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Unrolled build for rust-lang#119505
Rollup merge of rust-lang#119505 - fmease:no-host-param-for-trait-fns, r=fee1-dead Don't synthesize host effect params for trait associated functions marked const Fixes rust-lang#113378. r? fee1-dead or compiler
2 parents 1a47f5b + aa79904 commit d18f008

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17 files changed

+285
-64
lines changed

17 files changed

+285
-64
lines changed

‎compiler/rustc_ast_lowering/src/item.rs

+6-4
Original file line numberDiff line numberDiff line change
@@ -1241,11 +1241,13 @@ impl<'hir> LoweringContext<'_, 'hir> {
12411241
coroutine_kind: Option<CoroutineKind>,
12421242
) -> (&'hir hir::Generics<'hir>, hir::FnSig<'hir>) {
12431243
let header = self.lower_fn_header(sig.header);
1244+
// Don't pass along the user-provided constness of trait associated functions; we don't want to
1245+
// synthesize a host effect param for them. We reject `const` on them during AST validation.
1246+
let constness = if kind == FnDeclKind::Inherent { sig.header.constness } else { Const::No };
12441247
let itctx = ImplTraitContext::Universal;
1245-
let (generics, decl) =
1246-
self.lower_generics(generics, sig.header.constness, id, &itctx, |this| {
1247-
this.lower_fn_decl(&sig.decl, id, sig.span, kind, coroutine_kind)
1248-
});
1248+
let (generics, decl) = self.lower_generics(generics, constness, id, &itctx, |this| {
1249+
this.lower_fn_decl(&sig.decl, id, sig.span, kind, coroutine_kind)
1250+
});
12491251
(generics, hir::FnSig { header, decl, span: self.lower_span(sig.span) })
12501252
}
12511253

‎compiler/rustc_ast_passes/messages.ftl

+15-2
Original file line numberDiff line numberDiff line change
@@ -233,8 +233,21 @@ ast_passes_tilde_const_disallowed = `~const` is not allowed here
233233
.item = this item cannot have `~const` trait bounds
234234
235235
ast_passes_trait_fn_const =
236-
functions in traits cannot be declared const
237-
.label = functions in traits cannot be const
236+
functions in {$in_impl ->
237+
[true] trait impls
238+
*[false] traits
239+
} cannot be declared const
240+
.label = functions in {$in_impl ->
241+
[true] trait impls
242+
*[false] traits
243+
} cannot be const
244+
.const_context_label = this declares all associated functions implicitly const
245+
.remove_const_sugg = remove the `const`{$requires_multiple_changes ->
246+
[true] {" ..."}
247+
*[false] {""}
248+
}
249+
.make_impl_const_sugg = ... and declare the impl to be const instead
250+
.make_trait_const_sugg = ... and declare the trait to be a `#[const_trait]` instead
238251
239252
ast_passes_trait_object_single_bound = only a single explicit lifetime bound is permitted
240253

‎compiler/rustc_ast_passes/src/ast_validation.rs

+96-34
Original file line numberDiff line numberDiff line change
@@ -46,18 +46,29 @@ enum DisallowTildeConstContext<'a> {
4646
Item,
4747
}
4848

49+
enum TraitOrTraitImpl<'a> {
50+
Trait { span: Span, constness: Option<Span> },
51+
TraitImpl { constness: Const, polarity: ImplPolarity, trait_ref: &'a TraitRef },
52+
}
53+
54+
impl<'a> TraitOrTraitImpl<'a> {
55+
fn constness(&self) -> Option<Span> {
56+
match self {
57+
Self::Trait { constness: Some(span), .. }
58+
| Self::TraitImpl { constness: Const::Yes(span), .. } => Some(*span),
59+
_ => None,
60+
}
61+
}
62+
}
63+
4964
struct AstValidator<'a> {
5065
session: &'a Session,
5166
features: &'a Features,
5267

5368
/// The span of the `extern` in an `extern { ... }` block, if any.
5469
extern_mod: Option<&'a Item>,
5570

56-
/// Are we inside a trait impl?
57-
in_trait_impl: bool,
58-
59-
/// Are we inside a const trait defn or impl?
60-
in_const_trait_or_impl: bool,
71+
outer_trait_or_trait_impl: Option<TraitOrTraitImpl<'a>>,
6172

6273
has_proc_macro_decls: bool,
6374

@@ -78,24 +89,28 @@ struct AstValidator<'a> {
7889
impl<'a> AstValidator<'a> {
7990
fn with_in_trait_impl(
8091
&mut self,
81-
is_in: bool,
82-
constness: Option<Const>,
92+
trait_: Option<(Const, ImplPolarity, &'a TraitRef)>,
8393
f: impl FnOnce(&mut Self),
8494
) {
85-
let old = mem::replace(&mut self.in_trait_impl, is_in);
86-
let old_const = mem::replace(
87-
&mut self.in_const_trait_or_impl,
88-
matches!(constness, Some(Const::Yes(_))),
95+
let old = mem::replace(
96+
&mut self.outer_trait_or_trait_impl,
97+
trait_.map(|(constness, polarity, trait_ref)| TraitOrTraitImpl::TraitImpl {
98+
constness,
99+
polarity,
100+
trait_ref,
101+
}),
89102
);
90103
f(self);
91-
self.in_trait_impl = old;
92-
self.in_const_trait_or_impl = old_const;
104+
self.outer_trait_or_trait_impl = old;
93105
}
94106

95-
fn with_in_trait(&mut self, is_const: bool, f: impl FnOnce(&mut Self)) {
96-
let old = mem::replace(&mut self.in_const_trait_or_impl, is_const);
107+
fn with_in_trait(&mut self, span: Span, constness: Option<Span>, f: impl FnOnce(&mut Self)) {
108+
let old = mem::replace(
109+
&mut self.outer_trait_or_trait_impl,
110+
Some(TraitOrTraitImpl::Trait { span, constness }),
111+
);
97112
f(self);
98-
self.in_const_trait_or_impl = old;
113+
self.outer_trait_or_trait_impl = old;
99114
}
100115

101116
fn with_banned_impl_trait(&mut self, f: impl FnOnce(&mut Self)) {
@@ -291,10 +306,48 @@ impl<'a> AstValidator<'a> {
291306
}
292307
}
293308

294-
fn check_trait_fn_not_const(&self, constness: Const) {
295-
if let Const::Yes(span) = constness {
296-
self.dcx().emit_err(errors::TraitFnConst { span });
297-
}
309+
fn check_trait_fn_not_const(&self, constness: Const, parent: &TraitOrTraitImpl<'a>) {
310+
let Const::Yes(span) = constness else {
311+
return;
312+
};
313+
314+
let make_impl_const_sugg = if self.features.const_trait_impl
315+
&& let TraitOrTraitImpl::TraitImpl {
316+
constness: Const::No,
317+
polarity: ImplPolarity::Positive,
318+
trait_ref,
319+
} = parent
320+
{
321+
Some(trait_ref.path.span.shrink_to_lo())
322+
} else {
323+
None
324+
};
325+
326+
let make_trait_const_sugg = if self.features.const_trait_impl
327+
&& let TraitOrTraitImpl::Trait { span, constness: None } = parent
328+
{
329+
Some(span.shrink_to_lo())
330+
} else {
331+
None
332+
};
333+
334+
let parent_constness = parent.constness();
335+
self.dcx().emit_err(errors::TraitFnConst {
336+
span,
337+
in_impl: matches!(parent, TraitOrTraitImpl::TraitImpl { .. }),
338+
const_context_label: parent_constness,
339+
remove_const_sugg: (
340+
self.session.source_map().span_extend_while(span, |c| c == ' ').unwrap_or(span),
341+
match parent_constness {
342+
Some(_) => rustc_errors::Applicability::MachineApplicable,
343+
None => rustc_errors::Applicability::MaybeIncorrect,
344+
},
345+
),
346+
requires_multiple_changes: make_impl_const_sugg.is_some()
347+
|| make_trait_const_sugg.is_some(),
348+
make_impl_const_sugg,
349+
make_trait_const_sugg,
350+
});
298351
}
299352

300353
fn check_fn_decl(&self, fn_decl: &FnDecl, self_semantic: SelfSemantic) {
@@ -817,7 +870,7 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
817870
self_ty,
818871
items,
819872
}) => {
820-
self.with_in_trait_impl(true, Some(*constness), |this| {
873+
self.with_in_trait_impl(Some((*constness, *polarity, t)), |this| {
821874
this.visibility_not_permitted(
822875
&item.vis,
823876
errors::VisibilityNotPermittedNote::TraitImpl,
@@ -963,8 +1016,9 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
9631016
}
9641017
}
9651018
ItemKind::Trait(box Trait { is_auto, generics, bounds, items, .. }) => {
966-
let is_const_trait = attr::contains_name(&item.attrs, sym::const_trait);
967-
self.with_in_trait(is_const_trait, |this| {
1019+
let is_const_trait =
1020+
attr::find_by_name(&item.attrs, sym::const_trait).map(|attr| attr.span);
1021+
self.with_in_trait(item.span, is_const_trait, |this| {
9681022
if *is_auto == IsAuto::Yes {
9691023
// Auto traits cannot have generics, super traits nor contain items.
9701024
this.deny_generic_params(generics, item.ident.span);
@@ -977,8 +1031,9 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
9771031
// context for the supertraits.
9781032
this.visit_vis(&item.vis);
9791033
this.visit_ident(item.ident);
980-
let disallowed =
981-
(!is_const_trait).then(|| DisallowTildeConstContext::Trait(item.span));
1034+
let disallowed = is_const_trait
1035+
.is_none()
1036+
.then(|| DisallowTildeConstContext::Trait(item.span));
9821037
this.with_tilde_const(disallowed, |this| {
9831038
this.visit_generics(generics);
9841039
walk_list!(this, visit_param_bound, bounds, BoundKind::SuperTraits)
@@ -1342,7 +1397,12 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
13421397

13431398
let tilde_const_allowed =
13441399
matches!(fk.header(), Some(FnHeader { constness: ast::Const::Yes(_), .. }))
1345-
|| matches!(fk.ctxt(), Some(FnCtxt::Assoc(_)) if self.in_const_trait_or_impl);
1400+
|| matches!(fk.ctxt(), Some(FnCtxt::Assoc(_)))
1401+
&& self
1402+
.outer_trait_or_trait_impl
1403+
.as_ref()
1404+
.and_then(TraitOrTraitImpl::constness)
1405+
.is_some();
13461406

13471407
let disallowed = (!tilde_const_allowed).then(|| DisallowTildeConstContext::Fn(fk));
13481408
self.with_tilde_const(disallowed, |this| visit::walk_fn(this, fk));
@@ -1353,7 +1413,7 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
13531413
self.check_nomangle_item_asciionly(item.ident, item.span);
13541414
}
13551415

1356-
if ctxt == AssocCtxt::Trait || !self.in_trait_impl {
1416+
if ctxt == AssocCtxt::Trait || self.outer_trait_or_trait_impl.is_none() {
13571417
self.check_defaultness(item.span, item.kind.defaultness());
13581418
}
13591419

@@ -1401,10 +1461,10 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
14011461
);
14021462
}
14031463

1404-
if ctxt == AssocCtxt::Trait || self.in_trait_impl {
1464+
if let Some(parent) = &self.outer_trait_or_trait_impl {
14051465
self.visibility_not_permitted(&item.vis, errors::VisibilityNotPermittedNote::TraitImpl);
14061466
if let AssocItemKind::Fn(box Fn { sig, .. }) = &item.kind {
1407-
self.check_trait_fn_not_const(sig.header.constness);
1467+
self.check_trait_fn_not_const(sig.header.constness, parent);
14081468
}
14091469
}
14101470

@@ -1414,7 +1474,11 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
14141474

14151475
match &item.kind {
14161476
AssocItemKind::Fn(box Fn { sig, generics, body, .. })
1417-
if self.in_const_trait_or_impl
1477+
if self
1478+
.outer_trait_or_trait_impl
1479+
.as_ref()
1480+
.and_then(TraitOrTraitImpl::constness)
1481+
.is_some()
14181482
|| ctxt == AssocCtxt::Trait
14191483
|| matches!(sig.header.constness, Const::Yes(_)) =>
14201484
{
@@ -1430,8 +1494,7 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
14301494
);
14311495
self.visit_fn(kind, item.span, item.id);
14321496
}
1433-
_ => self
1434-
.with_in_trait_impl(false, None, |this| visit::walk_assoc_item(this, item, ctxt)),
1497+
_ => self.with_in_trait_impl(None, |this| visit::walk_assoc_item(this, item, ctxt)),
14351498
}
14361499
}
14371500
}
@@ -1547,8 +1610,7 @@ pub fn check_crate(
15471610
session,
15481611
features,
15491612
extern_mod: None,
1550-
in_trait_impl: false,
1551-
in_const_trait_or_impl: false,
1613+
outer_trait_or_trait_impl: None,
15521614
has_proc_macro_decls: false,
15531615
outer_impl_trait: None,
15541616
disallow_tilde_const: Some(DisallowTildeConstContext::Item),

‎compiler/rustc_ast_passes/src/errors.rs

+19-1
Original file line numberDiff line numberDiff line change
@@ -1,7 +1,7 @@
11
//! Errors emitted by ast_passes.
22
33
use rustc_ast::ParamKindOrd;
4-
use rustc_errors::AddToDiagnostic;
4+
use rustc_errors::{AddToDiagnostic, Applicability};
55
use rustc_macros::{Diagnostic, Subdiagnostic};
66
use rustc_span::{symbol::Ident, Span, Symbol};
77

@@ -49,6 +49,24 @@ pub struct TraitFnConst {
4949
#[primary_span]
5050
#[label]
5151
pub span: Span,
52+
pub in_impl: bool,
53+
#[label(ast_passes_const_context_label)]
54+
pub const_context_label: Option<Span>,
55+
#[suggestion(ast_passes_remove_const_sugg, code = "")]
56+
pub remove_const_sugg: (Span, Applicability),
57+
pub requires_multiple_changes: bool,
58+
#[suggestion(
59+
ast_passes_make_impl_const_sugg,
60+
code = "const ",
61+
applicability = "maybe-incorrect"
62+
)]
63+
pub make_impl_const_sugg: Option<Span>,
64+
#[suggestion(
65+
ast_passes_make_trait_const_sugg,
66+
code = "#[const_trait]\n",
67+
applicability = "maybe-incorrect"
68+
)]
69+
pub make_trait_const_sugg: Option<Span>,
5270
}
5371

5472
#[derive(Diagnostic)]

‎compiler/rustc_error_codes/src/error_codes/E0379.md

+4
Original file line numberDiff line numberDiff line change
@@ -6,6 +6,10 @@ Erroneous code example:
66
trait Foo {
77
const fn bar() -> u32; // error!
88
}
9+
10+
impl Foo for () {
11+
const fn bar() -> u32 { 0 } // error!
12+
}
913
```
1014

1115
Trait methods cannot be declared `const` by design. For more information, see

‎compiler/rustc_hir_analysis/src/collect/generics_of.rs

+4-1
Original file line numberDiff line numberDiff line change
@@ -315,7 +315,10 @@ pub(super) fn generics_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Generics {
315315

316316
if is_host_effect {
317317
if let Some(idx) = host_effect_index {
318-
bug!("parent also has host effect param? index: {idx}, def: {def_id:?}");
318+
tcx.dcx().span_delayed_bug(
319+
param.span,
320+
format!("parent also has host effect param? index: {idx}, def: {def_id:?}"),
321+
);
319322
}
320323

321324
host_effect_index = Some(index as usize);

‎tests/ui/consts/const-fn-mismatch.rs

+1-1
Original file line numberDiff line numberDiff line change
@@ -9,7 +9,7 @@ trait Foo {
99

1010
impl Foo for u32 {
1111
const fn f() -> u32 {
12-
//~^ ERROR functions in traits cannot be declared const
12+
//~^ ERROR functions in trait impls cannot be declared const
1313
22
1414
}
1515
}

‎tests/ui/consts/const-fn-mismatch.stderr

+5-2
Original file line numberDiff line numberDiff line change
@@ -1,8 +1,11 @@
1-
error[E0379]: functions in traits cannot be declared const
1+
error[E0379]: functions in trait impls cannot be declared const
22
--> $DIR/const-fn-mismatch.rs:11:5
33
|
44
LL | const fn f() -> u32 {
5-
| ^^^^^ functions in traits cannot be const
5+
| ^^^^^-
6+
| |
7+
| functions in trait impls cannot be const
8+
| help: remove the `const`
69

710
error: aborting due to 1 previous error
811

‎tests/ui/consts/const-fn-not-in-trait.stderr

+8-2
Original file line numberDiff line numberDiff line change
@@ -2,13 +2,19 @@ error[E0379]: functions in traits cannot be declared const
22
--> $DIR/const-fn-not-in-trait.rs:5:5
33
|
44
LL | const fn f() -> u32;
5-
| ^^^^^ functions in traits cannot be const
5+
| ^^^^^-
6+
| |
7+
| functions in traits cannot be const
8+
| help: remove the `const`
69

710
error[E0379]: functions in traits cannot be declared const
811
--> $DIR/const-fn-not-in-trait.rs:7:5
912
|
1013
LL | const fn g() -> u32 {
11-
| ^^^^^ functions in traits cannot be const
14+
| ^^^^^-
15+
| |
16+
| functions in traits cannot be const
17+
| help: remove the `const`
1218

1319
error: aborting due to 2 previous errors
1420

‎tests/ui/consts/issue-54954.stderr

+4-1
Original file line numberDiff line numberDiff line change
@@ -2,7 +2,10 @@ error[E0379]: functions in traits cannot be declared const
22
--> $DIR/issue-54954.rs:5:5
33
|
44
LL | const fn const_val<T: Sized>() -> usize {
5-
| ^^^^^ functions in traits cannot be const
5+
| ^^^^^-
6+
| |
7+
| functions in traits cannot be const
8+
| help: remove the `const`
69

710
error[E0790]: cannot call associated function on trait without specifying the corresponding `impl` type
811
--> $DIR/issue-54954.rs:1:24

‎tests/ui/feature-gates/feature-gate-min_const_fn.rs

+1-1
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@ trait Foo {
88
}
99

1010
impl Foo for u32 {
11-
const fn foo() -> u32 { 0 } //~ ERROR functions in traits cannot be declared const
11+
const fn foo() -> u32 { 0 } //~ ERROR functions in trait impls cannot be declared const
1212
}
1313

1414
trait Bar {}

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