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Rollup merge of rust-lang#95876 - fee1-dead:note-const-drop, r=oli-obk
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Add a note for unsatisfied `~const Drop` bounds

r? ```@oli-obk```
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matthiaskrgr authored Apr 11, 2022
2 parents a947ff6 + 7f54d68 commit ca331f5
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Showing 3 changed files with 33 additions and 17 deletions.
Original file line number Diff line number Diff line change
Expand Up @@ -440,6 +440,13 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
}
}

if Some(trait_ref.def_id()) == tcx.lang_items().drop_trait()
&& predicate_is_const
{
err.note("`~const Drop` was renamed to `~const Destruct`");
err.note("See <https://github.com/rust-lang/rust/pull/94901> for more details");
}

let explanation = if let ObligationCauseCode::MainFunctionType =
obligation.cause.code()
{
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12 changes: 1 addition & 11 deletions src/librustdoc/clean/mod.rs
Original file line number Diff line number Diff line change
Expand Up @@ -302,23 +302,13 @@ impl<'a> Clean<Option<WherePredicate>> for ty::Predicate<'a> {

impl<'a> Clean<Option<WherePredicate>> for ty::PolyTraitPredicate<'a> {
fn clean(&self, cx: &mut DocContext<'_>) -> Option<WherePredicate> {
// `T: ~const Drop` is not equivalent to `T: Drop`, and we don't currently document `~const` bounds
// because of its experimental status, so just don't show these.
// `T: ~const Destruct` is hidden because `T: Destruct` is a no-op.
if self.skip_binder().constness == ty::BoundConstness::ConstIfConst
&& [cx.tcx.lang_items().drop_trait(), cx.tcx.lang_items().destruct_trait()]
.iter()
.any(|tr| *tr == Some(self.skip_binder().def_id()))
&& Some(self.skip_binder().def_id()) == cx.tcx.lang_items().destruct_trait()
{
return None;
}

#[cfg(bootstrap)]
{
// FIXME: remove `lang_items().drop_trait()` from above logic,
// as well as the comment about `~const Drop` because it was renamed to `Destruct`.
}

let poly_trait_ref = self.map_bound(|pred| pred.trait_ref);
Some(WherePredicate::BoundPredicate {
ty: poly_trait_ref.skip_binder().self_ty().clean(cx),
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31 changes: 25 additions & 6 deletions src/test/rustdoc/rfc-2632-const-trait-impl.rs
Original file line number Diff line number Diff line change
@@ -1,5 +1,5 @@
// Test that we do not currently display `~const` in rustdoc
// as that syntax is currently provisional; `~const Drop` has
// as that syntax is currently provisional; `~const Destruct` has
// no effect on stable code so it should be hidden as well.
//
// To future blessers: make sure that `const_trait_impl` is
Expand All @@ -8,6 +8,8 @@
#![feature(const_trait_impl)]
#![crate_name = "foo"]

use std::marker::Destruct;

pub struct S<T>(T);

// @!has foo/trait.Tr.html '//pre[@class="rust trait"]/code/a[@class="trait"]' '~const'
Expand All @@ -20,22 +22,36 @@ pub trait Tr<T> {
// @!has - '//div[@id="method.a"]/h4[@class="code-header"]/span[@class="where"]' '~const'
// @has - '//div[@id="method.a"]/h4[@class="code-header"]/span[@class="where fmt-newline"]' ': Clone'
#[default_method_body_is_const]
fn a<A: ~const Clone>() where Option<A>: ~const Clone {}
fn a<A: ~const Clone + ~const Destruct>()
where
Option<A>: ~const Clone + ~const Destruct,
{
}
}

// @!has - '//section[@id="impl-Tr%3CT%3E"]/h3[@class="code-header in-band"]' '~const'
// @has - '//section[@id="impl-Tr%3CT%3E"]/h3[@class="code-header in-band"]/a[@class="trait"]' 'Clone'
// @!has - '//section[@id="impl-Tr%3CT%3E"]/h3[@class="code-header in-band"]/span[@class="where"]' '~const'
// @has - '//section[@id="impl-Tr%3CT%3E"]/h3[@class="code-header in-band"]/span[@class="where fmt-newline"]' ': Clone'
impl<T: ~const Clone> const Tr<T> for T where Option<T>: ~const Clone {
fn a<A: ~const Clone>() where Option<A>: ~const Clone {}
impl<T: ~const Clone + ~const Destruct> const Tr<T> for T
where
Option<T>: ~const Clone + ~const Destruct,
{
fn a<A: ~const Clone + ~const Destruct>()
where
Option<A>: ~const Clone + ~const Destruct,
{
}
}

// @!has foo/fn.foo.html '//pre[@class="rust fn"]/code/a[@class="trait"]' '~const'
// @has - '//pre[@class="rust fn"]/code/a[@class="trait"]' 'Clone'
// @!has - '//pre[@class="rust fn"]/code/span[@class="where fmt-newline"]' '~const'
// @has - '//pre[@class="rust fn"]/code/span[@class="where fmt-newline"]' ': Clone'
pub const fn foo<F: ~const Clone>() where Option<F>: ~const Clone {
pub const fn foo<F: ~const Clone + ~const Destruct>()
where
Option<F>: ~const Clone + ~const Destruct,
{
F::a()
}

Expand All @@ -44,7 +60,10 @@ impl<T> S<T> {
// @has - '//section[@id="method.foo"]/h4[@class="code-header"]/a[@class="trait"]' 'Clone'
// @!has - '//section[@id="method.foo"]/h4[@class="code-header"]/span[@class="where"]' '~const'
// @has - '//section[@id="method.foo"]/h4[@class="code-header"]/span[@class="where fmt-newline"]' ': Clone'
pub const fn foo<B: ~const Clone>() where B: ~const Clone {
pub const fn foo<B: ~const Clone + ~const Destruct>()
where
B: ~const Clone + ~const Destruct,
{
B::a()
}
}

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