bjoernager/rust
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assert that solver results are stable

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This commit is contained in:
lcnr 2023-01-27 10:01:16 +01:00
parent 9c3fe58917
commit 85e6f38e79
3 changed files with 46 additions and 8 deletions
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34
compiler/rustc_trait_selection/src/solve/mod.rs
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@ -174,6 +174,7 @@ impl<'tcx> InferCtxtEvalExt<'tcx> for InferCtxt<'tcx> {
search_graph: &mut search_graph,
infcx: self,
var_values: CanonicalVarValues::dummy(),
in_projection_eq_hack: false,
}
.evaluate_goal(goal);
@ -187,6 +188,10 @@ struct EvalCtxt<'a, 'tcx> {
var_values: CanonicalVarValues<'tcx>,
search_graph: &'a mut search_graph::SearchGraph<'tcx>,
/// This field is used by a debug assertion in [`EvalCtxt::evaluate_goal`],
/// see the comment in that method for more details.
in_projection_eq_hack: bool,
}
impl<'a, 'tcx> EvalCtxt<'a, 'tcx> {
@ -213,7 +218,8 @@ impl<'a, 'tcx> EvalCtxt<'a, 'tcx> {
loop {
let (ref infcx, goal, var_values) =
tcx.infer_ctxt().build_with_canonical(DUMMY_SP, &canonical_goal);
let mut ecx = EvalCtxt { infcx, var_values, search_graph };
let mut ecx =
EvalCtxt { infcx, var_values, search_graph, in_projection_eq_hack: false };
let result = ecx.compute_goal(goal);
// FIXME: `Response` should be `Copy`
@ -243,10 +249,28 @@ impl<'a, 'tcx> EvalCtxt<'a, 'tcx> {
let canonical_goal = self.infcx.canonicalize_query(goal, &mut orig_values);
let canonical_response =
EvalCtxt::evaluate_canonical_goal(self.tcx(), self.search_graph, canonical_goal)?;
Ok((
!canonical_response.value.var_values.is_identity(),
instantiate_canonical_query_response(self.infcx, &orig_values, canonical_response),
))
let has_changed = !canonical_response.value.var_values.is_identity();
let certainty =
instantiate_canonical_query_response(self.infcx, &orig_values, canonical_response);
// Check that rerunning this query with its inference constraints applied
// doesn't result in new inference constraints and has the same result.
//
// If we have projection goals like `<T as Trait>::Assoc == u32` we recursively
// call `exists<U> <T as Trait>::Assoc == U` to enable better caching. This goal
// could constrain `U` to `u32` which would cause this check to result in a
// solver cycle.
if cfg!(debug_assertions) && has_changed && !self.in_projection_eq_hack {
let mut orig_values = OriginalQueryValues::default();
let canonical_goal = self.infcx.canonicalize_query(goal, &mut orig_values);
let canonical_response =
EvalCtxt::evaluate_canonical_goal(self.tcx(), self.search_graph, canonical_goal)?;
assert!(canonical_response.value.var_values.is_identity());
assert_eq!(certainty, canonical_response.value.certainty);
}
Ok((has_changed, certainty))
}
fn compute_goal(&mut self, goal: Goal<'tcx, ty::Predicate<'tcx>>) -> QueryResult<'tcx> {