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Require that const param tys implement ConstParamTy

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This commit is contained in:
Boxy 2023-05-16 19:58:54 +01:00 committed by Michael Goulet
parent 642c92e630
commit bbf41279fa
2 changed files with 19 additions and 77 deletions
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91
compiler/rustc_hir_analysis/src/check/wfcheck.rs
View File

@ -829,83 +829,20 @@ fn check_param_wf(tcx: TyCtxt<'_>, param: &hir::GenericParam<'_>) {
let ty = tcx.type_of(param.def_id).subst_identity();
if tcx.features().adt_const_params {
if let Some(non_structural_match_ty) =
traits::search_for_adt_const_param_violation(param.span, tcx, ty)
{
// We use the same error code in both branches, because this is really the same
// issue: we just special-case the message for type parameters to make it
// clearer.
match non_structural_match_ty.kind() {
ty::Param(_) => {
// Const parameters may not have type parameters as their types,
// because we cannot be sure that the type parameter derives `PartialEq`
// and `Eq` (just implementing them is not enough for `structural_match`).
struct_span_err!(
tcx.sess,
hir_ty.span,
E0741,
"`{ty}` is not guaranteed to `#[derive(PartialEq, Eq)]`, so may not be \
used as the type of a const parameter",
)
.span_label(
hir_ty.span,
format!("`{ty}` may not derive both `PartialEq` and `Eq`"),
)
.note(
"it is not currently possible to use a type parameter as the type of a \
const parameter",
)
.emit();
}
ty::Float(_) => {
struct_span_err!(
tcx.sess,
hir_ty.span,
E0741,
"`{ty}` is forbidden as the type of a const generic parameter",
)
.note("floats do not derive `Eq` or `Ord`, which are required for const parameters")
.emit();
}
ty::FnPtr(_) => {
struct_span_err!(
tcx.sess,
hir_ty.span,
E0741,
"using function pointers as const generic parameters is forbidden",
)
.emit();
}
ty::RawPtr(_) => {
struct_span_err!(
tcx.sess,
hir_ty.span,
E0741,
"using raw pointers as const generic parameters is forbidden",
)
.emit();
}
_ => {
let mut diag = struct_span_err!(
tcx.sess,
hir_ty.span,
E0741,
"`{}` must be annotated with `#[derive(PartialEq, Eq)]` to be used as \
the type of a const parameter",
non_structural_match_ty,
);
if ty == non_structural_match_ty {
diag.span_label(
hir_ty.span,
format!("`{ty}` doesn't derive both `PartialEq` and `Eq`"),
);
}
diag.emit();
}
}
}
enter_wf_checking_ctxt(tcx, hir_ty.span, param.def_id, |wfcx| {
let trait_def_id =
tcx.require_lang_item(LangItem::ConstParamTy, Some(hir_ty.span));
wfcx.register_bound(
ObligationCause::new(
hir_ty.span,
param.def_id,
ObligationCauseCode::WellFormed(Some(hir_ty.span)),
),
wfcx.param_env,
ty,
trait_def_id,
);
});
} else {
let err_ty_str;
let mut is_ptr = true;

5
library/core/src/mem/transmutability.rs
View File

@ -1,3 +1,5 @@
use crate::marker::ConstParamTy;
/// Are values of a type transmutable into values of another type?
///
/// This trait is implemented on-the-fly by the compiler for types `Src` and `Self` when the bits of
@ -33,6 +35,9 @@ pub struct Assume {
pub validity: bool,
}
#[unstable(feature = "transmutability", issue = "99571")]
impl ConstParamTy for Assume {}
impl Assume {
/// Do not assume that *you* have ensured any safety properties are met.
#[unstable(feature = "transmutability", issue = "99571")]