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|
use std::convert::Infallible;
use std::marker::PhantomData;
use rustc_type_ir::data_structures::ensure_sufficient_stack;
use rustc_type_ir::search_graph::{self, PathKind};
use rustc_type_ir::solve::{CanonicalInput, Certainty, NoSolution, QueryResult};
use rustc_type_ir::{Interner, TypingMode};
use crate::canonical::response_no_constraints_raw;
use crate::delegate::SolverDelegate;
use crate::solve::{
EvalCtxt, FIXPOINT_STEP_LIMIT, has_no_inference_or_external_constraints, inspect,
};
/// This type is never constructed. We only use it to implement `search_graph::Delegate`
/// for all types which impl `SolverDelegate` and doing it directly fails in coherence.
pub(super) struct SearchGraphDelegate<D: SolverDelegate> {
_marker: PhantomData<D>,
}
pub(super) type SearchGraph<D> = search_graph::SearchGraph<SearchGraphDelegate<D>>;
impl<D, I> search_graph::Delegate for SearchGraphDelegate<D>
where
D: SolverDelegate<Interner = I>,
I: Interner,
{
type Cx = D::Interner;
const ENABLE_PROVISIONAL_CACHE: bool = true;
type ValidationScope = Infallible;
fn enter_validation_scope(
_cx: Self::Cx,
_input: CanonicalInput<I>,
) -> Option<Self::ValidationScope> {
None
}
const FIXPOINT_STEP_LIMIT: usize = FIXPOINT_STEP_LIMIT;
type ProofTreeBuilder = inspect::ProofTreeBuilder<D>;
fn inspect_is_noop(inspect: &mut Self::ProofTreeBuilder) -> bool {
inspect.is_noop()
}
const DIVIDE_AVAILABLE_DEPTH_ON_OVERFLOW: usize = 4;
fn initial_provisional_result(
cx: I,
kind: PathKind,
input: CanonicalInput<I>,
) -> QueryResult<I> {
match kind {
PathKind::Coinductive => response_no_constraints(cx, input, Certainty::Yes),
PathKind::Unknown | PathKind::ForcedAmbiguity => {
response_no_constraints(cx, input, Certainty::overflow(false))
}
// Even though we know these cycles to be unproductive, we still return
// overflow during coherence. This is both as we are not 100% confident in
// the implementation yet and any incorrect errors would be unsound there.
// The affected cases are also fairly artificial and not necessarily desirable
// so keeping this as ambiguity is fine for now.
//
// See `tests/ui/traits/next-solver/cycles/unproductive-in-coherence.rs` for an
// example where this would matter. We likely should change these cycles to `NoSolution`
// even in coherence once this is a bit more settled.
PathKind::Inductive => match input.typing_mode {
TypingMode::Coherence => {
response_no_constraints(cx, input, Certainty::overflow(false))
}
TypingMode::Analysis { .. }
| TypingMode::Borrowck { .. }
| TypingMode::PostBorrowckAnalysis { .. }
| TypingMode::PostAnalysis => Err(NoSolution),
},
}
}
fn is_initial_provisional_result(result: QueryResult<I>) -> Option<PathKind> {
match result {
Ok(response) => {
if has_no_inference_or_external_constraints(response) {
if response.value.certainty == Certainty::Yes {
return Some(PathKind::Coinductive);
} else if response.value.certainty == Certainty::overflow(false) {
return Some(PathKind::Unknown);
}
}
None
}
Err(NoSolution) => Some(PathKind::Inductive),
}
}
fn stack_overflow_result(cx: I, input: CanonicalInput<I>) -> QueryResult<I> {
response_no_constraints(cx, input, Certainty::overflow(true))
}
fn fixpoint_overflow_result(cx: I, input: CanonicalInput<I>) -> QueryResult<I> {
response_no_constraints(cx, input, Certainty::overflow(false))
}
fn is_ambiguous_result(result: QueryResult<I>) -> bool {
result.is_ok_and(|response| {
has_no_inference_or_external_constraints(response)
&& matches!(response.value.certainty, Certainty::Maybe { .. })
})
}
fn propagate_ambiguity(
cx: I,
for_input: CanonicalInput<I>,
from_result: QueryResult<I>,
) -> QueryResult<I> {
let certainty = from_result.unwrap().value.certainty;
response_no_constraints(cx, for_input, certainty)
}
fn compute_goal(
search_graph: &mut SearchGraph<D>,
cx: I,
input: CanonicalInput<I>,
inspect: &mut Self::ProofTreeBuilder,
) -> QueryResult<I> {
ensure_sufficient_stack(|| {
EvalCtxt::enter_canonical(cx, search_graph, input, inspect, |ecx, goal| {
let result = ecx.compute_goal(goal);
ecx.inspect.query_result(result);
result
})
})
}
}
fn response_no_constraints<I: Interner>(
cx: I,
input: CanonicalInput<I>,
certainty: Certainty,
) -> QueryResult<I> {
Ok(response_no_constraints_raw(
cx,
input.canonical.max_universe,
input.canonical.variables,
certainty,
))
}
|
