bjoernager/rust
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Disallow (min) specialization imps with no items

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Such implementations are usually mistakes and are not used in the
compiler or standard library (after this commit) so forbid them with
`min_specialization`.
This commit is contained in:
Matthew Jasper 2023-05-05 12:54:58 +01:00
parent dd9a7bf848
commit bd928a0b5e
11 changed files with 112 additions and 23 deletions
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9
compiler/rustc_hir_analysis/src/errors.rs
View file

@ -803,6 +803,15 @@ pub(crate) struct ClosureImplicitHrtb {
pub for_sp: Span,
}
#[derive(Diagnostic)]
#[diag(hir_analysis_empty_specialization)]
pub(crate) struct EmptySpecialization {
#[primary_span]
pub span: Span,
#[note]
pub base_impl_span: Span,
}
#[derive(Diagnostic)]
#[diag(hir_analysis_const_specialize)]
pub(crate) struct ConstSpecialize {

15
compiler/rustc_hir_analysis/src/impl_wf_check/min_specialization.rs
View file

@ -100,12 +100,19 @@ fn parent_specialization_node(tcx: TyCtxt<'_>, impl1_def_id: LocalDefId) -> Opti
// Implementing a normal trait isn't a specialization.
return None;
}
if trait_def.is_marker {
// Overlapping marker implementations are not really specializations.
return None;
}
Some(impl2_node)
}
/// Check that `impl1` is a sound specialization
#[instrument(level = "debug", skip(tcx))]
fn check_always_applicable(tcx: TyCtxt<'_>, impl1_def_id: LocalDefId, impl2_node: Node) {
let span = tcx.def_span(impl1_def_id);
check_has_items(tcx, impl1_def_id, impl2_node, span);
if let Some((impl1_substs, impl2_substs)) = get_impl_substs(tcx, impl1_def_id, impl2_node) {
let impl2_def_id = impl2_node.def_id();
debug!(?impl2_def_id, ?impl2_substs);
@ -116,7 +123,6 @@ fn check_always_applicable(tcx: TyCtxt<'_>, impl1_def_id: LocalDefId, impl2_node
unconstrained_parent_impl_substs(tcx, impl2_def_id, impl2_substs)
};
let span = tcx.def_span(impl1_def_id);
check_constness(tcx, impl1_def_id, impl2_node, span);
check_static_lifetimes(tcx, &parent_substs, span);
check_duplicate_params(tcx, impl1_substs, &parent_substs, span);
@ -124,6 +130,13 @@ fn check_always_applicable(tcx: TyCtxt<'_>, impl1_def_id: LocalDefId, impl2_node
}
}
fn check_has_items(tcx: TyCtxt<'_>, impl1_def_id: LocalDefId, impl2_node: Node, span: Span) {
if let Node::Impl(impl2_id) = impl2_node && tcx.associated_item_def_ids(impl1_def_id).is_empty() {
let base_impl_span = tcx.def_span(impl2_id);
tcx.sess.emit_err(errors::EmptySpecialization { span, base_impl_span });
}
}
/// Check that the specializing impl `impl1` is at least as const as the base
/// impl `impl2`
fn check_constness(tcx: TyCtxt<'_>, impl1_def_id: LocalDefId, impl2_node: Node, span: Span) {