285 lines
12 KiB
Rust
285 lines
12 KiB
Rust
use rustc_errors::ErrorReported;
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use rustc_hir::def_id::{DefId, LocalDefId};
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use rustc_infer::infer::TyCtxtInferExt;
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use rustc_middle::ty::subst::SubstsRef;
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use rustc_middle::ty::{self, Instance, TyCtxt, TypeFoldable};
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use rustc_span::{sym, DUMMY_SP};
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use rustc_target::spec::abi::Abi;
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use rustc_trait_selection::traits;
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use traits::{translate_substs, Reveal};
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use tracing::debug;
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fn resolve_instance<'tcx>(
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tcx: TyCtxt<'tcx>,
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key: ty::ParamEnvAnd<'tcx, (DefId, SubstsRef<'tcx>)>,
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) -> Result<Option<Instance<'tcx>>, ErrorReported> {
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let (param_env, (did, substs)) = key.into_parts();
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if let Some(did) = did.as_local() {
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if let Some(param_did) = tcx.opt_const_param_of(did) {
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return tcx.resolve_instance_of_const_arg(param_env.and((did, param_did, substs)));
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}
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}
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inner_resolve_instance(tcx, param_env.and((ty::WithOptConstParam::unknown(did), substs)))
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}
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fn resolve_instance_of_const_arg<'tcx>(
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tcx: TyCtxt<'tcx>,
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key: ty::ParamEnvAnd<'tcx, (LocalDefId, DefId, SubstsRef<'tcx>)>,
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) -> Result<Option<Instance<'tcx>>, ErrorReported> {
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let (param_env, (did, const_param_did, substs)) = key.into_parts();
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inner_resolve_instance(
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tcx,
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param_env.and((
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ty::WithOptConstParam { did: did.to_def_id(), const_param_did: Some(const_param_did) },
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substs,
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)),
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)
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}
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fn inner_resolve_instance<'tcx>(
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tcx: TyCtxt<'tcx>,
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key: ty::ParamEnvAnd<'tcx, (ty::WithOptConstParam<DefId>, SubstsRef<'tcx>)>,
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) -> Result<Option<Instance<'tcx>>, ErrorReported> {
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let (param_env, (def, substs)) = key.into_parts();
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debug!("resolve(def={:?}, substs={:?})", def.did, substs);
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let result = if let Some(trait_def_id) = tcx.trait_of_item(def.did) {
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debug!(" => associated item, attempting to find impl in param_env {:#?}", param_env);
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let item = tcx.associated_item(def.did);
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resolve_associated_item(tcx, &item, param_env, trait_def_id, substs)
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} else {
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let ty = tcx.type_of(def.def_id_for_type_of());
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let item_type = tcx.subst_and_normalize_erasing_regions(substs, param_env, ty);
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let def = match *item_type.kind() {
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ty::FnDef(..)
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if {
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let f = item_type.fn_sig(tcx);
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f.abi() == Abi::RustIntrinsic || f.abi() == Abi::PlatformIntrinsic
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} =>
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{
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debug!(" => intrinsic");
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ty::InstanceDef::Intrinsic(def.did)
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}
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ty::FnDef(def_id, substs) if Some(def_id) == tcx.lang_items().drop_in_place_fn() => {
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let ty = substs.type_at(0);
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if ty.needs_drop(tcx, param_env) {
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debug!(" => nontrivial drop glue");
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match *ty.kind() {
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ty::Closure(..)
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| ty::Generator(..)
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| ty::Tuple(..)
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| ty::Adt(..)
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| ty::Dynamic(..)
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| ty::Array(..)
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| ty::Slice(..) => {}
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// Drop shims can only be built from ADTs.
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_ => return Ok(None),
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}
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ty::InstanceDef::DropGlue(def_id, Some(ty))
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} else {
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debug!(" => trivial drop glue");
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ty::InstanceDef::DropGlue(def_id, None)
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}
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}
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_ => {
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debug!(" => free item");
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ty::InstanceDef::Item(def)
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}
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};
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Ok(Some(Instance { def, substs }))
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};
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debug!("resolve(def.did={:?}, substs={:?}) = {:?}", def.did, substs, result);
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result
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}
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fn resolve_associated_item<'tcx>(
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tcx: TyCtxt<'tcx>,
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trait_item: &ty::AssocItem,
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param_env: ty::ParamEnv<'tcx>,
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trait_id: DefId,
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rcvr_substs: SubstsRef<'tcx>,
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) -> Result<Option<Instance<'tcx>>, ErrorReported> {
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let def_id = trait_item.def_id;
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debug!(
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"resolve_associated_item(trait_item={:?}, \
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param_env={:?}, \
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trait_id={:?}, \
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rcvr_substs={:?})",
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def_id, param_env, trait_id, rcvr_substs
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);
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let trait_ref = ty::TraitRef::from_method(tcx, trait_id, rcvr_substs);
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let vtbl = tcx.codegen_fulfill_obligation((param_env, ty::Binder::bind(trait_ref)))?;
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// Now that we know which impl is being used, we can dispatch to
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// the actual function:
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Ok(match vtbl {
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traits::ImplSource::UserDefined(impl_data) => {
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debug!(
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"resolving ImplSource::UserDefined: {:?}, {:?}, {:?}, {:?}",
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param_env, trait_item, rcvr_substs, impl_data
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);
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assert!(!rcvr_substs.needs_infer());
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assert!(!trait_ref.needs_infer());
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let trait_def_id = tcx.trait_id_of_impl(impl_data.impl_def_id).unwrap();
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let trait_def = tcx.trait_def(trait_def_id);
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let leaf_def = trait_def
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.ancestors(tcx, impl_data.impl_def_id)?
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.leaf_def(tcx, trait_item.ident, trait_item.kind)
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.unwrap_or_else(|| {
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bug!("{:?} not found in {:?}", trait_item, impl_data.impl_def_id);
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});
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let substs = tcx.infer_ctxt().enter(|infcx| {
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let param_env = param_env.with_reveal_all_normalized(tcx);
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let substs = rcvr_substs.rebase_onto(tcx, trait_def_id, impl_data.substs);
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let substs = translate_substs(
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&infcx,
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param_env,
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impl_data.impl_def_id,
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substs,
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leaf_def.defining_node,
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);
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infcx.tcx.erase_regions(substs)
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});
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// Since this is a trait item, we need to see if the item is either a trait default item
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// or a specialization because we can't resolve those unless we can `Reveal::All`.
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// NOTE: This should be kept in sync with the similar code in
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// `rustc_trait_selection::traits::project::assemble_candidates_from_impls()`.
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let eligible = if leaf_def.is_final() {
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// Non-specializable items are always projectable.
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true
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} else {
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// Only reveal a specializable default if we're past type-checking
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// and the obligation is monomorphic, otherwise passes such as
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// transmute checking and polymorphic MIR optimizations could
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// get a result which isn't correct for all monomorphizations.
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if param_env.reveal() == Reveal::All {
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!trait_ref.still_further_specializable()
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} else {
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false
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}
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};
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if !eligible {
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return Ok(None);
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}
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let substs = tcx.erase_regions(substs);
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// Check if we just resolved an associated `const` declaration from
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// a `trait` to an associated `const` definition in an `impl`, where
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// the definition in the `impl` has the wrong type (for which an
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// error has already been/will be emitted elsewhere).
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//
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// NB: this may be expensive, we try to skip it in all the cases where
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// we know the error would've been caught (e.g. in an upstream crate).
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//
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// A better approach might be to just introduce a query (returning
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// `Result<(), ErrorReported>`) for the check that `rustc_typeck`
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// performs (i.e. that the definition's type in the `impl` matches
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// the declaration in the `trait`), so that we can cheaply check
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// here if it failed, instead of approximating it.
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if trait_item.kind == ty::AssocKind::Const
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&& trait_item.def_id != leaf_def.item.def_id
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&& leaf_def.item.def_id.is_local()
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{
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let normalized_type_of = |def_id, substs| {
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tcx.subst_and_normalize_erasing_regions(substs, param_env, tcx.type_of(def_id))
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};
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let original_ty = normalized_type_of(trait_item.def_id, rcvr_substs);
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let resolved_ty = normalized_type_of(leaf_def.item.def_id, substs);
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if original_ty != resolved_ty {
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let msg = format!(
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"Instance::resolve: inconsistent associated `const` type: \
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was `{}: {}` but resolved to `{}: {}`",
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tcx.def_path_str_with_substs(trait_item.def_id, rcvr_substs),
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original_ty,
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tcx.def_path_str_with_substs(leaf_def.item.def_id, substs),
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resolved_ty,
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);
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let span = tcx.def_span(leaf_def.item.def_id);
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tcx.sess.delay_span_bug(span, &msg);
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return Err(ErrorReported);
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}
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}
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Some(ty::Instance::new(leaf_def.item.def_id, substs))
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}
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traits::ImplSource::Generator(generator_data) => Some(Instance {
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def: ty::InstanceDef::Item(ty::WithOptConstParam::unknown(
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generator_data.generator_def_id,
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)),
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substs: generator_data.substs,
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}),
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traits::ImplSource::Closure(closure_data) => {
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let trait_closure_kind = tcx.fn_trait_kind_from_lang_item(trait_id).unwrap();
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Some(Instance::resolve_closure(
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tcx,
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closure_data.closure_def_id,
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closure_data.substs,
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trait_closure_kind,
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))
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}
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traits::ImplSource::FnPointer(ref data) => match data.fn_ty.kind() {
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ty::FnDef(..) | ty::FnPtr(..) => Some(Instance {
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def: ty::InstanceDef::FnPtrShim(trait_item.def_id, data.fn_ty),
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substs: rcvr_substs,
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}),
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_ => None,
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},
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traits::ImplSource::Object(ref data) => {
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let index = traits::get_vtable_index_of_object_method(tcx, data, def_id);
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Some(Instance { def: ty::InstanceDef::Virtual(def_id, index), substs: rcvr_substs })
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}
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traits::ImplSource::Builtin(..) => {
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if Some(trait_ref.def_id) == tcx.lang_items().clone_trait() {
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// FIXME(eddyb) use lang items for methods instead of names.
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let name = tcx.item_name(def_id);
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if name == sym::clone {
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let self_ty = trait_ref.self_ty();
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let is_copy = self_ty.is_copy_modulo_regions(tcx.at(DUMMY_SP), param_env);
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match self_ty.kind() {
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_ if is_copy => (),
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ty::Array(..) | ty::Closure(..) | ty::Tuple(..) => {}
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_ => return Ok(None),
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};
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Some(Instance {
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def: ty::InstanceDef::CloneShim(def_id, self_ty),
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substs: rcvr_substs,
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})
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} else {
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assert_eq!(name, sym::clone_from);
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// Use the default `fn clone_from` from `trait Clone`.
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let substs = tcx.erase_regions(rcvr_substs);
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Some(ty::Instance::new(def_id, substs))
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}
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} else {
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None
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}
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}
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traits::ImplSource::AutoImpl(..)
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| traits::ImplSource::Param(..)
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| traits::ImplSource::TraitAlias(..)
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| traits::ImplSource::DiscriminantKind(..) => None,
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})
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}
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pub fn provide(providers: &mut ty::query::Providers) {
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*providers =
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ty::query::Providers { resolve_instance, resolve_instance_of_const_arg, ..*providers };
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}
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