bjoernager/rust
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also try to normalize opaque types in alias-relate

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with this, alias-relate treats all aliases the same way
and it can be used for structural normalization.
This commit is contained in:
lcnr 2024-01-29 17:09:17 +01:00
parent 0a5b998c57
commit bbe2f6c0b2
5 changed files with 27 additions and 98 deletions
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86
compiler/rustc_trait_selection/src/solve/alias_relate.rs
View file

@ -3,27 +3,22 @@
//! of our more general approach to "lazy normalization".
//!
//! This is done by first normalizing both sides of the goal, ending up in
//! either a concrete type, rigid projection, opaque, or an infer variable.
//! either a concrete type, rigid alias, or an infer variable.
//! These are related further according to the rules below:
//!
//! (1.) If we end up with a rigid projection and a rigid projection, then we
//! relate those projections structurally.
//! (1.) If we end up with two rigid aliases, then we relate them structurally.
//!
//! (2.) If we end up with a rigid projection and an alias, then the opaque will
//! have its hidden type defined to be that rigid projection.
//!
//! (3.) If we end up with an opaque and an opaque, then we assemble two
//! candidates, one defining the LHS to be the hidden type of the RHS, and vice
//! versa.
//!
//! (4.) If we end up with an infer var and an opaque or rigid projection, then
//! (2.) If we end up with an infer var and a rigid alias, then
//! we assign the alias to the infer var.
//!
//! (5.) If we end up with an opaque and a rigid (non-projection) type, then we
//! define the hidden type of the opaque to be the rigid type.
//!
//! (6.) Otherwise, if we end with two rigid (non-projection) or infer types,
//! (3.) Otherwise, if we end with two rigid (non-projection) or infer types,
//! relate them structurally.
//!
//! Subtle: when relating an opaque to another type, we emit a
//! `NormalizesTo(opaque, ?fresh_var)` goal when trying to normalize the opaque.
//! This nested goal starts out as ambiguous and does not actually define the opaque.
//! However, if `?fresh_var` ends up geteting equated to another type, we retry the
//! `NormalizesTo` goal, at which point the opaque is actually defined.
use super::{EvalCtxt, GoalSource};
use rustc_infer::infer::DefineOpaqueTypes;
@ -59,31 +54,26 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
self.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
}
(Some(alias), None) => {
(Some(_), None) => {
if rhs.is_infer() {
self.relate(param_env, lhs, variance, rhs)?;
self.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
} else if alias.is_opaque(tcx) {
// FIXME: This doesn't account for variance.
self.define_opaque(param_env, alias, rhs)
} else {
Err(NoSolution)
}
}
(None, Some(alias)) => {
(None, Some(_)) => {
if lhs.is_infer() {
self.relate(param_env, lhs, variance, rhs)?;
self.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
} else if alias.is_opaque(tcx) {
// FIXME: This doesn't account for variance.
self.define_opaque(param_env, alias, lhs)
} else {
Err(NoSolution)
}
}
(Some(alias_lhs), Some(alias_rhs)) => {
self.relate_rigid_alias_or_opaque(param_env, alias_lhs, variance, alias_rhs)
self.relate(param_env, alias_lhs, variance, alias_rhs)?;
self.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
}
}
}
@ -118,52 +108,4 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
}
}
}
fn define_opaque(
&mut self,
param_env: ty::ParamEnv<'tcx>,
opaque: ty::AliasTy<'tcx>,
term: ty::Term<'tcx>,
) -> QueryResult<'tcx> {
self.add_goal(
GoalSource::Misc,
Goal::new(self.tcx(), param_env, ty::NormalizesTo { alias: opaque, term }),
);
self.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
}
fn relate_rigid_alias_or_opaque(
&mut self,
param_env: ty::ParamEnv<'tcx>,
lhs: ty::AliasTy<'tcx>,
variance: ty::Variance,
rhs: ty::AliasTy<'tcx>,
) -> QueryResult<'tcx> {
let tcx = self.tcx();
let mut candidates = vec![];
if lhs.is_opaque(tcx) {
candidates.extend(
self.probe_misc_candidate("define-lhs-opaque")
.enter(|ecx| ecx.define_opaque(param_env, lhs, rhs.to_ty(tcx).into())),
);
}
if rhs.is_opaque(tcx) {
candidates.extend(
self.probe_misc_candidate("define-rhs-opaque")
.enter(|ecx| ecx.define_opaque(param_env, rhs, lhs.to_ty(tcx).into())),
);
}
candidates.extend(self.probe_misc_candidate("args-relate").enter(|ecx| {
ecx.relate(param_env, lhs, variance, rhs)?;
ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
}));
if let Some(result) = self.try_merge_responses(&candidates) {
Ok(result)
} else {
self.flounder(&candidates)
}
}
}

27
compiler/rustc_trait_selection/src/solve/mod.rs
View file

@ -22,8 +22,7 @@ use rustc_middle::traits::solve::{
CanonicalResponse, Certainty, ExternalConstraintsData, Goal, GoalSource, IsNormalizesToHack,
QueryResult, Response,
};
use rustc_middle::traits::Reveal;
use rustc_middle::ty::{self, OpaqueTypeKey, Ty, TyCtxt, UniverseIndex};
use rustc_middle::ty::{self, Ty, TyCtxt, UniverseIndex};
use rustc_middle::ty::{
CoercePredicate, RegionOutlivesPredicate, SubtypePredicate, TypeOutlivesPredicate,
};
@ -292,32 +291,10 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
return None;
}
let ty::Alias(kind, alias) = *ty.kind() else {
let ty::Alias(_, alias) = *ty.kind() else {
return Some(ty);
};
// We do no always define opaque types eagerly to allow non-defining uses
// in the defining scope. However, if we can unify this opaque to an existing
// opaque, then we should attempt to eagerly reveal the opaque, and we fall
// through.
if let DefineOpaqueTypes::No = define_opaque_types
&& let Reveal::UserFacing = param_env.reveal()
&& let ty::Opaque = kind
&& let Some(def_id) = alias.def_id.as_local()
&& self.can_define_opaque_ty(def_id)
{
if self
.unify_existing_opaque_tys(
param_env,
OpaqueTypeKey { def_id, args: alias.args },
self.next_ty_infer(),
)
.is_empty()
{
return Some(ty);
}
}
match self.commit_if_ok(|this| {
let normalized_ty = this.next_ty_infer();
let normalizes_to_goal = Goal::new(