1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420
use std::cmp::Ordering;
use crate::infer::InferCtxt;
use rustc_middle::infer::canonical::Canonical;
use rustc_middle::infer::canonical::CanonicalTyVarKind;
use rustc_middle::infer::canonical::CanonicalVarInfo;
use rustc_middle::infer::canonical::CanonicalVarInfos;
use rustc_middle::infer::canonical::CanonicalVarKind;
use rustc_middle::ty::BoundRegionKind::BrAnon;
use rustc_middle::ty::BoundTyKind;
use rustc_middle::ty::TyCtxt;
use rustc_middle::ty::TypeVisitableExt;
use rustc_middle::ty::{self, Ty};
use rustc_middle::ty::{TypeFoldable, TypeFolder, TypeSuperFoldable};
/// Whether we're canonicalizing a query input or the query response.
///
/// When canonicalizing an input we're in the context of the caller
/// while canonicalizing the response happens in the context of the
/// query.
#[derive(Debug, Clone, Copy)]
pub enum CanonicalizeMode {
Input,
/// FIXME: We currently return region constraints referring to
/// placeholders and inference variables from a binder instantiated
/// inside of the query.
///
/// In the long term we should eagerly deal with these constraints
/// inside of the query and only propagate constraints which are
/// actually nameable by the caller.
Response {
/// The highest universe nameable by the caller.
///
/// All variables in a universe nameable by the caller get mapped
/// to the root universe in the response and then mapped back to
/// their correct universe when applying the query response in the
/// context of the caller.
///
/// This doesn't work for universes created inside of the query so
/// we do remember their universe in the response.
max_input_universe: ty::UniverseIndex,
},
}
pub struct Canonicalizer<'a, 'tcx> {
infcx: &'a InferCtxt<'tcx>,
canonicalize_mode: CanonicalizeMode,
variables: &'a mut Vec<ty::GenericArg<'tcx>>,
primitive_var_infos: Vec<CanonicalVarInfo<'tcx>>,
binder_index: ty::DebruijnIndex,
}
impl<'a, 'tcx> Canonicalizer<'a, 'tcx> {
#[instrument(level = "debug", skip(infcx), ret)]
pub fn canonicalize<T: TypeFoldable<TyCtxt<'tcx>>>(
infcx: &'a InferCtxt<'tcx>,
canonicalize_mode: CanonicalizeMode,
variables: &'a mut Vec<ty::GenericArg<'tcx>>,
value: T,
) -> Canonical<'tcx, T> {
let mut canonicalizer = Canonicalizer {
infcx,
canonicalize_mode,
variables,
primitive_var_infos: Vec::new(),
binder_index: ty::INNERMOST,
};
let value = value.fold_with(&mut canonicalizer);
assert!(!value.has_infer());
assert!(!value.has_placeholders());
let (max_universe, variables) = canonicalizer.finalize();
Canonical { max_universe, variables, value }
}
fn finalize(self) -> (ty::UniverseIndex, CanonicalVarInfos<'tcx>) {
let mut var_infos = self.primitive_var_infos;
// See the rustc-dev-guide section about how we deal with universes
// during canonicalization in the new solver.
match self.canonicalize_mode {
// We try to deduplicate as many query calls as possible and hide
// all information which should not matter for the solver.
//
// For this we compress universes as much as possible.
CanonicalizeMode::Input => {}
// When canonicalizing a response we map a universes already entered
// by the caller to the root universe and only return useful universe
// information for placeholders and inference variables created inside
// of the query.
CanonicalizeMode::Response { max_input_universe } => {
for var in var_infos.iter_mut() {
let uv = var.universe();
let new_uv = ty::UniverseIndex::from(
uv.index().saturating_sub(max_input_universe.index()),
);
*var = var.with_updated_universe(new_uv);
}
let max_universe = var_infos
.iter()
.map(|info| info.universe())
.max()
.unwrap_or(ty::UniverseIndex::ROOT);
let var_infos = self.infcx.tcx.mk_canonical_var_infos(&var_infos);
return (max_universe, var_infos);
}
}
// Given a `var_infos` with existentials `En` and universals `Un` in
// universes `n`, this algorithm compresses them in place so that:
//
// - the new universe indices are as small as possible
// - we only create a new universe if we would otherwise put a placeholder in
// the same compressed universe as an existential which cannot name it
//
// Let's walk through an example:
// - var_infos: [E0, U1, E5, U2, E2, E6, U6], curr_compressed_uv: 0, next_orig_uv: 0
// - var_infos: [E0, U1, E5, U2, E2, E6, U6], curr_compressed_uv: 0, next_orig_uv: 1
// - var_infos: [E0, U1, E5, U2, E2, E6, U6], curr_compressed_uv: 1, next_orig_uv: 2
// - var_infos: [E0, U1, E5, U1, E1, E6, U6], curr_compressed_uv: 1, next_orig_uv: 5
// - var_infos: [E0, U1, E1, U1, E1, E6, U6], curr_compressed_uv: 1, next_orig_uv: 6
// - var_infos: [E0, U1, E1, U1, E1, E2, U2], curr_compressed_uv: 2, next_orig_uv: -
//
// This algorithm runs in `O(n²)` where `n` is the number of different universe
// indices in the input. This should be fine as `n` is expected to be small.
let mut curr_compressed_uv = ty::UniverseIndex::ROOT;
let mut existential_in_new_uv = false;
let mut next_orig_uv = Some(ty::UniverseIndex::ROOT);
while let Some(orig_uv) = next_orig_uv.take() {
let mut update_uv = |var: &mut CanonicalVarInfo<'tcx>, orig_uv, is_existential| {
let uv = var.universe();
match uv.cmp(&orig_uv) {
Ordering::Less => (), // Already updated
Ordering::Equal => {
if is_existential {
existential_in_new_uv = true;
} else if existential_in_new_uv {
// `var` is a placeholder from a universe which is not nameable
// by an existential which we already put into the compressed
// universe `curr_compressed_uv`. We therefore have to create a
// new universe for `var`.
curr_compressed_uv = curr_compressed_uv.next_universe();
existential_in_new_uv = false;
}
*var = var.with_updated_universe(curr_compressed_uv);
}
Ordering::Greater => {
// We can ignore this variable in this iteration. We only look at
// universes which actually occur in the input for performance.
//
// For this we set `next_orig_uv` to the next smallest, not yet compressed,
// universe of the input.
if next_orig_uv.map_or(true, |curr_next_uv| uv.cannot_name(curr_next_uv)) {
next_orig_uv = Some(uv);
}
}
}
};
// For each universe which occurs in the input, we first iterate over all
// placeholders and then over all inference variables.
//
// Whenever we compress the universe of a placeholder, no existential with
// an already compressed universe can name that placeholder.
for is_existential in [false, true] {
for var in var_infos.iter_mut() {
// We simply put all regions from the input into the highest
// compressed universe, so we only deal with them at the end.
if !var.is_region() {
if is_existential == var.is_existential() {
update_uv(var, orig_uv, is_existential)
}
}
}
}
}
for var in var_infos.iter_mut() {
if var.is_region() {
assert!(var.is_existential());
*var = var.with_updated_universe(curr_compressed_uv);
}
}
let var_infos = self.infcx.tcx.mk_canonical_var_infos(&var_infos);
(curr_compressed_uv, var_infos)
}
}
impl<'tcx> TypeFolder<TyCtxt<'tcx>> for Canonicalizer<'_, 'tcx> {
fn interner(&self) -> TyCtxt<'tcx> {
self.infcx.tcx
}
fn fold_binder<T>(&mut self, t: ty::Binder<'tcx, T>) -> ty::Binder<'tcx, T>
where
T: TypeFoldable<TyCtxt<'tcx>>,
{
self.binder_index.shift_in(1);
let t = t.super_fold_with(self);
self.binder_index.shift_out(1);
t
}
fn fold_region(&mut self, r: ty::Region<'tcx>) -> ty::Region<'tcx> {
if let ty::ReVar(vid) = *r {
let resolved_region = self
.infcx
.inner
.borrow_mut()
.unwrap_region_constraints()
.opportunistic_resolve_var(self.infcx.tcx, vid);
assert_eq!(
r, resolved_region,
"region var should have been resolved, {r} -> {resolved_region}"
);
}
let kind = match *r {
ty::ReLateBound(..) => return r,
ty::ReStatic => match self.canonicalize_mode {
CanonicalizeMode::Input => CanonicalVarKind::Region(ty::UniverseIndex::ROOT),
CanonicalizeMode::Response { .. } => return r,
},
ty::ReErased | ty::ReFree(_) | ty::ReEarlyBound(_) => match self.canonicalize_mode {
CanonicalizeMode::Input => CanonicalVarKind::Region(ty::UniverseIndex::ROOT),
CanonicalizeMode::Response { .. } => bug!("unexpected region in response: {r:?}"),
},
ty::RePlaceholder(placeholder) => match self.canonicalize_mode {
// We canonicalize placeholder regions as existentials in query inputs.
CanonicalizeMode::Input => CanonicalVarKind::Region(ty::UniverseIndex::ROOT),
CanonicalizeMode::Response { max_input_universe } => {
// If we have a placeholder region inside of a query, it must be from
// a new universe.
if max_input_universe.can_name(placeholder.universe) {
bug!("new placeholder in universe {max_input_universe:?}: {r:?}");
}
CanonicalVarKind::PlaceholderRegion(placeholder)
}
},
ty::ReVar(_) => match self.canonicalize_mode {
CanonicalizeMode::Input => CanonicalVarKind::Region(ty::UniverseIndex::ROOT),
CanonicalizeMode::Response { .. } => {
CanonicalVarKind::Region(self.infcx.universe_of_region(r))
}
},
ty::ReError(_) => return r,
};
let existing_bound_var = match self.canonicalize_mode {
CanonicalizeMode::Input => None,
CanonicalizeMode::Response { .. } => {
self.variables.iter().position(|&v| v == r.into()).map(ty::BoundVar::from)
}
};
let var = existing_bound_var.unwrap_or_else(|| {
let var = ty::BoundVar::from(self.variables.len());
self.variables.push(r.into());
self.primitive_var_infos.push(CanonicalVarInfo { kind });
var
});
let br = ty::BoundRegion { var, kind: BrAnon };
ty::Region::new_late_bound(self.interner(), self.binder_index, br)
}
fn fold_ty(&mut self, t: Ty<'tcx>) -> Ty<'tcx> {
let kind = match *t.kind() {
ty::Infer(ty::TyVar(vid)) => {
assert_eq!(self.infcx.root_var(vid), vid, "ty vid should have been resolved");
let Err(ui) = self.infcx.probe_ty_var(vid) else {
bug!("ty var should have been resolved: {t}");
};
CanonicalVarKind::Ty(CanonicalTyVarKind::General(ui))
}
ty::Infer(ty::IntVar(vid)) => {
assert_eq!(self.infcx.opportunistic_resolve_int_var(vid), t);
CanonicalVarKind::Ty(CanonicalTyVarKind::Int)
}
ty::Infer(ty::FloatVar(vid)) => {
assert_eq!(self.infcx.opportunistic_resolve_float_var(vid), t);
CanonicalVarKind::Ty(CanonicalTyVarKind::Float)
}
ty::Infer(ty::FreshTy(_) | ty::FreshIntTy(_) | ty::FreshFloatTy(_)) => {
bug!("fresh var during canonicalization: {t:?}")
}
ty::Placeholder(placeholder) => match self.canonicalize_mode {
CanonicalizeMode::Input => CanonicalVarKind::PlaceholderTy(ty::Placeholder {
universe: placeholder.universe,
bound: ty::BoundTy {
var: ty::BoundVar::from_usize(self.variables.len()),
kind: ty::BoundTyKind::Anon,
},
}),
CanonicalizeMode::Response { .. } => CanonicalVarKind::PlaceholderTy(placeholder),
},
ty::Param(_) => match self.canonicalize_mode {
CanonicalizeMode::Input => CanonicalVarKind::PlaceholderTy(ty::Placeholder {
universe: ty::UniverseIndex::ROOT,
bound: ty::BoundTy {
var: ty::BoundVar::from_usize(self.variables.len()),
kind: ty::BoundTyKind::Anon,
},
}),
CanonicalizeMode::Response { .. } => bug!("param ty in response: {t:?}"),
},
ty::Bool
| ty::Char
| ty::Int(_)
| ty::Uint(_)
| ty::Float(_)
| ty::Adt(_, _)
| ty::Foreign(_)
| ty::Str
| ty::Array(_, _)
| ty::Slice(_)
| ty::RawPtr(_)
| ty::Ref(_, _, _)
| ty::FnDef(_, _)
| ty::FnPtr(_)
| ty::Dynamic(_, _, _)
| ty::Closure(_, _)
| ty::Generator(_, _, _)
| ty::GeneratorWitness(..)
| ty::Never
| ty::Tuple(_)
| ty::Alias(_, _)
| ty::Bound(_, _)
| ty::Error(_) => return t.super_fold_with(self),
};
let var = ty::BoundVar::from(
self.variables.iter().position(|&v| v == t.into()).unwrap_or_else(|| {
let var = self.variables.len();
self.variables.push(t.into());
self.primitive_var_infos.push(CanonicalVarInfo { kind });
var
}),
);
let bt = ty::BoundTy { var, kind: BoundTyKind::Anon };
Ty::new_bound(self.infcx.tcx, self.binder_index, bt)
}
fn fold_const(&mut self, c: ty::Const<'tcx>) -> ty::Const<'tcx> {
let kind = match c.kind() {
ty::ConstKind::Infer(ty::InferConst::Var(vid)) => {
assert_eq!(
self.infcx.root_const_var(vid),
vid,
"const var should have been resolved"
);
let Err(ui) = self.infcx.probe_const_var(vid) else {
bug!("const var should have been resolved");
};
// FIXME: we should fold this ty eventually
CanonicalVarKind::Const(ui, c.ty())
}
ty::ConstKind::Infer(ty::InferConst::EffectVar(vid)) => {
assert_eq!(
self.infcx.root_effect_var(vid),
vid,
"effect var should have been resolved"
);
let None = self.infcx.probe_effect_var(vid) else {
bug!("effect var should have been resolved");
};
CanonicalVarKind::Effect
}
ty::ConstKind::Infer(ty::InferConst::Fresh(_)) => {
bug!("fresh var during canonicalization: {c:?}")
}
ty::ConstKind::Placeholder(placeholder) => match self.canonicalize_mode {
CanonicalizeMode::Input => CanonicalVarKind::PlaceholderConst(
ty::Placeholder {
universe: placeholder.universe,
bound: ty::BoundVar::from(self.variables.len()),
},
c.ty(),
),
CanonicalizeMode::Response { .. } => {
CanonicalVarKind::PlaceholderConst(placeholder, c.ty())
}
},
ty::ConstKind::Param(_) => match self.canonicalize_mode {
CanonicalizeMode::Input => CanonicalVarKind::PlaceholderConst(
ty::Placeholder {
universe: ty::UniverseIndex::ROOT,
bound: ty::BoundVar::from(self.variables.len()),
},
c.ty(),
),
CanonicalizeMode::Response { .. } => bug!("param ty in response: {c:?}"),
},
ty::ConstKind::Bound(_, _)
| ty::ConstKind::Unevaluated(_)
| ty::ConstKind::Value(_)
| ty::ConstKind::Error(_)
| ty::ConstKind::Expr(_) => return c.super_fold_with(self),
};
let var = ty::BoundVar::from(
self.variables.iter().position(|&v| v == c.into()).unwrap_or_else(|| {
let var = self.variables.len();
self.variables.push(c.into());
self.primitive_var_infos.push(CanonicalVarInfo { kind });
var
}),
);
ty::Const::new_bound(self.infcx.tcx, self.binder_index, var, c.ty())
}
}