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Fold vtable_trait_upcasting_coercion_new_vptr_slot logic into obligation processing.

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This commit is contained in:
Charles Lew 2021-08-18 12:45:18 +08:00
parent 1e605023ec
commit 6b1c52ff25
11 changed files with 137 additions and 87 deletions
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63
compiler/rustc_trait_selection/src/traits/mod.rs
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@ -28,6 +28,7 @@ use crate::traits::query::evaluate_obligation::InferCtxtExt as _;
use rustc_errors::ErrorReported;
use rustc_hir as hir;
use rustc_hir::def_id::DefId;
use rustc_hir::lang_items::LangItem;
use rustc_middle::ty::fold::TypeFoldable;
use rustc_middle::ty::subst::{InternalSubsts, SubstsRef};
use rustc_middle::ty::{
@ -759,48 +760,38 @@ fn vtable_trait_first_method_offset<'tcx>(
pub fn vtable_trait_upcasting_coercion_new_vptr_slot(
tcx: TyCtxt<'tcx>,
key: (
ty::PolyTraitRef<'tcx>, // trait owning vtable
ty::PolyTraitRef<'tcx>, // super trait ref
Ty<'tcx>, // trait object type whose trait owning vtable
Ty<'tcx>, // trait object for supertrait
),
) -> Option<usize> {
let (trait_owning_vtable, super_trait_ref) = key;
let super_trait_did = super_trait_ref.def_id();
// FIXME: take substsref part into account here after upcasting coercion allows the same def_id occur
// multiple times.
let (source, target) = key;
debug_assert!(matches!(&source.kind(), &ty::Dynamic(..)));
debug_assert!(matches!(&target.kind(), &ty::Dynamic(..)));
let vtable_segment_callback = {
let mut vptr_offset = 0;
move |segment| {
match segment {
VtblSegment::MetadataDSA => {
vptr_offset += COMMON_VTABLE_ENTRIES.len();
}
VtblSegment::TraitOwnEntries { trait_ref, emit_vptr } => {
vptr_offset += util::count_own_vtable_entries(tcx, trait_ref);
if trait_ref.def_id() == super_trait_did {
if emit_vptr {
return ControlFlow::Break(Some(vptr_offset));
} else {
return ControlFlow::Break(None);
}
}
// this has been typecked-before, so diagnostics is not really needed.
let unsize_trait_did = tcx.require_lang_item(LangItem::Unsize, None);
if emit_vptr {
vptr_offset += 1;
}
}
}
ControlFlow::Continue(())
}
let trait_ref = ty::TraitRef {
def_id: unsize_trait_did,
substs: tcx.mk_substs_trait(source, &[target.into()]),
};
let obligation = Obligation::new(
ObligationCause::dummy(),
ty::ParamEnv::reveal_all(),
ty::Binder::dummy(ty::TraitPredicate { trait_ref, constness: hir::Constness::NotConst }),
);
let implsrc = tcx.infer_ctxt().enter(|infcx| {
let mut selcx = SelectionContext::new(&infcx);
selcx.select(&obligation).unwrap()
});
let implsrc_traitcasting = match implsrc {
Some(ImplSource::TraitUpcasting(data)) => data,
_ => bug!(),
};
if let Some(vptr_offset) =
prepare_vtable_segments(tcx, trait_owning_vtable, vtable_segment_callback)
{
vptr_offset
} else {
bug!("Failed to find info for expected trait in vtable");
}
implsrc_traitcasting.vtable_vptr_slot
}
pub fn provide(providers: &mut ty::query::Providers) {