b4d71ea6f8
It's inefficient, and the substitution there doesn't account for the extra regions used by NLL inference, so it's a bad thing to encourage. As it happens all callers already know if they have a closure or not, from what I can tell.
128 lines
4.6 KiB
Rust
128 lines
4.6 KiB
Rust
// Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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use rustc::hir::def_id::DefId;
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use rustc::middle::lang_items::DropInPlaceFnLangItem;
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use rustc::traits;
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use rustc::ty::adjustment::CustomCoerceUnsized;
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use rustc::ty::subst::Kind;
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use rustc::ty::{self, Ty, TyCtxt};
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pub use rustc::ty::Instance;
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fn fn_once_adapter_instance<'a, 'tcx>(
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tcx: TyCtxt<'a, 'tcx, 'tcx>,
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closure_did: DefId,
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substs: ty::ClosureSubsts<'tcx>,
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) -> Instance<'tcx> {
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debug!("fn_once_adapter_shim({:?}, {:?})",
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closure_did,
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substs);
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let fn_once = tcx.lang_items().fn_once_trait().unwrap();
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let call_once = tcx.associated_items(fn_once)
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.find(|it| it.kind == ty::AssociatedKind::Method)
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.unwrap().def_id;
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let def = ty::InstanceDef::ClosureOnceShim { call_once };
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let self_ty = tcx.mk_closure_from_closure_substs(
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closure_did, substs);
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let sig = substs.closure_sig(closure_did, tcx);
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let sig = tcx.erase_late_bound_regions_and_normalize(&sig);
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assert_eq!(sig.inputs().len(), 1);
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let substs = tcx.mk_substs([
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Kind::from(self_ty),
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Kind::from(sig.inputs()[0]),
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].iter().cloned());
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debug!("fn_once_adapter_shim: self_ty={:?} sig={:?}", self_ty, sig);
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Instance { def, substs }
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}
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fn needs_fn_once_adapter_shim(actual_closure_kind: ty::ClosureKind,
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trait_closure_kind: ty::ClosureKind)
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-> Result<bool, ()>
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{
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match (actual_closure_kind, trait_closure_kind) {
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(ty::ClosureKind::Fn, ty::ClosureKind::Fn) |
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(ty::ClosureKind::FnMut, ty::ClosureKind::FnMut) |
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(ty::ClosureKind::FnOnce, ty::ClosureKind::FnOnce) => {
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// No adapter needed.
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Ok(false)
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}
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(ty::ClosureKind::Fn, ty::ClosureKind::FnMut) => {
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// The closure fn `llfn` is a `fn(&self, ...)`. We want a
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// `fn(&mut self, ...)`. In fact, at trans time, these are
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// basically the same thing, so we can just return llfn.
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Ok(false)
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}
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(ty::ClosureKind::Fn, ty::ClosureKind::FnOnce) |
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(ty::ClosureKind::FnMut, ty::ClosureKind::FnOnce) => {
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// The closure fn `llfn` is a `fn(&self, ...)` or `fn(&mut
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// self, ...)`. We want a `fn(self, ...)`. We can produce
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// this by doing something like:
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//
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// fn call_once(self, ...) { call_mut(&self, ...) }
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// fn call_once(mut self, ...) { call_mut(&mut self, ...) }
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//
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// These are both the same at trans time.
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Ok(true)
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}
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_ => Err(()),
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}
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}
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pub fn resolve_closure<'a, 'tcx> (
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tcx: TyCtxt<'a, 'tcx, 'tcx>,
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def_id: DefId,
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substs: ty::ClosureSubsts<'tcx>,
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requested_kind: ty::ClosureKind)
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-> Instance<'tcx>
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{
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let actual_kind = substs.closure_kind(def_id, tcx);
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match needs_fn_once_adapter_shim(actual_kind, requested_kind) {
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Ok(true) => fn_once_adapter_instance(tcx, def_id, substs),
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_ => Instance::new(def_id, substs.substs)
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}
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}
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pub fn resolve_drop_in_place<'a, 'tcx>(
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tcx: TyCtxt<'a, 'tcx, 'tcx>,
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ty: Ty<'tcx>)
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-> ty::Instance<'tcx>
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{
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let def_id = tcx.require_lang_item(DropInPlaceFnLangItem);
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let substs = tcx.intern_substs(&[Kind::from(ty)]);
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Instance::resolve(tcx, ty::ParamEnv::empty(traits::Reveal::All), def_id, substs).unwrap()
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}
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pub fn custom_coerce_unsize_info<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
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source_ty: Ty<'tcx>,
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target_ty: Ty<'tcx>)
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-> CustomCoerceUnsized {
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let def_id = tcx.lang_items().coerce_unsized_trait().unwrap();
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let trait_ref = ty::Binder(ty::TraitRef {
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def_id: def_id,
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substs: tcx.mk_substs_trait(source_ty, &[target_ty])
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});
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match tcx.trans_fulfill_obligation( (ty::ParamEnv::empty(traits::Reveal::All), trait_ref)) {
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traits::VtableImpl(traits::VtableImplData { impl_def_id, .. }) => {
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tcx.coerce_unsized_info(impl_def_id).custom_kind.unwrap()
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}
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vtable => {
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bug!("invalid CoerceUnsized vtable: {:?}", vtable);
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}
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}
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}
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