diff --git a/compiler/rustc_ast_lowering/src/item.rs b/compiler/rustc_ast_lowering/src/item.rs
index 3848f3b778298..3e58570767d70 100644
--- a/compiler/rustc_ast_lowering/src/item.rs
+++ b/compiler/rustc_ast_lowering/src/item.rs
@@ -1254,11 +1254,13 @@ impl<'hir> LoweringContext<'_, 'hir> {
coroutine_kind: Option<CoroutineKind>,
) -> (&'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 itctx = ImplTraitContext::Universal;
- let (generics, decl) =
- self.lower_generics(generics, sig.header.constness, id, &itctx, |this| {
- this.lower_fn_decl(&sig.decl, id, sig.span, kind, coroutine_kind)
- });
+ let (generics, decl) = self.lower_generics(generics, constness, 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) })
}
diff --git a/compiler/rustc_ast_passes/messages.ftl b/compiler/rustc_ast_passes/messages.ftl
index b5612c1820d0c..feea02c679ce1 100644
--- a/compiler/rustc_ast_passes/messages.ftl
+++ b/compiler/rustc_ast_passes/messages.ftl
@@ -233,8 +233,21 @@ ast_passes_tilde_const_disallowed = `~const` is not allowed here
.item = this item cannot have `~const` trait bounds
ast_passes_trait_fn_const =
- functions in traits cannot be declared const
- .label = functions in traits cannot be const
+ functions in {$in_impl ->
+ [true] trait impls
+ *[false] traits
+ } cannot be declared const
+ .label = functions in {$in_impl ->
+ [true] trait impls
+ *[false] traits
+ } cannot be const
+ .const_context_label = this declares all associated functions implicitly const
+ .remove_const_sugg = remove the `const`{$requires_multiple_changes ->
+ [true] {" ..."}
+ *[false] {""}
+ }
+ .make_impl_const_sugg = ... and declare the impl to be const instead
+ .make_trait_const_sugg = ... and declare the trait to be a `#[const_trait]` instead
ast_passes_trait_object_single_bound = only a single explicit lifetime bound is permitted
diff --git a/compiler/rustc_ast_passes/src/ast_validation.rs b/compiler/rustc_ast_passes/src/ast_validation.rs
index bc5cf463f1204..b69d4cccaf04f 100644
--- a/compiler/rustc_ast_passes/src/ast_validation.rs
+++ b/compiler/rustc_ast_passes/src/ast_validation.rs
@@ -46,6 +46,21 @@ enum DisallowTildeConstContext<'a> {
Item,
}
+enum TraitOrTraitImpl<'a> {
+ Trait { span: Span, constness: Option<Span> },
+ TraitImpl { constness: Const, polarity: ImplPolarity, trait_ref: &'a TraitRef },
+}
+
+impl<'a> TraitOrTraitImpl<'a> {
+ fn constness(&self) -> Option<Span> {
+ match self {
+ Self::Trait { constness: Some(span), .. }
+ | Self::TraitImpl { constness: Const::Yes(span), .. } => Some(*span),
+ _ => None,
+ }
+ }
+}
+
struct AstValidator<'a> {
session: &'a Session,
features: &'a Features,
@@ -53,11 +68,7 @@ struct AstValidator<'a> {
/// The span of the `extern` in an `extern { ... }` block, if any.
extern_mod: Option<&'a Item>,
- /// Are we inside a trait impl?
- in_trait_impl: bool,
-
- /// Are we inside a const trait defn or impl?
- in_const_trait_or_impl: bool,
+ outer_trait_or_trait_impl: Option<TraitOrTraitImpl<'a>>,
has_proc_macro_decls: bool,
@@ -78,24 +89,28 @@ struct AstValidator<'a> {
impl<'a> AstValidator<'a> {
fn with_in_trait_impl(
&mut self,
- is_in: bool,
- constness: Option<Const>,
+ trait_: Option<(Const, ImplPolarity, &'a TraitRef)>,
f: impl FnOnce(&mut Self),
) {
- let old = mem::replace(&mut self.in_trait_impl, is_in);
- let old_const = mem::replace(
- &mut self.in_const_trait_or_impl,
- matches!(constness, Some(Const::Yes(_))),
+ let old = mem::replace(
+ &mut self.outer_trait_or_trait_impl,
+ trait_.map(|(constness, polarity, trait_ref)| TraitOrTraitImpl::TraitImpl {
+ constness,
+ polarity,
+ trait_ref,
+ }),
);
f(self);
- self.in_trait_impl = old;
- self.in_const_trait_or_impl = old_const;
+ self.outer_trait_or_trait_impl = old;
}
- fn with_in_trait(&mut self, is_const: bool, f: impl FnOnce(&mut Self)) {
- let old = mem::replace(&mut self.in_const_trait_or_impl, is_const);
+ fn with_in_trait(&mut self, span: Span, constness: Option<Span>, f: impl FnOnce(&mut Self)) {
+ let old = mem::replace(
+ &mut self.outer_trait_or_trait_impl,
+ Some(TraitOrTraitImpl::Trait { span, constness }),
+ );
f(self);
- self.in_const_trait_or_impl = old;
+ self.outer_trait_or_trait_impl = old;
}
fn with_banned_impl_trait(&mut self, f: impl FnOnce(&mut Self)) {
@@ -291,10 +306,48 @@ impl<'a> AstValidator<'a> {
}
}
- fn check_trait_fn_not_const(&self, constness: Const) {
- if let Const::Yes(span) = constness {
- self.dcx().emit_err(errors::TraitFnConst { span });
- }
+ fn check_trait_fn_not_const(&self, constness: Const, parent: &TraitOrTraitImpl<'a>) {
+ let Const::Yes(span) = constness else {
+ return;
+ };
+
+ let make_impl_const_sugg = if self.features.const_trait_impl
+ && let TraitOrTraitImpl::TraitImpl {
+ constness: Const::No,
+ polarity: ImplPolarity::Positive,
+ trait_ref,
+ } = parent
+ {
+ Some(trait_ref.path.span.shrink_to_lo())
+ } else {
+ None
+ };
+
+ let make_trait_const_sugg = if self.features.const_trait_impl
+ && let TraitOrTraitImpl::Trait { span, constness: None } = parent
+ {
+ Some(span.shrink_to_lo())
+ } else {
+ None
+ };
+
+ let parent_constness = parent.constness();
+ self.dcx().emit_err(errors::TraitFnConst {
+ span,
+ in_impl: matches!(parent, TraitOrTraitImpl::TraitImpl { .. }),
+ const_context_label: parent_constness,
+ remove_const_sugg: (
+ self.session.source_map().span_extend_while(span, |c| c == ' ').unwrap_or(span),
+ match parent_constness {
+ Some(_) => rustc_errors::Applicability::MachineApplicable,
+ None => rustc_errors::Applicability::MaybeIncorrect,
+ },
+ ),
+ requires_multiple_changes: make_impl_const_sugg.is_some()
+ || make_trait_const_sugg.is_some(),
+ make_impl_const_sugg,
+ make_trait_const_sugg,
+ });
}
fn check_fn_decl(&self, fn_decl: &FnDecl, self_semantic: SelfSemantic) {
@@ -817,7 +870,7 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
self_ty,
items,
}) => {
- self.with_in_trait_impl(true, Some(*constness), |this| {
+ self.with_in_trait_impl(Some((*constness, *polarity, t)), |this| {
this.visibility_not_permitted(
&item.vis,
errors::VisibilityNotPermittedNote::TraitImpl,
@@ -963,8 +1016,9 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
}
}
ItemKind::Trait(box Trait { is_auto, generics, bounds, items, .. }) => {
- let is_const_trait = attr::contains_name(&item.attrs, sym::const_trait);
- self.with_in_trait(is_const_trait, |this| {
+ let is_const_trait =
+ attr::find_by_name(&item.attrs, sym::const_trait).map(|attr| attr.span);
+ self.with_in_trait(item.span, is_const_trait, |this| {
if *is_auto == IsAuto::Yes {
// Auto traits cannot have generics, super traits nor contain items.
this.deny_generic_params(generics, item.ident.span);
@@ -977,8 +1031,9 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
// context for the supertraits.
this.visit_vis(&item.vis);
this.visit_ident(item.ident);
- let disallowed =
- (!is_const_trait).then(|| DisallowTildeConstContext::Trait(item.span));
+ let disallowed = is_const_trait
+ .is_none()
+ .then(|| DisallowTildeConstContext::Trait(item.span));
this.with_tilde_const(disallowed, |this| {
this.visit_generics(generics);
walk_list!(this, visit_param_bound, bounds, BoundKind::SuperTraits)
@@ -1342,7 +1397,12 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
let tilde_const_allowed =
matches!(fk.header(), Some(FnHeader { constness: ast::Const::Yes(_), .. }))
- || matches!(fk.ctxt(), Some(FnCtxt::Assoc(_)) if self.in_const_trait_or_impl);
+ || matches!(fk.ctxt(), Some(FnCtxt::Assoc(_)))
+ && self
+ .outer_trait_or_trait_impl
+ .as_ref()
+ .and_then(TraitOrTraitImpl::constness)
+ .is_some();
let disallowed = (!tilde_const_allowed).then(|| DisallowTildeConstContext::Fn(fk));
self.with_tilde_const(disallowed, |this| visit::walk_fn(this, fk));
@@ -1353,7 +1413,7 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
self.check_nomangle_item_asciionly(item.ident, item.span);
}
- if ctxt == AssocCtxt::Trait || !self.in_trait_impl {
+ if ctxt == AssocCtxt::Trait || self.outer_trait_or_trait_impl.is_none() {
self.check_defaultness(item.span, item.kind.defaultness());
}
@@ -1401,10 +1461,10 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
);
}
- if ctxt == AssocCtxt::Trait || self.in_trait_impl {
+ if let Some(parent) = &self.outer_trait_or_trait_impl {
self.visibility_not_permitted(&item.vis, errors::VisibilityNotPermittedNote::TraitImpl);
if let AssocItemKind::Fn(box Fn { sig, .. }) = &item.kind {
- self.check_trait_fn_not_const(sig.header.constness);
+ self.check_trait_fn_not_const(sig.header.constness, parent);
}
}
@@ -1414,7 +1474,11 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
match &item.kind {
AssocItemKind::Fn(box Fn { sig, generics, body, .. })
- if self.in_const_trait_or_impl
+ if self
+ .outer_trait_or_trait_impl
+ .as_ref()
+ .and_then(TraitOrTraitImpl::constness)
+ .is_some()
|| ctxt == AssocCtxt::Trait
|| matches!(sig.header.constness, Const::Yes(_)) =>
{
@@ -1430,8 +1494,7 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
);
self.visit_fn(kind, item.span, item.id);
}
- _ => self
- .with_in_trait_impl(false, None, |this| visit::walk_assoc_item(this, item, ctxt)),
+ _ => self.with_in_trait_impl(None, |this| visit::walk_assoc_item(this, item, ctxt)),
}
}
}
@@ -1547,8 +1610,7 @@ pub fn check_crate(
session,
features,
extern_mod: None,
- in_trait_impl: false,
- in_const_trait_or_impl: false,
+ outer_trait_or_trait_impl: None,
has_proc_macro_decls: false,
outer_impl_trait: None,
disallow_tilde_const: Some(DisallowTildeConstContext::Item),
diff --git a/compiler/rustc_ast_passes/src/errors.rs b/compiler/rustc_ast_passes/src/errors.rs
index 0cec4374be2ee..42ada39f51589 100644
--- a/compiler/rustc_ast_passes/src/errors.rs
+++ b/compiler/rustc_ast_passes/src/errors.rs
@@ -1,7 +1,7 @@
//! Errors emitted by ast_passes.
use rustc_ast::ParamKindOrd;
-use rustc_errors::AddToDiagnostic;
+use rustc_errors::{AddToDiagnostic, Applicability};
use rustc_macros::{Diagnostic, Subdiagnostic};
use rustc_span::{symbol::Ident, Span, Symbol};
@@ -49,6 +49,24 @@ pub struct TraitFnConst {
#[primary_span]
#[label]
pub span: Span,
+ pub in_impl: bool,
+ #[label(ast_passes_const_context_label)]
+ pub const_context_label: Option<Span>,
+ #[suggestion(ast_passes_remove_const_sugg, code = "")]
+ pub remove_const_sugg: (Span, Applicability),
+ pub requires_multiple_changes: bool,
+ #[suggestion(
+ ast_passes_make_impl_const_sugg,
+ code = "const ",
+ applicability = "maybe-incorrect"
+ )]
+ pub make_impl_const_sugg: Option<Span>,
+ #[suggestion(
+ ast_passes_make_trait_const_sugg,
+ code = "#[const_trait]\n",
+ applicability = "maybe-incorrect"
+ )]
+ pub make_trait_const_sugg: Option<Span>,
}
#[derive(Diagnostic)]
diff --git a/compiler/rustc_error_codes/src/error_codes/E0379.md b/compiler/rustc_error_codes/src/error_codes/E0379.md
index ab438e4144712..35f546cfdb737 100644
--- a/compiler/rustc_error_codes/src/error_codes/E0379.md
+++ b/compiler/rustc_error_codes/src/error_codes/E0379.md
@@ -6,6 +6,10 @@ Erroneous code example:
trait Foo {
const fn bar() -> u32; // error!
}
+
+impl Foo for () {
+ const fn bar() -> u32 { 0 } // error!
+}
```
Trait methods cannot be declared `const` by design. For more information, see
diff --git a/compiler/rustc_hir_analysis/src/collect/generics_of.rs b/compiler/rustc_hir_analysis/src/collect/generics_of.rs
index 5abc752309ad5..b44b2eefabbc6 100644
--- a/compiler/rustc_hir_analysis/src/collect/generics_of.rs
+++ b/compiler/rustc_hir_analysis/src/collect/generics_of.rs
@@ -315,7 +315,10 @@ pub(super) fn generics_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Generics {
if is_host_effect {
if let Some(idx) = host_effect_index {
- bug!("parent also has host effect param? index: {idx}, def: {def_id:?}");
+ tcx.dcx().span_delayed_bug(
+ param.span,
+ format!("parent also has host effect param? index: {idx}, def: {def_id:?}"),
+ );
}
host_effect_index = Some(index as usize);
diff --git a/tests/ui/consts/const-fn-mismatch.rs b/tests/ui/consts/const-fn-mismatch.rs
index 3107b8128e602..b17e4cedd3ff6 100644
--- a/tests/ui/consts/const-fn-mismatch.rs
+++ b/tests/ui/consts/const-fn-mismatch.rs
@@ -9,7 +9,7 @@ trait Foo {
impl Foo for u32 {
const fn f() -> u32 {
- //~^ ERROR functions in traits cannot be declared const
+ //~^ ERROR functions in trait impls cannot be declared const
22
}
}
diff --git a/tests/ui/consts/const-fn-mismatch.stderr b/tests/ui/consts/const-fn-mismatch.stderr
index beaf52c0cfb36..9e7d93b0c97bb 100644
--- a/tests/ui/consts/const-fn-mismatch.stderr
+++ b/tests/ui/consts/const-fn-mismatch.stderr
@@ -1,8 +1,11 @@
-error[E0379]: functions in traits cannot be declared const
+error[E0379]: functions in trait impls cannot be declared const
--> $DIR/const-fn-mismatch.rs:11:5
|
LL | const fn f() -> u32 {
- | ^^^^^ functions in traits cannot be const
+ | ^^^^^-
+ | |
+ | functions in trait impls cannot be const
+ | help: remove the `const`
error: aborting due to 1 previous error
diff --git a/tests/ui/consts/const-fn-not-in-trait.stderr b/tests/ui/consts/const-fn-not-in-trait.stderr
index 5d364eb882dba..04430610ad00c 100644
--- a/tests/ui/consts/const-fn-not-in-trait.stderr
+++ b/tests/ui/consts/const-fn-not-in-trait.stderr
@@ -2,13 +2,19 @@ error[E0379]: functions in traits cannot be declared const
--> $DIR/const-fn-not-in-trait.rs:5:5
|
LL | const fn f() -> u32;
- | ^^^^^ functions in traits cannot be const
+ | ^^^^^-
+ | |
+ | functions in traits cannot be const
+ | help: remove the `const`
error[E0379]: functions in traits cannot be declared const
--> $DIR/const-fn-not-in-trait.rs:7:5
|
LL | const fn g() -> u32 {
- | ^^^^^ functions in traits cannot be const
+ | ^^^^^-
+ | |
+ | functions in traits cannot be const
+ | help: remove the `const`
error: aborting due to 2 previous errors
diff --git a/tests/ui/consts/issue-54954.stderr b/tests/ui/consts/issue-54954.stderr
index b0701bab793c5..03c47030c0e3f 100644
--- a/tests/ui/consts/issue-54954.stderr
+++ b/tests/ui/consts/issue-54954.stderr
@@ -2,7 +2,10 @@ error[E0379]: functions in traits cannot be declared const
--> $DIR/issue-54954.rs:5:5
|
LL | const fn const_val<T: Sized>() -> usize {
- | ^^^^^ functions in traits cannot be const
+ | ^^^^^-
+ | |
+ | functions in traits cannot be const
+ | help: remove the `const`
error[E0790]: cannot call associated function on trait without specifying the corresponding `impl` type
--> $DIR/issue-54954.rs:1:24
diff --git a/tests/ui/feature-gates/feature-gate-min_const_fn.rs b/tests/ui/feature-gates/feature-gate-min_const_fn.rs
index 8f9b433009d3c..3d61a9eb93777 100644
--- a/tests/ui/feature-gates/feature-gate-min_const_fn.rs
+++ b/tests/ui/feature-gates/feature-gate-min_const_fn.rs
@@ -8,7 +8,7 @@ trait Foo {
}
impl Foo for u32 {
- const fn foo() -> u32 { 0 } //~ ERROR functions in traits cannot be declared const
+ const fn foo() -> u32 { 0 } //~ ERROR functions in trait impls cannot be declared const
}
trait Bar {}
diff --git a/tests/ui/feature-gates/feature-gate-min_const_fn.stderr b/tests/ui/feature-gates/feature-gate-min_const_fn.stderr
index d7a58591364ed..0b16f9abb7071 100644
--- a/tests/ui/feature-gates/feature-gate-min_const_fn.stderr
+++ b/tests/ui/feature-gates/feature-gate-min_const_fn.stderr
@@ -2,19 +2,28 @@ error[E0379]: functions in traits cannot be declared const
--> $DIR/feature-gate-min_const_fn.rs:6:5
|
LL | const fn foo() -> u32;
- | ^^^^^ functions in traits cannot be const
+ | ^^^^^-
+ | |
+ | functions in traits cannot be const
+ | help: remove the `const`
error[E0379]: functions in traits cannot be declared const
--> $DIR/feature-gate-min_const_fn.rs:7:5
|
LL | const fn bar() -> u32 { 0 }
- | ^^^^^ functions in traits cannot be const
+ | ^^^^^-
+ | |
+ | functions in traits cannot be const
+ | help: remove the `const`
-error[E0379]: functions in traits cannot be declared const
+error[E0379]: functions in trait impls cannot be declared const
--> $DIR/feature-gate-min_const_fn.rs:11:5
|
LL | const fn foo() -> u32 { 0 }
- | ^^^^^ functions in traits cannot be const
+ | ^^^^^-
+ | |
+ | functions in trait impls cannot be const
+ | help: remove the `const`
error: aborting due to 3 previous errors
diff --git a/tests/ui/mismatched_types/const-fn-in-trait.stderr b/tests/ui/mismatched_types/const-fn-in-trait.stderr
index 7d1fbe45c5302..06976933b2f94 100644
--- a/tests/ui/mismatched_types/const-fn-in-trait.stderr
+++ b/tests/ui/mismatched_types/const-fn-in-trait.stderr
@@ -2,13 +2,19 @@ error[E0379]: functions in traits cannot be declared const
--> $DIR/const-fn-in-trait.rs:3:5
|
LL | const fn g();
- | ^^^^^ functions in traits cannot be const
+ | ^^^^^-
+ | |
+ | functions in traits cannot be const
+ | help: remove the `const`
-error[E0379]: functions in traits cannot be declared const
+error[E0379]: functions in trait impls cannot be declared const
--> $DIR/const-fn-in-trait.rs:7:5
|
LL | const fn f() -> u32 { 22 }
- | ^^^^^ functions in traits cannot be const
+ | ^^^^^-
+ | |
+ | functions in trait impls cannot be const
+ | help: remove the `const`
error: aborting due to 2 previous errors
diff --git a/tests/ui/parser/fn-header-semantic-fail.rs b/tests/ui/parser/fn-header-semantic-fail.rs
index f8b58cad7c144..f01e1c2277c6f 100644
--- a/tests/ui/parser/fn-header-semantic-fail.rs
+++ b/tests/ui/parser/fn-header-semantic-fail.rs
@@ -26,10 +26,10 @@ fn main() {
impl X for Y {
async fn ft1() {} // OK.
unsafe fn ft2() {} // OK.
- const fn ft3() {} //~ ERROR functions in traits cannot be declared const
+ const fn ft3() {} //~ ERROR functions in trait impls cannot be declared const
extern "C" fn ft4() {}
const async unsafe extern "C" fn ft5() {}
- //~^ ERROR functions in traits cannot be declared const
+ //~^ ERROR functions in trait impls cannot be declared const
//~| ERROR functions cannot be both `const` and `async`
}
diff --git a/tests/ui/parser/fn-header-semantic-fail.stderr b/tests/ui/parser/fn-header-semantic-fail.stderr
index cdf01e0c5df64..696d8e01b6387 100644
--- a/tests/ui/parser/fn-header-semantic-fail.stderr
+++ b/tests/ui/parser/fn-header-semantic-fail.stderr
@@ -11,13 +11,19 @@ error[E0379]: functions in traits cannot be declared const
--> $DIR/fn-header-semantic-fail.rs:18:9
|
LL | const fn ft3();
- | ^^^^^ functions in traits cannot be const
+ | ^^^^^-
+ | |
+ | functions in traits cannot be const
+ | help: remove the `const`
error[E0379]: functions in traits cannot be declared const
--> $DIR/fn-header-semantic-fail.rs:20:9
|
LL | const async unsafe extern "C" fn ft5();
- | ^^^^^ functions in traits cannot be const
+ | ^^^^^-
+ | |
+ | functions in traits cannot be const
+ | help: remove the `const`
error: functions cannot be both `const` and `async`
--> $DIR/fn-header-semantic-fail.rs:20:9
@@ -28,17 +34,23 @@ LL | const async unsafe extern "C" fn ft5();
| | `async` because of this
| `const` because of this
-error[E0379]: functions in traits cannot be declared const
+error[E0379]: functions in trait impls cannot be declared const
--> $DIR/fn-header-semantic-fail.rs:29:9
|
LL | const fn ft3() {}
- | ^^^^^ functions in traits cannot be const
+ | ^^^^^-
+ | |
+ | functions in trait impls cannot be const
+ | help: remove the `const`
-error[E0379]: functions in traits cannot be declared const
+error[E0379]: functions in trait impls cannot be declared const
--> $DIR/fn-header-semantic-fail.rs:31:9
|
LL | const async unsafe extern "C" fn ft5() {}
- | ^^^^^ functions in traits cannot be const
+ | ^^^^^-
+ | |
+ | functions in trait impls cannot be const
+ | help: remove the `const`
error: functions cannot be both `const` and `async`
--> $DIR/fn-header-semantic-fail.rs:31:9
diff --git a/tests/ui/rfcs/rfc-2632-const-trait-impl/effects/trait-fn-const.rs b/tests/ui/rfcs/rfc-2632-const-trait-impl/effects/trait-fn-const.rs
new file mode 100644
index 0000000000000..891e87d3b97d4
--- /dev/null
+++ b/tests/ui/rfcs/rfc-2632-const-trait-impl/effects/trait-fn-const.rs
@@ -0,0 +1,21 @@
+// Regression test for issue #113378.
+#![feature(const_trait_impl, effects)]
+
+#[const_trait]
+trait Trait {
+ const fn fun(); //~ ERROR functions in traits cannot be declared const
+}
+
+impl const Trait for () {
+ const fn fun() {} //~ ERROR functions in trait impls cannot be declared const
+}
+
+impl Trait for u32 {
+ const fn fun() {} //~ ERROR functions in trait impls cannot be declared const
+}
+
+trait NonConst {
+ const fn fun(); //~ ERROR functions in traits cannot be declared const
+}
+
+fn main() {}
diff --git a/tests/ui/rfcs/rfc-2632-const-trait-impl/effects/trait-fn-const.stderr b/tests/ui/rfcs/rfc-2632-const-trait-impl/effects/trait-fn-const.stderr
new file mode 100644
index 0000000000000..4d0b03046d27d
--- /dev/null
+++ b/tests/ui/rfcs/rfc-2632-const-trait-impl/effects/trait-fn-const.stderr
@@ -0,0 +1,59 @@
+error[E0379]: functions in traits cannot be declared const
+ --> $DIR/trait-fn-const.rs:6:5
+ |
+LL | #[const_trait]
+ | -------------- this declares all associated functions implicitly const
+LL | trait Trait {
+LL | const fn fun();
+ | ^^^^^-
+ | |
+ | functions in traits cannot be const
+ | help: remove the `const`
+
+error[E0379]: functions in trait impls cannot be declared const
+ --> $DIR/trait-fn-const.rs:10:5
+ |
+LL | impl const Trait for () {
+ | ----- this declares all associated functions implicitly const
+LL | const fn fun() {}
+ | ^^^^^-
+ | |
+ | functions in trait impls cannot be const
+ | help: remove the `const`
+
+error[E0379]: functions in trait impls cannot be declared const
+ --> $DIR/trait-fn-const.rs:14:5
+ |
+LL | const fn fun() {}
+ | ^^^^^ functions in trait impls cannot be const
+ |
+help: remove the `const` ...
+ |
+LL - const fn fun() {}
+LL + fn fun() {}
+ |
+help: ... and declare the impl to be const instead
+ |
+LL | impl const Trait for u32 {
+ | +++++
+
+error[E0379]: functions in traits cannot be declared const
+ --> $DIR/trait-fn-const.rs:18:5
+ |
+LL | const fn fun();
+ | ^^^^^ functions in traits cannot be const
+ |
+help: remove the `const` ...
+ |
+LL - const fn fun();
+LL + fn fun();
+ |
+help: ... and declare the trait to be a `#[const_trait]` instead
+ |
+LL + #[const_trait]
+LL | trait NonConst {
+ |
+
+error: aborting due to 4 previous errors
+
+For more information about this error, try `rustc --explain E0379`.