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canonicalizer: keep 'static in the param_env
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@lcnr
lcnr committed Nov 26, 2024
1 parent bc87968 commit 9456bfe
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Showing 2 changed files with 102 additions and 40 deletions.
119 changes: 95 additions & 24 deletions compiler/rustc_next_trait_solver/src/canonicalizer.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -3,6 +3,7 @@ use std::cmp::Ordering;
use rustc_type_ir::data_structures::HashMap;
use rustc_type_ir::fold::{TypeFoldable, TypeFolder, TypeSuperFoldable};
use rustc_type_ir::inherent::*;
use rustc_type_ir::solve::{Goal, QueryInput};
use rustc_type_ir::visit::TypeVisitableExt;
use rustc_type_ir::{
self as ty, Canonical, CanonicalTyVarKind, CanonicalVarInfo, CanonicalVarKind, InferCtxtLike,
Expand All @@ -17,8 +18,11 @@ use crate::delegate::SolverDelegate;
/// while canonicalizing the response happens in the context of the
/// query.
#[derive(Debug, Clone, Copy)]
pub enum CanonicalizeMode {
Input,
enum CanonicalizeMode {
/// When canonicalizing the `param_env`, we keep `'static` as merging
/// trait candidates relies on it when deciding whether a where-bound
/// is trivial.
Input { keep_static: bool },
/// FIXME: We currently return region constraints referring to
/// placeholders and inference variables from a binder instantiated
/// inside of the query.
Expand Down Expand Up @@ -59,15 +63,15 @@ pub struct Canonicalizer<'a, D: SolverDelegate<Interner = I>, I: Interner> {
}

impl<'a, D: SolverDelegate<Interner = I>, I: Interner> Canonicalizer<'a, D, I> {
pub fn canonicalize<T: TypeFoldable<I>>(
pub fn canonicalize_response<T: TypeFoldable<I>>(
delegate: &'a D,
canonicalize_mode: CanonicalizeMode,
max_input_universe: ty::UniverseIndex,
variables: &'a mut Vec<I::GenericArg>,
value: T,
) -> ty::Canonical<I, T> {
let mut canonicalizer = Canonicalizer {
delegate,
canonicalize_mode,
canonicalize_mode: CanonicalizeMode::Response { max_input_universe },

variables,
variable_lookup_table: Default::default(),
Expand All @@ -80,9 +84,67 @@ impl<'a, D: SolverDelegate<Interner = I>, I: Interner> Canonicalizer<'a, D, I> {
let value = value.fold_with(&mut canonicalizer);
assert!(!value.has_infer(), "unexpected infer in {value:?}");
assert!(!value.has_placeholders(), "unexpected placeholders in {value:?}");

let (max_universe, variables) = canonicalizer.finalize();
Canonical { max_universe, variables, value }
}

/// When canonicalizing query inputs, we keep `'static` in the `param_env`
/// but erase it everywhere else. We generally don't want to depend on region
/// identity, so while it should not matter whether `'static` is kept in the
/// value or opaque type storage as well, this prevents us from accidentally
/// relying on it in the future.
///
/// We want to keep the option of canonicalizing `'static` to an existential
/// variable in the future by changing the way we detect global where-bounds.
pub fn canonicalize_input<P: TypeFoldable<I>>(
delegate: &'a D,
variables: &'a mut Vec<I::GenericArg>,
input: QueryInput<I, P>,
) -> ty::Canonical<I, QueryInput<I, P>> {
// First canonicalize the `param_env` while keeping `'static`
let mut env_canonicalizer = Canonicalizer {
delegate,
canonicalize_mode: CanonicalizeMode::Input { keep_static: true },

variables,
variable_lookup_table: Default::default(),
primitive_var_infos: Vec::new(),
binder_index: ty::INNERMOST,

cache: Default::default(),
};
let param_env = input.goal.param_env.fold_with(&mut env_canonicalizer);
debug_assert_eq!(env_canonicalizer.binder_index, ty::INNERMOST);
// Then canonicalize the rest of the input without keeping `'static`
// while *mostly* reusing the canonicalizer from above.
let mut rest_canonicalizer = Canonicalizer {
delegate,
canonicalize_mode: CanonicalizeMode::Input { keep_static: false },

variables: env_canonicalizer.variables,
// We're able to reuse the `variable_lookup_table` as whether or not
// it already contains an entry for `'static` does not matter.
variable_lookup_table: env_canonicalizer.variable_lookup_table,
primitive_var_infos: env_canonicalizer.primitive_var_infos,
binder_index: ty::INNERMOST,

// We do not reuse the cache as it may contain entries whose canonicalized
// value contains `'static`. While we could alternatively handle this by
// checking for `'static` when using cached entries, this does not
// feel worth the effort. I do not expect that a `ParamEnv` will ever
// contain large enough types for caching to be necessary.
cache: Default::default(),
};

let predicate = input.goal.predicate.fold_with(&mut rest_canonicalizer);
let goal = Goal { param_env, predicate };
let predefined_opaques_in_body =
input.predefined_opaques_in_body.fold_with(&mut rest_canonicalizer);
let value = QueryInput { goal, predefined_opaques_in_body };

assert!(!value.has_infer(), "unexpected infer in {value:?}");
assert!(!value.has_placeholders(), "unexpected placeholders in {value:?}");
let (max_universe, variables) = rest_canonicalizer.finalize();
Canonical { max_universe, variables, value }
}

Expand Down Expand Up @@ -126,7 +188,7 @@ impl<'a, D: SolverDelegate<Interner = I>, I: Interner> Canonicalizer<'a, D, I> {
// all information which should not matter for the solver.
//
// For this we compress universes as much as possible.
CanonicalizeMode::Input => {}
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
Expand Down Expand Up @@ -290,17 +352,15 @@ impl<'a, D: SolverDelegate<Interner = I>, I: Interner> Canonicalizer<'a, D, I> {
}
},
ty::Placeholder(placeholder) => match self.canonicalize_mode {
CanonicalizeMode::Input => CanonicalVarKind::PlaceholderTy(PlaceholderLike::new(
placeholder.universe(),
self.variables.len().into(),
)),
CanonicalizeMode::Input { .. } => CanonicalVarKind::PlaceholderTy(
PlaceholderLike::new(placeholder.universe(), self.variables.len().into()),
),
CanonicalizeMode::Response { .. } => CanonicalVarKind::PlaceholderTy(placeholder),
},
ty::Param(_) => match self.canonicalize_mode {
CanonicalizeMode::Input => CanonicalVarKind::PlaceholderTy(PlaceholderLike::new(
ty::UniverseIndex::ROOT,
self.variables.len().into(),
)),
CanonicalizeMode::Input { .. } => CanonicalVarKind::PlaceholderTy(
PlaceholderLike::new(ty::UniverseIndex::ROOT, self.variables.len().into()),
),
CanonicalizeMode::Response { .. } => panic!("param ty in response: {t:?}"),
},
ty::Bool
Expand Down Expand Up @@ -357,29 +417,38 @@ impl<D: SolverDelegate<Interner = I>, I: Interner> TypeFolder<I> for Canonicaliz
let kind = match r.kind() {
ty::ReBound(..) => return r,

// We may encounter `ReStatic` in item signatures or the hidden type
// of an opaque. `ReErased` should only be encountered in the hidden
// We don't canonicalize `ReStatic` in the `param_env` as we use it
// when checking whether a `ParamEnv` candidate is global.
ty::ReStatic => match self.canonicalize_mode {
CanonicalizeMode::Input { keep_static: false } => {
CanonicalVarKind::Region(ty::UniverseIndex::ROOT)
}
CanonicalizeMode::Input { keep_static: true }
| CanonicalizeMode::Response { .. } => return r,
},

// `ReErased` should only be encountered in the hidden
// type of an opaque for regions that are ignored for the purposes of
// captures.
//
// FIXME: We should investigate the perf implications of not uniquifying
// `ReErased`. We may be able to short-circuit registering region
// obligations if we encounter a `ReErased` on one side, for example.
ty::ReStatic | ty::ReErased | ty::ReError(_) => match self.canonicalize_mode {
CanonicalizeMode::Input => CanonicalVarKind::Region(ty::UniverseIndex::ROOT),
ty::ReErased | ty::ReError(_) => match self.canonicalize_mode {
CanonicalizeMode::Input { .. } => CanonicalVarKind::Region(ty::UniverseIndex::ROOT),
CanonicalizeMode::Response { .. } => return r,
},

ty::ReEarlyParam(_) | ty::ReLateParam(_) => match self.canonicalize_mode {
CanonicalizeMode::Input => CanonicalVarKind::Region(ty::UniverseIndex::ROOT),
CanonicalizeMode::Input { .. } => CanonicalVarKind::Region(ty::UniverseIndex::ROOT),
CanonicalizeMode::Response { .. } => {
panic!("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::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.
Expand All @@ -397,7 +466,9 @@ impl<D: SolverDelegate<Interner = I>, I: Interner> TypeFolder<I> for Canonicaliz
"region vid should have been resolved fully before canonicalization"
);
match self.canonicalize_mode {
CanonicalizeMode::Input => CanonicalVarKind::Region(ty::UniverseIndex::ROOT),
CanonicalizeMode::Input { keep_static: _ } => {
CanonicalVarKind::Region(ty::UniverseIndex::ROOT)
}
CanonicalizeMode::Response { .. } => {
CanonicalVarKind::Region(self.delegate.universe_of_lt(vid).unwrap())
}
Expand Down Expand Up @@ -434,15 +505,15 @@ impl<D: SolverDelegate<Interner = I>, I: Interner> TypeFolder<I> for Canonicaliz
ty::InferConst::Fresh(_) => todo!(),
},
ty::ConstKind::Placeholder(placeholder) => match self.canonicalize_mode {
CanonicalizeMode::Input => CanonicalVarKind::PlaceholderConst(
CanonicalizeMode::Input { .. } => CanonicalVarKind::PlaceholderConst(
PlaceholderLike::new(placeholder.universe(), self.variables.len().into()),
),
CanonicalizeMode::Response { .. } => {
CanonicalVarKind::PlaceholderConst(placeholder)
}
},
ty::ConstKind::Param(_) => match self.canonicalize_mode {
CanonicalizeMode::Input => CanonicalVarKind::PlaceholderConst(
CanonicalizeMode::Input { .. } => CanonicalVarKind::PlaceholderConst(
PlaceholderLike::new(ty::UniverseIndex::ROOT, self.variables.len().into()),
),
CanonicalizeMode::Response { .. } => panic!("param ty in response: {c:?}"),
Expand Down
23 changes: 7 additions & 16 deletions compiler/rustc_next_trait_solver/src/solve/eval_ctxt/canonical.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -18,7 +18,7 @@ use rustc_type_ir::relate::solver_relating::RelateExt;
use rustc_type_ir::{self as ty, Canonical, CanonicalVarValues, InferCtxtLike, Interner};
use tracing::{debug, instrument, trace};

use crate::canonicalizer::{CanonicalizeMode, Canonicalizer};
use crate::canonicalizer::Canonicalizer;
use crate::delegate::SolverDelegate;
use crate::resolve::EagerResolver;
use crate::solve::eval_ctxt::NestedGoals;
Expand Down Expand Up @@ -60,17 +60,13 @@ where
(goal, opaque_types).fold_with(&mut EagerResolver::new(self.delegate));

let mut orig_values = Default::default();
let canonical = Canonicalizer::canonicalize(
self.delegate,
CanonicalizeMode::Input,
&mut orig_values,
QueryInput {
let canonical =
Canonicalizer::canonicalize_input(self.delegate, &mut orig_values, QueryInput {
goal,
predefined_opaques_in_body: self
.cx()
.mk_predefined_opaques_in_body(PredefinedOpaquesData { opaque_types }),
},
);
});
let query_input = ty::CanonicalQueryInput { canonical, typing_mode: self.typing_mode() };
(orig_values, query_input)
}
Expand Down Expand Up @@ -148,9 +144,9 @@ where
.region_constraints
.retain(|outlives| outlives.0.as_region().map_or(true, |re| re != outlives.1));

let canonical = Canonicalizer::canonicalize(
let canonical = Canonicalizer::canonicalize_response(
self.delegate,
CanonicalizeMode::Response { max_input_universe: self.max_input_universe },
self.max_input_universe,
&mut Default::default(),
Response {
var_values,
Expand Down Expand Up @@ -428,12 +424,7 @@ where
let var_values = CanonicalVarValues { var_values: delegate.cx().mk_args(var_values) };
let state = inspect::State { var_values, data };
let state = state.fold_with(&mut EagerResolver::new(delegate));
Canonicalizer::canonicalize(
delegate,
CanonicalizeMode::Response { max_input_universe },
&mut vec![],
state,
)
Canonicalizer::canonicalize_response(delegate, max_input_universe, &mut vec![], state)
}

// FIXME: needs to be pub to be accessed by downstream
Expand Down

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