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Rollup merge of #31184 - arielb1:remove-implicator, r=nikomatsakis

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it is pre-RFC1214 junk and completely useless.

r? @nikomatsakis
This commit is contained in:
Manish Goregaokar 2016-01-26 13:11:57 +05:30
commit ced313cf19
3 changed files with 1 additions and 503 deletions
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1
src/librustc/lib.rs
View File

@ -108,7 +108,6 @@ pub mod middle {
pub mod free_region;
pub mod intrinsicck;
pub mod infer;
pub mod implicator;
pub mod lang_items;
pub mod liveness;
pub mod mem_categorization;

454
src/librustc/middle/implicator.rs
View File

@ -1,454 +0,0 @@
// Copyright 2012 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
// #![warn(deprecated_mode)]
use middle::def_id::DefId;
use middle::infer::{InferCtxt, GenericKind};
use middle::subst::Substs;
use middle::traits;
use middle::ty::{self, ToPredicate, Ty};
use middle::ty::fold::{TypeFoldable, TypeFolder};
use syntax::ast;
use syntax::codemap::Span;
use util::common::ErrorReported;
use util::nodemap::FnvHashSet;
// Helper functions related to manipulating region types.
#[derive(Debug)]
pub enum Implication<'tcx> {
RegionSubRegion(Option<Ty<'tcx>>, ty::Region, ty::Region),
RegionSubGeneric(Option<Ty<'tcx>>, ty::Region, GenericKind<'tcx>),
Predicate(DefId, ty::Predicate<'tcx>),
}
struct Implicator<'a, 'tcx: 'a> {
infcx: &'a InferCtxt<'a,'tcx>,
body_id: ast::NodeId,
stack: Vec<(ty::Region, Option<Ty<'tcx>>)>,
span: Span,
out: Vec<Implication<'tcx>>,
visited: FnvHashSet<Ty<'tcx>>,
}
/// This routine computes the well-formedness constraints that must hold for the type `ty` to
/// appear in a context with lifetime `outer_region`
pub fn implications<'a,'tcx>(
infcx: &'a InferCtxt<'a,'tcx>,
body_id: ast::NodeId,
ty: Ty<'tcx>,
outer_region: ty::Region,
span: Span)
-> Vec<Implication<'tcx>>
{
debug!("implications(body_id={}, ty={:?}, outer_region={:?})",
body_id,
ty,
outer_region);
let mut stack = Vec::new();
stack.push((outer_region, None));
let mut wf = Implicator { infcx: infcx,
body_id: body_id,
span: span,
stack: stack,
out: Vec::new(),
visited: FnvHashSet() };
wf.accumulate_from_ty(ty);
debug!("implications: out={:?}", wf.out);
wf.out
}
impl<'a, 'tcx> Implicator<'a, 'tcx> {
fn tcx(&self) -> &'a ty::ctxt<'tcx> {
self.infcx.tcx
}
fn accumulate_from_ty(&mut self, ty: Ty<'tcx>) {
debug!("accumulate_from_ty(ty={:?})",
ty);
// When expanding out associated types, we can visit a cyclic
// set of types. Issue #23003.
if !self.visited.insert(ty) {
return;
}
match ty.sty {
ty::TyBool |
ty::TyChar |
ty::TyInt(..) |
ty::TyUint(..) |
ty::TyFloat(..) |
ty::TyBareFn(..) |
ty::TyError |
ty::TyStr => {
// No borrowed content reachable here.
}
ty::TyClosure(_, ref substs) => {
// FIXME(#27086). We do not accumulate from substs, since they
// don't represent reachable data. This means that, in
// practice, some of the lifetime parameters might not
// be in scope when the body runs, so long as there is
// no reachable data with that lifetime. For better or
// worse, this is consistent with fn types, however,
// which can also encapsulate data in this fashion
// (though it's somewhat harder, and typically
// requires virtual dispatch).
//
// Note that changing this (in a naive way, at least)
// causes regressions for what appears to be perfectly
// reasonable code like this:
//
// ```
// fn foo<'a>(p: &Data<'a>) {
// bar(|q: &mut Parser| q.read_addr())
// }
// fn bar(p: Box<FnMut(&mut Parser)+'static>) {
// }
// ```
//
// Note that `p` (and `'a`) are not used in the
// closure at all, but to meet the requirement that
// the closure type `C: 'static` (so it can be coerced
// to the object type), we get the requirement that
// `'a: 'static` since `'a` appears in the closure
// type `C`.
//
// A smarter fix might "prune" unused `func_substs` --
// this would avoid breaking simple examples like
// this, but would still break others (which might
// indeed be invalid, depending on your POV). Pruning
// would be a subtle process, since we have to see
// what func/type parameters are used and unused,
// taking into consideration UFCS and so forth.
for &upvar_ty in &substs.upvar_tys {
self.accumulate_from_ty(upvar_ty);
}
}
ty::TyTrait(ref t) => {
let required_region_bounds =
object_region_bounds(self.tcx(), &t.principal, t.bounds.builtin_bounds);
self.accumulate_from_object_ty(ty, t.bounds.region_bound, required_region_bounds)
}
ty::TyEnum(def, substs) |
ty::TyStruct(def, substs) => {
let item_scheme = def.type_scheme(self.tcx());
self.accumulate_from_adt(ty, def.did, &item_scheme.generics, substs)
}
ty::TyArray(t, _) |
ty::TySlice(t) |
ty::TyRawPtr(ty::TypeAndMut { ty: t, .. }) |
ty::TyBox(t) => {
self.accumulate_from_ty(t)
}
ty::TyRef(r_b, mt) => {
self.accumulate_from_rptr(ty, *r_b, mt.ty);
}
ty::TyParam(p) => {
self.push_param_constraint_from_top(p);
}
ty::TyProjection(ref data) => {
// `<T as TraitRef<..>>::Name`
self.push_projection_constraint_from_top(data);
}
ty::TyTuple(ref tuptys) => {
for &tupty in tuptys {
self.accumulate_from_ty(tupty);
}
}
ty::TyInfer(_) => {
// This should not happen, BUT:
//
// Currently we uncover region relationships on
// entering the fn check. We should do this after
// the fn check, then we can call this case a bug().
}
}
}
fn accumulate_from_rptr(&mut self,
ty: Ty<'tcx>,
r_b: ty::Region,
ty_b: Ty<'tcx>) {
// We are walking down a type like this, and current
// position is indicated by caret:
//
// &'a &'b ty_b
// ^
//
// At this point, top of stack will be `'a`. We must
// require that `'a <= 'b`.
self.push_region_constraint_from_top(r_b);
// Now we push `'b` onto the stack, because it must
// constrain any borrowed content we find within `T`.
self.stack.push((r_b, Some(ty)));
self.accumulate_from_ty(ty_b);
self.stack.pop().unwrap();
}
/// Pushes a constraint that `r_b` must outlive the top region on the stack.
fn push_region_constraint_from_top(&mut self,
r_b: ty::Region) {
// Indicates that we have found borrowed content with a lifetime
// of at least `r_b`. This adds a constraint that `r_b` must
// outlive the region `r_a` on top of the stack.
//
// As an example, imagine walking a type like:
//
// &'a &'b T
// ^
//
// when we hit the inner pointer (indicated by caret), `'a` will
// be on top of stack and `'b` will be the lifetime of the content
// we just found. So we add constraint that `'a <= 'b`.
let &(r_a, opt_ty) = self.stack.last().unwrap();
self.push_sub_region_constraint(opt_ty, r_a, r_b);
}
/// Pushes a constraint that `r_a <= r_b`, due to `opt_ty`
fn push_sub_region_constraint(&mut self,
opt_ty: Option<Ty<'tcx>>,
r_a: ty::Region,
r_b: ty::Region) {
self.out.push(Implication::RegionSubRegion(opt_ty, r_a, r_b));
}
/// Pushes a constraint that `param_ty` must outlive the top region on the stack.
fn push_param_constraint_from_top(&mut self,
param_ty: ty::ParamTy) {
let &(region, opt_ty) = self.stack.last().unwrap();
self.push_param_constraint(region, opt_ty, param_ty);
}
/// Pushes a constraint that `projection_ty` must outlive the top region on the stack.
fn push_projection_constraint_from_top(&mut self,
projection_ty: &ty::ProjectionTy<'tcx>) {
let &(region, opt_ty) = self.stack.last().unwrap();
self.out.push(Implication::RegionSubGeneric(
opt_ty, region, GenericKind::Projection(projection_ty.clone())));
}
/// Pushes a constraint that `region <= param_ty`, due to `opt_ty`
fn push_param_constraint(&mut self,
region: ty::Region,
opt_ty: Option<Ty<'tcx>>,
param_ty: ty::ParamTy) {
self.out.push(Implication::RegionSubGeneric(
opt_ty, region, GenericKind::Param(param_ty)));
}
fn accumulate_from_adt(&mut self,
ty: Ty<'tcx>,
def_id: DefId,
_generics: &ty::Generics<'tcx>,
substs: &Substs<'tcx>)
{
let predicates =
self.tcx().lookup_predicates(def_id).instantiate(self.tcx(), substs);
let predicates = match self.fully_normalize(&predicates) {
Ok(predicates) => predicates,
Err(ErrorReported) => { return; }
};
for predicate in predicates.predicates.as_slice() {
match *predicate {
ty::Predicate::Trait(..) => { }
ty::Predicate::Equate(..) => { }
ty::Predicate::Projection(..) => { }
ty::Predicate::RegionOutlives(ref data) => {
match self.tcx().no_late_bound_regions(data) {
None => { }
Some(ty::OutlivesPredicate(r_a, r_b)) => {
self.push_sub_region_constraint(Some(ty), r_b, r_a);
}
}
}
ty::Predicate::TypeOutlives(ref data) => {
match self.tcx().no_late_bound_regions(data) {
None => { }
Some(ty::OutlivesPredicate(ty_a, r_b)) => {
self.stack.push((r_b, Some(ty)));
self.accumulate_from_ty(ty_a);
self.stack.pop().unwrap();
}
}
}
ty::Predicate::ObjectSafe(_) |
ty::Predicate::WellFormed(_) => {
}
}
}
let obligations = predicates.predicates
.into_iter()
.map(|pred| Implication::Predicate(def_id, pred));
self.out.extend(obligations);
let variances = self.tcx().item_variances(def_id);
self.accumulate_from_substs(substs, Some(&variances));
}
fn accumulate_from_substs(&mut self,
substs: &Substs<'tcx>,
variances: Option<&ty::ItemVariances>)
{
let mut tmp_variances = None;
let variances = variances.unwrap_or_else(|| {
tmp_variances = Some(ty::ItemVariances {
types: substs.types.map(|_| ty::Variance::Invariant),
regions: substs.regions().map(|_| ty::Variance::Invariant),
});
tmp_variances.as_ref().unwrap()
});
for (&region, &variance) in substs.regions().iter().zip(&variances.regions) {
match variance {
ty::Contravariant | ty::Invariant => {
// If any data with this lifetime is reachable
// within, it must be at least contravariant.
self.push_region_constraint_from_top(region)
}
ty::Covariant | ty::Bivariant => { }
}
}
for (&ty, &variance) in substs.types.iter().zip(&variances.types) {
match variance {
ty::Covariant | ty::Invariant => {
// If any data of this type is reachable within,
// it must be at least covariant.
self.accumulate_from_ty(ty);
}
ty::Contravariant | ty::Bivariant => { }
}
}
}
fn accumulate_from_object_ty(&mut self,
ty: Ty<'tcx>,
region_bound: ty::Region,
required_region_bounds: Vec<ty::Region>)
{
// Imagine a type like this:
//
// trait Foo { }
// trait Bar<'c> : 'c { }
//
// &'b (Foo+'c+Bar<'d>)
// ^
//
// In this case, the following relationships must hold:
//
// 'b <= 'c
// 'd <= 'c
//
// The first conditions is due to the normal region pointer
// rules, which say that a reference cannot outlive its
// referent.
//
// The final condition may be a bit surprising. In particular,
// you may expect that it would have been `'c <= 'd`, since
// usually lifetimes of outer things are conservative
// approximations for inner things. However, it works somewhat
// differently with trait objects: here the idea is that if the
// user specifies a region bound (`'c`, in this case) it is the
// "master bound" that *implies* that bounds from other traits are
// all met. (Remember that *all bounds* in a type like
// `Foo+Bar+Zed` must be met, not just one, hence if we write
// `Foo<'x>+Bar<'y>`, we know that the type outlives *both* 'x and
// 'y.)
//
// Note: in fact we only permit builtin traits, not `Bar<'d>`, I
// am looking forward to the future here.
// The content of this object type must outlive
// `bounds.region_bound`:
let r_c = region_bound;
self.push_region_constraint_from_top(r_c);
// And then, in turn, to be well-formed, the
// `region_bound` that user specified must imply the
// region bounds required from all of the trait types:
for &r_d in &required_region_bounds {
// Each of these is an instance of the `'c <= 'b`
// constraint above
self.out.push(Implication::RegionSubRegion(Some(ty), r_d, r_c));
}
}
fn fully_normalize<T>(&self, value: &T) -> Result<T,ErrorReported>
where T : TypeFoldable<'tcx>
{
let value =
traits::fully_normalize(self.infcx,
traits::ObligationCause::misc(self.span, self.body_id),
value);
match value {
Ok(value) => Ok(value),
Err(errors) => {
// I don't like reporting these errors here, but I
// don't know where else to report them just now. And
// I don't really expect errors to arise here
// frequently. I guess the best option would be to
// propagate them out.
traits::report_fulfillment_errors(self.infcx, &errors);
Err(ErrorReported)
}
}
}
}
/// Given an object type like `SomeTrait+Send`, computes the lifetime
/// bounds that must hold on the elided self type. These are derived
/// from the declarations of `SomeTrait`, `Send`, and friends -- if
/// they declare `trait SomeTrait : 'static`, for example, then
/// `'static` would appear in the list. The hard work is done by
/// `ty::required_region_bounds`, see that for more information.
pub fn object_region_bounds<'tcx>(
tcx: &ty::ctxt<'tcx>,
principal: &ty::PolyTraitRef<'tcx>,
others: ty::BuiltinBounds)
-> Vec<ty::Region>
{
// Since we don't actually *know* the self type for an object,
// this "open(err)" serves as a kind of dummy standin -- basically
// a skolemized type.
let open_ty = tcx.mk_infer(ty::FreshTy(0));
// Note that we preserve the overall binding levels here.
assert!(!open_ty.has_escaping_regions());
let substs = tcx.mk_substs(principal.0.substs.with_self_ty(open_ty));
let trait_refs = vec!(ty::Binder(ty::TraitRef::new(principal.0.def_id, substs)));
let mut predicates = others.to_predicates(tcx, open_ty);
predicates.extend(trait_refs.iter().map(|t| t.to_predicate()));
tcx.required_region_bounds(open_ty, predicates)
}

47
src/librustc_typeck/check/regionck.rs
View File

@ -86,7 +86,6 @@ use astconv::AstConv;
use check::dropck;
use check::FnCtxt;
use middle::free_region::FreeRegionMap;
use middle::implicator::{self, Implication};
use middle::mem_categorization as mc;
use middle::mem_categorization::Categorization;
use middle::region::{self, CodeExtent};
@ -365,12 +364,7 @@ impl<'a, 'tcx> Rcx<'a, 'tcx> {
r_o, r_o.cause);
let sup_type = self.resolve_type(r_o.sup_type);
let origin = self.code_to_origin(r_o.cause.span, sup_type, &r_o.cause.code);
if r_o.sub_region != ty::ReEmpty {
type_must_outlive(self, origin, sup_type, r_o.sub_region);
} else {
self.visit_old_school_wf(node_id, sup_type, origin);
}
}
// Processing the region obligations should not cause the list to grow further:
@ -378,47 +372,6 @@ impl<'a, 'tcx> Rcx<'a, 'tcx> {
self.fcx.inh.infcx.fulfillment_cx.borrow().region_obligations(node_id).len());
}
fn visit_old_school_wf(&mut self,
body_id: ast::NodeId,
ty: Ty<'tcx>,
origin: infer::SubregionOrigin<'tcx>) {
// As a weird kind of hack, we use a region of empty as a signal
// to mean "old-school WF rules". The only reason the old-school
// WF rules are not encoded using WF is that this leads to errors,
// and we want to phase those in gradually.
// FIXME(#27579) remove this weird special case once we phase in new WF rules completely
let implications = implicator::implications(self.infcx(),
body_id,
ty,
ty::ReEmpty,
origin.span());
let origin_for_ty = |ty: Option<Ty<'tcx>>| match ty {
None => origin.clone(),
Some(ty) => infer::ReferenceOutlivesReferent(ty, origin.span()),
};
for implication in implications {
match implication {
Implication::RegionSubRegion(ty, r1, r2) => {
self.fcx.mk_subr(origin_for_ty(ty), r1, r2);
}
Implication::RegionSubGeneric(ty, r1, GenericKind::Param(param_ty)) => {
param_ty_must_outlive(self, origin_for_ty(ty), r1, param_ty);
}
Implication::RegionSubGeneric(ty, r1, GenericKind::Projection(proj_ty)) => {
projection_must_outlive(self, origin_for_ty(ty), r1, proj_ty);
}
Implication::Predicate(def_id, predicate) => {
let cause = traits::ObligationCause::new(origin.span(),
body_id,
traits::ItemObligation(def_id));
let obligation = traits::Obligation::new(cause, predicate);
self.fcx.register_predicate(obligation);
}
}
}
}
fn code_to_origin(&self,
span: Span,
sup_type: Ty<'tcx>,