Skip to content

Commit

Permalink
Auto merge of #95776 - cjgillot:ast-lifetimes-static, r=petrochenkov
Browse files Browse the repository at this point in the history 
Enforce static lifetimes in consts during late resolution

This PR moves the handling of implicitly and explicitly static lifetimes in constants from HIR to the AST.
  • Loading branch information
@bors
bors committed Apr 30, 2022
2 parents 9a98c63 + 7d990a8 commit 76d4862
Show file tree
Hide file tree
Showing 8 changed files with 314 additions and 146 deletions.
48 changes: 39 additions & 9 deletions compiler/rustc_resolve/src/late.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -199,6 +199,16 @@ enum LifetimeRibKind {
/// This rib declares generic parameters.
Generics { parent: NodeId, span: Span, kind: LifetimeBinderKind },

/// FIXME(const_generics): This patches over an ICE caused by non-'static lifetimes in const
/// generics. We are disallowing this until we can decide on how we want to handle non-'static
/// lifetimes in const generics. See issue #74052 for discussion.
ConstGeneric,

/// Non-static lifetimes are prohibited in anonymous constants under `min_const_generics`.
/// This function will emit an error if `generic_const_exprs` is not enabled, the body identified by
/// `body_id` is an anonymous constant and `lifetime_ref` is non-static.
AnonConst,

/// For **Modern** cases, create a new anonymous region parameter
/// and reference that.
///
Expand Down Expand Up @@ -527,7 +537,9 @@ impl<'a: 'ast, 'ast> Visitor<'ast> for LateResolutionVisitor<'a, '_, 'ast> {
}
fn visit_anon_const(&mut self, constant: &'ast AnonConst) {
// We deal with repeat expressions explicitly in `resolve_expr`.
self.resolve_anon_const(constant, IsRepeatExpr::No);
self.with_lifetime_rib(LifetimeRibKind::AnonConst, |this| {
this.resolve_anon_const(constant, IsRepeatExpr::No);
})
}
fn visit_expr(&mut self, expr: &'ast Expr) {
self.resolve_expr(expr, None);
Expand Down Expand Up @@ -1102,14 +1114,18 @@ impl<'a: 'ast, 'b, 'ast> LateResolutionVisitor<'a, 'b, 'ast> {

this.ribs[TypeNS].push(Rib::new(ConstParamTyRibKind));
this.ribs[ValueNS].push(Rib::new(ConstParamTyRibKind));
this.visit_ty(ty);
this.with_lifetime_rib(LifetimeRibKind::ConstGeneric, |this| {
this.visit_ty(ty)
});
this.ribs[TypeNS].pop().unwrap();
this.ribs[ValueNS].pop().unwrap();

if let Some(ref expr) = default {
this.ribs[TypeNS].push(forward_ty_ban_rib);
this.ribs[ValueNS].push(forward_const_ban_rib);
this.visit_anon_const(expr);
this.with_lifetime_rib(LifetimeRibKind::ConstGeneric, |this| {
this.resolve_anon_const(expr, IsRepeatExpr::No)
});
forward_const_ban_rib = this.ribs[ValueNS].pop().unwrap();
forward_ty_ban_rib = this.ribs[TypeNS].pop().unwrap();
}
Expand Down Expand Up @@ -1158,8 +1174,19 @@ impl<'a: 'ast, 'b, 'ast> LateResolutionVisitor<'a, 'b, 'ast> {
return;
}

if let LifetimeRibKind::Item = rib.kind {
break;
match rib.kind {
LifetimeRibKind::Item => break,
LifetimeRibKind::ConstGeneric => {
self.emit_non_static_lt_in_const_generic_error(lifetime);
self.r.lifetimes_res_map.insert(lifetime.id, LifetimeRes::Error);
return;
}
LifetimeRibKind::AnonConst => {
self.maybe_emit_forbidden_non_static_lifetime_error(lifetime);
self.r.lifetimes_res_map.insert(lifetime.id, LifetimeRes::Error);
return;
}
_ => {}
}
}

Expand Down Expand Up @@ -3065,9 +3092,7 @@ impl<'a: 'ast, 'b, 'ast> LateResolutionVisitor<'a, 'b, 'ast> {
is_repeat,
constant.value.is_potential_trivial_const_param(),
None,
|this| {
visit::walk_anon_const(this, constant);
},
|this| visit::walk_anon_const(this, constant),
);
}

Expand Down Expand Up @@ -3218,7 +3243,12 @@ impl<'a: 'ast, 'b, 'ast> LateResolutionVisitor<'a, 'b, 'ast> {
}
ExprKind::Repeat(ref elem, ref ct) => {
self.visit_expr(elem);
self.resolve_anon_const(ct, IsRepeatExpr::Yes);
self.with_lifetime_rib(LifetimeRibKind::AnonConst, |this| {
this.resolve_anon_const(ct, IsRepeatExpr::Yes)
});
}
ExprKind::ConstBlock(ref ct) => {
self.resolve_anon_const(ct, IsRepeatExpr::No);
}
ExprKind::Index(ref elem, ref idx) => {
self.resolve_expr(elem, Some(expr));
Expand Down
77 changes: 31 additions & 46 deletions compiler/rustc_resolve/src/late/diagnostics.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1886,6 +1886,37 @@ impl<'a: 'ast, 'ast> LateResolutionVisitor<'a, '_, 'ast> {

err.emit();
}

crate fn emit_non_static_lt_in_const_generic_error(&self, lifetime_ref: &ast::Lifetime) {
struct_span_err!(
self.r.session,
lifetime_ref.ident.span,
E0771,
"use of non-static lifetime `{}` in const generic",
lifetime_ref.ident
)
.note(
"for more information, see issue #74052 \
<https://github.com/rust-lang/rust/issues/74052>",
)
.emit();
}

/// Non-static lifetimes are prohibited in anonymous constants under `min_const_generics`.
/// This function will emit an error if `generic_const_exprs` is not enabled, the body identified by
/// `body_id` is an anonymous constant and `lifetime_ref` is non-static.
crate fn maybe_emit_forbidden_non_static_lifetime_error(&self, lifetime_ref: &ast::Lifetime) {
let feature_active = self.r.session.features_untracked().generic_const_exprs;
if !feature_active {
feature_err(
&self.r.session.parse_sess,
sym::generic_const_exprs,
lifetime_ref.ident.span,
"a non-static lifetime is not allowed in a `const`",
)
.emit();
}
}
}

impl<'tcx> LifetimeContext<'_, 'tcx> {
Expand Down Expand Up @@ -1982,24 +2013,6 @@ impl<'tcx> LifetimeContext<'_, 'tcx> {
}
}

// FIXME(const_generics): This patches over an ICE caused by non-'static lifetimes in const
// generics. We are disallowing this until we can decide on how we want to handle non-'static
// lifetimes in const generics. See issue #74052 for discussion.
crate fn emit_non_static_lt_in_const_generic_error(&self, lifetime_ref: &hir::Lifetime) {
let mut err = struct_span_err!(
self.tcx.sess,
lifetime_ref.span,
E0771,
"use of non-static lifetime `{}` in const generic",
lifetime_ref
);
err.note(
"for more information, see issue #74052 \
<https://github.com/rust-lang/rust/issues/74052>",
);
err.emit();
}

crate fn is_trait_ref_fn_scope(&mut self, trait_ref: &'tcx hir::PolyTraitRef<'tcx>) -> bool {
if let def::Res::Def(_, did) = trait_ref.trait_ref.path.res {
if [
Expand Down Expand Up @@ -2401,32 +2414,4 @@ impl<'tcx> LifetimeContext<'_, 'tcx> {
_ => unreachable!(),
}
}

/// Non-static lifetimes are prohibited in anonymous constants under `min_const_generics`.
/// This function will emit an error if `generic_const_exprs` is not enabled, the body identified by
/// `body_id` is an anonymous constant and `lifetime_ref` is non-static.
crate fn maybe_emit_forbidden_non_static_lifetime_error(
&self,
body_id: hir::BodyId,
lifetime_ref: &'tcx hir::Lifetime,
) {
let is_anon_const = matches!(
self.tcx.def_kind(self.tcx.hir().body_owner_def_id(body_id)),
hir::def::DefKind::AnonConst
);
let is_allowed_lifetime = matches!(
lifetime_ref.name,
hir::LifetimeName::Implicit | hir::LifetimeName::Static | hir::LifetimeName::Underscore
);

if !self.tcx.lazy_normalization() && is_anon_const && !is_allowed_lifetime {
feature_err(
&self.tcx.sess.parse_sess,
sym::generic_const_exprs,
lifetime_ref.span,
"a non-static lifetime is not allowed in a `const`",
)
.emit();
}
}
}
15 changes: 0 additions & 15 deletions compiler/rustc_resolve/src/late/lifetimes.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -164,8 +164,6 @@ crate struct LifetimeContext<'a, 'tcx> {
map: &'a mut NamedRegionMap,
scope: ScopeRef<'a>,

is_in_const_generic: bool,

/// Indicates that we only care about the definition of a trait. This should
/// be false if the `Item` we are resolving lifetimes for is not a trait or
/// we eventually need lifetimes resolve for trait items.
Expand Down Expand Up @@ -452,7 +450,6 @@ fn do_resolve(
tcx,
map: &mut named_region_map,
scope: ROOT_SCOPE,
is_in_const_generic: false,
trait_definition_only,
labels_in_fn: vec![],
xcrate_object_lifetime_defaults: Default::default(),
Expand Down Expand Up @@ -1266,10 +1263,6 @@ impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> {
self.insert_lifetime(lifetime_ref, Region::Static);
return;
}
if self.is_in_const_generic && lifetime_ref.name != LifetimeName::Error {
self.emit_non_static_lt_in_const_generic_error(lifetime_ref);
return;
}
self.resolve_lifetime_ref(lifetime_ref);
}

Expand Down Expand Up @@ -1341,14 +1334,11 @@ impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> {
}
}
GenericParamKind::Const { ref ty, default } => {
let was_in_const_generic = this.is_in_const_generic;
this.is_in_const_generic = true;
walk_list!(this, visit_param_bound, param.bounds);
this.visit_ty(&ty);
if let Some(default) = default {
this.visit_body(this.tcx.hir().body(default.body));
}
this.is_in_const_generic = was_in_const_generic;
}
}
}
Expand Down Expand Up @@ -1798,7 +1788,6 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
tcx: *tcx,
map,
scope: &wrap_scope,
is_in_const_generic: self.is_in_const_generic,
trait_definition_only: self.trait_definition_only,
labels_in_fn,
xcrate_object_lifetime_defaults,
Expand Down Expand Up @@ -2254,10 +2243,6 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
let result = loop {
match *scope {
Scope::Body { id, s } => {
// Non-static lifetimes are prohibited in anonymous constants without
// `generic_const_exprs`.
self.maybe_emit_forbidden_non_static_lifetime_error(id, lifetime_ref);

outermost_body = Some(id);
scope = s;
}
Expand Down
Loading

0 comments on commit 76d4862

Please sign in to comment.