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//! Miscellaneous type-system utilities that are too small to deserve their own modules.
use crate::infer::InferCtxtExt as _;
use crate::traits::{self, ObligationCause};
use rustc_hir as hir;
use rustc_infer::infer::TyCtxtInferExt;
use rustc_middle::ty::{self, Ty, TyCtxt, TypeVisitable};
use crate::traits::error_reporting::InferCtxtExt;
#[derive(Clone)]
pub enum CopyImplementationError<'tcx> {
InfrigingFields(Vec<(&'tcx ty::FieldDef, Ty<'tcx>)>),
NotAnAdt,
HasDestructor,
}
pub fn can_type_implement_copy<'tcx>(
tcx: TyCtxt<'tcx>,
param_env: ty::ParamEnv<'tcx>,
self_type: Ty<'tcx>,
parent_cause: ObligationCause<'tcx>,
) -> Result<(), CopyImplementationError<'tcx>> {
// FIXME: (@jroesch) float this code up
tcx.infer_ctxt().enter(|infcx| {
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 mut infringing = Vec::new();
for variant in adt.variants() {
for field in &variant.fields {
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_param_types_or_consts()
{
parent_cause.clone()
} else {
ObligationCause::dummy_with_span(span)
};
let ctx = traits::FulfillmentContext::new();
match traits::fully_normalize(&infcx, ctx, cause, param_env, ty) {
Ok(ty) => {
if !infcx.type_is_copy_modulo_regions(param_env, ty, span) {
infringing.push((field, ty));
}
}
Err(errors) => {
infcx.report_fulfillment_errors(&errors, None, false);
}
};
}
}
if !infringing.is_empty() {
return Err(CopyImplementationError::InfrigingFields(infringing));
}
if adt.has_dtor(tcx) {
return Err(CopyImplementationError::HasDestructor);
}
Ok(())
})
}
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