Rollup merge of #103351 - oli-obk:tilde_const_impls, r=fee1-dead

Require Drop impls to have the same constness on its bounds as the bounds on the struct have

r? ``@fee1-dead``

compiler/rustc_ast_passes/src/ast_validation.rs

@@ -252,20 +252,6 @@ impl<'a> AstValidator<'a> {
         }
     }
 
-    fn visit_struct_field_def(&mut self, field: &'a FieldDef) {
-        if let Some(ident) = field.ident {
-            if ident.name == kw::Underscore {
-                self.visit_vis(&field.vis);
-                self.visit_ident(ident);
-                self.visit_ty_common(&field.ty);
-                self.walk_ty(&field.ty);
-                walk_list!(self, visit_attribute, &field.attrs);
-                return;
-            }
-        }
-        self.visit_field_def(field);
-    }
-
     fn err_handler(&self) -> &rustc_errors::Handler {
         &self.session.diagnostic()
     }
@@ -1006,8 +992,8 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
         visit::walk_lifetime(self, lifetime);
     }
 
-    fn visit_field_def(&mut self, s: &'a FieldDef) {
+    fn visit_field_def(&mut self, field: &'a FieldDef) {
-        visit::walk_field_def(self, s)
+        visit::walk_field_def(self, field)
     }
 
     fn visit_item(&mut self, item: &'a Item) {
@@ -1195,42 +1181,10 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
                     self.check_mod_file_item_asciionly(item.ident);
                 }
             }
-            ItemKind::Struct(ref vdata, ref generics) => match vdata {
+            ItemKind::Union(ref 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(ref fields, ..) => {
-                    self.visit_vis(&item.vis);
-                    self.visit_ident(item.ident);
-                    self.visit_generics(generics);
-                    self.with_banned_assoc_ty_bound(|this| {
-                        walk_list!(this, visit_struct_field_def, fields);
-                    });
-                    walk_list!(self, visit_attribute, &item.attrs);
-                    return;
-                }
-                _ => {}
-            },
-            ItemKind::Union(ref vdata, ref generics) => {
                 if vdata.fields().is_empty() {
                     self.err_handler().span_err(item.span, "unions cannot have zero fields");
                 }
-                match vdata {
-                    VariantData::Struct(ref fields, ..) => {
-                        self.visit_vis(&item.vis);
-                        self.visit_ident(item.ident);
-                        self.visit_generics(generics);
-                        self.with_banned_assoc_ty_bound(|this| {
-                            walk_list!(this, visit_struct_field_def, fields);
-                        });
-                        walk_list!(self, visit_attribute, &item.attrs);
-                        return;
-                    }
-                    _ => {}
-                }
             }
             ItemKind::Const(def, .., None) => {
                 self.check_defaultness(item.span, def);

compiler/rustc_hir_analysis/src/check/dropck.rs

@@ -184,13 +184,7 @@ fn ensure_drop_predicates_are_implied_by_item_defn<'tcx>(
             let p = p.kind();
             match (predicate.skip_binder(), p.skip_binder()) {
                 (ty::PredicateKind::Trait(a), ty::PredicateKind::Trait(b)) => {
-                    // Since struct predicates cannot have ~const, project the impl predicate
+                    relator.relate(predicate.rebind(a), p.rebind(b)).is_ok()
-                    // onto one that ignores the constness. This is equivalent to saying that
-                    // we match a `Trait` bound on the struct with a `Trait` or `~const Trait`
-                    // in the impl.
-                    let non_const_a =
-                        ty::TraitPredicate { constness: ty::BoundConstness::NotConst, ..a };
-                    relator.relate(predicate.rebind(non_const_a), p.rebind(b)).is_ok()
                 }
                 (ty::PredicateKind::Projection(a), ty::PredicateKind::Projection(b)) => {
                     relator.relate(predicate.rebind(a), p.rebind(b)).is_ok()

src/test/ui/rfc-2632-const-trait-impl/const-drop-fail.precise.stderr

@@ -45,34 +45,55 @@ note: required by a bound in `check`
 LL | const fn check<T: ~const Destruct>(_: T) {}
    |                   ^^^^^^^^^^^^^^^ required by this bound in `check`
 
-error[E0277]: the trait bound `ConstDropImplWithBounds<NonTrivialDrop>: ~const Destruct` is not satisfied
+error[E0277]: the trait bound `NonTrivialDrop: ~const A` is not satisfied
+  --> $DIR/const-drop-fail.rs:48:47
+   |
+LL |     ConstDropImplWithBounds::<NonTrivialDrop>(PhantomData),
+   |     ----------------------------------------- ^^^^^^^^^^^ the trait `~const A` is not implemented for `NonTrivialDrop`
+   |     |
+   |     required by a bound introduced by this call
+   |
+note: the trait `A` is implemented for `NonTrivialDrop`, but that implementation is not `const`
+  --> $DIR/const-drop-fail.rs:48:47
+   |
+LL |     ConstDropImplWithBounds::<NonTrivialDrop>(PhantomData),
+   |                                               ^^^^^^^^^^^
+note: required by a bound in `ConstDropImplWithBounds`
+  --> $DIR/const-drop-fail.rs:27:35
+   |
+LL | struct ConstDropImplWithBounds<T: ~const A>(PhantomData<T>);
+   |                                   ^^^^^^^^ required by this bound in `ConstDropImplWithBounds`
+
+error[E0277]: the trait bound `NonTrivialDrop: ~const A` is not satisfied
   --> $DIR/const-drop-fail.rs:48:5
    |
-LL |         const _: () = check($exp);
-   |                       ----- required by a bound introduced by this call
-...
 LL |     ConstDropImplWithBounds::<NonTrivialDrop>(PhantomData),
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `~const Destruct` is not implemented for `ConstDropImplWithBounds<NonTrivialDrop>`
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `~const A` is not implemented for `NonTrivialDrop`
    |
-note: required for `ConstDropImplWithBounds<NonTrivialDrop>` to implement `~const Destruct`
+note: the trait `A` is implemented for `NonTrivialDrop`, but that implementation is not `const`
-  --> $DIR/const-drop-fail.rs:29:25
+  --> $DIR/const-drop-fail.rs:48:5
    |
-LL | impl<T: ~const A> const Drop for ConstDropImplWithBounds<T> {
+LL |     ConstDropImplWithBounds::<NonTrivialDrop>(PhantomData),
-   |                         ^^^^     ^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-   = note: 1 redundant requirement hidden
+note: required by a bound in `ConstDropImplWithBounds`
-   = note: required for `ConstDropImplWithBounds<NonTrivialDrop>` to implement `~const Destruct`
+  --> $DIR/const-drop-fail.rs:27:35
-note: required by a bound in `check`
-  --> $DIR/const-drop-fail.rs:35:19
    |
-LL | const fn check<T: ~const Destruct>(_: T) {}
+LL | struct ConstDropImplWithBounds<T: ~const A>(PhantomData<T>);
-   |                   ^^^^^^^^^^^^^^^ required by this bound in `check`
+   |                                   ^^^^^^^^ required by this bound in `ConstDropImplWithBounds`
-help: consider borrowing here
-   |
-LL |     &ConstDropImplWithBounds::<NonTrivialDrop>(PhantomData),
-   |     +
-LL |     &mut ConstDropImplWithBounds::<NonTrivialDrop>(PhantomData),
-   |     ++++
 
-error: aborting due to 3 previous errors
+error[E0367]: `Drop` impl requires `T: ~const A` but the struct it is implemented for does not
+  --> $DIR/const-drop-fail.rs:55:9
+   |
+LL | impl<T: ~const A> const Drop for ConstDropImplWithNonConstBounds<T> {
+   |         ^^^^^^^^
+   |
+note: the implementor must specify the same requirement
+  --> $DIR/const-drop-fail.rs:53:1
+   |
+LL | struct ConstDropImplWithNonConstBounds<T: A>(PhantomData<T>);
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-For more information about this error, try `rustc --explain E0277`.
+error: aborting due to 5 previous errors
+
+Some errors have detailed explanations: E0277, E0367.
+For more information about an error, try `rustc --explain E0277`.

src/test/ui/rfc-2632-const-trait-impl/const-drop-fail.rs

@@ -24,7 +24,7 @@ trait A { fn a() { } }
 
 impl A for NonTrivialDrop {}
 
-struct ConstDropImplWithBounds<T: A>(PhantomData<T>);
+struct ConstDropImplWithBounds<T: ~const A>(PhantomData<T>);
 
 impl<T: ~const A> const Drop for ConstDropImplWithBounds<T> {
     fn drop(&mut self) {
@@ -47,6 +47,16 @@ check_all! {
     //~^ ERROR can't drop
     ConstDropImplWithBounds::<NonTrivialDrop>(PhantomData),
     //~^ ERROR the trait bound
+    //~| ERROR the trait bound
+}
+
+struct ConstDropImplWithNonConstBounds<T: A>(PhantomData<T>);
+
+impl<T: ~const A> const Drop for ConstDropImplWithNonConstBounds<T> {
+//~^ ERROR `Drop` impl requires `T: ~const A` but the struct it is implemented for does not
+    fn drop(&mut self) {
+        T::a();
+    }
 }
 
 fn main() {}

src/test/ui/rfc-2632-const-trait-impl/const-drop-fail.stock.stderr

@@ -45,34 +45,55 @@ note: required by a bound in `check`
 LL | const fn check<T: ~const Destruct>(_: T) {}
    |                   ^^^^^^^^^^^^^^^ required by this bound in `check`
 
-error[E0277]: the trait bound `ConstDropImplWithBounds<NonTrivialDrop>: ~const Destruct` is not satisfied
+error[E0277]: the trait bound `NonTrivialDrop: ~const A` is not satisfied
+  --> $DIR/const-drop-fail.rs:48:47
+   |
+LL |     ConstDropImplWithBounds::<NonTrivialDrop>(PhantomData),
+   |     ----------------------------------------- ^^^^^^^^^^^ the trait `~const A` is not implemented for `NonTrivialDrop`
+   |     |
+   |     required by a bound introduced by this call
+   |
+note: the trait `A` is implemented for `NonTrivialDrop`, but that implementation is not `const`
+  --> $DIR/const-drop-fail.rs:48:47
+   |
+LL |     ConstDropImplWithBounds::<NonTrivialDrop>(PhantomData),
+   |                                               ^^^^^^^^^^^
+note: required by a bound in `ConstDropImplWithBounds`
+  --> $DIR/const-drop-fail.rs:27:35
+   |
+LL | struct ConstDropImplWithBounds<T: ~const A>(PhantomData<T>);
+   |                                   ^^^^^^^^ required by this bound in `ConstDropImplWithBounds`
+
+error[E0277]: the trait bound `NonTrivialDrop: ~const A` is not satisfied
   --> $DIR/const-drop-fail.rs:48:5
    |
-LL |         const _: () = check($exp);
-   |                       ----- required by a bound introduced by this call
-...
 LL |     ConstDropImplWithBounds::<NonTrivialDrop>(PhantomData),
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `~const Destruct` is not implemented for `ConstDropImplWithBounds<NonTrivialDrop>`
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `~const A` is not implemented for `NonTrivialDrop`
    |
-note: required for `ConstDropImplWithBounds<NonTrivialDrop>` to implement `~const Destruct`
+note: the trait `A` is implemented for `NonTrivialDrop`, but that implementation is not `const`
-  --> $DIR/const-drop-fail.rs:29:25
+  --> $DIR/const-drop-fail.rs:48:5
    |
-LL | impl<T: ~const A> const Drop for ConstDropImplWithBounds<T> {
+LL |     ConstDropImplWithBounds::<NonTrivialDrop>(PhantomData),
-   |                         ^^^^     ^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-   = note: 1 redundant requirement hidden
+note: required by a bound in `ConstDropImplWithBounds`
-   = note: required for `ConstDropImplWithBounds<NonTrivialDrop>` to implement `~const Destruct`
+  --> $DIR/const-drop-fail.rs:27:35
-note: required by a bound in `check`
-  --> $DIR/const-drop-fail.rs:35:19
    |
-LL | const fn check<T: ~const Destruct>(_: T) {}
+LL | struct ConstDropImplWithBounds<T: ~const A>(PhantomData<T>);
-   |                   ^^^^^^^^^^^^^^^ required by this bound in `check`
+   |                                   ^^^^^^^^ required by this bound in `ConstDropImplWithBounds`
-help: consider borrowing here
-   |
-LL |     &ConstDropImplWithBounds::<NonTrivialDrop>(PhantomData),
-   |     +
-LL |     &mut ConstDropImplWithBounds::<NonTrivialDrop>(PhantomData),
-   |     ++++
 
-error: aborting due to 3 previous errors
+error[E0367]: `Drop` impl requires `T: ~const A` but the struct it is implemented for does not
+  --> $DIR/const-drop-fail.rs:55:9
+   |
+LL | impl<T: ~const A> const Drop for ConstDropImplWithNonConstBounds<T> {
+   |         ^^^^^^^^
+   |
+note: the implementor must specify the same requirement
+  --> $DIR/const-drop-fail.rs:53:1
+   |
+LL | struct ConstDropImplWithNonConstBounds<T: A>(PhantomData<T>);
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-For more information about this error, try `rustc --explain E0277`.
+error: aborting due to 5 previous errors
+
+Some errors have detailed explanations: E0277, E0367.
+For more information about an error, try `rustc --explain E0277`.

src/test/ui/rfc-2632-const-trait-impl/const-drop.rs

@@ -60,7 +60,7 @@ mod t {
         fn foo() {}
     }
 
-    pub struct ConstDropWithBound<T: SomeTrait>(pub core::marker::PhantomData<T>);
+    pub struct ConstDropWithBound<T: ~const SomeTrait>(pub core::marker::PhantomData<T>);
 
     impl<T: ~const SomeTrait> const Drop for ConstDropWithBound<T> {
         fn drop(&mut self) {

src/test/ui/rfc-2632-const-trait-impl/tilde_const_on_impl_bound.rs

@@ -0,0 +1,17 @@
+// check-pass
+#![feature(const_trait_impl)]
+
+#[const_trait]
+trait Foo {
+    fn foo(&self) {}
+}
+
+struct Bar<T>(T);
+
+impl<T: ~const Foo> Bar<T> {
+    const fn foo(&self) {
+        self.0.foo()
+    }
+}
+
+fn main() {}