738 lines
25 KiB
Rust
738 lines
25 KiB
Rust
//! See `README.md`.
|
|
|
|
use std::ops::Range;
|
|
use std::{cmp, fmt, mem};
|
|
|
|
use rustc_data_structures::fx::FxHashMap;
|
|
use rustc_data_structures::undo_log::UndoLogs;
|
|
use rustc_data_structures::unify as ut;
|
|
use rustc_index::IndexVec;
|
|
use rustc_macros::{TypeFoldable, TypeVisitable};
|
|
use rustc_middle::ty::{self, ReBound, ReStatic, ReVar, Region, RegionVid, Ty, TyCtxt};
|
|
use rustc_middle::{bug, span_bug};
|
|
use tracing::{debug, instrument};
|
|
|
|
use self::CombineMapType::*;
|
|
use self::UndoLog::*;
|
|
use super::{MiscVariable, RegionVariableOrigin, Rollback, SubregionOrigin};
|
|
use crate::infer::snapshot::undo_log::{InferCtxtUndoLogs, Snapshot};
|
|
use crate::infer::unify_key::{RegionVariableValue, RegionVidKey};
|
|
|
|
mod leak_check;
|
|
|
|
#[derive(Clone, Default)]
|
|
pub struct RegionConstraintStorage<'tcx> {
|
|
/// For each `RegionVid`, the corresponding `RegionVariableOrigin`.
|
|
pub(super) var_infos: IndexVec<RegionVid, RegionVariableInfo>,
|
|
|
|
pub(super) data: RegionConstraintData<'tcx>,
|
|
|
|
/// For a given pair of regions (R1, R2), maps to a region R3 that
|
|
/// is designated as their LUB (edges R1 <= R3 and R2 <= R3
|
|
/// exist). This prevents us from making many such regions.
|
|
lubs: CombineMap<'tcx>,
|
|
|
|
/// For a given pair of regions (R1, R2), maps to a region R3 that
|
|
/// is designated as their GLB (edges R3 <= R1 and R3 <= R2
|
|
/// exist). This prevents us from making many such regions.
|
|
glbs: CombineMap<'tcx>,
|
|
|
|
/// When we add a R1 == R2 constraint, we currently add (a) edges
|
|
/// R1 <= R2 and R2 <= R1 and (b) we unify the two regions in this
|
|
/// table. You can then call `opportunistic_resolve_var` early
|
|
/// which will map R1 and R2 to some common region (i.e., either
|
|
/// R1 or R2). This is important when fulfillment, dropck and other such
|
|
/// code is iterating to a fixed point, because otherwise we sometimes
|
|
/// would wind up with a fresh stream of region variables that have been
|
|
/// equated but appear distinct.
|
|
pub(super) unification_table: ut::UnificationTableStorage<RegionVidKey<'tcx>>,
|
|
|
|
/// a flag set to true when we perform any unifications; this is used
|
|
/// to micro-optimize `take_and_reset_data`
|
|
any_unifications: bool,
|
|
}
|
|
|
|
pub struct RegionConstraintCollector<'a, 'tcx> {
|
|
storage: &'a mut RegionConstraintStorage<'tcx>,
|
|
undo_log: &'a mut InferCtxtUndoLogs<'tcx>,
|
|
}
|
|
|
|
pub type VarInfos = IndexVec<RegionVid, RegionVariableInfo>;
|
|
|
|
/// The full set of region constraints gathered up by the collector.
|
|
/// Describes constraints between the region variables and other
|
|
/// regions, as well as other conditions that must be verified, or
|
|
/// assumptions that can be made.
|
|
#[derive(Debug, Default, Clone)]
|
|
pub struct RegionConstraintData<'tcx> {
|
|
/// Constraints of the form `A <= B`, where either `A` or `B` can
|
|
/// be a region variable (or neither, as it happens).
|
|
pub constraints: Vec<(Constraint<'tcx>, SubregionOrigin<'tcx>)>,
|
|
|
|
/// A "verify" is something that we need to verify after inference
|
|
/// is done, but which does not directly affect inference in any
|
|
/// way.
|
|
///
|
|
/// An example is a `A <= B` where neither `A` nor `B` are
|
|
/// inference variables.
|
|
pub verifys: Vec<Verify<'tcx>>,
|
|
}
|
|
|
|
/// Represents a constraint that influences the inference process.
|
|
#[derive(Clone, Copy, PartialEq, Eq, Debug, Hash)]
|
|
pub enum Constraint<'tcx> {
|
|
/// A region variable is a subregion of another.
|
|
VarSubVar(RegionVid, RegionVid),
|
|
|
|
/// A concrete region is a subregion of region variable.
|
|
RegSubVar(Region<'tcx>, RegionVid),
|
|
|
|
/// A region variable is a subregion of a concrete region. This does not
|
|
/// directly affect inference, but instead is checked after
|
|
/// inference is complete.
|
|
VarSubReg(RegionVid, Region<'tcx>),
|
|
|
|
/// A constraint where neither side is a variable. This does not
|
|
/// directly affect inference, but instead is checked after
|
|
/// inference is complete.
|
|
RegSubReg(Region<'tcx>, Region<'tcx>),
|
|
}
|
|
|
|
impl Constraint<'_> {
|
|
pub fn involves_placeholders(&self) -> bool {
|
|
match self {
|
|
Constraint::VarSubVar(_, _) => false,
|
|
Constraint::VarSubReg(_, r) | Constraint::RegSubVar(r, _) => r.is_placeholder(),
|
|
Constraint::RegSubReg(r, s) => r.is_placeholder() || s.is_placeholder(),
|
|
}
|
|
}
|
|
}
|
|
|
|
#[derive(Debug, Clone)]
|
|
pub struct Verify<'tcx> {
|
|
pub kind: GenericKind<'tcx>,
|
|
pub origin: SubregionOrigin<'tcx>,
|
|
pub region: Region<'tcx>,
|
|
pub bound: VerifyBound<'tcx>,
|
|
}
|
|
|
|
#[derive(Copy, Clone, PartialEq, Eq, Hash, TypeFoldable, TypeVisitable)]
|
|
pub enum GenericKind<'tcx> {
|
|
Param(ty::ParamTy),
|
|
Placeholder(ty::PlaceholderType),
|
|
Alias(ty::AliasTy<'tcx>),
|
|
}
|
|
|
|
/// Describes the things that some `GenericKind` value `G` is known to
|
|
/// outlive. Each variant of `VerifyBound` can be thought of as a
|
|
/// function:
|
|
/// ```ignore (pseudo-rust)
|
|
/// fn(min: Region) -> bool { .. }
|
|
/// ```
|
|
/// where `true` means that the region `min` meets that `G: min`.
|
|
/// (False means nothing.)
|
|
///
|
|
/// So, for example, if we have the type `T` and we have in scope that
|
|
/// `T: 'a` and `T: 'b`, then the verify bound might be:
|
|
/// ```ignore (pseudo-rust)
|
|
/// fn(min: Region) -> bool {
|
|
/// ('a: min) || ('b: min)
|
|
/// }
|
|
/// ```
|
|
/// This is described with an `AnyRegion('a, 'b)` node.
|
|
#[derive(Debug, Clone, TypeFoldable, TypeVisitable)]
|
|
pub enum VerifyBound<'tcx> {
|
|
/// See [`VerifyIfEq`] docs
|
|
IfEq(ty::Binder<'tcx, VerifyIfEq<'tcx>>),
|
|
|
|
/// Given a region `R`, expands to the function:
|
|
///
|
|
/// ```ignore (pseudo-rust)
|
|
/// fn(min) -> bool {
|
|
/// R: min
|
|
/// }
|
|
/// ```
|
|
///
|
|
/// This is used when we can establish that `G: R` -- therefore,
|
|
/// if `R: min`, then by transitivity `G: min`.
|
|
OutlivedBy(Region<'tcx>),
|
|
|
|
/// Given a region `R`, true if it is `'empty`.
|
|
IsEmpty,
|
|
|
|
/// Given a set of bounds `B`, expands to the function:
|
|
///
|
|
/// ```ignore (pseudo-rust)
|
|
/// fn(min) -> bool {
|
|
/// exists (b in B) { b(min) }
|
|
/// }
|
|
/// ```
|
|
///
|
|
/// In other words, if we meet some bound in `B`, that suffices.
|
|
/// This is used when all the bounds in `B` are known to apply to `G`.
|
|
AnyBound(Vec<VerifyBound<'tcx>>),
|
|
|
|
/// Given a set of bounds `B`, expands to the function:
|
|
///
|
|
/// ```ignore (pseudo-rust)
|
|
/// fn(min) -> bool {
|
|
/// forall (b in B) { b(min) }
|
|
/// }
|
|
/// ```
|
|
///
|
|
/// In other words, if we meet *all* bounds in `B`, that suffices.
|
|
/// This is used when *some* bound in `B` is known to suffice, but
|
|
/// we don't know which.
|
|
AllBounds(Vec<VerifyBound<'tcx>>),
|
|
}
|
|
|
|
/// This is a "conditional bound" that checks the result of inference
|
|
/// and supplies a bound if it ended up being relevant. It's used in situations
|
|
/// like this:
|
|
///
|
|
/// ```rust,ignore (pseudo-Rust)
|
|
/// fn foo<'a, 'b, T: SomeTrait<'a>>
|
|
/// where
|
|
/// <T as SomeTrait<'a>>::Item: 'b
|
|
/// ```
|
|
///
|
|
/// If we have an obligation like `<T as SomeTrait<'?x>>::Item: 'c`, then
|
|
/// we don't know yet whether it suffices to show that `'b: 'c`. If `'?x` winds
|
|
/// up being equal to `'a`, then the where-clauses on function applies, and
|
|
/// in that case we can show `'b: 'c`. But if `'?x` winds up being something
|
|
/// else, the bound isn't relevant.
|
|
///
|
|
/// In the [`VerifyBound`], this struct is enclosed in `Binder` to account
|
|
/// for cases like
|
|
///
|
|
/// ```rust,ignore (pseudo-Rust)
|
|
/// where for<'a> <T as SomeTrait<'a>::Item: 'a
|
|
/// ```
|
|
///
|
|
/// The idea is that we have to find some instantiation of `'a` that can
|
|
/// make `<T as SomeTrait<'a>>::Item` equal to the final value of `G`,
|
|
/// the generic we are checking.
|
|
///
|
|
/// ```ignore (pseudo-rust)
|
|
/// fn(min) -> bool {
|
|
/// exists<'a> {
|
|
/// if G == K {
|
|
/// B(min)
|
|
/// } else {
|
|
/// false
|
|
/// }
|
|
/// }
|
|
/// }
|
|
/// ```
|
|
#[derive(Debug, Copy, Clone, TypeFoldable, TypeVisitable)]
|
|
pub struct VerifyIfEq<'tcx> {
|
|
/// Type which must match the generic `G`
|
|
pub ty: Ty<'tcx>,
|
|
|
|
/// Bound that applies if `ty` is equal.
|
|
pub bound: Region<'tcx>,
|
|
}
|
|
|
|
#[derive(Copy, Clone, PartialEq, Eq, Hash)]
|
|
pub(crate) struct TwoRegions<'tcx> {
|
|
a: Region<'tcx>,
|
|
b: Region<'tcx>,
|
|
}
|
|
|
|
#[derive(Copy, Clone, PartialEq)]
|
|
pub(crate) enum UndoLog<'tcx> {
|
|
/// We added `RegionVid`.
|
|
AddVar(RegionVid),
|
|
|
|
/// We added the given `constraint`.
|
|
AddConstraint(usize),
|
|
|
|
/// We added the given `verify`.
|
|
AddVerify(usize),
|
|
|
|
/// We added a GLB/LUB "combination variable".
|
|
AddCombination(CombineMapType, TwoRegions<'tcx>),
|
|
}
|
|
|
|
#[derive(Copy, Clone, PartialEq)]
|
|
pub(crate) enum CombineMapType {
|
|
Lub,
|
|
Glb,
|
|
}
|
|
|
|
type CombineMap<'tcx> = FxHashMap<TwoRegions<'tcx>, RegionVid>;
|
|
|
|
#[derive(Debug, Clone, Copy)]
|
|
pub struct RegionVariableInfo {
|
|
pub origin: RegionVariableOrigin,
|
|
// FIXME: This is only necessary for `fn take_and_reset_data` and
|
|
// `lexical_region_resolve`. We should rework `lexical_region_resolve`
|
|
// in the near/medium future anyways and could move the unverse info
|
|
// for `fn take_and_reset_data` into a separate table which is
|
|
// only populated when needed.
|
|
//
|
|
// For both of these cases it is fine that this can diverge from the
|
|
// actual universe of the variable, which is directly stored in the
|
|
// unification table for unknown region variables. At some point we could
|
|
// stop emitting bidirectional outlives constraints if equate succeeds.
|
|
// This would be currently unsound as it would cause us to drop the universe
|
|
// changes in `lexical_region_resolve`.
|
|
pub universe: ty::UniverseIndex,
|
|
}
|
|
|
|
pub(crate) struct RegionSnapshot {
|
|
any_unifications: bool,
|
|
}
|
|
|
|
impl<'tcx> RegionConstraintStorage<'tcx> {
|
|
#[inline]
|
|
pub(crate) fn with_log<'a>(
|
|
&'a mut self,
|
|
undo_log: &'a mut InferCtxtUndoLogs<'tcx>,
|
|
) -> RegionConstraintCollector<'a, 'tcx> {
|
|
RegionConstraintCollector { storage: self, undo_log }
|
|
}
|
|
}
|
|
|
|
impl<'tcx> RegionConstraintCollector<'_, 'tcx> {
|
|
pub fn num_region_vars(&self) -> usize {
|
|
self.storage.var_infos.len()
|
|
}
|
|
|
|
/// Takes (and clears) the current set of constraints. Note that
|
|
/// the set of variables remains intact, but all relationships
|
|
/// between them are reset. This is used during NLL checking to
|
|
/// grab the set of constraints that arose from a particular
|
|
/// operation.
|
|
///
|
|
/// We don't want to leak relationships between variables between
|
|
/// points because just because (say) `r1 == r2` was true at some
|
|
/// point P in the graph doesn't imply that it will be true at
|
|
/// some other point Q, in NLL.
|
|
///
|
|
/// Not legal during a snapshot.
|
|
pub fn take_and_reset_data(&mut self) -> RegionConstraintData<'tcx> {
|
|
assert!(!UndoLogs::<UndoLog<'_>>::in_snapshot(&self.undo_log));
|
|
|
|
// If you add a new field to `RegionConstraintCollector`, you
|
|
// should think carefully about whether it needs to be cleared
|
|
// or updated in some way.
|
|
let RegionConstraintStorage {
|
|
var_infos: _,
|
|
data,
|
|
lubs,
|
|
glbs,
|
|
unification_table: _,
|
|
any_unifications,
|
|
} = self.storage;
|
|
|
|
// Clear the tables of (lubs, glbs), so that we will create
|
|
// fresh regions if we do a LUB operation. As it happens,
|
|
// LUB/GLB are not performed by the MIR type-checker, which is
|
|
// the one that uses this method, but it's good to be correct.
|
|
lubs.clear();
|
|
glbs.clear();
|
|
|
|
let data = mem::take(data);
|
|
|
|
// Clear all unifications and recreate the variables a "now
|
|
// un-unified" state. Note that when we unify `a` and `b`, we
|
|
// also insert `a <= b` and a `b <= a` edges, so the
|
|
// `RegionConstraintData` contains the relationship here.
|
|
if *any_unifications {
|
|
*any_unifications = false;
|
|
// Manually inlined `self.unification_table_mut()` as `self` is used in the closure.
|
|
ut::UnificationTable::with_log(&mut self.storage.unification_table, &mut self.undo_log)
|
|
.reset_unifications(|key| RegionVariableValue::Unknown {
|
|
universe: self.storage.var_infos[key.vid].universe,
|
|
});
|
|
}
|
|
|
|
data
|
|
}
|
|
|
|
pub fn data(&self) -> &RegionConstraintData<'tcx> {
|
|
&self.storage.data
|
|
}
|
|
|
|
pub(super) fn start_snapshot(&self) -> RegionSnapshot {
|
|
debug!("RegionConstraintCollector: start_snapshot");
|
|
RegionSnapshot { any_unifications: self.storage.any_unifications }
|
|
}
|
|
|
|
pub(super) fn rollback_to(&mut self, snapshot: RegionSnapshot) {
|
|
debug!("RegionConstraintCollector: rollback_to({:?})", snapshot);
|
|
self.storage.any_unifications = snapshot.any_unifications;
|
|
}
|
|
|
|
pub(super) fn new_region_var(
|
|
&mut self,
|
|
universe: ty::UniverseIndex,
|
|
origin: RegionVariableOrigin,
|
|
) -> RegionVid {
|
|
let vid = self.storage.var_infos.push(RegionVariableInfo { origin, universe });
|
|
|
|
let u_vid = self.unification_table_mut().new_key(RegionVariableValue::Unknown { universe });
|
|
assert_eq!(vid, u_vid.vid);
|
|
self.undo_log.push(AddVar(vid));
|
|
debug!("created new region variable {:?} in {:?} with origin {:?}", vid, universe, origin);
|
|
vid
|
|
}
|
|
|
|
/// Returns the origin for the given variable.
|
|
pub(super) fn var_origin(&self, vid: RegionVid) -> RegionVariableOrigin {
|
|
self.storage.var_infos[vid].origin
|
|
}
|
|
|
|
fn add_constraint(&mut self, constraint: Constraint<'tcx>, origin: SubregionOrigin<'tcx>) {
|
|
// cannot add constraints once regions are resolved
|
|
debug!("RegionConstraintCollector: add_constraint({:?})", constraint);
|
|
|
|
let index = self.storage.data.constraints.len();
|
|
self.storage.data.constraints.push((constraint, origin));
|
|
self.undo_log.push(AddConstraint(index));
|
|
}
|
|
|
|
fn add_verify(&mut self, verify: Verify<'tcx>) {
|
|
// cannot add verifys once regions are resolved
|
|
debug!("RegionConstraintCollector: add_verify({:?})", verify);
|
|
|
|
// skip no-op cases known to be satisfied
|
|
if let VerifyBound::AllBounds(ref bs) = verify.bound
|
|
&& bs.is_empty()
|
|
{
|
|
return;
|
|
}
|
|
|
|
let index = self.storage.data.verifys.len();
|
|
self.storage.data.verifys.push(verify);
|
|
self.undo_log.push(AddVerify(index));
|
|
}
|
|
|
|
pub(super) fn make_eqregion(
|
|
&mut self,
|
|
origin: SubregionOrigin<'tcx>,
|
|
a: Region<'tcx>,
|
|
b: Region<'tcx>,
|
|
) {
|
|
if a != b {
|
|
// Eventually, it would be nice to add direct support for
|
|
// equating regions.
|
|
self.make_subregion(origin.clone(), a, b);
|
|
self.make_subregion(origin, b, a);
|
|
|
|
match (a.kind(), b.kind()) {
|
|
(ty::ReVar(a), ty::ReVar(b)) => {
|
|
debug!("make_eqregion: unifying {:?} with {:?}", a, b);
|
|
if self.unification_table_mut().unify_var_var(a, b).is_ok() {
|
|
self.storage.any_unifications = true;
|
|
}
|
|
}
|
|
(ty::ReVar(vid), _) => {
|
|
debug!("make_eqregion: unifying {:?} with {:?}", vid, b);
|
|
if self
|
|
.unification_table_mut()
|
|
.unify_var_value(vid, RegionVariableValue::Known { value: b })
|
|
.is_ok()
|
|
{
|
|
self.storage.any_unifications = true;
|
|
};
|
|
}
|
|
(_, ty::ReVar(vid)) => {
|
|
debug!("make_eqregion: unifying {:?} with {:?}", a, vid);
|
|
if self
|
|
.unification_table_mut()
|
|
.unify_var_value(vid, RegionVariableValue::Known { value: a })
|
|
.is_ok()
|
|
{
|
|
self.storage.any_unifications = true;
|
|
};
|
|
}
|
|
(_, _) => {}
|
|
}
|
|
}
|
|
}
|
|
|
|
#[instrument(skip(self, origin), level = "debug")]
|
|
pub(super) fn make_subregion(
|
|
&mut self,
|
|
origin: SubregionOrigin<'tcx>,
|
|
sub: Region<'tcx>,
|
|
sup: Region<'tcx>,
|
|
) {
|
|
// cannot add constraints once regions are resolved
|
|
debug!("origin = {:#?}", origin);
|
|
|
|
match (sub.kind(), sup.kind()) {
|
|
(ReBound(..), _) | (_, ReBound(..)) => {
|
|
span_bug!(origin.span(), "cannot relate bound region: {:?} <= {:?}", sub, sup);
|
|
}
|
|
(_, ReStatic) => {
|
|
// all regions are subregions of static, so we can ignore this
|
|
}
|
|
(ReVar(sub_id), ReVar(sup_id)) => {
|
|
self.add_constraint(Constraint::VarSubVar(sub_id, sup_id), origin);
|
|
}
|
|
(_, ReVar(sup_id)) => {
|
|
self.add_constraint(Constraint::RegSubVar(sub, sup_id), origin);
|
|
}
|
|
(ReVar(sub_id), _) => {
|
|
self.add_constraint(Constraint::VarSubReg(sub_id, sup), origin);
|
|
}
|
|
_ => {
|
|
self.add_constraint(Constraint::RegSubReg(sub, sup), origin);
|
|
}
|
|
}
|
|
}
|
|
|
|
pub(super) fn verify_generic_bound(
|
|
&mut self,
|
|
origin: SubregionOrigin<'tcx>,
|
|
kind: GenericKind<'tcx>,
|
|
sub: Region<'tcx>,
|
|
bound: VerifyBound<'tcx>,
|
|
) {
|
|
self.add_verify(Verify { kind, origin, region: sub, bound });
|
|
}
|
|
|
|
pub(super) fn lub_regions(
|
|
&mut self,
|
|
tcx: TyCtxt<'tcx>,
|
|
origin: SubregionOrigin<'tcx>,
|
|
a: Region<'tcx>,
|
|
b: Region<'tcx>,
|
|
) -> Region<'tcx> {
|
|
// cannot add constraints once regions are resolved
|
|
debug!("RegionConstraintCollector: lub_regions({:?}, {:?})", a, b);
|
|
if a.is_static() || b.is_static() {
|
|
a // nothing lives longer than static
|
|
} else if a == b {
|
|
a // LUB(a,a) = a
|
|
} else {
|
|
self.combine_vars(tcx, Lub, a, b, origin)
|
|
}
|
|
}
|
|
|
|
pub(super) fn glb_regions(
|
|
&mut self,
|
|
tcx: TyCtxt<'tcx>,
|
|
origin: SubregionOrigin<'tcx>,
|
|
a: Region<'tcx>,
|
|
b: Region<'tcx>,
|
|
) -> Region<'tcx> {
|
|
// cannot add constraints once regions are resolved
|
|
debug!("RegionConstraintCollector: glb_regions({:?}, {:?})", a, b);
|
|
if a.is_static() {
|
|
b // static lives longer than everything else
|
|
} else if b.is_static() {
|
|
a // static lives longer than everything else
|
|
} else if a == b {
|
|
a // GLB(a,a) = a
|
|
} else {
|
|
self.combine_vars(tcx, Glb, a, b, origin)
|
|
}
|
|
}
|
|
|
|
/// Resolves a region var to its value in the unification table, if it exists.
|
|
/// Otherwise, it is resolved to the root `ReVar` in the table.
|
|
pub fn opportunistic_resolve_var(
|
|
&mut self,
|
|
tcx: TyCtxt<'tcx>,
|
|
vid: ty::RegionVid,
|
|
) -> ty::Region<'tcx> {
|
|
let mut ut = self.unification_table_mut();
|
|
let root_vid = ut.find(vid).vid;
|
|
match ut.probe_value(root_vid) {
|
|
RegionVariableValue::Known { value } => value,
|
|
RegionVariableValue::Unknown { .. } => ty::Region::new_var(tcx, root_vid),
|
|
}
|
|
}
|
|
|
|
pub fn probe_value(
|
|
&mut self,
|
|
vid: ty::RegionVid,
|
|
) -> Result<ty::Region<'tcx>, ty::UniverseIndex> {
|
|
match self.unification_table_mut().probe_value(vid) {
|
|
RegionVariableValue::Known { value } => Ok(value),
|
|
RegionVariableValue::Unknown { universe } => Err(universe),
|
|
}
|
|
}
|
|
|
|
fn combine_map(&mut self, t: CombineMapType) -> &mut CombineMap<'tcx> {
|
|
match t {
|
|
Glb => &mut self.storage.glbs,
|
|
Lub => &mut self.storage.lubs,
|
|
}
|
|
}
|
|
|
|
fn combine_vars(
|
|
&mut self,
|
|
tcx: TyCtxt<'tcx>,
|
|
t: CombineMapType,
|
|
a: Region<'tcx>,
|
|
b: Region<'tcx>,
|
|
origin: SubregionOrigin<'tcx>,
|
|
) -> Region<'tcx> {
|
|
let vars = TwoRegions { a, b };
|
|
if let Some(&c) = self.combine_map(t).get(&vars) {
|
|
return ty::Region::new_var(tcx, c);
|
|
}
|
|
let a_universe = self.universe(a);
|
|
let b_universe = self.universe(b);
|
|
let c_universe = cmp::max(a_universe, b_universe);
|
|
let c = self.new_region_var(c_universe, MiscVariable(origin.span()));
|
|
self.combine_map(t).insert(vars, c);
|
|
self.undo_log.push(AddCombination(t, vars));
|
|
let new_r = ty::Region::new_var(tcx, c);
|
|
for old_r in [a, b] {
|
|
match t {
|
|
Glb => self.make_subregion(origin.clone(), new_r, old_r),
|
|
Lub => self.make_subregion(origin.clone(), old_r, new_r),
|
|
}
|
|
}
|
|
debug!("combine_vars() c={:?}", c);
|
|
new_r
|
|
}
|
|
|
|
pub fn universe(&mut self, region: Region<'tcx>) -> ty::UniverseIndex {
|
|
match region.kind() {
|
|
ty::ReStatic
|
|
| ty::ReErased
|
|
| ty::ReLateParam(..)
|
|
| ty::ReEarlyParam(..)
|
|
| ty::ReError(_) => ty::UniverseIndex::ROOT,
|
|
ty::RePlaceholder(placeholder) => placeholder.universe,
|
|
ty::ReVar(vid) => match self.probe_value(vid) {
|
|
Ok(value) => self.universe(value),
|
|
Err(universe) => universe,
|
|
},
|
|
ty::ReBound(..) => bug!("universe(): encountered bound region {:?}", region),
|
|
}
|
|
}
|
|
|
|
pub fn vars_since_snapshot(
|
|
&self,
|
|
value_count: usize,
|
|
) -> (Range<RegionVid>, Vec<RegionVariableOrigin>) {
|
|
let range =
|
|
RegionVid::from(value_count)..RegionVid::from(self.storage.unification_table.len());
|
|
(
|
|
range.clone(),
|
|
(range.start..range.end).map(|index| self.storage.var_infos[index].origin).collect(),
|
|
)
|
|
}
|
|
|
|
/// See `InferCtxt::region_constraints_added_in_snapshot`.
|
|
pub fn region_constraints_added_in_snapshot(&self, mark: &Snapshot<'tcx>) -> bool {
|
|
self.undo_log
|
|
.region_constraints_in_snapshot(mark)
|
|
.any(|&elt| matches!(elt, AddConstraint(_)))
|
|
}
|
|
|
|
#[inline]
|
|
fn unification_table_mut(&mut self) -> super::UnificationTable<'_, 'tcx, RegionVidKey<'tcx>> {
|
|
ut::UnificationTable::with_log(&mut self.storage.unification_table, self.undo_log)
|
|
}
|
|
}
|
|
|
|
impl fmt::Debug for RegionSnapshot {
|
|
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
|
|
write!(f, "RegionSnapshot")
|
|
}
|
|
}
|
|
|
|
impl<'tcx> fmt::Debug for GenericKind<'tcx> {
|
|
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
|
|
match *self {
|
|
GenericKind::Param(ref p) => write!(f, "{p:?}"),
|
|
GenericKind::Placeholder(ref p) => write!(f, "{p:?}"),
|
|
GenericKind::Alias(ref p) => write!(f, "{p:?}"),
|
|
}
|
|
}
|
|
}
|
|
|
|
impl<'tcx> fmt::Display for GenericKind<'tcx> {
|
|
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
|
|
match *self {
|
|
GenericKind::Param(ref p) => write!(f, "{p}"),
|
|
GenericKind::Placeholder(ref p) => write!(f, "{p:?}"),
|
|
GenericKind::Alias(ref p) => write!(f, "{p}"),
|
|
}
|
|
}
|
|
}
|
|
|
|
impl<'tcx> GenericKind<'tcx> {
|
|
pub fn to_ty(&self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
|
|
match *self {
|
|
GenericKind::Param(ref p) => p.to_ty(tcx),
|
|
GenericKind::Placeholder(ref p) => Ty::new_placeholder(tcx, *p),
|
|
GenericKind::Alias(ref p) => p.to_ty(tcx),
|
|
}
|
|
}
|
|
}
|
|
|
|
impl<'tcx> VerifyBound<'tcx> {
|
|
pub fn must_hold(&self) -> bool {
|
|
match self {
|
|
VerifyBound::IfEq(..) => false,
|
|
VerifyBound::OutlivedBy(re) => re.is_static(),
|
|
VerifyBound::IsEmpty => false,
|
|
VerifyBound::AnyBound(bs) => bs.iter().any(|b| b.must_hold()),
|
|
VerifyBound::AllBounds(bs) => bs.iter().all(|b| b.must_hold()),
|
|
}
|
|
}
|
|
|
|
pub fn cannot_hold(&self) -> bool {
|
|
match self {
|
|
VerifyBound::IfEq(..) => false,
|
|
VerifyBound::IsEmpty => false,
|
|
VerifyBound::OutlivedBy(_) => false,
|
|
VerifyBound::AnyBound(bs) => bs.iter().all(|b| b.cannot_hold()),
|
|
VerifyBound::AllBounds(bs) => bs.iter().any(|b| b.cannot_hold()),
|
|
}
|
|
}
|
|
|
|
pub fn or(self, vb: VerifyBound<'tcx>) -> VerifyBound<'tcx> {
|
|
if self.must_hold() || vb.cannot_hold() {
|
|
self
|
|
} else if self.cannot_hold() || vb.must_hold() {
|
|
vb
|
|
} else {
|
|
VerifyBound::AnyBound(vec![self, vb])
|
|
}
|
|
}
|
|
}
|
|
|
|
impl<'tcx> RegionConstraintData<'tcx> {
|
|
/// Returns `true` if this region constraint data contains no constraints, and `false`
|
|
/// otherwise.
|
|
pub fn is_empty(&self) -> bool {
|
|
let RegionConstraintData { constraints, verifys } = self;
|
|
constraints.is_empty() && verifys.is_empty()
|
|
}
|
|
}
|
|
|
|
impl<'tcx> Rollback<UndoLog<'tcx>> for RegionConstraintStorage<'tcx> {
|
|
fn reverse(&mut self, undo: UndoLog<'tcx>) {
|
|
match undo {
|
|
AddVar(vid) => {
|
|
self.var_infos.pop().unwrap();
|
|
assert_eq!(self.var_infos.len(), vid.index());
|
|
}
|
|
AddConstraint(index) => {
|
|
self.data.constraints.pop().unwrap();
|
|
assert_eq!(self.data.constraints.len(), index);
|
|
}
|
|
AddVerify(index) => {
|
|
self.data.verifys.pop();
|
|
assert_eq!(self.data.verifys.len(), index);
|
|
}
|
|
AddCombination(Glb, ref regions) => {
|
|
self.glbs.remove(regions);
|
|
}
|
|
AddCombination(Lub, ref regions) => {
|
|
self.lubs.remove(regions);
|
|
}
|
|
}
|
|
}
|
|
}
|