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//! Miscellaneous type-system utilities that are too small to deserve their own modules.
use crate::traits::{self, ObligationCause, ObligationCtxt};
use rustc_data_structures::fx::FxIndexSet;
use rustc_hir as hir;
use rustc_infer::infer::canonical::Canonical;
use rustc_infer::infer::{RegionResolutionError, TyCtxtInferExt};
use rustc_infer::traits::query::NoSolution;
use rustc_infer::{infer::outlives::env::OutlivesEnvironment, traits::FulfillmentError};
use rustc_middle::ty::{self, ParamEnv, Ty, TyCtxt, TypeVisitableExt};
use rustc_span::DUMMY_SP;
use super::outlives_bounds::InferCtxtExt;
pub enum CopyImplementationError<'tcx> {
InfrigingFields(Vec<(&'tcx ty::FieldDef, Ty<'tcx>, InfringingFieldsReason<'tcx>)>),
NotAnAdt,
HasDestructor,
}
pub enum InfringingFieldsReason<'tcx> {
Fulfill(Vec<FulfillmentError<'tcx>>),
Regions(Vec<RegionResolutionError<'tcx>>),
}
/// 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 unnormalized_ty = field.ty(tcx, substs);
if unnormalized_ty.references_error() {
continue;
}
let field_span = tcx.def_span(field.did);
let field_ty_span = match tcx.hir().get_if_local(field.did) {
Some(hir::Node::Field(field_def)) => field_def.ty.span,
_ => field_span,
};
// 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 normalization_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(field_ty_span)
};
let ty = ocx.normalize(&normalization_cause, param_env, unnormalized_ty);
let normalization_errors = ocx.select_where_possible();
// NOTE: The post-normalization type may also reference errors,
// such as when we project to a missing type or we have a mismatch
// between expected and found const-generic types. Don't report an
// additional copy error here, since it's not typically useful.
if !normalization_errors.is_empty() || ty.references_error() {
tcx.sess.delay_span_bug(field_span, format!("couldn't normalize struct field `{unnormalized_ty}` when checking Copy implementation"));
continue;
}
ocx.register_bound(
ObligationCause::dummy_with_span(field_ty_span),
param_env,
ty,
copy_def_id,
);
let errors = ocx.select_all_or_error();
if !errors.is_empty() {
infringing.push((field, ty, InfringingFieldsReason::Fulfill(errors)));
}
// Check regions assuming the self type of the impl is WF
let outlives_env = OutlivesEnvironment::with_bounds(
param_env,
infcx.implied_bounds_tys(
param_env,
parent_cause.body_id,
FxIndexSet::from_iter([self_type]),
),
);
let errors = infcx.resolve_regions(&outlives_env);
if !errors.is_empty() {
infringing.push((field, ty, InfringingFieldsReason::Regions(errors)));
}
}
}
if !infringing.is_empty() {
return Err(CopyImplementationError::InfrigingFields(infringing));
}
if adt.has_dtor(tcx) {
return Err(CopyImplementationError::HasDestructor);
}
Ok(())
}
pub fn check_tys_might_be_eq<'tcx>(
tcx: TyCtxt<'tcx>,
canonical: Canonical<'tcx, (ParamEnv<'tcx>, Ty<'tcx>, Ty<'tcx>)>,
) -> Result<(), NoSolution> {
let (infcx, (param_env, ty_a, ty_b), _) =
tcx.infer_ctxt().build_with_canonical(DUMMY_SP, &canonical);
let ocx = ObligationCtxt::new(&infcx);
let result = ocx.eq(&ObligationCause::dummy(), param_env, ty_a, ty_b);
// use `select_where_possible` instead of `select_all_or_error` so that
// we don't get errors from obligations being ambiguous.
let errors = ocx.select_where_possible();
if errors.len() > 0 || result.is_err() { Err(NoSolution) } else { Ok(()) }
}
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