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Introduce const Trait (always-const trait bounds)

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This commit is contained in:
León Orell Valerian Liehr
2023-12-18 17:55:55 +01:00
parent 2fe50cd72c
commit 3eb48a35c8
69 changed files with 505 additions and 223 deletions
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86
compiler/rustc_ast_lowering/src/lib.rs
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@@ -1324,7 +1324,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
span: t.span,
},
itctx,
ast::Const::No,
ast::BoundConstness::Never,
);
let bounds = this.arena.alloc_from_iter([bound]);
let lifetime_bound = this.elided_dyn_bound(t.span);
@@ -1435,7 +1435,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
polarity: BoundPolarity::Positive | BoundPolarity::Negative(_),
constness,
},
) => Some(this.lower_poly_trait_ref(ty, itctx, (*constness).into())),
) => Some(this.lower_poly_trait_ref(ty, itctx, *constness)),
// We can safely ignore constness here, since AST validation
// will take care of invalid modifier combinations.
GenericBound::Trait(
@@ -2174,7 +2174,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
fn lower_trait_ref(
&mut self,
constness: ast::Const,
constness: ast::BoundConstness,
p: &TraitRef,
itctx: &ImplTraitContext,
) -> hir::TraitRef<'hir> {
@@ -2197,7 +2197,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
&mut self,
p: &PolyTraitRef,
itctx: &ImplTraitContext,
constness: ast::Const,
constness: ast::BoundConstness,
) -> hir::PolyTraitRef<'hir> {
let bound_generic_params =
self.lower_lifetime_binder(p.trait_ref.ref_id, &p.bound_generic_params);
@@ -2322,9 +2322,11 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
&mut self,
modifiers: TraitBoundModifiers,
) -> hir::TraitBoundModifier {
// Invalid modifier combinations will cause an error during AST validation.
// Arbitrarily pick a placeholder for them to make compilation proceed.
match (modifiers.constness, modifiers.polarity) {
(BoundConstness::Never, BoundPolarity::Positive) => hir::TraitBoundModifier::None,
(BoundConstness::Never, BoundPolarity::Maybe(_)) => hir::TraitBoundModifier::Maybe,
(_, BoundPolarity::Maybe(_)) => hir::TraitBoundModifier::Maybe,
(BoundConstness::Never, BoundPolarity::Negative(_)) => {
if self.tcx.features().negative_bounds {
hir::TraitBoundModifier::Negative
@@ -2332,15 +2334,8 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
hir::TraitBoundModifier::None
}
}
(BoundConstness::Maybe(_), BoundPolarity::Positive) => {
hir::TraitBoundModifier::MaybeConst
}
// Invalid modifier combinations will cause an error during AST validation.
// Arbitrarily pick a placeholder for compilation to proceed.
(BoundConstness::Maybe(_), BoundPolarity::Maybe(_)) => hir::TraitBoundModifier::Maybe,
(BoundConstness::Maybe(_), BoundPolarity::Negative(_)) => {
hir::TraitBoundModifier::MaybeConst
}
(BoundConstness::Always(_), _) => hir::TraitBoundModifier::Const,
(BoundConstness::Maybe(_), _) => hir::TraitBoundModifier::MaybeConst,
}
}
@@ -2558,45 +2553,62 @@ struct GenericArgsCtor<'hir> {
}
impl<'hir> GenericArgsCtor<'hir> {
fn push_constness(&mut self, lcx: &mut LoweringContext<'_, 'hir>, constness: ast::Const) {
fn push_constness(
&mut self,
lcx: &mut LoweringContext<'_, 'hir>,
constness: ast::BoundConstness,
) {
if !lcx.tcx.features().effects {
return;
}
// if bound is non-const, don't add host effect param
let ast::Const::Yes(span) = constness else { return };
let (span, body) = match constness {
BoundConstness::Never => return,
BoundConstness::Always(span) => {
let span = lcx.lower_span(span);
let span = lcx.lower_span(span);
let body = hir::ExprKind::Lit(
lcx.arena.alloc(hir::Lit { node: LitKind::Bool(false), span }),
);
let id = lcx.next_node_id();
let hir_id = lcx.next_id();
(span, body)
}
BoundConstness::Maybe(span) => {
let span = lcx.lower_span(span);
let Some(host_param_id) = lcx.host_param_id else {
lcx.dcx().span_delayed_bug(
span,
"no host param id for call in const yet no errors reported",
);
return;
};
let Some(host_param_id) = lcx.host_param_id else {
lcx.dcx().span_delayed_bug(
span,
"no host param id for call in const yet no errors reported",
);
return;
};
let body = lcx.lower_body(|lcx| {
(&[], {
let hir_id = lcx.next_id();
let res = Res::Def(DefKind::ConstParam, host_param_id.to_def_id());
let expr_kind = hir::ExprKind::Path(hir::QPath::Resolved(
let body = hir::ExprKind::Path(hir::QPath::Resolved(
None,
lcx.arena.alloc(hir::Path {
span,
res,
segments: arena_vec![lcx; hir::PathSegment::new(Ident {
name: sym::host,
span,
}, hir_id, res)],
segments: arena_vec![
lcx;
hir::PathSegment::new(
Ident { name: sym::host, span },
hir_id,
res
)
],
}),
));
lcx.expr(span, expr_kind)
})
});
(span, body)
}
};
let body = lcx.lower_body(|lcx| (&[], lcx.expr(span, body)));
let id = lcx.next_node_id();
let hir_id = lcx.next_id();
let def_id = lcx.create_def(
lcx.current_hir_id_owner.def_id,