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Disable the evaluation cache when in intercrate mode

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It's possible to use the same `InferCtxt` with both
an intercrate and non-intercrate `SelectionContext`. However,
the local (inferctxt) evaluation cache is not aware of this
distinction, so this kind of `InferCtxt` re-use will pollute
the cache wth bad results.

This commit avoids the issue by disabling the evaluation cache
entirely during intercrate mode.
This commit is contained in:
Aaron Hill 2021-09-15 18:17:38 -05:00
parent c3c0f80d60
commit 6d1f4d2fed
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GPG key ID: B4087E510E98B164
1 changed files with 16 additions and 0 deletions
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16
compiler/rustc_trait_selection/src/traits/select/mod.rs
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@ -982,6 +982,14 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
param_env: ty::ParamEnv<'tcx>,
trait_ref: ty::ConstnessAnd<ty::PolyTraitRef<'tcx>>,
) -> Option<EvaluationResult> {
// Neither the global nor local cache is aware of intercrate
// mode, so don't do any caching. In particular, we might
// re-use the same `InferCtxt` with both an intercrate
// and non-intercrate `SelectionContext`
if self.intercrate {
return None;
}
let tcx = self.tcx();
if self.can_use_global_caches(param_env) {
if let Some(res) = tcx.evaluation_cache.get(&param_env.and(trait_ref), tcx) {
@ -1004,6 +1012,14 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
return;
}
// Neither the global nor local cache is aware of intercrate
// mode, so don't do any caching. In particular, we might
// re-use the same `InferCtxt` with both an intercrate
// and non-intercrate `SelectionContext`
if self.intercrate {
return;
}
if self.can_use_global_caches(param_env) {
if !trait_ref.needs_infer() {
debug!(?trait_ref, ?result, "insert_evaluation_cache global");