bjoernager/rust
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Rollup merge of #133325 - compiler-errors:const-spec, r=lcnr,fee1-dead

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Reimplement `~const` trait specialization

Reimplement const specialization. We need this for `PartialEq` constification :)

r? lcnr
This commit is contained in:
Matthias Krüger 2024-12-03 07:48:32 +01:00 • committed by GitHub
commit 8aa5853b58
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GPG key ID: B5690EEEBB952194
14 changed files with 274 additions and 74 deletions
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2
compiler/rustc_hir_analysis/messages.ftl
View file

@ -113,8 +113,6 @@ hir_analysis_const_param_ty_impl_on_unsized =
the trait `ConstParamTy` may not be implemented for this type
.label = type is not `Sized`
hir_analysis_const_specialize = cannot specialize on const impl with non-const impl
hir_analysis_copy_impl_on_non_adt =
the trait `Copy` cannot be implemented for this type
.label = type is not a structure or enumeration

7
compiler/rustc_hir_analysis/src/errors.rs
View file

@ -1079,13 +1079,6 @@ pub(crate) struct EmptySpecialization {
pub base_impl_span: Span,
}
#[derive(Diagnostic)]
#[diag(hir_analysis_const_specialize)]
pub(crate) struct ConstSpecialize {
#[primary_span]
pub span: Span,
}
#[derive(Diagnostic)]
#[diag(hir_analysis_static_specialize)]
pub(crate) struct StaticSpecialize {

26
compiler/rustc_hir_analysis/src/impl_wf_check/min_specialization.rs
View file

@ -66,7 +66,6 @@
//! on traits with methods can.
use rustc_data_structures::fx::FxHashSet;
use rustc_hir as hir;
use rustc_hir::def_id::{DefId, LocalDefId};
use rustc_infer::infer::TyCtxtInferExt;
use rustc_infer::infer::outlives::env::OutlivesEnvironment;
@ -134,7 +133,6 @@ fn check_always_applicable(
unconstrained_parent_impl_args(tcx, impl2_def_id, impl2_args)
};
res = res.and(check_constness(tcx, impl1_def_id, impl2_node, span));
res = res.and(check_static_lifetimes(tcx, &parent_args, span));
res = res.and(check_duplicate_params(tcx, impl1_args, parent_args, span));
res = res.and(check_predicates(tcx, impl1_def_id, impl1_args, impl2_node, impl2_args, span));
@ -157,30 +155,6 @@ fn check_has_items(
Ok(())
}
/// 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,
) -> Result<(), ErrorGuaranteed> {
if impl2_node.is_from_trait() {
// This isn't a specialization
return Ok(());
}
let impl1_constness = tcx.constness(impl1_def_id.to_def_id());
let impl2_constness = tcx.constness(impl2_node.def_id());
if let hir::Constness::Const = impl2_constness {
if let hir::Constness::NotConst = impl1_constness {
return Err(tcx.dcx().emit_err(errors::ConstSpecialize { span }));
}
}
Ok(())
}
/// Given a specializing impl `impl1`, and the base impl `impl2`, returns two
/// generic parameters `(S1, S2)` that equate their trait references.
/// The returned types are expressed in terms of the generics of `impl1`.