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Rollup merge of #100789 - compiler-errors:issue-99662, r=spastorino

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Use separate infcx to solve obligations during negative coherence

I feel like I fixed this already but I may have fixed it then forgot to push the branch...

Also fixes up some redundant param-envs being passed around (since they're already passed around in the `Obligation`)

Fixes #99662

r? ``@spastorino``
This commit is contained in:
Matthias Krüger 2022-08-23 06:55:26 +02:00 • committed by GitHub
commit 579dfa42be
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4 changed files with 26 additions and 15 deletions
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21
compiler/rustc_trait_selection/src/traits/coherence.rs
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@ -342,10 +342,8 @@ fn equate<'cx, 'tcx>(
};
let selcx = &mut SelectionContext::new(&infcx);
let opt_failing_obligation = obligations
.into_iter()
.chain(more_obligations)
.find(|o| negative_impl_exists(selcx, impl_env, o));
let opt_failing_obligation =
obligations.into_iter().chain(more_obligations).find(|o| negative_impl_exists(selcx, o));
if let Some(failing_obligation) = opt_failing_obligation {
debug!("overlap: obligation unsatisfiable {:?}", failing_obligation);
@ -359,18 +357,15 @@ fn equate<'cx, 'tcx>(
#[instrument(level = "debug", skip(selcx))]
fn negative_impl_exists<'cx, 'tcx>(
selcx: &SelectionContext<'cx, 'tcx>,
param_env: ty::ParamEnv<'tcx>,
o: &PredicateObligation<'tcx>,
) -> bool {
let infcx = &selcx.infcx().fork();
if resolve_negative_obligation(infcx, param_env, o) {
if resolve_negative_obligation(selcx.infcx().fork(), o) {
return true;
}
// Try to prove a negative obligation exists for super predicates
for o in util::elaborate_predicates(infcx.tcx, iter::once(o.predicate)) {
if resolve_negative_obligation(infcx, param_env, &o) {
for o in util::elaborate_predicates(selcx.tcx(), iter::once(o.predicate)) {
if resolve_negative_obligation(selcx.infcx().fork(), &o) {
return true;
}
}
@ -380,8 +375,7 @@ fn negative_impl_exists<'cx, 'tcx>(
#[instrument(level = "debug", skip(infcx))]
fn resolve_negative_obligation<'cx, 'tcx>(
infcx: &InferCtxt<'cx, 'tcx>,
param_env: ty::ParamEnv<'tcx>,
infcx: InferCtxt<'cx, 'tcx>,
o: &PredicateObligation<'tcx>,
) -> bool {
let tcx = infcx.tcx;
@ -390,7 +384,8 @@ fn resolve_negative_obligation<'cx, 'tcx>(
return false;
};
let errors = super::fully_solve_obligation(infcx, o);
let param_env = o.param_env;
let errors = super::fully_solve_obligation(&infcx, o);
if !errors.is_empty() {
return false;
}