diff options
| -rw-r--r-- | compiler/rustc_trait_selection/src/solve/search_graph/mod.rs | 13 |
1 files changed, 8 insertions, 5 deletions
diff --git a/compiler/rustc_trait_selection/src/solve/search_graph/mod.rs b/compiler/rustc_trait_selection/src/solve/search_graph/mod.rs index 7514c7ee551..a2ca4bc189c 100644 --- a/compiler/rustc_trait_selection/src/solve/search_graph/mod.rs +++ b/compiler/rustc_trait_selection/src/solve/search_graph/mod.rs @@ -7,7 +7,7 @@ use cache::ProvisionalCache; use overflow::OverflowData; use rustc_index::vec::IndexVec; use rustc_middle::ty::TyCtxt; -use std::collections::hash_map::Entry; +use std::{collections::hash_map::Entry, mem}; rustc_index::newtype_index! { pub struct StackDepth {} @@ -134,12 +134,15 @@ impl<'tcx> SearchGraph<'tcx> { let provisional_entry_index = *cache.lookup_table.get(&goal).unwrap(); let provisional_entry = &mut cache.entries[provisional_entry_index]; let depth = provisional_entry.depth; + // We eagerly update the response in the cache here. If we have to reevaluate + // this goal we use the new response when hitting a cycle, and we definitely + // want to access the final response whenever we look at the cache. + let prev_response = mem::replace(&mut provisional_entry.response, response); + // Was the current goal the root of a cycle and was the provisional response // different from the final one. - if has_been_used && provisional_entry.response != response { - // If so, update the provisional reponse for this goal... - provisional_entry.response = response; - // ...remove all entries whose result depends on this goal + if has_been_used && prev_response != response { + // If so, remove all entries whose result depends on this goal // from the provisional cache... // // That's not completely correct, as a nested goal can also |