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make dropck_outlives into a proper canonicalized type query

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This commit is contained in:
Michael Goulet 2022-11-09 18:46:57 +00:00
parent ed6a7cc228
commit 63217e08cc
1 changed files with 88 additions and 101 deletions
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189
compiler/rustc_traits/src/dropck_outlives.rs
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@ -2,20 +2,18 @@ use rustc_data_structures::fx::FxHashSet;
use rustc_hir::def_id::DefId; use rustc_hir::def_id::DefId;
use rustc_infer::infer::canonical::{Canonical, QueryResponse}; use rustc_infer::infer::canonical::{Canonical, QueryResponse};
use rustc_infer::infer::TyCtxtInferExt; use rustc_infer::infer::TyCtxtInferExt;
use rustc_infer::traits::TraitEngineExt as _;
use rustc_middle::ty::query::Providers; use rustc_middle::ty::query::Providers;
use rustc_middle::ty::InternalSubsts; use rustc_middle::ty::InternalSubsts;
use rustc_middle::ty::{self, EarlyBinder, ParamEnvAnd, Ty, TyCtxt}; use rustc_middle::ty::{self, EarlyBinder, ParamEnvAnd, Ty, TyCtxt};
use rustc_span::source_map::{Span, DUMMY_SP}; use rustc_span::source_map::{Span, DUMMY_SP};
use rustc_trait_selection::infer::InferCtxtBuilderExt;
use rustc_trait_selection::traits::query::dropck_outlives::trivial_dropck_outlives; use rustc_trait_selection::traits::query::dropck_outlives::trivial_dropck_outlives;
use rustc_trait_selection::traits::query::dropck_outlives::{ use rustc_trait_selection::traits::query::dropck_outlives::{
DropckConstraint, DropckOutlivesResult, DropckConstraint, DropckOutlivesResult,
}; };
use rustc_trait_selection::traits::query::normalize::AtExt; use rustc_trait_selection::traits::query::normalize::AtExt;
use rustc_trait_selection::traits::query::{CanonicalTyGoal, NoSolution}; use rustc_trait_selection::traits::query::{CanonicalTyGoal, NoSolution};
use rustc_trait_selection::traits::{ use rustc_trait_selection::traits::{Normalized, ObligationCause};
Normalized, ObligationCause, TraitEngine, TraitEngineExt as _,
};
pub(crate) fn provide(p: &mut Providers) { pub(crate) fn provide(p: &mut Providers) {
*p = Providers { dropck_outlives, adt_dtorck_constraint, ..*p }; *p = Providers { dropck_outlives, adt_dtorck_constraint, ..*p };
@ -27,120 +25,109 @@ fn dropck_outlives<'tcx>(
) -> Result<&'tcx Canonical<'tcx, QueryResponse<'tcx, DropckOutlivesResult<'tcx>>>, NoSolution> { ) -> Result<&'tcx Canonical<'tcx, QueryResponse<'tcx, DropckOutlivesResult<'tcx>>>, NoSolution> {
debug!("dropck_outlives(goal={:#?})", canonical_goal); debug!("dropck_outlives(goal={:#?})", canonical_goal);
let (ref infcx, goal, canonical_inference_vars) = tcx.infer_ctxt().enter_canonical_trait_query(&canonical_goal, |ocx, goal| {
tcx.infer_ctxt().build_with_canonical(DUMMY_SP, &canonical_goal); let tcx = ocx.infcx.tcx;
let tcx = infcx.tcx; let ParamEnvAnd { param_env, value: for_ty } = goal;
let ParamEnvAnd { param_env, value: for_ty } = goal;
let mut result = DropckOutlivesResult { kinds: vec![], overflows: vec![] }; let mut result = DropckOutlivesResult { kinds: vec![], overflows: vec![] };
// A stack of types left to process. Each round, we pop // A stack of types left to process. Each round, we pop
// something from the stack and invoke // something from the stack and invoke
// `dtorck_constraint_for_ty`. This may produce new types that // `dtorck_constraint_for_ty`. This may produce new types that
// have to be pushed on the stack. This continues until we have explored // have to be pushed on the stack. This continues until we have explored
// all the reachable types from the type `for_ty`. // all the reachable types from the type `for_ty`.
// //
// Example: Imagine that we have the following code: // Example: Imagine that we have the following code:
// //
// ```rust // ```rust
// struct A { // struct A {
// value: B, // value: B,
// children: Vec<A>, // children: Vec<A>,
// } // }
// //
// struct B { // struct B {
// value: u32 // value: u32
// } // }
// //
// fn f() { // fn f() {
// let a: A = ...; // let a: A = ...;
// .. // ..
// } // here, `a` is dropped // } // here, `a` is dropped
// ``` // ```
// //
// at the point where `a` is dropped, we need to figure out // at the point where `a` is dropped, we need to figure out
// which types inside of `a` contain region data that may be // which types inside of `a` contain region data that may be
// accessed by any destructors in `a`. We begin by pushing `A` // accessed by any destructors in `a`. We begin by pushing `A`
// onto the stack, as that is the type of `a`. We will then // onto the stack, as that is the type of `a`. We will then
// invoke `dtorck_constraint_for_ty` which will expand `A` // invoke `dtorck_constraint_for_ty` which will expand `A`
// into the types of its fields `(B, Vec<A>)`. These will get // into the types of its fields `(B, Vec<A>)`. These will get
// pushed onto the stack. Eventually, expanding `Vec<A>` will // pushed onto the stack. Eventually, expanding `Vec<A>` will
// lead to us trying to push `A` a second time -- to prevent // lead to us trying to push `A` a second time -- to prevent
// infinite recursion, we notice that `A` was already pushed // infinite recursion, we notice that `A` was already pushed
// once and stop. // once and stop.
let mut ty_stack = vec![(for_ty, 0)]; let mut ty_stack = vec![(for_ty, 0)];
// Set used to detect infinite recursion. // Set used to detect infinite recursion.
let mut ty_set = FxHashSet::default(); let mut ty_set = FxHashSet::default();
let mut fulfill_cx = <dyn TraitEngine<'_>>::new(infcx.tcx); let cause = ObligationCause::dummy();
let mut constraints = DropckConstraint::empty();
while let Some((ty, depth)) = ty_stack.pop() {
debug!(
"{} kinds, {} overflows, {} ty_stack",
result.kinds.len(),
result.overflows.len(),
ty_stack.len()
);
dtorck_constraint_for_ty(tcx, DUMMY_SP, for_ty, depth, ty, &mut constraints)?;
let cause = ObligationCause::dummy(); // "outlives" represent types/regions that may be touched
let mut constraints = DropckConstraint::empty(); // by a destructor.
while let Some((ty, depth)) = ty_stack.pop() { result.kinds.append(&mut constraints.outlives);
debug!( result.overflows.append(&mut constraints.overflows);
"{} kinds, {} overflows, {} ty_stack",
result.kinds.len(),
result.overflows.len(),
ty_stack.len()
);
dtorck_constraint_for_ty(tcx, DUMMY_SP, for_ty, depth, ty, &mut constraints)?;
// "outlives" represent types/regions that may be touched // If we have even one overflow, we should stop trying to evaluate further --
// by a destructor. // chances are, the subsequent overflows for this evaluation won't provide useful
result.kinds.append(&mut constraints.outlives); // information and will just decrease the speed at which we can emit these errors
result.overflows.append(&mut constraints.overflows); // (since we'll be printing for just that much longer for the often enormous types
// that result here).
if !result.overflows.is_empty() {
break;
}
// If we have even one overflow, we should stop trying to evaluate further -- // dtorck types are "types that will get dropped but which
// chances are, the subsequent overflows for this evaluation won't provide useful // do not themselves define a destructor", more or less. We have
// information and will just decrease the speed at which we can emit these errors // to push them onto the stack to be expanded.
// (since we'll be printing for just that much longer for the often enormous types for ty in constraints.dtorck_types.drain(..) {
// that result here). let Normalized { value: ty, obligations } =
if !result.overflows.is_empty() { ocx.infcx.at(&cause, param_env).normalize(ty)?;
break; ocx.register_obligations(obligations);
}
// dtorck types are "types that will get dropped but which debug!("dropck_outlives: ty from dtorck_types = {:?}", ty);
// do not themselves define a destructor", more or less. We have
// to push them onto the stack to be expanded.
for ty in constraints.dtorck_types.drain(..) {
match infcx.at(&cause, param_env).normalize(ty) {
Ok(Normalized { value: ty, obligations }) => {
fulfill_cx.register_predicate_obligations(infcx, obligations);
debug!("dropck_outlives: ty from dtorck_types = {:?}", ty); match ty.kind() {
// All parameters live for the duration of the
// function.
ty::Param(..) => {}
match ty.kind() { // A projection that we couldn't resolve - it
// All parameters live for the duration of the // might have a destructor.
// function. ty::Projection(..) | ty::Opaque(..) => {
ty::Param(..) => {} result.kinds.push(ty.into());
}
// A projection that we couldn't resolve - it _ => {
// might have a destructor. if ty_set.insert(ty) {
ty::Projection(..) | ty::Opaque(..) => { ty_stack.push((ty, depth + 1));
result.kinds.push(ty.into());
}
_ => {
if ty_set.insert(ty) {
ty_stack.push((ty, depth + 1));
}
} }
} }
} }
// We don't actually expect to fail to normalize.
// That implies a WF error somewhere else.
Err(NoSolution) => {
return Err(NoSolution);
}
} }
} }
}
debug!("dropck_outlives: result = {:#?}", result); debug!("dropck_outlives: result = {:#?}", result);
Ok(result)
infcx.make_canonicalized_query_response(canonical_inference_vars, result, &mut *fulfill_cx) })
} }
/// Returns a set of constraints that needs to be satisfied in /// Returns a set of constraints that needs to be satisfied in