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|
//! Miscellaneous type-system utilities that are too small to deserve their own modules.
use crate::traits::{self, ObligationCause};
use rustc_data_structures::fx::FxIndexSet;
use rustc_hir as hir;
use rustc_infer::infer::outlives::env::OutlivesEnvironment;
use rustc_infer::infer::TyCtxtInferExt;
use rustc_middle::ty::{self, Ty, TyCtxt, TypeVisitable};
use crate::traits::error_reporting::TypeErrCtxtExt;
use super::outlives_bounds::InferCtxtExt;
#[derive(Clone)]
pub enum CopyImplementationError<'tcx> {
InfrigingFields(Vec<(&'tcx ty::FieldDef, Ty<'tcx>)>),
NotAnAdt,
HasDestructor,
}
/// Checks that the fields of the type (an ADT) all implement copy.
///
/// If fields don't implement copy, return an error containing a list of
/// those violating fields. If it's not an ADT, returns `Err(NotAnAdt)`.
pub fn type_allowed_to_implement_copy<'tcx>(
tcx: TyCtxt<'tcx>,
param_env: ty::ParamEnv<'tcx>,
self_type: Ty<'tcx>,
parent_cause: ObligationCause<'tcx>,
) -> Result<(), CopyImplementationError<'tcx>> {
let (adt, substs) = match self_type.kind() {
// These types used to have a builtin impl.
// Now libcore provides that impl.
ty::Uint(_)
| ty::Int(_)
| ty::Bool
| ty::Float(_)
| ty::Char
| ty::RawPtr(..)
| ty::Never
| ty::Ref(_, _, hir::Mutability::Not)
| ty::Array(..) => return Ok(()),
ty::Adt(adt, substs) => (adt, substs),
_ => return Err(CopyImplementationError::NotAnAdt),
};
let copy_def_id = tcx.require_lang_item(hir::LangItem::Copy, Some(parent_cause.span));
let mut infringing = Vec::new();
for variant in adt.variants() {
for field in &variant.fields {
// Do this per-field to get better error messages.
let infcx = tcx.infer_ctxt().build();
let ocx = traits::ObligationCtxt::new(&infcx);
let ty = field.ty(tcx, substs);
if ty.references_error() {
continue;
}
let span = tcx.def_span(field.did);
// FIXME(compiler-errors): This gives us better spans for bad
// projection types like in issue-50480.
// If the ADT has substs, point to the cause we are given.
// If it does not, then this field probably doesn't normalize
// to begin with, and point to the bad field's span instead.
let cause = if field
.ty(tcx, traits::InternalSubsts::identity_for_item(tcx, adt.did()))
.has_non_region_param()
{
parent_cause.clone()
} else {
ObligationCause::dummy_with_span(span)
};
let ty = ocx.normalize(&cause, param_env, ty);
let normalization_errors = ocx.select_where_possible();
if !normalization_errors.is_empty() {
// Don't report this as a field that doesn't implement Copy,
// but instead just implement this as a field that isn't WF.
infcx.err_ctxt().report_fulfillment_errors(&normalization_errors, None);
continue;
}
ocx.register_bound(cause, param_env, ty, copy_def_id);
if !ocx.select_all_or_error().is_empty() {
infringing.push((field, ty));
}
// Check regions assuming the self type of the impl is WF
let outlives_env = OutlivesEnvironment::with_bounds(
param_env,
Some(&infcx),
infcx.implied_bounds_tys(
param_env,
parent_cause.body_id,
FxIndexSet::from_iter([self_type]),
),
);
infcx.process_registered_region_obligations(
outlives_env.region_bound_pairs(),
param_env,
);
if !infcx.resolve_regions(&outlives_env).is_empty() {
infringing.push((field, ty));
}
}
}
if !infringing.is_empty() {
return Err(CopyImplementationError::InfrigingFields(infringing));
}
if adt.has_dtor(tcx) {
return Err(CopyImplementationError::HasDestructor);
}
Ok(())
}
|
