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Remove dead code and extend test coverage and diagnostics around it

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We lost the following comment during refactorings:

The current code for niche-filling relies on variant indices instead of actual discriminants, so enums with explicit discriminants (RFC 2363) would misbehave.
This commit is contained in:
Oli Scherer
2025-07-24 08:15:03 +00:00
parent 3c30dbbe31
commit e44a7386c2
6 changed files with 65 additions and 48 deletions
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38
compiler/rustc_hir_analysis/src/check/check.rs
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@@ -1642,20 +1642,40 @@ fn check_enum(tcx: TyCtxt<'_>, def_id: LocalDefId) {
if def.repr().int.is_none() {
let is_unit = |var: &ty::VariantDef| matches!(var.ctor_kind(), Some(CtorKind::Const));
let has_disr = |var: &ty::VariantDef| matches!(var.discr, ty::VariantDiscr::Explicit(_));
let get_disr = |var: &ty::VariantDef| match var.discr {
ty::VariantDiscr::Explicit(disr) => Some(disr),
ty::VariantDiscr::Relative(_) => None,
};
let has_non_units = def.variants().iter().any(|var| !is_unit(var));
let disr_units = def.variants().iter().any(|var| is_unit(var) && has_disr(var));
let disr_non_unit = def.variants().iter().any(|var| !is_unit(var) && has_disr(var));
let non_unit = def.variants().iter().find(|var| !is_unit(var));
let disr_unit =
def.variants().iter().filter(|var| is_unit(var)).find_map(|var| get_disr(var));
let disr_non_unit =
def.variants().iter().filter(|var| !is_unit(var)).find_map(|var| get_disr(var));
if disr_non_unit || (disr_units && has_non_units) {
struct_span_code_err!(
if disr_non_unit.is_some() || (disr_unit.is_some() && non_unit.is_some()) {
let mut err = struct_span_code_err!(
tcx.dcx(),
tcx.def_span(def_id),
E0732,
"`#[repr(inttype)]` must be specified"
)
.emit();
"`#[repr(inttype)]` must be specified for enums with explicit discriminants and non-unit variants"
);
if let Some(disr_non_unit) = disr_non_unit {
err.span_label(
tcx.def_span(disr_non_unit),
"explicit discriminant on non-unit variant specified here",
);
} else {
err.span_label(
tcx.def_span(disr_unit.unwrap()),
"explicit discriminant specified here",
);
err.span_label(
tcx.def_span(non_unit.unwrap().def_id),
"non-unit discriminant declared here",
);
}
err.emit();
}
}