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Remove #[rustc_host], use internal desugaring #118605

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Dec 6, 2023
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Remove #[rustc_host], use internal desugaring #118605

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55 changes: 16 additions & 39 deletions compiler/rustc_ast_lowering/src/item.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -561,11 +561,10 @@ impl<'hir> LoweringContext<'_, 'hir> {
.params
.iter()
.find(|param| {
parent_hir
.attrs
.get(param.hir_id.local_id)
.iter()
.any(|attr| attr.has_name(sym::rustc_host))
matches!(
param.kind,
hir::GenericParamKind::Const { is_host_effect: true, .. }
)
})
.map(|param| param.def_id);
}
Expand Down Expand Up @@ -1352,27 +1351,17 @@ impl<'hir> LoweringContext<'_, 'hir> {
let host_param_parts = if let Const::Yes(span) = constness
&& self.tcx.features().effects
{
if let Some(param) =
generics.params.iter().find(|x| x.attrs.iter().any(|x| x.has_name(sym::rustc_host)))
{
// user has manually specified a `rustc_host` param, in this case, we set
// the param id so that lowering logic can use that. But we don't create
// another host param, so this gives `None`.
self.host_param_id = Some(self.local_def_id(param.id));
None
} else {
let param_node_id = self.next_node_id();
let hir_id = self.next_id();
let def_id = self.create_def(
self.local_def_id(parent_node_id),
param_node_id,
sym::host,
DefKind::ConstParam,
span,
);
self.host_param_id = Some(def_id);
Some((span, hir_id, def_id))
}
let param_node_id = self.next_node_id();
let hir_id = self.next_id();
let def_id = self.create_def(
self.local_def_id(parent_node_id),
param_node_id,
sym::host,
DefKind::ConstParam,
span,
);
self.host_param_id = Some(def_id);
Some((span, hir_id, def_id))
} else {
None
};
Expand Down Expand Up @@ -1436,19 +1425,6 @@ impl<'hir> LoweringContext<'_, 'hir> {
self.children.push((def_id, hir::MaybeOwner::NonOwner(hir_id)));
self.children.push((anon_const, hir::MaybeOwner::NonOwner(const_id)));

let attr_id = self.tcx.sess.parse_sess.attr_id_generator.mk_attr_id();

let attrs = self.arena.alloc_from_iter([Attribute {
kind: AttrKind::Normal(P(NormalAttr::from_ident(Ident::new(
sym::rustc_host,
span,
)))),
span,
id: attr_id,
style: AttrStyle::Outer,
}]);
self.attrs.insert(hir_id.local_id, attrs);

let const_body = self.lower_body(|this| {
(
&[],
Expand Down Expand Up @@ -1490,6 +1466,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
hir_id: const_id,
body: const_body,
}),
is_host_effect: true,
},
colon_span: None,
pure_wrt_drop: false,
Expand Down
12 changes: 2 additions & 10 deletions compiler/rustc_ast_lowering/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -2108,7 +2108,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
let default = default.as_ref().map(|def| self.lower_anon_const(def));
(
hir::ParamName::Plain(self.lower_ident(param.ident)),
hir::GenericParamKind::Const { ty, default },
hir::GenericParamKind::Const { ty, default, is_host_effect: false },
)
}
}
Expand Down Expand Up @@ -2536,22 +2536,14 @@ impl<'hir> GenericArgsCtor<'hir> {
})
});

let attr_id = lcx.tcx.sess.parse_sess.attr_id_generator.mk_attr_id();
let attr = lcx.arena.alloc(Attribute {
kind: AttrKind::Normal(P(NormalAttr::from_ident(Ident::new(sym::rustc_host, span)))),
span,
id: attr_id,
style: AttrStyle::Outer,
});
lcx.attrs.insert(hir_id.local_id, std::slice::from_ref(attr));

let def_id = lcx.create_def(
lcx.current_hir_id_owner.def_id,
id,
kw::Empty,
DefKind::AnonConst,
span,
);

lcx.children.push((def_id, hir::MaybeOwner::NonOwner(hir_id)));
self.args.push(hir::GenericArg::Const(hir::ConstArg {
value: hir::AnonConst { def_id, hir_id, body },
Expand Down
6 changes: 0 additions & 6 deletions compiler/rustc_feature/src/builtin_attrs.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -719,12 +719,6 @@ pub const BUILTIN_ATTRIBUTES: &[BuiltinAttribute] = &[
and it is only intended to be used in `alloc`."
),

rustc_attr!(
rustc_host, AttributeType::Normal, template!(Word), ErrorFollowing,
"#[rustc_host] annotates const generic parameters as the `host` effect param, \
and it is only intended for internal use and as a desugaring."
),

BuiltinAttribute {
name: sym::rustc_diagnostic_item,
// FIXME: This can be `true` once we always use `tcx.is_diagnostic_item`.
Expand Down
1 change: 1 addition & 0 deletions compiler/rustc_hir/src/hir.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -487,6 +487,7 @@ pub enum GenericParamKind<'hir> {
ty: &'hir Ty<'hir>,
/// Optional default value for the const generic param
default: Option<AnonConst>,
is_host_effect: bool,
},
}

Expand Down
2 changes: 1 addition & 1 deletion compiler/rustc_hir/src/intravisit.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -874,7 +874,7 @@ pub fn walk_generic_param<'v, V: Visitor<'v>>(visitor: &mut V, param: &'v Generi
match param.kind {
GenericParamKind::Lifetime { .. } => {}
GenericParamKind::Type { ref default, .. } => walk_list!(visitor, visit_ty, default),
GenericParamKind::Const { ref ty, ref default } => {
GenericParamKind::Const { ref ty, ref default, is_host_effect: _ } => {
visitor.visit_ty(ty);
if let Some(ref default) = default {
visitor.visit_const_param_default(param.hir_id, default);
Expand Down
2 changes: 1 addition & 1 deletion compiler/rustc_hir_analysis/src/check/wfcheck.rs
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Expand Up @@ -859,7 +859,7 @@ fn check_param_wf(tcx: TyCtxt<'_>, param: &hir::GenericParam<'_>) -> Result<(),
hir::GenericParamKind::Lifetime { .. } | hir::GenericParamKind::Type { .. } => Ok(()),

// Const parameters are well formed if their type is structural match.
hir::GenericParamKind::Const { ty: hir_ty, default: _ } => {
hir::GenericParamKind::Const { ty: hir_ty, default: _, is_host_effect: _ } => {
let ty = tcx.type_of(param.def_id).instantiate_identity();

if tcx.features().adt_const_params {
Expand Down
2 changes: 1 addition & 1 deletion compiler/rustc_hir_analysis/src/collect.rs
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Expand Up @@ -1383,7 +1383,7 @@ fn impl_trait_ref(
let last_segment = path_segments.len() - 1;
let mut args = *path_segments[last_segment].args();
let last_arg = args.args.len() - 1;
assert!(matches!(args.args[last_arg], hir::GenericArg::Const(anon_const) if tcx.has_attr(anon_const.value.def_id, sym::rustc_host)));
assert!(matches!(args.args[last_arg], hir::GenericArg::Const(anon_const) if anon_const.is_desugared_from_effects));
args.args = &args.args[..args.args.len() - 1];
path_segments[last_segment].args = Some(&args);
let path = hir::Path {
Expand Down
16 changes: 7 additions & 9 deletions compiler/rustc_hir_analysis/src/collect/generics_of.rs
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Expand Up @@ -9,7 +9,7 @@ use rustc_hir::def_id::LocalDefId;
use rustc_middle::ty::{self, TyCtxt};
use rustc_session::lint;
use rustc_span::symbol::{kw, Symbol};
use rustc_span::{sym, Span};
use rustc_span::Span;

pub(super) fn generics_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Generics {
use rustc_hir::*;
Expand Down Expand Up @@ -298,13 +298,11 @@ pub(super) fn generics_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Generics {
kind,
})
}
GenericParamKind::Const { default, .. } => {
let is_host_param = tcx.has_attr(param.def_id, sym::rustc_host);

GenericParamKind::Const { ty: _, default, is_host_effect } => {
if !matches!(allow_defaults, Defaults::Allowed)
&& default.is_some()
// `rustc_host` effect params are allowed to have defaults.
&& !is_host_param
// `host` effect params are allowed to have defaults.
&& !is_host_effect
{
tcx.sess.span_err(
param.span,
Expand All @@ -315,7 +313,7 @@ pub(super) fn generics_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Generics {

let index = next_index();

if is_host_param {
if is_host_effect {
if let Some(idx) = host_effect_index {
bug!("parent also has host effect param? index: {idx}, def: {def_id:?}");
}
Expand All @@ -330,7 +328,7 @@ pub(super) fn generics_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Generics {
pure_wrt_drop: param.pure_wrt_drop,
kind: ty::GenericParamDefKind::Const {
has_default: default.is_some(),
is_host_effect: is_host_param,
is_host_effect,
},
})
}
Expand Down Expand Up @@ -489,7 +487,7 @@ struct AnonConstInParamTyDetector {

impl<'v> Visitor<'v> for AnonConstInParamTyDetector {
fn visit_generic_param(&mut self, p: &'v hir::GenericParam<'v>) {
if let GenericParamKind::Const { ty, default: _ } = p.kind {
if let GenericParamKind::Const { ty, default: _, is_host_effect: _ } = p.kind {
let prev = self.in_param_ty;
self.in_param_ty = true;
self.visit_ty(ty);
Expand Down
2 changes: 1 addition & 1 deletion compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -992,7 +992,7 @@ impl<'a, 'tcx> Visitor<'tcx> for BoundVarContext<'a, 'tcx> {
self.visit_ty(ty);
}
}
GenericParamKind::Const { ty, default } => {
GenericParamKind::Const { ty, default, is_host_effect: _ } => {
self.visit_ty(ty);
if let Some(default) = default {
self.visit_body(self.tcx.hir().body(default.body));
Expand Down
2 changes: 1 addition & 1 deletion compiler/rustc_hir_pretty/src/lib.rs
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Expand Up @@ -2126,7 +2126,7 @@ impl<'a> State<'a> {
self.print_type(default);
}
}
GenericParamKind::Const { ty, ref default } => {
GenericParamKind::Const { ty, ref default, is_host_effect: _ } => {
self.word_space(":");
self.print_type(ty);
if let Some(default) = default {
Expand Down
6 changes: 3 additions & 3 deletions compiler/rustc_lint/src/nonstandard_style.rs
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Expand Up @@ -534,9 +534,9 @@ impl<'tcx> LateLintPass<'tcx> for NonUpperCaseGlobals {
}

fn check_generic_param(&mut self, cx: &LateContext<'_>, param: &hir::GenericParam<'_>) {
if let GenericParamKind::Const { .. } = param.kind {
// `rustc_host` params are explicitly allowed to be lowercase.
if cx.tcx.has_attr(param.def_id, sym::rustc_host) {
if let GenericParamKind::Const { is_host_effect, .. } = param.kind {
// `host` params are explicitly allowed to be lowercase.
if is_host_effect {
return;
}
NonUpperCaseGlobals::check_upper_case(cx, "const parameter", &param.name.ident());
Expand Down
2 changes: 1 addition & 1 deletion compiler/rustc_middle/src/ty/context.rs
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Expand Up @@ -2186,7 +2186,7 @@ impl<'tcx> TyCtxt<'tcx> {
hir::Node::Item(hir::Item {
kind: hir::ItemKind::Impl(hir::Impl { generics, .. }),
..
}) if generics.params.iter().any(|p| self.has_attr(p.def_id, sym::rustc_host))
}) if generics.params.iter().any(|p| matches!(p.kind, hir::GenericParamKind::Const { is_host_effect: true, .. }))
)
}

Expand Down
9 changes: 7 additions & 2 deletions compiler/rustc_passes/src/lang_items.rs
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Expand Up @@ -21,7 +21,7 @@ use rustc_hir::{LangItem, LanguageItems, Target};
use rustc_middle::ty::TyCtxt;
use rustc_session::cstore::ExternCrate;
use rustc_span::symbol::kw::Empty;
use rustc_span::{sym, Span};
use rustc_span::Span;

use rustc_middle::query::Providers;

Expand Down Expand Up @@ -162,7 +162,12 @@ impl<'tcx> LanguageItemCollector<'tcx> {
generics
.params
.iter()
.filter(|p| !self.tcx.has_attr(p.def_id, sym::rustc_host))
.filter(|p| {
!matches!(
p.kind,
hir::GenericParamKind::Const { is_host_effect: true, .. }
)
})
.count(),
generics.span,
),
Expand Down
1 change: 0 additions & 1 deletion compiler/rustc_span/src/symbol.rs
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Expand Up @@ -1393,7 +1393,6 @@ symbols! {
rustc_expected_cgu_reuse,
rustc_has_incoherent_inherent_impls,
rustc_hidden_type_of_opaques,
rustc_host,
rustc_if_this_changed,
rustc_inherit_overflow_checks,
rustc_insignificant_dtor,
Expand Down
13 changes: 7 additions & 6 deletions src/librustdoc/clean/mod.rs
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Expand Up @@ -595,13 +595,13 @@ fn clean_generic_param<'tcx>(
},
)
}
hir::GenericParamKind::Const { ty, default } => (
hir::GenericParamKind::Const { ty, default, is_host_effect } => (
param.name.ident().name,
GenericParamDefKind::Const {
ty: Box::new(clean_ty(ty, cx)),
default: default
.map(|ct| Box::new(ty::Const::from_anon_const(cx.tcx, ct.def_id).to_string())),
is_host_effect: cx.tcx.has_attr(param.def_id, sym::rustc_host),
is_host_effect,
},
),
};
Expand Down Expand Up @@ -2536,11 +2536,12 @@ fn clean_generic_args<'tcx>(
}
hir::GenericArg::Lifetime(_) => GenericArg::Lifetime(Lifetime::elided()),
hir::GenericArg::Type(ty) => GenericArg::Type(clean_ty(ty, cx)),
// Checking for `#[rustc_host]` on the `AnonConst` not only accounts for the case
// Checking for `is_desugared_from_effects` on the `AnonConst` not only accounts for the case
// where the argument is `host` but for all possible cases (e.g., `true`, `false`).
hir::GenericArg::Const(ct)
if cx.tcx.has_attr(ct.value.def_id, sym::rustc_host) =>
{
hir::GenericArg::Const(hir::ConstArg {
is_desugared_from_effects: true,
..
}) => {
return None;
}
hir::GenericArg::Const(ct) => GenericArg::Const(Box::new(clean_const(ct, cx))),
Expand Down
13 changes: 7 additions & 6 deletions tests/ui/rfcs/rfc-2632-const-trait-impl/effects/helloworld.rs
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Expand Up @@ -3,15 +3,16 @@
// gate-test-effects
// ^ effects doesn't have a gate so we will trick tidy into thinking this is a gate test

#![feature(const_trait_impl, effects, rustc_attrs)]
#![feature(const_trait_impl, effects, core_intrinsics, const_eval_select)]

// ensure we are passing in the correct host effect in always const contexts.

pub const fn hmm<T, #[rustc_host] const host: bool = true>() -> usize {
if host {
1
} else {
0
pub const fn hmm<T>() -> usize {
// FIXME(const_trait_impl): maybe we should have a way to refer to the (hidden) effect param
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could be a const intrinsic that just looks like this code does!

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Yeah, might be nice to base const_eval_select and others on a single const function that returns a bool in the future.

fn one() -> usize { 1 }
const fn zero() -> usize { 0 }
unsafe {
std::intrinsics::const_eval_select((), zero, one)
}
}

Expand Down
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