
Expand Down Expand Up @@ -3994,6 +4014,8 @@ impl ItemKind {
| ItemKind::ForeignMod(_)
| ItemKind::GlobalAsm(_)
| ItemKind::Impl(_)
| ItemKind::AutoImpl(_)
| ItemKind::ExternImpl(_)
| ItemKind::MacCall(_)
| ItemKind::DelegationMac(_) => None,
}
Expand All @@ -4006,7 +4028,13 @@ impl ItemKind {
Use(..) | Static(..) | Const(..) | Fn(..) | Mod(..) | GlobalAsm(..) | TyAlias(..)
| Struct(..) | Union(..) | Trait(..) | TraitAlias(..) | MacroDef(..)
| Delegation(..) | DelegationMac(..) => "a",
ExternCrate(..) | ForeignMod(..) | MacCall(..) | Enum(..) | Impl { .. } => "an",
ExternCrate(..)
| ForeignMod(..)
| MacCall(..)
| Enum(..)
| Impl { .. }
| AutoImpl(..)
| ExternImpl(..) => "an",
}
}

Expand All @@ -4029,6 +4057,8 @@ impl ItemKind {
ItemKind::MacCall(..) => "item macro invocation",
ItemKind::MacroDef(..) => "macro definition",
ItemKind::Impl { .. } => "implementation",
ItemKind::AutoImpl { .. } => "`auto` implementation",
ItemKind::ExternImpl { .. } => "`extern` implementation",
ItemKind::Delegation(..) => "delegated function",
ItemKind::DelegationMac(..) => "delegation",
}
Expand Down Expand Up @@ -4076,6 +4106,8 @@ pub enum AssocItemKind {
Delegation(Box<Delegation>),
/// An associated list or glob delegation item.
DelegationMac(Box<DelegationMac>),
/// An `auto impl` item
AutoImpl(Box<AutoImpl>),
}

impl AssocItemKind {
Expand All @@ -4086,15 +4118,21 @@ impl AssocItemKind {
| AssocItemKind::Type(box TyAlias { ident, .. })
| AssocItemKind::Delegation(box Delegation { ident, .. }) => Some(ident),

AssocItemKind::MacCall(_) | AssocItemKind::DelegationMac(_) => None,
AssocItemKind::MacCall(_)
| AssocItemKind::DelegationMac(_)
| AssocItemKind::AutoImpl(_) => None,
}
}

pub fn defaultness(&self) -> Defaultness {
match *self {
Self::Const(box ConstItem { defaultness, .. })
| Self::Fn(box Fn { defaultness, .. })
| Self::Type(box TyAlias { defaultness, .. }) => defaultness,
| Self::Type(box TyAlias { defaultness, .. })
| Self::AutoImpl(box AutoImpl {
of_trait: box TraitImplHeader { defaultness, .. },
..
}) => defaultness,
Self::MacCall(..) | Self::Delegation(..) | Self::DelegationMac(..) => {
Defaultness::Final
}
Expand All @@ -4111,6 +4149,7 @@ impl From<AssocItemKind> for ItemKind {
AssocItemKind::MacCall(a) => ItemKind::MacCall(a),
AssocItemKind::Delegation(delegation) => ItemKind::Delegation(delegation),
AssocItemKind::DelegationMac(delegation) => ItemKind::DelegationMac(delegation),
AssocItemKind::AutoImpl(ai) => ItemKind::AutoImpl(ai),
}
}
}
Expand All @@ -4126,6 +4165,7 @@ impl TryFrom<ItemKind> for AssocItemKind {
ItemKind::MacCall(a) => AssocItemKind::MacCall(a),
ItemKind::Delegation(d) => AssocItemKind::Delegation(d),
ItemKind::DelegationMac(d) => AssocItemKind::DelegationMac(d),
ItemKind::AutoImpl(ai) => AssocItemKind::AutoImpl(ai),
_ => return Err(item_kind),
})
}
Expand Down
29 changes: 29 additions & 0 deletions compiler/rustc_ast/src/visit.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -557,6 +557,8 @@ macro_rules! common_visitor_and_walkers {
//fn visit_assoc_item(AssocItem, _ctxt: AssocCtxt);
fn visit_assoc_item_constraint(AssocItemConstraint);
fn visit_attribute(Attribute);
fn visit_auto_impl(AutoImpl);
fn visit_extern_impl(ExternImpl);
fn visit_block(Block);
//fn visit_nested_use_tree((UseTree, NodeId));
fn visit_capture_by(CaptureBy);
Expand Down Expand Up @@ -842,6 +844,10 @@ macro_rules! common_visitor_and_walkers {
visit_visitable!($($mut)? vis, ident, generics, variant_data),
ItemKind::Impl(impl_) =>
visit_visitable!($($mut)? vis, impl_),
ItemKind::AutoImpl(auto_impl_) =>
visit_visitable!($($mut)? vis, auto_impl_),
ItemKind::ExternImpl(extern_impl_) =>
visit_visitable!($($mut)? vis, extern_impl_),
ItemKind::Trait(trait_) =>
visit_visitable!($($mut)? vis, trait_),
ItemKind::TraitAlias(box TraitAlias { constness, ident, generics, bounds}) => {
Expand Down Expand Up @@ -887,6 +893,8 @@ macro_rules! common_visitor_and_walkers {
visit_visitable!($($mut)? vis, delegation),
AssocItemKind::DelegationMac(dm) =>
visit_visitable!($($mut)? vis, dm),
AssocItemKind::AutoImpl(ai) =>
visit_visitable!($($mut)? vis, ai),
}
V::Result::output()
}
Expand Down Expand Up @@ -951,6 +959,27 @@ macro_rules! common_visitor_and_walkers {
V::Result::output()
});

impl_walkable!(|&$($mut)? $($lt)? self: AutoImpl, vis: &mut V| {
let AutoImpl { generics, of_trait, items, constness } = self;
let TraitImplHeader { defaultness, safety, polarity, trait_ref } = &$($mut)? **of_trait;

try_visit!(vis.visit_generics(generics));
visit_visitable!($($mut)? vis, defaultness, safety, constness, polarity, trait_ref);

visit_visitable_with!($($mut)? vis, items, AssocCtxt::Impl { of_trait: true });
V::Result::output()
});

impl_walkable!(|&$($mut)? $($lt)? self: ExternImpl, vis: &mut V| {
let ExternImpl { generics, of_trait } = self;
let TraitImplHeader { defaultness, safety, polarity, trait_ref } = &$($mut)? **of_trait;

try_visit!(vis.visit_generics(generics));
visit_visitable!($($mut)? vis, defaultness, safety, polarity, trait_ref);

V::Result::output()
});

// Special case to call `visit_method_receiver_expr`.
impl_walkable!(|&$($mut)? $($lt)? self: MethodCall, vis: &mut V| {
let MethodCall { seg, receiver, args, span } = self;
Expand Down
68 changes: 67 additions & 1 deletion compiler/rustc_ast_lowering/src/item.rs
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Original file line number Diff line number Diff line change
@@ -1,7 +1,7 @@
use rustc_abi::ExternAbi;
use rustc_ast::visit::AssocCtxt;
use rustc_ast::*;
use rustc_errors::{E0570, ErrorGuaranteed, struct_span_code_err};
use rustc_errors::{E0570, ErrorGuaranteed, FatalError, struct_span_code_err};
use rustc_hir::attrs::{AttributeKind, EiiImplResolution};
use rustc_hir::def::{DefKind, PerNS, Res};
use rustc_hir::def_id::{CRATE_DEF_ID, LocalDefId};
Expand All @@ -11,6 +11,7 @@ use rustc_hir::{
use rustc_index::{IndexSlice, IndexVec};
use rustc_middle::span_bug;
use rustc_middle::ty::{ResolverAstLowering, TyCtxt};
use rustc_session::parse::feature_err;
use rustc_span::def_id::DefId;
use rustc_span::edit_distance::find_best_match_for_name;
use rustc_span::{DUMMY_SP, DesugaringKind, Ident, Span, Symbol, kw, sym};
Expand Down Expand Up @@ -215,6 +216,8 @@ impl<'hir> LoweringContext<'_, 'hir> {
| ItemKind::Trait(..)
| ItemKind::TraitAlias(..)
| ItemKind::Impl(..)
| ItemKind::AutoImpl(..)
| ItemKind::ExternImpl(..)
| ItemKind::MacCall(..)
| ItemKind::MacroDef(..)
| ItemKind::Delegation(..)
Expand Down Expand Up @@ -489,6 +492,16 @@ impl<'hir> LoweringContext<'_, 'hir> {
constness,
})
}
ItemKind::AutoImpl(..) | ItemKind::ExternImpl(..) => {
feature_err(
self.tcx.sess,
sym::supertrait_auto_impl,
span,
"feature is under construction",
)
.emit();
FatalError.raise()
}
ItemKind::Trait(box Trait {
constness,
is_auto,
Expand Down Expand Up @@ -1009,6 +1022,49 @@ impl<'hir> LoweringContext<'_, 'hir> {
true,
)
}
AssocItemKind::AutoImpl(ai) => {
let tcx = self.tcx;
if !tcx.features().supertrait_auto_impl() {
feature_err(
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@petrochenkov petrochenkov Dec 3, 2025

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Feature gating once in the parser should be enough.

&tcx.sess,
sym::supertrait_auto_impl,
i.span,
"feature is under construction",
)
.emit();
FatalError.raise();
}
let generics = tcx.arena.alloc(hir::Generics {
has_where_clause_predicates: false,
params: &[],
predicates: &[],
where_clause_span: DUMMY_SP,
span: DUMMY_SP,
});
(
Ident::dummy(),
&*generics,
hir::TraitItemKind::AutoImpl(
tcx.arena.alloc(self.lower_poly_trait_ref_inner(
&ai.generics.params,
&TraitBoundModifiers {
constness: BoundConstness::Never,
asyncness: BoundAsyncness::Normal,
polarity: match ai.of_trait.polarity {
ImplPolarity::Positive => BoundPolarity::Positive,
ImplPolarity::Negative(span) => BoundPolarity::Negative(span),
},
},
&ai.of_trait.trait_ref,
ai.of_trait.trait_ref.path.span,
RelaxedBoundPolicy::Forbidden(RelaxedBoundForbiddenReason::SuperTrait),
ImplTraitContext::Disallowed(ImplTraitPosition::Generic),
)),
&[],
),
false,
)
}
AssocItemKind::Type(box TyAlias {
ident,
generics,
Expand Down Expand Up @@ -1214,6 +1270,16 @@ impl<'hir> LoweringContext<'_, 'hir> {
),
)
}
AssocItemKind::AutoImpl(_) => {
feature_err(
&self.tcx.sess,
sym::supertrait_auto_impl,
i.span,
"feature is under construction",
)
.emit();
FatalError.raise();
}
AssocItemKind::Delegation(box delegation) => {
let delegation_results = self.lower_delegation(delegation, i.id);
(
Expand Down
24 changes: 22 additions & 2 deletions compiler/rustc_ast_lowering/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -2110,21 +2110,41 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
PolyTraitRef { bound_generic_params, modifiers, trait_ref, span, parens: _ }: &PolyTraitRef,
rbp: RelaxedBoundPolicy<'_>,
itctx: ImplTraitContext,
) -> hir::PolyTraitRef<'hir> {
self.lower_poly_trait_ref_inner(
bound_generic_params,
modifiers,
trait_ref,
*span,
rbp,
itctx,
)
}

#[instrument(level = "debug", skip(self))]
fn lower_poly_trait_ref_inner(
&mut self,
bound_generic_params: &[GenericParam],
modifiers: &TraitBoundModifiers,
trait_ref: &TraitRef,
span: Span,
rbp: RelaxedBoundPolicy<'_>,
itctx: ImplTraitContext,
) -> hir::PolyTraitRef<'hir> {
let bound_generic_params =
self.lower_lifetime_binder(trait_ref.ref_id, bound_generic_params);
let trait_ref = self.lower_trait_ref(*modifiers, trait_ref, itctx);
let modifiers = self.lower_trait_bound_modifiers(*modifiers);

if let ast::BoundPolarity::Maybe(_) = modifiers.polarity {
self.validate_relaxed_bound(trait_ref, *span, rbp);
self.validate_relaxed_bound(trait_ref, span, rbp);
}

hir::PolyTraitRef {
bound_generic_params,
modifiers,
trait_ref,
span: self.lower_span(*span),
span: self.lower_span(span),
}
}

Expand Down
3 changes: 3 additions & 0 deletions compiler/rustc_ast_passes/messages.ftl
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Original file line number Diff line number Diff line change
Expand Up @@ -50,6 +50,9 @@ ast_passes_auto_generic = auto traits cannot have generic parameters
.label = auto trait cannot have generic parameters
.suggestion = remove the parameters

ast_passes_auto_impl_outside_trait_or_impl_trait =
`auto impl` is outside a `trait` block or trait-`impl` block

ast_passes_auto_items = auto traits cannot have associated items
.label = {ast_passes_auto_items}
.suggestion = remove the associated items
Expand Down
5 changes: 5 additions & 0 deletions compiler/rustc_ast_passes/src/ast_validation.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1420,6 +1420,11 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
}
visit::walk_item(self, item);
}

ItemKind::AutoImpl(..) => {
self.dcx().emit_err(errors::AutoImplOutsideTraitOrImplTrait { span: item.span });
}

_ => visit::walk_item(self, item),
}

Expand Down
7 changes: 7 additions & 0 deletions compiler/rustc_ast_passes/src/errors.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -491,6 +491,13 @@ pub(crate) struct NestedImplTrait {
pub inner: Span,
}

#[derive(Diagnostic)]
#[diag(ast_passes_auto_impl_outside_trait_or_impl_trait)]
pub(crate) struct AutoImplOutsideTraitOrImplTrait {
#[primary_span]
pub(crate) span: Span,
}

#[derive(Diagnostic)]
#[diag(ast_passes_at_least_one_trait)]
pub(crate) struct AtLeastOneTrait {
Expand Down
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