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Auto merge of #120639 - fee1-dead-contrib:new-effects-desugaring, r=o…
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…li-obk

Implement new effects desugaring

cc `@rust-lang/project-const-traits.` Will write down notes once I have finished.

* [x] See if we want `T: Tr` to desugar into `T: Tr, T::Effects: Compat<true>`
* [x] Fix ICEs on `type Assoc: ~const Tr` and `type Assoc<T: ~const Tr>`
* [ ] add types and traits to minicore test
* [ ] update rustc-dev-guide

Fixes #119717
Fixes #123664
Fixes #124857
Fixes #126148
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@bors
bors committed Jun 29, 2024
2 parents d1b7355 + 65a0bee commit ba1d7f4
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Showing 175 changed files with 2,225 additions and 1,567 deletions.
1 change: 0 additions & 1 deletion compiler/rustc_ast_lowering/src/expr.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -103,7 +103,6 @@ impl<'hir> LoweringContext<'_, 'hir> {
ParamMode::Optional,
ParenthesizedGenericArgs::Err,
ImplTraitContext::Disallowed(ImplTraitPosition::Path),
None,
// Method calls can't have bound modifiers
None,
));
Expand Down
111 changes: 74 additions & 37 deletions compiler/rustc_ast_lowering/src/item.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -56,7 +56,7 @@ impl<'a, 'hir> ItemLowerer<'a, 'hir> {
owner: NodeId,
f: impl FnOnce(&mut LoweringContext<'_, 'hir>) -> hir::OwnerNode<'hir>,
) {
let mut lctx = LoweringContext::new(self.tcx, self.resolver);
let mut lctx = LoweringContext::new(self.tcx, self.resolver, self.ast_index);
lctx.with_hir_id_owner(owner, |lctx| f(lctx));

for (def_id, info) in lctx.children {
Expand Down Expand Up @@ -190,6 +190,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
let (generics, (ty, body_id)) = self.lower_generics(
generics,
Const::No,
false,
id,
ImplTraitContext::Disallowed(ImplTraitPosition::Generic),
|this| {
Expand Down Expand Up @@ -221,7 +222,7 @@ impl<'hir> LoweringContext<'_, 'hir> {

let itctx = ImplTraitContext::Universal;
let (generics, decl) =
this.lower_generics(generics, header.constness, id, itctx, |this| {
this.lower_generics(generics, header.constness, false, id, itctx, |this| {
this.lower_fn_decl(
decl,
id,
Expand Down Expand Up @@ -265,6 +266,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
let (generics, ty) = self.lower_generics(
&generics,
Const::No,
false,
id,
ImplTraitContext::Disallowed(ImplTraitPosition::Generic),
|this| match ty {
Expand Down Expand Up @@ -293,6 +295,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
let (generics, variants) = self.lower_generics(
generics,
Const::No,
false,
id,
ImplTraitContext::Disallowed(ImplTraitPosition::Generic),
|this| {
Expand All @@ -307,6 +310,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
let (generics, struct_def) = self.lower_generics(
generics,
Const::No,
false,
id,
ImplTraitContext::Disallowed(ImplTraitPosition::Generic),
|this| this.lower_variant_data(hir_id, struct_def),
Expand All @@ -317,6 +321,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
let (generics, vdata) = self.lower_generics(
generics,
Const::No,
false,
id,
ImplTraitContext::Disallowed(ImplTraitPosition::Generic),
|this| this.lower_variant_data(hir_id, vdata),
Expand Down Expand Up @@ -348,12 +353,9 @@ impl<'hir> LoweringContext<'_, 'hir> {
// parent lifetime.
let itctx = ImplTraitContext::Universal;
let (generics, (trait_ref, lowered_ty)) =
self.lower_generics(ast_generics, *constness, id, itctx, |this| {
self.lower_generics(ast_generics, Const::No, false, id, itctx, |this| {
let modifiers = TraitBoundModifiers {
constness: match *constness {
Const::Yes(span) => BoundConstness::Maybe(span),
Const::No => BoundConstness::Never,
},
constness: BoundConstness::Never,
asyncness: BoundAsyncness::Normal,
// we don't use this in bound lowering
polarity: BoundPolarity::Positive,
Expand Down Expand Up @@ -389,6 +391,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
ImplPolarity::Negative(s) => ImplPolarity::Negative(self.lower_span(*s)),
};
hir::ItemKind::Impl(self.arena.alloc(hir::Impl {
constness: self.lower_constness(*constness),
safety: self.lower_safety(*safety, hir::Safety::Safe),
polarity,
defaultness,
Expand All @@ -400,15 +403,10 @@ impl<'hir> LoweringContext<'_, 'hir> {
}))
}
ItemKind::Trait(box Trait { is_auto, safety, generics, bounds, items }) => {
// FIXME(const_trait_impl, effects, fee1-dead) this should be simplified if possible
let constness = attrs
.unwrap_or(&[])
.iter()
.find(|x| x.has_name(sym::const_trait))
.map_or(Const::No, |x| Const::Yes(x.span));
let (generics, (safety, items, bounds)) = self.lower_generics(
generics,
constness,
Const::No,
false,
id,
ImplTraitContext::Disallowed(ImplTraitPosition::Generic),
|this| {
Expand All @@ -429,6 +427,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
let (generics, bounds) = self.lower_generics(
generics,
Const::No,
false,
id,
ImplTraitContext::Disallowed(ImplTraitPosition::Generic),
|this| {
Expand Down Expand Up @@ -609,30 +608,45 @@ impl<'hir> LoweringContext<'_, 'hir> {
// This is used to track which lifetimes have already been defined,
// and which need to be replicated when lowering an async fn.

let generics = match parent_hir.node().expect_item().kind {
let parent_item = parent_hir.node().expect_item();
let constness = match parent_item.kind {
hir::ItemKind::Impl(impl_) => {
self.is_in_trait_impl = impl_.of_trait.is_some();
&impl_.generics
// N.B. the impl should always lower to methods that have `const host: bool` params if the trait
// is const. It doesn't matter whether the `impl` itself is const. Disallowing const fn from
// calling non-const impls are done through associated types.
if let Some(def_id) = impl_.of_trait.and_then(|tr| tr.trait_def_id()) {
if let Some(local_def) = def_id.as_local() {
match &self.ast_index[local_def] {
AstOwner::Item(ast::Item { attrs, .. }) => attrs
.iter()
.find(|attr| attr.has_name(sym::const_trait))
.map_or(Const::No, |attr| Const::Yes(attr.span)),
_ => Const::No,
}
} else {
self.tcx
.get_attr(def_id, sym::const_trait)
.map_or(Const::No, |attr| Const::Yes(attr.span))
}
} else {
Const::No
}
}
hir::ItemKind::Trait(_, _, generics, _, _) => generics,
hir::ItemKind::Trait(_, _, _, _, _) => parent_hir
.attrs
.get(parent_item.hir_id().local_id)
.iter()
.find(|attr| attr.has_name(sym::const_trait))
.map_or(Const::No, |attr| Const::Yes(attr.span)),
kind => {
span_bug!(item.span, "assoc item has unexpected kind of parent: {}", kind.descr())
}
};

if self.tcx.features().effects {
self.host_param_id = generics
.params
.iter()
.find(|param| {
matches!(param.kind, hir::GenericParamKind::Const { is_host_effect: true, .. })
})
.map(|param| param.def_id);
}

match ctxt {
AssocCtxt::Trait => hir::OwnerNode::TraitItem(self.lower_trait_item(item)),
AssocCtxt::Impl => hir::OwnerNode::ImplItem(self.lower_impl_item(item)),
AssocCtxt::Trait => hir::OwnerNode::TraitItem(self.lower_trait_item(item, constness)),
AssocCtxt::Impl => hir::OwnerNode::ImplItem(self.lower_impl_item(item, constness)),
}
}

Expand All @@ -648,7 +662,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
let fdec = &sig.decl;
let itctx = ImplTraitContext::Universal;
let (generics, (fn_dec, fn_args)) =
self.lower_generics(generics, Const::No, i.id, itctx, |this| {
self.lower_generics(generics, Const::No, false, i.id, itctx, |this| {
(
// Disallow `impl Trait` in foreign items.
this.lower_fn_decl(
Expand Down Expand Up @@ -765,7 +779,11 @@ impl<'hir> LoweringContext<'_, 'hir> {
}
}

fn lower_trait_item(&mut self, i: &AssocItem) -> &'hir hir::TraitItem<'hir> {
fn lower_trait_item(
&mut self,
i: &AssocItem,
trait_constness: Const,
) -> &'hir hir::TraitItem<'hir> {
let hir_id = self.lower_node_id(i.id);
self.lower_attrs(hir_id, &i.attrs);
let trait_item_def_id = hir_id.expect_owner();
Expand All @@ -775,6 +793,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
let (generics, kind) = self.lower_generics(
generics,
Const::No,
false,
i.id,
ImplTraitContext::Disallowed(ImplTraitPosition::Generic),
|this| {
Expand All @@ -795,6 +814,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
i.id,
FnDeclKind::Trait,
sig.header.coroutine_kind,
trait_constness,
);
(generics, hir::TraitItemKind::Fn(sig, hir::TraitFn::Required(names)), false)
}
Expand All @@ -813,6 +833,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
i.id,
FnDeclKind::Trait,
sig.header.coroutine_kind,
trait_constness,
);
(generics, hir::TraitItemKind::Fn(sig, hir::TraitFn::Provided(body_id)), true)
}
Expand All @@ -822,6 +843,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
let (generics, kind) = self.lower_generics(
&generics,
Const::No,
false,
i.id,
ImplTraitContext::Disallowed(ImplTraitPosition::Generic),
|this| {
Expand Down Expand Up @@ -894,7 +916,11 @@ impl<'hir> LoweringContext<'_, 'hir> {
self.expr(span, hir::ExprKind::Err(guar))
}

fn lower_impl_item(&mut self, i: &AssocItem) -> &'hir hir::ImplItem<'hir> {
fn lower_impl_item(
&mut self,
i: &AssocItem,
constness_of_trait: Const,
) -> &'hir hir::ImplItem<'hir> {
// Since `default impl` is not yet implemented, this is always true in impls.
let has_value = true;
let (defaultness, _) = self.lower_defaultness(i.kind.defaultness(), has_value);
Expand All @@ -905,6 +931,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
AssocItemKind::Const(box ConstItem { generics, ty, expr, .. }) => self.lower_generics(
generics,
Const::No,
false,
i.id,
ImplTraitContext::Disallowed(ImplTraitPosition::Generic),
|this| {
Expand All @@ -930,6 +957,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
i.id,
if self.is_in_trait_impl { FnDeclKind::Impl } else { FnDeclKind::Inherent },
sig.header.coroutine_kind,
constness_of_trait,
);

(generics, hir::ImplItemKind::Fn(sig, body_id))
Expand All @@ -940,6 +968,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
self.lower_generics(
&generics,
Const::No,
false,
i.id,
ImplTraitContext::Disallowed(ImplTraitPosition::Generic),
|this| match ty {
Expand Down Expand Up @@ -1352,15 +1381,18 @@ impl<'hir> LoweringContext<'_, 'hir> {
id: NodeId,
kind: FnDeclKind,
coroutine_kind: Option<CoroutineKind>,
parent_constness: Const,
) -> (&'hir hir::Generics<'hir>, hir::FnSig<'hir>) {
let header = self.lower_fn_header(sig.header);
// Don't pass along the user-provided constness of trait associated functions; we don't want to
// synthesize a host effect param for them. We reject `const` on them during AST validation.
let constness = if kind == FnDeclKind::Inherent { sig.header.constness } else { Const::No };
let constness =
if kind == FnDeclKind::Inherent { sig.header.constness } else { parent_constness };
let itctx = ImplTraitContext::Universal;
let (generics, decl) = self.lower_generics(generics, constness, id, itctx, |this| {
this.lower_fn_decl(&sig.decl, id, sig.span, kind, coroutine_kind)
});
let (generics, decl) =
self.lower_generics(generics, constness, kind == FnDeclKind::Impl, id, itctx, |this| {
this.lower_fn_decl(&sig.decl, id, sig.span, kind, coroutine_kind)
});
(generics, hir::FnSig { header, decl, span: self.lower_span(sig.span) })
}

Expand Down Expand Up @@ -1436,6 +1468,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
&mut self,
generics: &Generics,
constness: Const,
force_append_constness: bool,
parent_node_id: NodeId,
itctx: ImplTraitContext,
f: impl FnOnce(&mut Self) -> T,
Expand Down Expand Up @@ -1496,7 +1529,9 @@ impl<'hir> LoweringContext<'_, 'hir> {
// if the effects feature is enabled. This needs to be done before we lower where
// clauses since where clauses need to bind to the DefId of the host param
let host_param_parts = if let Const::Yes(span) = constness
&& self.tcx.features().effects
// if this comes from implementing a `const` trait, we must force constness to be appended
// to the impl item, no matter whether effects is enabled.
&& (self.tcx.features().effects || force_append_constness)
{
let span = self.lower_span(span);
let param_node_id = self.next_node_id();
Expand Down Expand Up @@ -1609,13 +1644,15 @@ impl<'hir> LoweringContext<'_, 'hir> {
}),
)),
)),
// FIXME(effects) we might not need a default.
default: Some(self.arena.alloc(hir::AnonConst {
def_id: anon_const,
hir_id: const_id,
body: const_body,
span,
})),
is_host_effect: true,
synthetic: true,
},
colon_span: None,
pure_wrt_drop: false,
Expand Down
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