Skip to content

Commit 8ce5d78

Browse files
fmeasefmease
committed
Deny more ~const trait bounds
1 parent 9ab0749 commit 8ce5d78

25 files changed

+444
-134
lines changed

‎compiler/rustc_ast_passes/messages.ftl

+4-1
Original file line numberDiff line numberDiff line change
@@ -214,9 +214,12 @@ ast_passes_static_without_body =
214214
.suggestion = provide a definition for the static
215215
216216
ast_passes_tilde_const_disallowed = `~const` is not allowed here
217-
.trait = trait objects cannot have `~const` trait bounds
218217
.closure = closures cannot have `~const` trait bounds
219218
.function = this function is not `const`, so it cannot have `~const` trait bounds
219+
.trait = this trait is not a `#[const_trait]`, so it cannot have `~const` trait bounds
220+
.impl = this impl is not `const`, so it cannot have `~const` trait bounds
221+
.object = trait objects cannot have `~const` trait bounds
222+
.item = this item cannot have `~const` trait bounds
220223
221224
ast_passes_trait_fn_const =
222225
functions in traits cannot be declared const

‎compiler/rustc_ast_passes/src/ast_validation.rs

+30-45
Original file line numberDiff line numberDiff line change
@@ -40,6 +40,9 @@ enum SelfSemantic {
4040
enum DisallowTildeConstContext<'a> {
4141
TraitObject,
4242
Fn(FnKind<'a>),
43+
Trait(Span),
44+
Impl(Span),
45+
Item,
4346
}
4447

4548
struct AstValidator<'a> {
@@ -110,18 +113,6 @@ impl<'a> AstValidator<'a> {
110113
self.disallow_tilde_const = old;
111114
}
112115

113-
fn with_tilde_const_allowed(&mut self, f: impl FnOnce(&mut Self)) {
114-
self.with_tilde_const(None, f)
115-
}
116-
117-
fn with_banned_tilde_const(
118-
&mut self,
119-
ctx: DisallowTildeConstContext<'a>,
120-
f: impl FnOnce(&mut Self),
121-
) {
122-
self.with_tilde_const(Some(ctx), f)
123-
}
124-
125116
fn check_type_alias_where_clause_location(
126117
&mut self,
127118
ty_alias: &TyAlias,
@@ -173,7 +164,7 @@ impl<'a> AstValidator<'a> {
173164
self.with_impl_trait(Some(t.span), |this| visit::walk_ty(this, t))
174165
}
175166
TyKind::TraitObject(..) => self
176-
.with_banned_tilde_const(DisallowTildeConstContext::TraitObject, |this| {
167+
.with_tilde_const(Some(DisallowTildeConstContext::TraitObject), |this| {
177168
visit::walk_ty(this, t)
178169
}),
179170
TyKind::Path(qself, path) => {
@@ -822,11 +813,9 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
822813

823814
this.visit_vis(&item.vis);
824815
this.visit_ident(item.ident);
825-
if let Const::Yes(_) = constness {
826-
this.with_tilde_const_allowed(|this| this.visit_generics(generics));
827-
} else {
828-
this.visit_generics(generics);
829-
}
816+
let disallowed = matches!(constness, Const::No)
817+
.then(|| DisallowTildeConstContext::Impl(item.span));
818+
this.with_tilde_const(disallowed, |this| this.visit_generics(generics));
830819
this.visit_trait_ref(t);
831820
this.visit_ty(self_ty);
832821

@@ -840,10 +829,10 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
840829
polarity,
841830
defaultness,
842831
constness,
843-
generics: _,
832+
generics,
844833
of_trait: None,
845834
self_ty,
846-
items: _,
835+
items,
847836
}) => {
848837
let error =
849838
|annotation_span, annotation, only_trait: bool| errors::InherentImplCannot {
@@ -875,6 +864,14 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
875864
if let &Const::Yes(span) = constness {
876865
self.err_handler().emit_err(error(span, "`const`", true));
877866
}
867+
868+
self.visit_vis(&item.vis);
869+
self.visit_ident(item.ident);
870+
self.with_tilde_const(None, |this| this.visit_generics(generics));
871+
self.visit_ty(self_ty);
872+
walk_list!(self, visit_assoc_item, items, AssocCtxt::Impl);
873+
walk_list!(self, visit_attribute, &item.attrs);
874+
return; // Avoid visiting again.
878875
}
879876
ItemKind::Fn(box Fn { defaultness, sig, generics, body }) => {
880877
self.check_defaultness(item.span, *defaultness);
@@ -955,8 +952,10 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
955952
// context for the supertraits.
956953
this.visit_vis(&item.vis);
957954
this.visit_ident(item.ident);
958-
this.visit_generics(generics);
959-
this.with_tilde_const_allowed(|this| {
955+
let disallowed =
956+
(!is_const_trait).then(|| DisallowTildeConstContext::Trait(item.span));
957+
this.with_tilde_const(disallowed, |this| {
958+
this.visit_generics(generics);
960959
walk_list!(this, visit_param_bound, bounds, BoundKind::SuperTraits)
961960
});
962961
walk_list!(this, visit_assoc_item, items, AssocCtxt::Trait);
@@ -976,16 +975,11 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
976975
}
977976
}
978977
ItemKind::Struct(vdata, generics) => match vdata {
979-
// Duplicating the `Visitor` logic allows catching all cases
980-
// of `Anonymous(Struct, Union)` outside of a field struct or union.
981-
//
982-
// Inside `visit_ty` the validator catches every `Anonymous(Struct, Union)` it
983-
// encounters, and only on `ItemKind::Struct` and `ItemKind::Union`
984-
// it uses `visit_ty_common`, which doesn't contain that specific check.
985978
VariantData::Struct(fields, ..) => {
986979
self.visit_vis(&item.vis);
987980
self.visit_ident(item.ident);
988981
self.visit_generics(generics);
982+
// Permit `Anon{Struct,Union}` as field type.
989983
walk_list!(self, visit_struct_field_def, fields);
990984
walk_list!(self, visit_attribute, &item.attrs);
991985
return;
@@ -1001,6 +995,7 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
1001995
self.visit_vis(&item.vis);
1002996
self.visit_ident(item.ident);
1003997
self.visit_generics(generics);
998+
// Permit `Anon{Struct,Union}` as field type.
1004999
walk_list!(self, visit_struct_field_def, fields);
10051000
walk_list!(self, visit_attribute, &item.attrs);
10061001
return;
@@ -1189,15 +1184,18 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
11891184
if let Some(reason) = &self.disallow_tilde_const =>
11901185
{
11911186
let reason = match reason {
1192-
DisallowTildeConstContext::TraitObject => {
1193-
errors::TildeConstReason::TraitObject
1194-
}
11951187
DisallowTildeConstContext::Fn(FnKind::Closure(..)) => {
11961188
errors::TildeConstReason::Closure
11971189
}
11981190
DisallowTildeConstContext::Fn(FnKind::Fn(_, ident, ..)) => {
11991191
errors::TildeConstReason::Function { ident: ident.span }
12001192
}
1193+
&DisallowTildeConstContext::Trait(span) => errors::TildeConstReason::Trait { span },
1194+
&DisallowTildeConstContext::Impl(span) => errors::TildeConstReason::Impl { span },
1195+
DisallowTildeConstContext::TraitObject => {
1196+
errors::TildeConstReason::TraitObject
1197+
}
1198+
DisallowTildeConstContext::Item => errors::TildeConstReason::Item,
12011199
};
12021200
self.err_handler()
12031201
.emit_err(errors::TildeConstDisallowed { span: bound.span(), reason });
@@ -1305,7 +1303,6 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
13051303
|| matches!(fk.ctxt(), Some(FnCtxt::Assoc(_)) if self.in_const_trait_or_impl);
13061304

13071305
let disallowed = (!tilde_const_allowed).then(|| DisallowTildeConstContext::Fn(fk));
1308-
13091306
self.with_tilde_const(disallowed, |this| visit::walk_fn(this, fk));
13101307
}
13111308

@@ -1374,18 +1371,6 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
13741371
}
13751372

13761373
match &item.kind {
1377-
AssocItemKind::Type(box TyAlias { generics, bounds, ty, .. })
1378-
if ctxt == AssocCtxt::Trait =>
1379-
{
1380-
self.visit_vis(&item.vis);
1381-
self.visit_ident(item.ident);
1382-
walk_list!(self, visit_attribute, &item.attrs);
1383-
self.with_tilde_const_allowed(|this| {
1384-
this.visit_generics(generics);
1385-
walk_list!(this, visit_param_bound, bounds, BoundKind::Bound);
1386-
});
1387-
walk_list!(self, visit_ty, ty);
1388-
}
13891374
AssocItemKind::Fn(box Fn { sig, generics, body, .. })
13901375
if self.in_const_trait_or_impl
13911376
|| ctxt == AssocCtxt::Trait
@@ -1537,7 +1522,7 @@ pub fn check_crate(
15371522
in_const_trait_or_impl: false,
15381523
has_proc_macro_decls: false,
15391524
outer_impl_trait: None,
1540-
disallow_tilde_const: None,
1525+
disallow_tilde_const: Some(DisallowTildeConstContext::Item),
15411526
is_impl_trait_banned: false,
15421527
lint_buffer: lints,
15431528
};

‎compiler/rustc_ast_passes/src/errors.rs

+14-2
Original file line numberDiff line numberDiff line change
@@ -551,15 +551,27 @@ pub struct TildeConstDisallowed {
551551

552552
#[derive(Subdiagnostic)]
553553
pub enum TildeConstReason {
554-
#[note(ast_passes_trait)]
555-
TraitObject,
556554
#[note(ast_passes_closure)]
557555
Closure,
558556
#[note(ast_passes_function)]
559557
Function {
560558
#[primary_span]
561559
ident: Span,
562560
},
561+
#[note(ast_passes_trait)]
562+
Trait {
563+
#[primary_span]
564+
span: Span,
565+
},
566+
#[note(ast_passes_impl)]
567+
Impl {
568+
#[primary_span]
569+
span: Span,
570+
},
571+
#[note(ast_passes_object)]
572+
TraitObject,
573+
#[note(ast_passes_item)]
574+
Item,
563575
}
564576

565577
#[derive(Diagnostic)]

‎tests/ui/generic-const-items/const-trait-impl.rs

+2-2
Original file line numberDiff line numberDiff line change
@@ -7,8 +7,8 @@
77
#![allow(incomplete_features)]
88
#![crate_type = "lib"]
99

10-
// FIXME(generic_const_items): Interpret `~const` as always-const.
11-
const CREATE<T: ~const Create>: T = T::create();
10+
// FIXME(generic_const_items, effects): Introduce `const` bounds to make this work.
11+
const CREATE<T: Create>: T = T::create();
1212

1313
pub const K0: i32 = CREATE::<i32>;
1414
pub const K1: i32 = CREATE; // arg inferred

‎tests/ui/generic-const-items/const-trait-impl.stderr

+3-3
Original file line numberDiff line numberDiff line change
@@ -1,8 +1,8 @@
11
error[E0015]: cannot call non-const fn `<T as Create>::create` in constants
2-
--> $DIR/const-trait-impl.rs:11:37
2+
--> $DIR/const-trait-impl.rs:11:30
33
|
4-
LL | const CREATE<T: ~const Create>: T = T::create();
5-
| ^^^^^^^^^^^
4+
LL | const CREATE<T: Create>: T = T::create();
5+
| ^^^^^^^^^^^
66
|
77
= note: calls in constants are limited to constant functions, tuple structs and tuple variants
88

‎tests/ui/rfcs/rfc-2632-const-trait-impl/assoc-type-const-bound-usage.stderr

+9-1
Original file line numberDiff line numberDiff line change
@@ -1,3 +1,11 @@
1+
error: `~const` is not allowed here
2+
--> $DIR/assoc-type-const-bound-usage.rs:7:17
3+
|
4+
LL | type Assoc: ~const Foo;
5+
| ^^^^^^^^^^
6+
|
7+
= note: this item cannot have `~const` trait bounds
8+
19
error[E0308]: mismatched types
210
--> $DIR/assoc-type-const-bound-usage.rs:12:5
311
|
@@ -7,6 +15,6 @@ LL | <T as Foo>::Assoc::foo();
715
= note: expected constant `host`
816
found constant `true`
917

10-
error: aborting due to previous error
18+
error: aborting due to 2 previous errors
1119

1220
For more information about this error, try `rustc --explain E0308`.

‎tests/ui/rfcs/rfc-2632-const-trait-impl/assoc-type.stderr

+9-1
Original file line numberDiff line numberDiff line change
@@ -1,8 +1,16 @@
1+
error: `~const` is not allowed here
2+
--> $DIR/assoc-type.rs:17:15
3+
|
4+
LL | type Bar: ~const std::ops::Add;
5+
| ^^^^^^^^^^^^^^^^^^^^
6+
|
7+
= note: this item cannot have `~const` trait bounds
8+
19
error: ~const can only be applied to `#[const_trait]` traits
210
--> $DIR/assoc-type.rs:17:22
311
|
412
LL | type Bar: ~const std::ops::Add;
513
| ^^^^^^^^^^^^^
614

7-
error: aborting due to previous error
15+
error: aborting due to 2 previous errors
816

‎tests/ui/rfcs/rfc-2632-const-trait-impl/effects/const-bound-on-not-const-associated-fn.rs renamed to ‎tests/ui/rfcs/rfc-2632-const-trait-impl/const-bound-on-not-const-associated-fn.rs

+1-1
Original file line numberDiff line numberDiff line change
@@ -1,4 +1,4 @@
1-
#![feature(const_trait_impl, effects)]
1+
#![feature(const_trait_impl)]
22

33
#[const_trait]
44
trait MyTrait {

‎tests/ui/rfcs/rfc-2632-const-trait-impl/effects/const-bound-on-not-const-associated-fn.stderr renamed to ‎tests/ui/rfcs/rfc-2632-const-trait-impl/const-bound-on-not-const-associated-fn.stderr

File renamed without changes.

‎tests/ui/rfcs/rfc-2632-const-trait-impl/const-drop.precise.stderr

+6-15
Original file line numberDiff line numberDiff line change
@@ -1,19 +1,10 @@
1-
error[E0493]: destructor of `T` cannot be evaluated at compile-time
2-
--> $DIR/const-drop.rs:19:32
1+
error: `~const` is not allowed here
2+
--> $DIR/const-drop.rs:67:38
33
|
4-
LL | const fn a<T: ~const Destruct>(_: T) {}
5-
| ^ - value is dropped here
6-
| |
7-
| the destructor for this type cannot be evaluated in constant functions
8-
9-
error[E0493]: destructor of `S<'_>` cannot be evaluated at compile-time
10-
--> $DIR/const-drop.rs:24:13
4+
LL | pub struct ConstDropWithBound<T: ~const SomeTrait>(pub core::marker::PhantomData<T>);
5+
| ^^^^^^^^^^^^^^^^
116
|
12-
LL | let _ = S(&mut c);
13-
| ^^^^^^^^^- value is dropped here
14-
| |
15-
| the destructor for this type cannot be evaluated in constant functions
7+
= note: this item cannot have `~const` trait bounds
168

17-
error: aborting due to 2 previous errors
9+
error: aborting due to previous error
1810

19-
For more information about this error, try `rustc --explain E0493`.

‎tests/ui/rfcs/rfc-2632-const-trait-impl/const-drop.rs

+1
Original file line numberDiff line numberDiff line change
@@ -63,6 +63,7 @@ mod t {
6363
fn foo() {}
6464
}
6565

66+
// FIXME(effects): This should be a `const` bound instead of a `~const` one.
6667
pub struct ConstDropWithBound<T: ~const SomeTrait>(pub core::marker::PhantomData<T>);
6768

6869
impl<T: ~const SomeTrait> const Drop for ConstDropWithBound<T> {

‎tests/ui/rfcs/rfc-2632-const-trait-impl/const-drop.stock.stderr

+6-15
Original file line numberDiff line numberDiff line change
@@ -1,19 +1,10 @@
1-
error[E0493]: destructor of `T` cannot be evaluated at compile-time
2-
--> $DIR/const-drop.rs:19:32
1+
error: `~const` is not allowed here
2+
--> $DIR/const-drop.rs:67:38
33
|
4-
LL | const fn a<T: ~const Destruct>(_: T) {}
5-
| ^ - value is dropped here
6-
| |
7-
| the destructor for this type cannot be evaluated in constant functions
8-
9-
error[E0493]: destructor of `S<'_>` cannot be evaluated at compile-time
10-
--> $DIR/const-drop.rs:24:13
4+
LL | pub struct ConstDropWithBound<T: ~const SomeTrait>(pub core::marker::PhantomData<T>);
5+
| ^^^^^^^^^^^^^^^^
116
|
12-
LL | let _ = S(&mut c);
13-
| ^^^^^^^^^- value is dropped here
14-
| |
15-
| the destructor for this type cannot be evaluated in constant functions
7+
= note: this item cannot have `~const` trait bounds
168

17-
error: aborting due to 2 previous errors
9+
error: aborting due to previous error
1810

19-
For more information about this error, try `rustc --explain E0493`.

‎tests/ui/rfcs/rfc-2632-const-trait-impl/issue-90052.rs

-9
This file was deleted.

‎tests/ui/rfcs/rfc-2632-const-trait-impl/issue-90052.stderr

-14
This file was deleted.

‎tests/ui/rfcs/rfc-2632-const-trait-impl/specialization/const-default-bound-non-const-specialized-bound.rs

+1-5
Original file line numberDiff line numberDiff line change
@@ -18,11 +18,7 @@ trait Bar {
1818
fn bar();
1919
}
2020

21-
// bgr360: I was only able to exercise the code path that raises the
22-
// "missing ~const qualifier" error by making this base impl non-const, even
23-
// though that doesn't really make sense to do. As seen below, if the base impl
24-
// is made const, rustc fails earlier with an overlapping impl failure.
25-
impl<T> Bar for T
21+
impl<T> const Bar for T
2622
where
2723
T: ~const Foo,
2824
{

0 commit comments

Comments
 (0)