blob: 144197b0bec61e948d25b60c30a6b05d22b03fee [file] [log] [blame]
use rustc_data_structures::stack::ensure_sufficient_stack;
use rustc_hir::def_id::DefId;
use rustc_infer::infer::at::ToTrace;
use rustc_infer::infer::canonical::CanonicalVarValues;
use rustc_infer::infer::{
BoundRegionConversionTime, DefineOpaqueTypes, InferCtxt, InferOk, TyCtxtInferExt,
};
use rustc_infer::traits::query::NoSolution;
use rustc_infer::traits::solve::{MaybeCause, NestedNormalizationGoals};
use rustc_infer::traits::ObligationCause;
use rustc_macros::{extension, HashStable};
use rustc_middle::bug;
use rustc_middle::infer::canonical::CanonicalVarInfos;
use rustc_middle::traits::solve::inspect;
use rustc_middle::traits::solve::{
CanonicalInput, CanonicalResponse, Certainty, PredefinedOpaques, PredefinedOpaquesData,
QueryResult,
};
use rustc_middle::traits::specialization_graph;
use rustc_middle::ty::{
self, InferCtxtLike, OpaqueTypeKey, Ty, TyCtxt, TypeFoldable, TypeSuperVisitable,
TypeVisitable, TypeVisitableExt, TypeVisitor,
};
use rustc_session::config::DumpSolverProofTree;
use rustc_span::DUMMY_SP;
use std::io::Write;
use std::ops::ControlFlow;
use crate::traits::coherence;
use crate::traits::vtable::{count_own_vtable_entries, prepare_vtable_segments, VtblSegment};
use super::inspect::ProofTreeBuilder;
use super::{search_graph, GoalEvaluationKind, FIXPOINT_STEP_LIMIT};
use super::{search_graph::SearchGraph, Goal};
use super::{GoalSource, SolverMode};
pub use select::InferCtxtSelectExt;
pub(super) mod canonical;
mod probe;
mod select;
pub struct EvalCtxt<'a, 'tcx> {
/// The inference context that backs (mostly) inference and placeholder terms
/// instantiated while solving goals.
///
/// NOTE: The `InferCtxt` that backs the `EvalCtxt` is intentionally private,
/// because the `InferCtxt` is much more general than `EvalCtxt`. Methods such
/// as `take_registered_region_obligations` can mess up query responses,
/// using `At::normalize` is totally wrong, calling `evaluate_root_goal` can
/// cause coinductive unsoundness, etc.
///
/// Methods that are generally of use for trait solving are *intentionally*
/// re-declared through the `EvalCtxt` below, often with cleaner signatures
/// since we don't care about things like `ObligationCause`s and `Span`s here.
/// If some `InferCtxt` method is missing, please first think defensively about
/// the method's compatibility with this solver, or if an existing one does
/// the job already.
infcx: &'a InferCtxt<'tcx>,
/// The variable info for the `var_values`, only used to make an ambiguous response
/// with no constraints.
variables: CanonicalVarInfos<'tcx>,
/// Whether we're currently computing a `NormalizesTo` goal. Unlike other goals,
/// `NormalizesTo` goals act like functions with the expected term always being
/// fully unconstrained. This would weaken inference however, as the nested goals
/// never get the inference constraints from the actual normalized-to type. Because
/// of this we return any ambiguous nested goals from `NormalizesTo` to the caller
/// when then adds these to its own context. The caller is always an `AliasRelate`
/// goal so this never leaks out of the solver.
is_normalizes_to_goal: bool,
pub(super) var_values: CanonicalVarValues<'tcx>,
predefined_opaques_in_body: PredefinedOpaques<'tcx>,
/// The highest universe index nameable by the caller.
///
/// When we enter a new binder inside of the query we create new universes
/// which the caller cannot name. We have to be careful with variables from
/// these new universes when creating the query response.
///
/// Both because these new universes can prevent us from reaching a fixpoint
/// if we have a coinductive cycle and because that's the only way we can return
/// new placeholders to the caller.
pub(super) max_input_universe: ty::UniverseIndex,
pub(super) search_graph: &'a mut SearchGraph<'tcx>,
nested_goals: NestedGoals<'tcx>,
// Has this `EvalCtxt` errored out with `NoSolution` in `try_evaluate_added_goals`?
//
// If so, then it can no longer be used to make a canonical query response,
// since subsequent calls to `try_evaluate_added_goals` have possibly dropped
// ambiguous goals. Instead, a probe needs to be introduced somewhere in the
// evaluation code.
tainted: Result<(), NoSolution>,
pub(super) inspect: ProofTreeBuilder<'tcx>,
}
#[derive(Default, Debug, Clone)]
pub(super) struct NestedGoals<'tcx> {
/// These normalizes-to goals are treated specially during the evaluation
/// loop. In each iteration we take the RHS of the projection, replace it with
/// a fresh inference variable, and only after evaluating that goal do we
/// equate the fresh inference variable with the actual RHS of the predicate.
///
/// This is both to improve caching, and to avoid using the RHS of the
/// projection predicate to influence the normalizes-to candidate we select.
///
/// Forgetting to replace the RHS with a fresh inference variable when we evaluate
/// this goal results in an ICE..
pub(super) normalizes_to_goals: Vec<Goal<'tcx, ty::NormalizesTo<'tcx>>>,
/// The rest of the goals which have not yet processed or remain ambiguous.
pub(super) goals: Vec<(GoalSource, Goal<'tcx, ty::Predicate<'tcx>>)>,
}
impl<'tcx> NestedGoals<'tcx> {
pub(super) fn new() -> Self {
Self { normalizes_to_goals: Vec::new(), goals: Vec::new() }
}
pub(super) fn is_empty(&self) -> bool {
self.normalizes_to_goals.is_empty() && self.goals.is_empty()
}
}
#[derive(PartialEq, Eq, Debug, Hash, HashStable, Clone, Copy)]
pub enum GenerateProofTree {
Yes,
IfEnabled,
Never,
}
#[extension(pub trait InferCtxtEvalExt<'tcx>)]
impl<'tcx> InferCtxt<'tcx> {
/// Evaluates a goal from **outside** of the trait solver.
///
/// Using this while inside of the solver is wrong as it uses a new
/// search graph which would break cycle detection.
#[instrument(level = "debug", skip(self))]
fn evaluate_root_goal(
&self,
goal: Goal<'tcx, ty::Predicate<'tcx>>,
generate_proof_tree: GenerateProofTree,
) -> (Result<(bool, Certainty), NoSolution>, Option<inspect::GoalEvaluation<'tcx>>) {
EvalCtxt::enter_root(self, generate_proof_tree, |ecx| {
ecx.evaluate_goal(GoalEvaluationKind::Root, GoalSource::Misc, goal)
})
}
}
impl<'a, 'tcx> EvalCtxt<'a, 'tcx> {
pub(super) fn solver_mode(&self) -> SolverMode {
self.search_graph.solver_mode()
}
pub(super) fn set_is_normalizes_to_goal(&mut self) {
self.is_normalizes_to_goal = true;
}
/// Creates a root evaluation context and search graph. This should only be
/// used from outside of any evaluation, and other methods should be preferred
/// over using this manually (such as [`InferCtxtEvalExt::evaluate_root_goal`]).
pub(super) fn enter_root<R>(
infcx: &InferCtxt<'tcx>,
generate_proof_tree: GenerateProofTree,
f: impl FnOnce(&mut EvalCtxt<'_, 'tcx>) -> R,
) -> (R, Option<inspect::GoalEvaluation<'tcx>>) {
let mode = if infcx.intercrate { SolverMode::Coherence } else { SolverMode::Normal };
let mut search_graph = search_graph::SearchGraph::new(mode);
let mut ecx = EvalCtxt {
infcx,
search_graph: &mut search_graph,
nested_goals: NestedGoals::new(),
inspect: ProofTreeBuilder::new_maybe_root(infcx.tcx, generate_proof_tree),
// Only relevant when canonicalizing the response,
// which we don't do within this evaluation context.
predefined_opaques_in_body: infcx
.tcx
.mk_predefined_opaques_in_body(PredefinedOpaquesData::default()),
max_input_universe: ty::UniverseIndex::ROOT,
variables: ty::List::empty(),
var_values: CanonicalVarValues::dummy(),
is_normalizes_to_goal: false,
tainted: Ok(()),
};
let result = f(&mut ecx);
let tree = ecx.inspect.finalize();
if let (Some(tree), DumpSolverProofTree::Always) = (
&tree,
infcx.tcx.sess.opts.unstable_opts.next_solver.map(|c| c.dump_tree).unwrap_or_default(),
) {
let mut lock = std::io::stdout().lock();
let _ = lock.write_fmt(format_args!("{tree:?}\n"));
let _ = lock.flush();
}
assert!(
ecx.nested_goals.is_empty(),
"root `EvalCtxt` should not have any goals added to it"
);
assert!(search_graph.is_empty());
(result, tree)
}
/// Creates a nested evaluation context that shares the same search graph as the
/// one passed in. This is suitable for evaluation, granted that the search graph
/// has had the nested goal recorded on its stack ([`SearchGraph::with_new_goal`]),
/// but it's preferable to use other methods that call this one rather than this
/// method directly.
///
/// This function takes care of setting up the inference context, setting the anchor,
/// and registering opaques from the canonicalized input.
fn enter_canonical<R>(
tcx: TyCtxt<'tcx>,
search_graph: &'a mut search_graph::SearchGraph<'tcx>,
canonical_input: CanonicalInput<'tcx>,
canonical_goal_evaluation: &mut ProofTreeBuilder<'tcx>,
f: impl FnOnce(&mut EvalCtxt<'_, 'tcx>, Goal<'tcx, ty::Predicate<'tcx>>) -> R,
) -> R {
let intercrate = match search_graph.solver_mode() {
SolverMode::Normal => false,
SolverMode::Coherence => true,
};
let (ref infcx, input, var_values) = tcx
.infer_ctxt()
.intercrate(intercrate)
.with_next_trait_solver(true)
.build_with_canonical(DUMMY_SP, &canonical_input);
let mut ecx = EvalCtxt {
infcx,
variables: canonical_input.variables,
var_values,
is_normalizes_to_goal: false,
predefined_opaques_in_body: input.predefined_opaques_in_body,
max_input_universe: canonical_input.max_universe,
search_graph,
nested_goals: NestedGoals::new(),
tainted: Ok(()),
inspect: canonical_goal_evaluation.new_goal_evaluation_step(var_values, input),
};
for &(key, ty) in &input.predefined_opaques_in_body.opaque_types {
let hidden_ty = ty::OpaqueHiddenType { ty, span: DUMMY_SP };
ecx.infcx.inject_new_hidden_type_unchecked(key, hidden_ty);
}
if !ecx.nested_goals.is_empty() {
panic!("prepopulating opaque types shouldn't add goals: {:?}", ecx.nested_goals);
}
let result = f(&mut ecx, input.goal);
ecx.inspect.probe_final_state(ecx.infcx, ecx.max_input_universe);
canonical_goal_evaluation.goal_evaluation_step(ecx.inspect);
// When creating a query response we clone the opaque type constraints
// instead of taking them. This would cause an ICE here, since we have
// assertions against dropping an `InferCtxt` without taking opaques.
// FIXME: Once we remove support for the old impl we can remove this.
let _ = infcx.take_opaque_types();
result
}
/// The entry point of the solver.
///
/// This function deals with (coinductive) cycles, overflow, and caching
/// and then calls [`EvalCtxt::compute_goal`] which contains the actual
/// logic of the solver.
///
/// Instead of calling this function directly, use either [EvalCtxt::evaluate_goal]
/// if you're inside of the solver or [InferCtxtEvalExt::evaluate_root_goal] if you're
/// outside of it.
#[instrument(level = "debug", skip(tcx, search_graph, goal_evaluation), ret)]
fn evaluate_canonical_goal(
tcx: TyCtxt<'tcx>,
search_graph: &'a mut search_graph::SearchGraph<'tcx>,
canonical_input: CanonicalInput<'tcx>,
goal_evaluation: &mut ProofTreeBuilder<'tcx>,
) -> QueryResult<'tcx> {
let mut canonical_goal_evaluation =
goal_evaluation.new_canonical_goal_evaluation(canonical_input);
// Deal with overflow, caching, and coinduction.
//
// The actual solver logic happens in `ecx.compute_goal`.
let result = ensure_sufficient_stack(|| {
search_graph.with_new_goal(
tcx,
canonical_input,
&mut canonical_goal_evaluation,
|search_graph, canonical_goal_evaluation| {
EvalCtxt::enter_canonical(
tcx,
search_graph,
canonical_input,
canonical_goal_evaluation,
|ecx, goal| {
let result = ecx.compute_goal(goal);
ecx.inspect.query_result(result);
result
},
)
},
)
});
canonical_goal_evaluation.query_result(result);
goal_evaluation.canonical_goal_evaluation(canonical_goal_evaluation);
result
}
/// Recursively evaluates `goal`, returning whether any inference vars have
/// been constrained and the certainty of the result.
fn evaluate_goal(
&mut self,
goal_evaluation_kind: GoalEvaluationKind,
source: GoalSource,
goal: Goal<'tcx, ty::Predicate<'tcx>>,
) -> Result<(bool, Certainty), NoSolution> {
let (normalization_nested_goals, has_changed, certainty) =
self.evaluate_goal_raw(goal_evaluation_kind, source, goal)?;
assert!(normalization_nested_goals.is_empty());
Ok((has_changed, certainty))
}
/// Recursively evaluates `goal`, returning the nested goals in case
/// the nested goal is a `NormalizesTo` goal.
///
/// As all other goal kinds do not return any nested goals and
/// `NormalizesTo` is only used by `AliasRelate`, all other callsites
/// should use [`EvalCtxt::evaluate_goal`] which discards that empty
/// storage.
// FIXME(-Znext-solver=coinduction): `_source` is currently unused but will
// be necessary once we implement the new coinduction approach.
pub(super) fn evaluate_goal_raw(
&mut self,
goal_evaluation_kind: GoalEvaluationKind,
_source: GoalSource,
goal: Goal<'tcx, ty::Predicate<'tcx>>,
) -> Result<(NestedNormalizationGoals<'tcx>, bool, Certainty), NoSolution> {
let (orig_values, canonical_goal) = self.canonicalize_goal(goal);
let mut goal_evaluation =
self.inspect.new_goal_evaluation(goal, &orig_values, goal_evaluation_kind);
let canonical_response = EvalCtxt::evaluate_canonical_goal(
self.tcx(),
self.search_graph,
canonical_goal,
&mut goal_evaluation,
);
let canonical_response = match canonical_response {
Err(e) => {
self.inspect.goal_evaluation(goal_evaluation);
return Err(e);
}
Ok(response) => response,
};
let (normalization_nested_goals, certainty, has_changed) = self
.instantiate_response_discarding_overflow(
goal.param_env,
orig_values,
canonical_response,
);
self.inspect.goal_evaluation(goal_evaluation);
// FIXME: We previously had an assert here that checked that recomputing
// a goal after applying its constraints did not change its response.
//
// This assert was removed as it did not hold for goals constraining
// an inference variable to a recursive alias, e.g. in
// tests/ui/traits/next-solver/overflow/recursive-self-normalization.rs.
//
// Once we have decided on how to handle trait-system-refactor-initiative#75,
// we should re-add an assert here.
Ok((normalization_nested_goals, has_changed, certainty))
}
fn instantiate_response_discarding_overflow(
&mut self,
param_env: ty::ParamEnv<'tcx>,
original_values: Vec<ty::GenericArg<'tcx>>,
response: CanonicalResponse<'tcx>,
) -> (NestedNormalizationGoals<'tcx>, Certainty, bool) {
if let Certainty::Maybe(MaybeCause::Overflow { .. }) = response.value.certainty {
return (NestedNormalizationGoals::empty(), response.value.certainty, false);
}
let has_changed = !response.value.var_values.is_identity_modulo_regions()
|| !response.value.external_constraints.opaque_types.is_empty();
let (normalization_nested_goals, certainty) =
self.instantiate_and_apply_query_response(param_env, original_values, response);
(normalization_nested_goals, certainty, has_changed)
}
fn compute_goal(&mut self, goal: Goal<'tcx, ty::Predicate<'tcx>>) -> QueryResult<'tcx> {
let Goal { param_env, predicate } = goal;
let kind = predicate.kind();
if let Some(kind) = kind.no_bound_vars() {
match kind {
ty::PredicateKind::Clause(ty::ClauseKind::Trait(predicate)) => {
self.compute_trait_goal(Goal { param_env, predicate })
}
ty::PredicateKind::Clause(ty::ClauseKind::Projection(predicate)) => {
self.compute_projection_goal(Goal { param_env, predicate })
}
ty::PredicateKind::Clause(ty::ClauseKind::TypeOutlives(predicate)) => {
self.compute_type_outlives_goal(Goal { param_env, predicate })
}
ty::PredicateKind::Clause(ty::ClauseKind::RegionOutlives(predicate)) => {
self.compute_region_outlives_goal(Goal { param_env, predicate })
}
ty::PredicateKind::Clause(ty::ClauseKind::ConstArgHasType(ct, ty)) => {
self.compute_const_arg_has_type_goal(Goal { param_env, predicate: (ct, ty) })
}
ty::PredicateKind::Subtype(predicate) => {
self.compute_subtype_goal(Goal { param_env, predicate })
}
ty::PredicateKind::Coerce(predicate) => {
self.compute_coerce_goal(Goal { param_env, predicate })
}
ty::PredicateKind::ObjectSafe(trait_def_id) => {
self.compute_object_safe_goal(trait_def_id)
}
ty::PredicateKind::Clause(ty::ClauseKind::WellFormed(arg)) => {
self.compute_well_formed_goal(Goal { param_env, predicate: arg })
}
ty::PredicateKind::Clause(ty::ClauseKind::ConstEvaluatable(ct)) => {
self.compute_const_evaluatable_goal(Goal { param_env, predicate: ct })
}
ty::PredicateKind::ConstEquate(_, _) => {
bug!("ConstEquate should not be emitted when `-Znext-solver` is active")
}
ty::PredicateKind::NormalizesTo(predicate) => {
self.compute_normalizes_to_goal(Goal { param_env, predicate })
}
ty::PredicateKind::AliasRelate(lhs, rhs, direction) => self
.compute_alias_relate_goal(Goal {
param_env,
predicate: (lhs, rhs, direction),
}),
ty::PredicateKind::Ambiguous => {
self.evaluate_added_goals_and_make_canonical_response(Certainty::AMBIGUOUS)
}
}
} else {
self.infcx.enter_forall(kind, |kind| {
let goal = goal.with(self.tcx(), ty::Binder::dummy(kind));
self.add_goal(GoalSource::InstantiateHigherRanked, goal);
self.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
})
}
}
#[instrument(level = "trace", skip(self))]
pub(super) fn add_normalizes_to_goal(&mut self, goal: Goal<'tcx, ty::NormalizesTo<'tcx>>) {
self.inspect.add_normalizes_to_goal(self.infcx, self.max_input_universe, goal);
self.nested_goals.normalizes_to_goals.push(goal);
}
#[instrument(level = "debug", skip(self))]
pub(super) fn add_goal(&mut self, source: GoalSource, goal: Goal<'tcx, ty::Predicate<'tcx>>) {
self.inspect.add_goal(self.infcx, self.max_input_universe, source, goal);
self.nested_goals.goals.push((source, goal));
}
// Recursively evaluates all the goals added to this `EvalCtxt` to completion, returning
// the certainty of all the goals.
#[instrument(level = "trace", skip(self))]
pub(super) fn try_evaluate_added_goals(&mut self) -> Result<Certainty, NoSolution> {
self.inspect.start_evaluate_added_goals();
let mut response = Ok(Certainty::overflow(false));
for _ in 0..FIXPOINT_STEP_LIMIT {
// FIXME: This match is a bit ugly, it might be nice to change the inspect
// stuff to use a closure instead. which should hopefully simplify this a bit.
match self.evaluate_added_goals_step() {
Ok(Some(cert)) => {
response = Ok(cert);
break;
}
Ok(None) => {}
Err(NoSolution) => {
response = Err(NoSolution);
break;
}
}
}
self.inspect.evaluate_added_goals_result(response);
if response.is_err() {
self.tainted = Err(NoSolution);
}
response
}
/// Iterate over all added goals: returning `Ok(Some(_))` in case we can stop rerunning.
///
/// Goals for the next step get directly added to the nested goals of the `EvalCtxt`.
fn evaluate_added_goals_step(&mut self) -> Result<Option<Certainty>, NoSolution> {
let tcx = self.tcx();
self.inspect.start_evaluate_added_goals_step();
let mut goals = core::mem::take(&mut self.nested_goals);
// If this loop did not result in any progress, what's our final certainty.
let mut unchanged_certainty = Some(Certainty::Yes);
for goal in goals.normalizes_to_goals {
// Replace the goal with an unconstrained infer var, so the
// RHS does not affect projection candidate assembly.
let unconstrained_rhs = self.next_term_infer_of_kind(goal.predicate.term);
let unconstrained_goal = goal.with(
tcx,
ty::NormalizesTo { alias: goal.predicate.alias, term: unconstrained_rhs },
);
let (NestedNormalizationGoals(nested_goals), _, certainty) = self.evaluate_goal_raw(
GoalEvaluationKind::Nested,
GoalSource::Misc,
unconstrained_goal,
)?;
// Add the nested goals from normalization to our own nested goals.
trace!(?nested_goals);
goals.goals.extend(nested_goals);
// Finally, equate the goal's RHS with the unconstrained var.
//
// SUBTLE:
// We structurally relate aliases here. This is necessary
// as we otherwise emit a nested `AliasRelate` goal in case the
// returned term is a rigid alias, resulting in overflow.
//
// It is correct as both `goal.predicate.term` and `unconstrained_rhs`
// start out as an unconstrained inference variable so any aliases get
// fully normalized when instantiating it.
//
// FIXME: Strictly speaking this may be incomplete if the normalized-to
// type contains an ambiguous alias referencing bound regions. We should
// consider changing this to only use "shallow structural equality".
self.eq_structurally_relating_aliases(
goal.param_env,
goal.predicate.term,
unconstrained_rhs,
)?;
// We only look at the `projection_ty` part here rather than
// looking at the "has changed" return from evaluate_goal,
// because we expect the `unconstrained_rhs` part of the predicate
// to have changed -- that means we actually normalized successfully!
let with_resolved_vars = self.resolve_vars_if_possible(goal);
if goal.predicate.alias != with_resolved_vars.predicate.alias {
unchanged_certainty = None;
}
match certainty {
Certainty::Yes => {}
Certainty::Maybe(_) => {
self.nested_goals.normalizes_to_goals.push(with_resolved_vars);
unchanged_certainty = unchanged_certainty.map(|c| c.unify_with(certainty));
}
}
}
for (source, goal) in goals.goals {
let (has_changed, certainty) =
self.evaluate_goal(GoalEvaluationKind::Nested, source, goal)?;
if has_changed {
unchanged_certainty = None;
}
match certainty {
Certainty::Yes => {}
Certainty::Maybe(_) => {
self.nested_goals.goals.push((source, goal));
unchanged_certainty = unchanged_certainty.map(|c| c.unify_with(certainty));
}
}
}
Ok(unchanged_certainty)
}
/// Record impl args in the proof tree for later access by `InspectCandidate`.
pub(crate) fn record_impl_args(&mut self, impl_args: ty::GenericArgsRef<'tcx>) {
self.inspect.record_impl_args(self.infcx, self.max_input_universe, impl_args)
}
}
impl<'tcx> EvalCtxt<'_, 'tcx> {
pub(super) fn tcx(&self) -> TyCtxt<'tcx> {
self.infcx.tcx
}
pub(super) fn next_ty_infer(&mut self) -> Ty<'tcx> {
let ty = self.infcx.next_ty_var(DUMMY_SP);
self.inspect.add_var_value(ty);
ty
}
pub(super) fn next_const_infer(&mut self, ty: Ty<'tcx>) -> ty::Const<'tcx> {
let ct = self.infcx.next_const_var(ty, DUMMY_SP);
self.inspect.add_var_value(ct);
ct
}
/// Returns a ty infer or a const infer depending on whether `kind` is a `Ty` or `Const`.
/// If `kind` is an integer inference variable this will still return a ty infer var.
pub(super) fn next_term_infer_of_kind(&mut self, kind: ty::Term<'tcx>) -> ty::Term<'tcx> {
match kind.unpack() {
ty::TermKind::Ty(_) => self.next_ty_infer().into(),
ty::TermKind::Const(ct) => self.next_const_infer(ct.ty()).into(),
}
}
/// Is the projection predicate is of the form `exists<T> <Ty as Trait>::Assoc = T`.
///
/// This is the case if the `term` does not occur in any other part of the predicate
/// and is able to name all other placeholder and inference variables.
#[instrument(level = "trace", skip(self), ret)]
pub(super) fn term_is_fully_unconstrained(
&self,
goal: Goal<'tcx, ty::NormalizesTo<'tcx>>,
) -> bool {
let universe_of_term = match goal.predicate.term.unpack() {
ty::TermKind::Ty(ty) => {
if let &ty::Infer(ty::TyVar(vid)) = ty.kind() {
self.infcx.universe_of_ty(vid).unwrap()
} else {
return false;
}
}
ty::TermKind::Const(ct) => {
if let ty::ConstKind::Infer(ty::InferConst::Var(vid)) = ct.kind() {
self.infcx.universe_of_ct(vid).unwrap()
} else {
return false;
}
}
};
struct ContainsTermOrNotNameable<'a, 'tcx> {
term: ty::Term<'tcx>,
universe_of_term: ty::UniverseIndex,
infcx: &'a InferCtxt<'tcx>,
}
impl<'a, 'tcx> ContainsTermOrNotNameable<'a, 'tcx> {
fn check_nameable(&self, universe: ty::UniverseIndex) -> ControlFlow<()> {
if self.universe_of_term.can_name(universe) {
ControlFlow::Continue(())
} else {
ControlFlow::Break(())
}
}
}
impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for ContainsTermOrNotNameable<'_, 'tcx> {
type Result = ControlFlow<()>;
fn visit_ty(&mut self, t: Ty<'tcx>) -> Self::Result {
match *t.kind() {
ty::Infer(ty::TyVar(vid)) => {
if let ty::TermKind::Ty(term) = self.term.unpack()
&& let Some(term_vid) = term.ty_vid()
&& self.infcx.root_var(vid) == self.infcx.root_var(term_vid)
{
ControlFlow::Break(())
} else {
self.check_nameable(self.infcx.universe_of_ty(vid).unwrap())
}
}
ty::Placeholder(p) => self.check_nameable(p.universe),
_ => {
if t.has_non_region_infer() || t.has_placeholders() {
t.super_visit_with(self)
} else {
ControlFlow::Continue(())
}
}
}
}
fn visit_const(&mut self, c: ty::Const<'tcx>) -> Self::Result {
match c.kind() {
ty::ConstKind::Infer(ty::InferConst::Var(vid)) => {
if let ty::TermKind::Const(term) = self.term.unpack()
&& let ty::ConstKind::Infer(ty::InferConst::Var(term_vid)) = term.kind()
&& self.infcx.root_const_var(vid) == self.infcx.root_const_var(term_vid)
{
ControlFlow::Break(())
} else {
self.check_nameable(self.infcx.universe_of_ct(vid).unwrap())
}
}
ty::ConstKind::Placeholder(p) => self.check_nameable(p.universe),
_ => {
if c.has_non_region_infer() || c.has_placeholders() {
c.super_visit_with(self)
} else {
ControlFlow::Continue(())
}
}
}
}
}
let mut visitor = ContainsTermOrNotNameable {
infcx: self.infcx,
universe_of_term,
term: goal.predicate.term,
};
goal.predicate.alias.visit_with(&mut visitor).is_continue()
&& goal.param_env.visit_with(&mut visitor).is_continue()
}
#[instrument(level = "trace", skip(self, param_env), ret)]
pub(super) fn eq<T: ToTrace<'tcx>>(
&mut self,
param_env: ty::ParamEnv<'tcx>,
lhs: T,
rhs: T,
) -> Result<(), NoSolution> {
self.infcx
.at(&ObligationCause::dummy(), param_env)
// New solver ignores DefineOpaqueTypes, so choose Yes for consistency
.eq(DefineOpaqueTypes::Yes, lhs, rhs)
.map(|InferOk { value: (), obligations }| {
self.add_goals(GoalSource::Misc, obligations.into_iter().map(|o| o.into()));
})
.map_err(|e| {
trace!(?e, "failed to equate");
NoSolution
})
}
/// This should be used when relating a rigid alias with another type.
///
/// Normally we emit a nested `AliasRelate` when equating an inference
/// variable and an alias. This causes us to instead constrain the inference
/// variable to the alias without emitting a nested alias relate goals.
#[instrument(level = "trace", skip(self, param_env), ret)]
pub(super) fn relate_rigid_alias_non_alias(
&mut self,
param_env: ty::ParamEnv<'tcx>,
alias: ty::AliasTy<'tcx>,
variance: ty::Variance,
term: ty::Term<'tcx>,
) -> Result<(), NoSolution> {
// NOTE: this check is purely an optimization, the structural eq would
// always fail if the term is not an inference variable.
if term.is_infer() {
let tcx = self.tcx();
// We need to relate `alias` to `term` treating only the outermost
// constructor as rigid, relating any contained generic arguments as
// normal. We do this by first structurally equating the `term`
// with the alias constructor instantiated with unconstrained infer vars,
// and then relate this with the whole `alias`.
//
// Alternatively we could modify `Equate` for this case by adding another
// variant to `StructurallyRelateAliases`.
let identity_args = self.fresh_args_for_item(alias.def_id);
let rigid_ctor = ty::AliasTy::new(tcx, alias.def_id, identity_args);
let ctor_ty = rigid_ctor.to_ty(tcx);
let InferOk { value: (), obligations } = self
.infcx
.at(&ObligationCause::dummy(), param_env)
.trace(term, ctor_ty.into())
.eq_structurally_relating_aliases(term, ctor_ty.into())?;
debug_assert!(obligations.is_empty());
self.relate(param_env, alias, variance, rigid_ctor)
} else {
Err(NoSolution)
}
}
/// This sohuld only be used when we're either instantiating a previously
/// unconstrained "return value" or when we're sure that all aliases in
/// the types are rigid.
#[instrument(level = "trace", skip(self, param_env), ret)]
pub(super) fn eq_structurally_relating_aliases<T: ToTrace<'tcx>>(
&mut self,
param_env: ty::ParamEnv<'tcx>,
lhs: T,
rhs: T,
) -> Result<(), NoSolution> {
let cause = ObligationCause::dummy();
let InferOk { value: (), obligations } = self
.infcx
.at(&cause, param_env)
.trace(lhs, rhs)
.eq_structurally_relating_aliases(lhs, rhs)?;
assert!(obligations.is_empty());
Ok(())
}
#[instrument(level = "trace", skip(self, param_env), ret)]
pub(super) fn sub<T: ToTrace<'tcx>>(
&mut self,
param_env: ty::ParamEnv<'tcx>,
sub: T,
sup: T,
) -> Result<(), NoSolution> {
self.infcx
.at(&ObligationCause::dummy(), param_env)
// New solver ignores DefineOpaqueTypes, so choose Yes for consistency
.sub(DefineOpaqueTypes::Yes, sub, sup)
.map(|InferOk { value: (), obligations }| {
self.add_goals(GoalSource::Misc, obligations.into_iter().map(|o| o.into()));
})
.map_err(|e| {
trace!(?e, "failed to subtype");
NoSolution
})
}
#[instrument(level = "trace", skip(self, param_env), ret)]
pub(super) fn relate<T: ToTrace<'tcx>>(
&mut self,
param_env: ty::ParamEnv<'tcx>,
lhs: T,
variance: ty::Variance,
rhs: T,
) -> Result<(), NoSolution> {
self.infcx
.at(&ObligationCause::dummy(), param_env)
// New solver ignores DefineOpaqueTypes, so choose Yes for consistency
.relate(DefineOpaqueTypes::Yes, lhs, variance, rhs)
.map(|InferOk { value: (), obligations }| {
self.add_goals(GoalSource::Misc, obligations.into_iter().map(|o| o.into()));
})
.map_err(|e| {
trace!(?e, "failed to relate");
NoSolution
})
}
/// Equates two values returning the nested goals without adding them
/// to the nested goals of the `EvalCtxt`.
///
/// If possible, try using `eq` instead which automatically handles nested
/// goals correctly.
#[instrument(level = "trace", skip(self, param_env), ret)]
pub(super) fn eq_and_get_goals<T: ToTrace<'tcx>>(
&self,
param_env: ty::ParamEnv<'tcx>,
lhs: T,
rhs: T,
) -> Result<Vec<Goal<'tcx, ty::Predicate<'tcx>>>, NoSolution> {
self.infcx
.at(&ObligationCause::dummy(), param_env)
// New solver ignores DefineOpaqueTypes, so choose Yes for consistency
.eq(DefineOpaqueTypes::Yes, lhs, rhs)
.map(|InferOk { value: (), obligations }| {
obligations.into_iter().map(|o| o.into()).collect()
})
.map_err(|e| {
trace!(?e, "failed to equate");
NoSolution
})
}
pub(super) fn instantiate_binder_with_infer<T: TypeFoldable<TyCtxt<'tcx>> + Copy>(
&self,
value: ty::Binder<'tcx, T>,
) -> T {
self.infcx.instantiate_binder_with_fresh_vars(
DUMMY_SP,
BoundRegionConversionTime::HigherRankedType,
value,
)
}
pub(super) fn enter_forall<T: TypeFoldable<TyCtxt<'tcx>> + Copy, U>(
&self,
value: ty::Binder<'tcx, T>,
f: impl FnOnce(T) -> U,
) -> U {
self.infcx.enter_forall(value, f)
}
pub(super) fn resolve_vars_if_possible<T>(&self, value: T) -> T
where
T: TypeFoldable<TyCtxt<'tcx>>,
{
self.infcx.resolve_vars_if_possible(value)
}
pub(super) fn fresh_args_for_item(&mut self, def_id: DefId) -> ty::GenericArgsRef<'tcx> {
let args = self.infcx.fresh_args_for_item(DUMMY_SP, def_id);
for arg in args {
self.inspect.add_var_value(arg);
}
args
}
pub(super) fn translate_args(
&self,
param_env: ty::ParamEnv<'tcx>,
source_impl: DefId,
source_args: ty::GenericArgsRef<'tcx>,
target_node: specialization_graph::Node,
) -> ty::GenericArgsRef<'tcx> {
crate::traits::translate_args(self.infcx, param_env, source_impl, source_args, target_node)
}
pub(super) fn register_ty_outlives(&self, ty: Ty<'tcx>, lt: ty::Region<'tcx>) {
self.infcx.register_region_obligation_with_cause(ty, lt, &ObligationCause::dummy());
}
pub(super) fn register_region_outlives(&self, a: ty::Region<'tcx>, b: ty::Region<'tcx>) {
// `b : a` ==> `a <= b`
// (inlined from `InferCtxt::region_outlives_predicate`)
self.infcx.sub_regions(
rustc_infer::infer::SubregionOrigin::RelateRegionParamBound(DUMMY_SP),
b,
a,
);
}
/// Computes the list of goals required for `arg` to be well-formed
pub(super) fn well_formed_goals(
&self,
param_env: ty::ParamEnv<'tcx>,
arg: ty::GenericArg<'tcx>,
) -> Option<impl Iterator<Item = Goal<'tcx, ty::Predicate<'tcx>>>> {
crate::traits::wf::unnormalized_obligations(self.infcx, param_env, arg)
.map(|obligations| obligations.into_iter().map(|obligation| obligation.into()))
}
pub(super) fn is_transmutable(
&self,
src_and_dst: rustc_transmute::Types<'tcx>,
assume: rustc_transmute::Assume,
) -> Result<Certainty, NoSolution> {
use rustc_transmute::Answer;
// FIXME(transmutability): This really should be returning nested goals for `Answer::If*`
match rustc_transmute::TransmuteTypeEnv::new(self.infcx).is_transmutable(
ObligationCause::dummy(),
src_and_dst,
assume,
) {
Answer::Yes => Ok(Certainty::Yes),
Answer::No(_) | Answer::If(_) => Err(NoSolution),
}
}
pub(super) fn trait_ref_is_knowable(
&mut self,
param_env: ty::ParamEnv<'tcx>,
trait_ref: ty::TraitRef<'tcx>,
) -> Result<bool, NoSolution> {
let infcx = self.infcx;
let lazily_normalize_ty = |ty| self.structurally_normalize_ty(param_env, ty);
coherence::trait_ref_is_knowable(infcx, trait_ref, lazily_normalize_ty)
.map(|is_knowable| is_knowable.is_ok())
}
pub(super) fn can_define_opaque_ty(&self, def_id: impl Into<DefId>) -> bool {
self.infcx.can_define_opaque_ty(def_id)
}
pub(super) fn insert_hidden_type(
&mut self,
opaque_type_key: OpaqueTypeKey<'tcx>,
param_env: ty::ParamEnv<'tcx>,
hidden_ty: Ty<'tcx>,
) -> Result<(), NoSolution> {
let mut obligations = Vec::new();
self.infcx.insert_hidden_type(
opaque_type_key,
&ObligationCause::dummy(),
param_env,
hidden_ty,
&mut obligations,
)?;
self.add_goals(GoalSource::Misc, obligations.into_iter().map(|o| o.into()));
Ok(())
}
pub(super) fn add_item_bounds_for_hidden_type(
&mut self,
opaque_def_id: DefId,
opaque_args: ty::GenericArgsRef<'tcx>,
param_env: ty::ParamEnv<'tcx>,
hidden_ty: Ty<'tcx>,
) {
let mut obligations = Vec::new();
self.infcx.add_item_bounds_for_hidden_type(
opaque_def_id,
opaque_args,
ObligationCause::dummy(),
param_env,
hidden_ty,
&mut obligations,
);
self.add_goals(GoalSource::Misc, obligations.into_iter().map(|o| o.into()));
}
// Do something for each opaque/hidden pair defined with `def_id` in the
// current inference context.
pub(super) fn unify_existing_opaque_tys(
&mut self,
param_env: ty::ParamEnv<'tcx>,
key: ty::OpaqueTypeKey<'tcx>,
ty: Ty<'tcx>,
) -> Vec<CanonicalResponse<'tcx>> {
// FIXME: Super inefficient to be cloning this...
let opaques = self.infcx.clone_opaque_types_for_query_response();
let mut values = vec![];
for (candidate_key, candidate_ty) in opaques {
if candidate_key.def_id != key.def_id {
continue;
}
values.extend(
self.probe(|result| inspect::ProbeKind::OpaqueTypeStorageLookup {
result: *result,
})
.enter(|ecx| {
for (a, b) in std::iter::zip(candidate_key.args, key.args) {
ecx.eq(param_env, a, b)?;
}
ecx.eq(param_env, candidate_ty, ty)?;
ecx.add_item_bounds_for_hidden_type(
candidate_key.def_id.to_def_id(),
candidate_key.args,
param_env,
candidate_ty,
);
ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
}),
);
}
values
}
// Try to evaluate a const, or return `None` if the const is too generic.
// This doesn't mean the const isn't evaluatable, though, and should be treated
// as an ambiguity rather than no-solution.
pub(super) fn try_const_eval_resolve(
&self,
param_env: ty::ParamEnv<'tcx>,
unevaluated: ty::UnevaluatedConst<'tcx>,
ty: Ty<'tcx>,
) -> Option<ty::Const<'tcx>> {
use rustc_middle::mir::interpret::ErrorHandled;
match self.infcx.const_eval_resolve(param_env, unevaluated, DUMMY_SP) {
Ok(Some(val)) => Some(ty::Const::new_value(self.tcx(), val, ty)),
Ok(None) | Err(ErrorHandled::TooGeneric(_)) => None,
Err(ErrorHandled::Reported(e, _)) => {
Some(ty::Const::new_error(self.tcx(), e.into(), ty))
}
}
}
/// Walk through the vtable of a principal trait ref, executing a `supertrait_visitor`
/// for every trait ref encountered (including the principal). Passes both the vtable
/// base and the (optional) vptr slot.
pub(super) fn walk_vtable(
&mut self,
principal: ty::PolyTraitRef<'tcx>,
mut supertrait_visitor: impl FnMut(&mut Self, ty::PolyTraitRef<'tcx>, usize, Option<usize>),
) {
let tcx = self.tcx();
let mut offset = 0;
prepare_vtable_segments::<()>(tcx, principal, |segment| {
match segment {
VtblSegment::MetadataDSA => {
offset += TyCtxt::COMMON_VTABLE_ENTRIES.len();
}
VtblSegment::TraitOwnEntries { trait_ref, emit_vptr } => {
let own_vtable_entries = count_own_vtable_entries(tcx, trait_ref);
supertrait_visitor(
self,
trait_ref,
offset,
emit_vptr.then(|| offset + own_vtable_entries),
);
offset += own_vtable_entries;
if emit_vptr {
offset += 1;
}
}
}
ControlFlow::Continue(())
});
}
}