Deny more `~const` trait bounds

25 files changed, 444 insertions, 134 deletions

diff --git a/compiler/rustc_ast_passes/messages.ftl b/compiler/rustc_ast_passes/messages.ftl
index 43020a93078..5ce2383b973 100644
--- a/compiler/rustc_ast_passes/messages.ftl
+++ b/compiler/rustc_ast_passes/messages.ftl
@@ -214,9 +214,12 @@ ast_passes_static_without_body =
     .suggestion = provide a definition for the static
 
 ast_passes_tilde_const_disallowed = `~const` is not allowed here
-    .trait = trait objects cannot have `~const` trait bounds
     .closure = closures cannot have `~const` trait bounds
     .function = this function is not `const`, so it cannot have `~const` trait bounds
+    .trait = this trait is not a `#[const_trait]`, so it cannot have `~const` trait bounds
+    .impl = this impl is not `const`, so it cannot have `~const` trait bounds
+    .object = trait objects cannot have `~const` trait bounds
+    .item = this item cannot have `~const` trait bounds
 
 ast_passes_trait_fn_const =
     functions in traits cannot be declared const
diff --git a/compiler/rustc_ast_passes/src/ast_validation.rs b/compiler/rustc_ast_passes/src/ast_validation.rs
index 0477c7b2ba9..12a38433953 100644
--- a/compiler/rustc_ast_passes/src/ast_validation.rs
+++ b/compiler/rustc_ast_passes/src/ast_validation.rs
@@ -40,6 +40,9 @@ enum SelfSemantic {
 enum DisallowTildeConstContext<'a> {
     TraitObject,
     Fn(FnKind<'a>),
+    Trait(Span),
+    Impl(Span),
+    Item,
 }
 
 struct AstValidator<'a> {
@@ -110,18 +113,6 @@ impl<'a> AstValidator<'a> {
         self.disallow_tilde_const = old;
     }
 
-    fn with_tilde_const_allowed(&mut self, f: impl FnOnce(&mut Self)) {
-        self.with_tilde_const(None, f)
-    }
-
-    fn with_banned_tilde_const(
-        &mut self,
-        ctx: DisallowTildeConstContext<'a>,
-        f: impl FnOnce(&mut Self),
-    ) {
-        self.with_tilde_const(Some(ctx), f)
-    }
-
     fn check_type_alias_where_clause_location(
         &mut self,
         ty_alias: &TyAlias,
@@ -173,7 +164,7 @@ impl<'a> AstValidator<'a> {
                 self.with_impl_trait(Some(t.span), |this| visit::walk_ty(this, t))
             }
             TyKind::TraitObject(..) => self
-                .with_banned_tilde_const(DisallowTildeConstContext::TraitObject, |this| {
+                .with_tilde_const(Some(DisallowTildeConstContext::TraitObject), |this| {
                     visit::walk_ty(this, t)
                 }),
             TyKind::Path(qself, path) => {
@@ -822,11 +813,9 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
 
                     this.visit_vis(&item.vis);
                     this.visit_ident(item.ident);
-                    if let Const::Yes(_) = constness {
-                        this.with_tilde_const_allowed(|this| this.visit_generics(generics));
-                    } else {
-                        this.visit_generics(generics);
-                    }
+                    let disallowed = matches!(constness, Const::No)
+                        .then(|| DisallowTildeConstContext::Impl(item.span));
+                    this.with_tilde_const(disallowed, |this| this.visit_generics(generics));
                     this.visit_trait_ref(t);
                     this.visit_ty(self_ty);
 
@@ -840,10 +829,10 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
                 polarity,
                 defaultness,
                 constness,
-                generics: _,
+                generics,
                 of_trait: None,
                 self_ty,
-                items: _,
+                items,
             }) => {
                 let error =
                     |annotation_span, annotation, only_trait: bool| errors::InherentImplCannot {
@@ -875,6 +864,14 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
                 if let &Const::Yes(span) = constness {
                     self.err_handler().emit_err(error(span, "`const`", true));
                 }
+
+                self.visit_vis(&item.vis);
+                self.visit_ident(item.ident);
+                self.with_tilde_const(None, |this| this.visit_generics(generics));
+                self.visit_ty(self_ty);
+                walk_list!(self, visit_assoc_item, items, AssocCtxt::Impl);
+                walk_list!(self, visit_attribute, &item.attrs);
+                return; // Avoid visiting again.
             }
             ItemKind::Fn(box Fn { defaultness, sig, generics, body }) => {
                 self.check_defaultness(item.span, *defaultness);
@@ -955,8 +952,10 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
                     // context for the supertraits.
                     this.visit_vis(&item.vis);
                     this.visit_ident(item.ident);
-                    this.visit_generics(generics);
-                    this.with_tilde_const_allowed(|this| {
+                    let disallowed =
+                        (!is_const_trait).then(|| DisallowTildeConstContext::Trait(item.span));
+                    this.with_tilde_const(disallowed, |this| {
+                        this.visit_generics(generics);
                         walk_list!(this, visit_param_bound, bounds, BoundKind::SuperTraits)
                     });
                     walk_list!(this, visit_assoc_item, items, AssocCtxt::Trait);
@@ -976,16 +975,11 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
                 }
             }
             ItemKind::Struct(vdata, generics) => match vdata {
-                // Duplicating the `Visitor` logic allows catching all cases
-                // of `Anonymous(Struct, Union)` outside of a field struct or union.
-                //
-                // Inside `visit_ty` the validator catches every `Anonymous(Struct, Union)` it
-                // encounters, and only on `ItemKind::Struct` and `ItemKind::Union`
-                // it uses `visit_ty_common`, which doesn't contain that specific check.
                 VariantData::Struct(fields, ..) => {
                     self.visit_vis(&item.vis);
                     self.visit_ident(item.ident);
                     self.visit_generics(generics);
+                    // Permit `Anon{Struct,Union}` as field type.
                     walk_list!(self, visit_struct_field_def, fields);
                     walk_list!(self, visit_attribute, &item.attrs);
                     return;
@@ -1001,6 +995,7 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
                         self.visit_vis(&item.vis);
                         self.visit_ident(item.ident);
                         self.visit_generics(generics);
+                        // Permit `Anon{Struct,Union}` as field type.
                         walk_list!(self, visit_struct_field_def, fields);
                         walk_list!(self, visit_attribute, &item.attrs);
                         return;
@@ -1189,15 +1184,18 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
                     if let Some(reason) = &self.disallow_tilde_const =>
                 {
                     let reason = match reason {
-                        DisallowTildeConstContext::TraitObject => {
-                            errors::TildeConstReason::TraitObject
-                        }
                         DisallowTildeConstContext::Fn(FnKind::Closure(..)) => {
                             errors::TildeConstReason::Closure
                         }
                         DisallowTildeConstContext::Fn(FnKind::Fn(_, ident, ..)) => {
                             errors::TildeConstReason::Function { ident: ident.span }
                         }
+                        &DisallowTildeConstContext::Trait(span) => errors::TildeConstReason::Trait { span },
+                        &DisallowTildeConstContext::Impl(span) => errors::TildeConstReason::Impl { span },
+                        DisallowTildeConstContext::TraitObject => {
+                            errors::TildeConstReason::TraitObject
+                        }
+                        DisallowTildeConstContext::Item => errors::TildeConstReason::Item,
                     };
                     self.err_handler()
                         .emit_err(errors::TildeConstDisallowed { span: bound.span(), reason });
@@ -1305,7 +1303,6 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
                 || matches!(fk.ctxt(), Some(FnCtxt::Assoc(_)) if self.in_const_trait_or_impl);
 
         let disallowed = (!tilde_const_allowed).then(|| DisallowTildeConstContext::Fn(fk));
-
         self.with_tilde_const(disallowed, |this| visit::walk_fn(this, fk));
     }
 
@@ -1374,18 +1371,6 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
         }
 
         match &item.kind {
-            AssocItemKind::Type(box TyAlias { generics, bounds, ty, .. })
-                if ctxt == AssocCtxt::Trait =>
-            {
-                self.visit_vis(&item.vis);
-                self.visit_ident(item.ident);
-                walk_list!(self, visit_attribute, &item.attrs);
-                self.with_tilde_const_allowed(|this| {
-                    this.visit_generics(generics);
-                    walk_list!(this, visit_param_bound, bounds, BoundKind::Bound);
-                });
-                walk_list!(self, visit_ty, ty);
-            }
             AssocItemKind::Fn(box Fn { sig, generics, body, .. })
                 if self.in_const_trait_or_impl
                     || ctxt == AssocCtxt::Trait
@@ -1537,7 +1522,7 @@ pub fn check_crate(
         in_const_trait_or_impl: false,
         has_proc_macro_decls: false,
         outer_impl_trait: None,
-        disallow_tilde_const: None,
+        disallow_tilde_const: Some(DisallowTildeConstContext::Item),
         is_impl_trait_banned: false,
         lint_buffer: lints,
     };
diff --git a/compiler/rustc_ast_passes/src/errors.rs b/compiler/rustc_ast_passes/src/errors.rs
index e74d94e4347..60afb8adc04 100644
--- a/compiler/rustc_ast_passes/src/errors.rs
+++ b/compiler/rustc_ast_passes/src/errors.rs
@@ -551,8 +551,6 @@ pub struct TildeConstDisallowed {
 
 #[derive(Subdiagnostic)]
 pub enum TildeConstReason {
-    #[note(ast_passes_trait)]
-    TraitObject,
     #[note(ast_passes_closure)]
     Closure,
     #[note(ast_passes_function)]
@@ -560,6 +558,20 @@ pub enum TildeConstReason {
         #[primary_span]
         ident: Span,
     },
+    #[note(ast_passes_trait)]
+    Trait {
+        #[primary_span]
+        span: Span,
+    },
+    #[note(ast_passes_impl)]
+    Impl {
+        #[primary_span]
+        span: Span,
+    },
+    #[note(ast_passes_object)]
+    TraitObject,
+    #[note(ast_passes_item)]
+    Item,
 }
 
 #[derive(Diagnostic)]
diff --git a/tests/ui/generic-const-items/const-trait-impl.rs b/tests/ui/generic-const-items/const-trait-impl.rs
index d30f7af170d..43cdf818c46 100644
--- a/tests/ui/generic-const-items/const-trait-impl.rs
+++ b/tests/ui/generic-const-items/const-trait-impl.rs
@@ -7,8 +7,8 @@
 #![allow(incomplete_features)]
 #![crate_type = "lib"]
 
-// FIXME(generic_const_items): Interpret `~const` as always-const.
-const CREATE<T: ~const Create>: T = T::create();
+// FIXME(generic_const_items, effects): Introduce `const` bounds to make this work.
+const CREATE<T: Create>: T = T::create();
 
 pub const K0: i32 = CREATE::<i32>;
 pub const K1: i32 = CREATE; // arg inferred
diff --git a/tests/ui/generic-const-items/const-trait-impl.stderr b/tests/ui/generic-const-items/const-trait-impl.stderr
index 34360c581d5..64aa8adf8a7 100644
--- a/tests/ui/generic-const-items/const-trait-impl.stderr
+++ b/tests/ui/generic-const-items/const-trait-impl.stderr
@@ -1,8 +1,8 @@
 error[E0015]: cannot call non-const fn `<T as Create>::create` in constants
-  --> $DIR/const-trait-impl.rs:11:37
+  --> $DIR/const-trait-impl.rs:11:30
    |
-LL | const CREATE<T: ~const Create>: T = T::create();
-   |                                     ^^^^^^^^^^^
+LL | const CREATE<T: Create>: T = T::create();
+   |                              ^^^^^^^^^^^
    |
    = note: calls in constants are limited to constant functions, tuple structs and tuple variants
 
diff --git a/tests/ui/rfcs/rfc-2632-const-trait-impl/assoc-type-const-bound-usage.stderr b/tests/ui/rfcs/rfc-2632-const-trait-impl/assoc-type-const-bound-usage.stderr
index 6d436018bf4..e6b663c47d7 100644
--- a/tests/ui/rfcs/rfc-2632-const-trait-impl/assoc-type-const-bound-usage.stderr
+++ b/tests/ui/rfcs/rfc-2632-const-trait-impl/assoc-type-const-bound-usage.stderr
@@ -1,3 +1,11 @@
+error: `~const` is not allowed here
+  --> $DIR/assoc-type-const-bound-usage.rs:7:17
+   |
+LL |     type Assoc: ~const Foo;
+   |                 ^^^^^^^^^^
+   |
+   = note: this item cannot have `~const` trait bounds
+
 error[E0308]: mismatched types
   --> $DIR/assoc-type-const-bound-usage.rs:12:5
    |
@@ -7,6 +15,6 @@ LL |     <T as Foo>::Assoc::foo();
    = note: expected constant `host`
               found constant `true`
 
-error: aborting due to previous error
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0308`.
diff --git a/tests/ui/rfcs/rfc-2632-const-trait-impl/assoc-type.stderr b/tests/ui/rfcs/rfc-2632-const-trait-impl/assoc-type.stderr
index 0cffae1da8d..7df16ca5a3b 100644
--- a/tests/ui/rfcs/rfc-2632-const-trait-impl/assoc-type.stderr
+++ b/tests/ui/rfcs/rfc-2632-const-trait-impl/assoc-type.stderr
@@ -1,8 +1,16 @@
+error: `~const` is not allowed here
+  --> $DIR/assoc-type.rs:17:15
+   |
+LL |     type Bar: ~const std::ops::Add;
+   |               ^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: this item cannot have `~const` trait bounds
+
 error: ~const can only be applied to `#[const_trait]` traits
   --> $DIR/assoc-type.rs:17:22
    |
 LL |     type Bar: ~const std::ops::Add;
    |                      ^^^^^^^^^^^^^
 
-error: aborting due to previous error
+error: aborting due to 2 previous errors
 
diff --git a/tests/ui/rfcs/rfc-2632-const-trait-impl/effects/const-bound-on-not-const-associated-fn.rs b/tests/ui/rfcs/rfc-2632-const-trait-impl/const-bound-on-not-const-associated-fn.rs
index 1e22ddcea8d..0025449c492 100644
--- a/tests/ui/rfcs/rfc-2632-const-trait-impl/effects/const-bound-on-not-const-associated-fn.rs
+++ b/tests/ui/rfcs/rfc-2632-const-trait-impl/const-bound-on-not-const-associated-fn.rs
@@ -1,4 +1,4 @@
-#![feature(const_trait_impl, effects)]
+#![feature(const_trait_impl)]
 
 #[const_trait]
 trait MyTrait {
diff --git a/tests/ui/rfcs/rfc-2632-const-trait-impl/effects/const-bound-on-not-const-associated-fn.stderr b/tests/ui/rfcs/rfc-2632-const-trait-impl/const-bound-on-not-const-associated-fn.stderr
index 9210f642706..9210f642706 100644
--- a/tests/ui/rfcs/rfc-2632-const-trait-impl/effects/const-bound-on-not-const-associated-fn.stderr
+++ b/tests/ui/rfcs/rfc-2632-const-trait-impl/const-bound-on-not-const-associated-fn.stderr
diff --git a/tests/ui/rfcs/rfc-2632-const-trait-impl/const-drop.precise.stderr b/tests/ui/rfcs/rfc-2632-const-trait-impl/const-drop.precise.stderr
index 23e36887025..be75e852e0a 100644
--- a/tests/ui/rfcs/rfc-2632-const-trait-impl/const-drop.precise.stderr
+++ b/tests/ui/rfcs/rfc-2632-const-trait-impl/const-drop.precise.stderr
@@ -1,19 +1,10 @@
-error[E0493]: destructor of `T` cannot be evaluated at compile-time
-  --> $DIR/const-drop.rs:19:32
+error: `~const` is not allowed here
+  --> $DIR/const-drop.rs:67:38
    |
-LL | const fn a<T: ~const Destruct>(_: T) {}
-   |                                ^      - value is dropped here
-   |                                |
-   |                                the destructor for this type cannot be evaluated in constant functions
-
-error[E0493]: destructor of `S<'_>` cannot be evaluated at compile-time
-  --> $DIR/const-drop.rs:24:13
+LL |     pub struct ConstDropWithBound<T: ~const SomeTrait>(pub core::marker::PhantomData<T>);
+   |                                      ^^^^^^^^^^^^^^^^
    |
-LL |     let _ = S(&mut c);
-   |             ^^^^^^^^^- value is dropped here
-   |             |
-   |             the destructor for this type cannot be evaluated in constant functions
+   = note: this item cannot have `~const` trait bounds
 
-error: aborting due to 2 previous errors
+error: aborting due to previous error
 
-For more information about this error, try `rustc --explain E0493`.
diff --git a/tests/ui/rfcs/rfc-2632-const-trait-impl/const-drop.rs b/tests/ui/rfcs/rfc-2632-const-trait-impl/const-drop.rs
index 0a9cf638a2d..9da84cdb052 100644
--- a/tests/ui/rfcs/rfc-2632-const-trait-impl/const-drop.rs
+++ b/tests/ui/rfcs/rfc-2632-const-trait-impl/const-drop.rs
@@ -63,6 +63,7 @@ mod t {
         fn foo() {}
     }
 
+    // FIXME(effects): This should be a `const` bound instead of a `~const` one.
     pub struct ConstDropWithBound<T: ~const SomeTrait>(pub core::marker::PhantomData<T>);
 
     impl<T: ~const SomeTrait> const Drop for ConstDropWithBound<T> {
diff --git a/tests/ui/rfcs/rfc-2632-const-trait-impl/const-drop.stock.stderr b/tests/ui/rfcs/rfc-2632-const-trait-impl/const-drop.stock.stderr
index 23e36887025..be75e852e0a 100644
--- a/tests/ui/rfcs/rfc-2632-const-trait-impl/const-drop.stock.stderr
+++ b/tests/ui/rfcs/rfc-2632-const-trait-impl/const-drop.stock.stderr
@@ -1,19 +1,10 @@
-error[E0493]: destructor of `T` cannot be evaluated at compile-time
-  --> $DIR/const-drop.rs:19:32
+error: `~const` is not allowed here
+  --> $DIR/const-drop.rs:67:38
    |
-LL | const fn a<T: ~const Destruct>(_: T) {}
-   |                                ^      - value is dropped here
-   |                                |
-   |                                the destructor for this type cannot be evaluated in constant functions
-
-error[E0493]: destructor of `S<'_>` cannot be evaluated at compile-time
-  --> $DIR/const-drop.rs:24:13
+LL |     pub struct ConstDropWithBound<T: ~const SomeTrait>(pub core::marker::PhantomData<T>);
+   |                                      ^^^^^^^^^^^^^^^^
    |
-LL |     let _ = S(&mut c);
-   |             ^^^^^^^^^- value is dropped here
-   |             |
-   |             the destructor for this type cannot be evaluated in constant functions
+   = note: this item cannot have `~const` trait bounds
 
-error: aborting due to 2 previous errors
+error: aborting due to previous error
 
-For more information about this error, try `rustc --explain E0493`.
diff --git a/tests/ui/rfcs/rfc-2632-const-trait-impl/issue-90052.rs b/tests/ui/rfcs/rfc-2632-const-trait-impl/issue-90052.rs
deleted file mode 100644
index 21ddf4ab4e5..00000000000
--- a/tests/ui/rfcs/rfc-2632-const-trait-impl/issue-90052.rs
+++ /dev/null
@@ -1,9 +0,0 @@
-#![feature(const_trait_impl)]
-
-#[const_trait]
-trait Bar {}
-
-fn foo<T>() where T: ~const Bar {}
-//~^ ERROR `~const` is not allowed
-
-fn main() {}
diff --git a/tests/ui/rfcs/rfc-2632-const-trait-impl/issue-90052.stderr b/tests/ui/rfcs/rfc-2632-const-trait-impl/issue-90052.stderr
deleted file mode 100644
index b2a9365378b..00000000000
--- a/tests/ui/rfcs/rfc-2632-const-trait-impl/issue-90052.stderr
+++ /dev/null
@@ -1,14 +0,0 @@
-error: `~const` is not allowed here
-  --> $DIR/issue-90052.rs:6:22
-   |
-LL | fn foo<T>() where T: ~const Bar {}
-   |                      ^^^^^^^^^^
-   |
-note: this function is not `const`, so it cannot have `~const` trait bounds
-  --> $DIR/issue-90052.rs:6:4
-   |
-LL | fn foo<T>() where T: ~const Bar {}
-   |    ^^^
-
-error: aborting due to previous error
-
diff --git a/tests/ui/rfcs/rfc-2632-const-trait-impl/specialization/const-default-bound-non-const-specialized-bound.rs b/tests/ui/rfcs/rfc-2632-const-trait-impl/specialization/const-default-bound-non-const-specialized-bound.rs
index 3db59631ef8..234b0dd0063 100644
--- a/tests/ui/rfcs/rfc-2632-const-trait-impl/specialization/const-default-bound-non-const-specialized-bound.rs
+++ b/tests/ui/rfcs/rfc-2632-const-trait-impl/specialization/const-default-bound-non-const-specialized-bound.rs
@@ -18,11 +18,7 @@ trait Bar {
     fn bar();
 }
 
-// bgr360: I was only able to exercise the code path that raises the
-// "missing ~const qualifier" error by making this base impl non-const, even
-// though that doesn't really make sense to do. As seen below, if the base impl
-// is made const, rustc fails earlier with an overlapping impl failure.
-impl<T> Bar for T
+impl<T> const Bar for T
 where
     T: ~const Foo,
 {
diff --git a/tests/ui/rfcs/rfc-2632-const-trait-impl/super-traits-fail-2.nn.stderr b/tests/ui/rfcs/rfc-2632-const-trait-impl/super-traits-fail-2.nn.stderr
index b60399c57dc..204f0f9f89f 100644
--- a/tests/ui/rfcs/rfc-2632-const-trait-impl/super-traits-fail-2.nn.stderr
+++ b/tests/ui/rfcs/rfc-2632-const-trait-impl/super-traits-fail-2.nn.stderr
@@ -1,3 +1,15 @@
+error: `~const` is not allowed here
+  --> $DIR/super-traits-fail-2.rs:11:12
+   |
+LL | trait Bar: ~const Foo {}
+   |            ^^^^^^^^^^
+   |
+note: this trait is not a `#[const_trait]`, so it cannot have `~const` trait bounds
+  --> $DIR/super-traits-fail-2.rs:11:1
+   |
+LL | trait Bar: ~const Foo {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^
+
 error: ~const can only be applied to `#[const_trait]` traits
   --> $DIR/super-traits-fail-2.rs:11:19
    |
@@ -12,5 +24,5 @@ LL | trait Bar: ~const Foo {}
    |
    = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
-error: aborting due to 2 previous errors
+error: aborting due to 3 previous errors
 
diff --git a/tests/ui/rfcs/rfc-2632-const-trait-impl/super-traits-fail-2.yn.stderr b/tests/ui/rfcs/rfc-2632-const-trait-impl/super-traits-fail-2.yn.stderr
index 5d34156a519..06330958b8e 100644
--- a/tests/ui/rfcs/rfc-2632-const-trait-impl/super-traits-fail-2.yn.stderr
+++ b/tests/ui/rfcs/rfc-2632-const-trait-impl/super-traits-fail-2.yn.stderr
@@ -1,11 +1,14 @@
-error[E0015]: cannot call non-const fn `<T as Foo>::a` in constant functions
-  --> $DIR/super-traits-fail-2.rs:16:7
+error: `~const` is not allowed here
+  --> $DIR/super-traits-fail-2.rs:11:12
    |
-LL |     x.a();
-   |       ^^^
+LL | trait Bar: ~const Foo {}
+   |            ^^^^^^^^^^
    |
-   = note: calls in constant functions are limited to constant functions, tuple structs and tuple variants
+note: this trait is not a `#[const_trait]`, so it cannot have `~const` trait bounds
+  --> $DIR/super-traits-fail-2.rs:11:1
+   |
+LL | trait Bar: ~const Foo {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: aborting due to previous error
 
-For more information about this error, try `rustc --explain E0015`.
diff --git a/tests/ui/rfcs/rfc-2632-const-trait-impl/super-traits-fail-3.nn.stderr b/tests/ui/rfcs/rfc-2632-const-trait-impl/super-traits-fail-3.nn.stderr
index eb12a236d8c..77b13a351e2 100644
--- a/tests/ui/rfcs/rfc-2632-const-trait-impl/super-traits-fail-3.nn.stderr
+++ b/tests/ui/rfcs/rfc-2632-const-trait-impl/super-traits-fail-3.nn.stderr
@@ -1,3 +1,15 @@
+error: `~const` is not allowed here
+  --> $DIR/super-traits-fail-3.rs:13:12
+   |
+LL | trait Bar: ~const Foo {}
+   |            ^^^^^^^^^^
+   |
+note: this trait is not a `#[const_trait]`, so it cannot have `~const` trait bounds
+  --> $DIR/super-traits-fail-3.rs:13:1
+   |
+LL | trait Bar: ~const Foo {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^
+
 error: ~const can only be applied to `#[const_trait]` traits
   --> $DIR/super-traits-fail-3.rs:13:19
    |
@@ -13,10 +25,10 @@ LL | trait Bar: ~const Foo {}
    = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
 error: ~const can only be applied to `#[const_trait]` traits
-  --> $DIR/super-traits-fail-3.rs:17:24
+  --> $DIR/super-traits-fail-3.rs:18:24
    |
 LL | const fn foo<T: ~const Bar>(x: &T) {
    |                        ^^^
 
-error: aborting due to 3 previous errors
+error: aborting due to 4 previous errors
 
diff --git a/tests/ui/rfcs/rfc-2632-const-trait-impl/super-traits-fail-3.rs b/tests/ui/rfcs/rfc-2632-const-trait-impl/super-traits-fail-3.rs
index 16c592830d7..5994057b2db 100644
--- a/tests/ui/rfcs/rfc-2632-const-trait-impl/super-traits-fail-3.rs
+++ b/tests/ui/rfcs/rfc-2632-const-trait-impl/super-traits-fail-3.rs
@@ -13,6 +13,7 @@ trait Foo {
 trait Bar: ~const Foo {}
 //[ny,nn]~^ ERROR: ~const can only be applied to `#[const_trait]`
 //[ny,nn]~| ERROR: ~const can only be applied to `#[const_trait]`
+//[yn,nn]~^^^ ERROR: `~const` is not allowed here
 
 const fn foo<T: ~const Bar>(x: &T) {
     //[yn,nn]~^ ERROR: ~const can only be applied to `#[const_trait]`
diff --git a/tests/ui/rfcs/rfc-2632-const-trait-impl/super-traits-fail-3.yn.stderr b/tests/ui/rfcs/rfc-2632-const-trait-impl/super-traits-fail-3.yn.stderr
index 58225b94591..2e41eb9b4c4 100644
--- a/tests/ui/rfcs/rfc-2632-const-trait-impl/super-traits-fail-3.yn.stderr
+++ b/tests/ui/rfcs/rfc-2632-const-trait-impl/super-traits-fail-3.yn.stderr
@@ -1,8 +1,20 @@
+error: `~const` is not allowed here
+  --> $DIR/super-traits-fail-3.rs:13:12
+   |
+LL | trait Bar: ~const Foo {}
+   |            ^^^^^^^^^^
+   |
+note: this trait is not a `#[const_trait]`, so it cannot have `~const` trait bounds
+  --> $DIR/super-traits-fail-3.rs:13:1
+   |
+LL | trait Bar: ~const Foo {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^
+
 error: ~const can only be applied to `#[const_trait]` traits
-  --> $DIR/super-traits-fail-3.rs:17:24
+  --> $DIR/super-traits-fail-3.rs:18:24
    |
 LL | const fn foo<T: ~const Bar>(x: &T) {
    |                        ^^^
 
-error: aborting due to previous error
+error: aborting due to 2 previous errors
 
diff --git a/tests/ui/rfcs/rfc-2632-const-trait-impl/super-traits-fail-3.yy.stderr b/tests/ui/rfcs/rfc-2632-const-trait-impl/super-traits-fail-3.yy.stderr
index 6bc643e6871..d81d9aa94da 100644
--- a/tests/ui/rfcs/rfc-2632-const-trait-impl/super-traits-fail-3.yy.stderr
+++ b/tests/ui/rfcs/rfc-2632-const-trait-impl/super-traits-fail-3.yy.stderr
@@ -1,5 +1,5 @@
 error[E0015]: cannot call non-const fn `<T as Foo>::a` in constant functions
-  --> $DIR/super-traits-fail-3.rs:19:7
+  --> $DIR/super-traits-fail-3.rs:20:7
    |
 LL |     x.a();
    |       ^^^
diff --git a/tests/ui/rfcs/rfc-2632-const-trait-impl/tilde-const-invalid-places.rs b/tests/ui/rfcs/rfc-2632-const-trait-impl/tilde-const-invalid-places.rs
index 95f7aaba0fc..bbe1194f7a3 100644
--- a/tests/ui/rfcs/rfc-2632-const-trait-impl/tilde-const-invalid-places.rs
+++ b/tests/ui/rfcs/rfc-2632-const-trait-impl/tilde-const-invalid-places.rs
@@ -1,7 +1,55 @@
 #![feature(const_trait_impl)]
-#![feature(associated_type_bounds)]
 
-struct TildeQuestion<T: ~const ?Sized>(std::marker::PhantomData<T>);
-//~^ ERROR `~const` and `?` are mutually exclusive
+#[const_trait]
+trait Trait {}
+
+// Regression test for issue #90052.
+fn non_const_function<T: ~const Trait>() {} //~ ERROR `~const` is not allowed
+
+struct Struct<T: ~const Trait> { field: T } //~ ERROR `~const` is not allowed here
+struct TupleStruct<T: ~const Trait>(T); //~ ERROR `~const` is not allowed here
+struct UnitStruct<T: ~const Trait>; //~ ERROR `~const` is not allowed here
+
+enum Enum<T: ~const Trait> { Variant(T) } //~ ERROR `~const` is not allowed here
+
+union Union<T: ~const Trait> { field: T } //~ ERROR `~const` is not allowed here
+
+type Type<T: ~const Trait> = T; //~ ERROR `~const` is not allowed here
+
+const CONSTANT<T: ~const Trait>: () = (); //~ ERROR `~const` is not allowed here
+//~^ ERROR generic const items are experimental
+
+trait NonConstTrait {
+    type Type<T: ~const Trait>: ~const Trait;
+    //~^ ERROR `~const` is not allowed
+    //~| ERROR `~const` is not allowed
+    fn non_const_function<T: ~const Trait>(); //~ ERROR `~const` is not allowed
+    const CONSTANT<T: ~const Trait>: (); //~ ERROR `~const` is not allowed
+    //~^ ERROR generic const items are experimental
+}
+
+impl NonConstTrait for () {
+    type Type<T: ~const Trait> = (); //~ ERROR `~const` is not allowed
+    fn non_const_function<T: ~const Trait>() {} //~ ERROR `~const` is not allowed
+    const CONSTANT<T: ~const Trait>: () = (); //~ ERROR `~const` is not allowed
+    //~^ ERROR generic const items are experimental
+}
+
+struct Implementor;
+
+impl Implementor {
+    type Type<T: ~const Trait> = (); //~ ERROR `~const` is not allowed
+    //~^ ERROR inherent associated types are unstable
+    fn non_const_function<T: ~const Trait>() {} //~ ERROR `~const` is not allowed
+    const CONSTANT<T: ~const Trait>: () = (); //~ ERROR `~const` is not allowed
+    //~^ ERROR generic const items are experimental
+}
+
+// non-const traits
+trait Child0: ~const Trait {} //~ ERROR `~const` is not allowed
+trait Child1 where Self: ~const Trait {} //~ ERROR `~const` is not allowed
+
+// non-const impl
+impl<T: ~const Trait> Trait for T {} //~ ERROR `~const` is not allowed
 
 fn main() {}
diff --git a/tests/ui/rfcs/rfc-2632-const-trait-impl/tilde-const-invalid-places.stderr b/tests/ui/rfcs/rfc-2632-const-trait-impl/tilde-const-invalid-places.stderr
index d20f146df3f..c14f9a99035 100644
--- a/tests/ui/rfcs/rfc-2632-const-trait-impl/tilde-const-invalid-places.stderr
+++ b/tests/ui/rfcs/rfc-2632-const-trait-impl/tilde-const-invalid-places.stderr
@@ -1,8 +1,244 @@
-error: `~const` and `?` are mutually exclusive
-  --> $DIR/tilde-const-invalid-places.rs:4:25
+error: `~const` is not allowed here
+  --> $DIR/tilde-const-invalid-places.rs:7:26
    |
-LL | struct TildeQuestion<T: ~const ?Sized>(std::marker::PhantomData<T>);
-   |                         ^^^^^^^^^^^^^
+LL | fn non_const_function<T: ~const Trait>() {}
+   |                          ^^^^^^^^^^^^
+   |
+note: this function is not `const`, so it cannot have `~const` trait bounds
+  --> $DIR/tilde-const-invalid-places.rs:7:4
+   |
+LL | fn non_const_function<T: ~const Trait>() {}
+   |    ^^^^^^^^^^^^^^^^^^
+
+error: `~const` is not allowed here
+  --> $DIR/tilde-const-invalid-places.rs:9:18
+   |
+LL | struct Struct<T: ~const Trait> { field: T }
+   |                  ^^^^^^^^^^^^
+   |
+   = note: this item cannot have `~const` trait bounds
+
+error: `~const` is not allowed here
+  --> $DIR/tilde-const-invalid-places.rs:10:23
+   |
+LL | struct TupleStruct<T: ~const Trait>(T);
+   |                       ^^^^^^^^^^^^
+   |
+   = note: this item cannot have `~const` trait bounds
+
+error: `~const` is not allowed here
+  --> $DIR/tilde-const-invalid-places.rs:11:22
+   |
+LL | struct UnitStruct<T: ~const Trait>;
+   |                      ^^^^^^^^^^^^
+   |
+   = note: this item cannot have `~const` trait bounds
+
+error: `~const` is not allowed here
+  --> $DIR/tilde-const-invalid-places.rs:13:14
+   |
+LL | enum Enum<T: ~const Trait> { Variant(T) }
+   |              ^^^^^^^^^^^^
+   |
+   = note: this item cannot have `~const` trait bounds
+
+error: `~const` is not allowed here
+  --> $DIR/tilde-const-invalid-places.rs:15:16
+   |
+LL | union Union<T: ~const Trait> { field: T }
+   |                ^^^^^^^^^^^^
+   |
+   = note: this item cannot have `~const` trait bounds
+
+error: `~const` is not allowed here
+  --> $DIR/tilde-const-invalid-places.rs:17:14
+   |
+LL | type Type<T: ~const Trait> = T;
+   |              ^^^^^^^^^^^^
+   |
+   = note: this item cannot have `~const` trait bounds
+
+error: `~const` is not allowed here
+  --> $DIR/tilde-const-invalid-places.rs:19:19
+   |
+LL | const CONSTANT<T: ~const Trait>: () = ();
+   |                   ^^^^^^^^^^^^
+   |
+   = note: this item cannot have `~const` trait bounds
+
+error: `~const` is not allowed here
+  --> $DIR/tilde-const-invalid-places.rs:23:18
+   |
+LL |     type Type<T: ~const Trait>: ~const Trait;
+   |                  ^^^^^^^^^^^^
+   |
+   = note: this item cannot have `~const` trait bounds
+
+error: `~const` is not allowed here
+  --> $DIR/tilde-const-invalid-places.rs:23:33
+   |
+LL |     type Type<T: ~const Trait>: ~const Trait;
+   |                                 ^^^^^^^^^^^^
+   |
+   = note: this item cannot have `~const` trait bounds
+
+error: `~const` is not allowed here
+  --> $DIR/tilde-const-invalid-places.rs:26:30
+   |
+LL |     fn non_const_function<T: ~const Trait>();
+   |                              ^^^^^^^^^^^^
+   |
+note: this function is not `const`, so it cannot have `~const` trait bounds
+  --> $DIR/tilde-const-invalid-places.rs:26:8
+   |
+LL |     fn non_const_function<T: ~const Trait>();
+   |        ^^^^^^^^^^^^^^^^^^
+
+error: `~const` is not allowed here
+  --> $DIR/tilde-const-invalid-places.rs:27:23
+   |
+LL |     const CONSTANT<T: ~const Trait>: ();
+   |                       ^^^^^^^^^^^^
+   |
+   = note: this item cannot have `~const` trait bounds
+
+error: `~const` is not allowed here
+  --> $DIR/tilde-const-invalid-places.rs:32:18
+   |
+LL |     type Type<T: ~const Trait> = ();
+   |                  ^^^^^^^^^^^^
+   |
+   = note: this item cannot have `~const` trait bounds
+
+error: `~const` is not allowed here
+  --> $DIR/tilde-const-invalid-places.rs:33:30
+   |
+LL |     fn non_const_function<T: ~const Trait>() {}
+   |                              ^^^^^^^^^^^^
+   |
+note: this function is not `const`, so it cannot have `~const` trait bounds
+  --> $DIR/tilde-const-invalid-places.rs:33:8
+   |
+LL |     fn non_const_function<T: ~const Trait>() {}
+   |        ^^^^^^^^^^^^^^^^^^
+
+error: `~const` is not allowed here
+  --> $DIR/tilde-const-invalid-places.rs:34:23
+   |
+LL |     const CONSTANT<T: ~const Trait>: () = ();
+   |                       ^^^^^^^^^^^^
+   |
+   = note: this item cannot have `~const` trait bounds
+
+error: `~const` is not allowed here
+  --> $DIR/tilde-const-invalid-places.rs:41:18
+   |
+LL |     type Type<T: ~const Trait> = ();
+   |                  ^^^^^^^^^^^^
+   |
+   = note: this item cannot have `~const` trait bounds
+
+error: `~const` is not allowed here
+  --> $DIR/tilde-const-invalid-places.rs:43:30
+   |
+LL |     fn non_const_function<T: ~const Trait>() {}
+   |                              ^^^^^^^^^^^^
+   |
+note: this function is not `const`, so it cannot have `~const` trait bounds
+  --> $DIR/tilde-const-invalid-places.rs:43:8
+   |
+LL |     fn non_const_function<T: ~const Trait>() {}
+   |        ^^^^^^^^^^^^^^^^^^
+
+error: `~const` is not allowed here
+  --> $DIR/tilde-const-invalid-places.rs:44:23
+   |
+LL |     const CONSTANT<T: ~const Trait>: () = ();
+   |                       ^^^^^^^^^^^^
+   |
+   = note: this item cannot have `~const` trait bounds
+
+error: `~const` is not allowed here
+  --> $DIR/tilde-const-invalid-places.rs:49:15
+   |
+LL | trait Child0: ~const Trait {}
+   |               ^^^^^^^^^^^^
+   |
+note: this trait is not a `#[const_trait]`, so it cannot have `~const` trait bounds
+  --> $DIR/tilde-const-invalid-places.rs:49:1
+   |
+LL | trait Child0: ~const Trait {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: `~const` is not allowed here
+  --> $DIR/tilde-const-invalid-places.rs:50:26
+   |
+LL | trait Child1 where Self: ~const Trait {}
+   |                          ^^^^^^^^^^^^
+   |
+note: this trait is not a `#[const_trait]`, so it cannot have `~const` trait bounds
+  --> $DIR/tilde-const-invalid-places.rs:50:1
+   |
+LL | trait Child1 where Self: ~const Trait {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: `~const` is not allowed here
+  --> $DIR/tilde-const-invalid-places.rs:53:9
+   |
+LL | impl<T: ~const Trait> Trait for T {}
+   |         ^^^^^^^^^^^^
+   |
+note: this impl is not `const`, so it cannot have `~const` trait bounds
+  --> $DIR/tilde-const-invalid-places.rs:53:1
+   |
+LL | impl<T: ~const Trait> Trait for T {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error[E0658]: generic const items are experimental
+  --> $DIR/tilde-const-invalid-places.rs:19:15
+   |
+LL | const CONSTANT<T: ~const Trait>: () = ();
+   |               ^^^^^^^^^^^^^^^^^
+   |
+   = note: see issue #113521 <https://github.com/rust-lang/rust/issues/113521> for more information
+   = help: add `#![feature(generic_const_items)]` to the crate attributes to enable
+
+error[E0658]: generic const items are experimental
+  --> $DIR/tilde-const-invalid-places.rs:27:19
+   |
+LL |     const CONSTANT<T: ~const Trait>: ();
+   |                   ^^^^^^^^^^^^^^^^^
+   |
+   = note: see issue #113521 <https://github.com/rust-lang/rust/issues/113521> for more information
+   = help: add `#![feature(generic_const_items)]` to the crate attributes to enable
+
+error[E0658]: generic const items are experimental
+  --> $DIR/tilde-const-invalid-places.rs:34:19
+   |
+LL |     const CONSTANT<T: ~const Trait>: () = ();
+   |                   ^^^^^^^^^^^^^^^^^
+   |
+   = note: see issue #113521 <https://github.com/rust-lang/rust/issues/113521> for more information
+   = help: add `#![feature(generic_const_items)]` to the crate attributes to enable
+
+error[E0658]: generic const items are experimental
+  --> $DIR/tilde-const-invalid-places.rs:44:19
+   |
+LL |     const CONSTANT<T: ~const Trait>: () = ();
+   |                   ^^^^^^^^^^^^^^^^^
+   |
+   = note: see issue #113521 <https://github.com/rust-lang/rust/issues/113521> for more information
+   = help: add `#![feature(generic_const_items)]` to the crate attributes to enable
+
+error[E0658]: inherent associated types are unstable
+  --> $DIR/tilde-const-invalid-places.rs:41:5
+   |
+LL |     type Type<T: ~const Trait> = ();
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: see issue #8995 <https://github.com/rust-lang/rust/issues/8995> for more information
+   = help: add `#![feature(inherent_associated_types)]` to the crate attributes to enable
 
-error: aborting due to previous error
+error: aborting due to 26 previous errors
 
+For more information about this error, try `rustc --explain E0658`.
diff --git a/tests/ui/rfcs/rfc-2632-const-trait-impl/tilde-const-maybe-trait.rs b/tests/ui/rfcs/rfc-2632-const-trait-impl/tilde-const-maybe-trait.rs
new file mode 100644
index 00000000000..ed911d965d6
--- /dev/null
+++ b/tests/ui/rfcs/rfc-2632-const-trait-impl/tilde-const-maybe-trait.rs
@@ -0,0 +1,6 @@
+#![feature(const_trait_impl)]
+
+const fn tilde_question<T: ~const ?Sized>() {}
+//~^ ERROR `~const` and `?` are mutually exclusive
+
+fn main() {}
diff --git a/tests/ui/rfcs/rfc-2632-const-trait-impl/tilde-const-maybe-trait.stderr b/tests/ui/rfcs/rfc-2632-const-trait-impl/tilde-const-maybe-trait.stderr
new file mode 100644
index 00000000000..ce74ff8dde7
--- /dev/null
+++ b/tests/ui/rfcs/rfc-2632-const-trait-impl/tilde-const-maybe-trait.stderr
@@ -0,0 +1,8 @@
+error: `~const` and `?` are mutually exclusive
+  --> $DIR/tilde-const-maybe-trait.rs:3:28
+   |
+LL | const fn tilde_question<T: ~const ?Sized>() {}
+   |                            ^^^^^^^^^^^^^
+
+error: aborting due to previous error
+