diff options
Diffstat (limited to 'compiler')
4 files changed, 25 insertions, 35 deletions
diff --git a/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/canonical.rs b/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/canonical.rs index 1c00f5f8b41..5acfec3dee3 100644 --- a/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/canonical.rs +++ b/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/canonical.rs @@ -122,6 +122,21 @@ where (certainty, NestedNormalizationGoals::empty()) }; + if let Certainty::Maybe(cause @ MaybeCause::Overflow { .. }) = certainty { + // If we have overflow, it's probable that we're substituting a type + // into itself infinitely and any partial substitutions in the query + // response are probably not useful anyways, so just return an empty + // query response. + // + // This may prevent us from potentially useful inference, e.g. + // 2 candidates, one ambiguous and one overflow, which both + // have the same inference constraints. + // + // Changing this to retain some constraints in the future + // won't be a breaking change, so this is good enough for now. + return Ok(self.make_ambiguous_response_no_constraints(cause)); + } + let external_constraints = self.compute_external_query_constraints(certainty, normalization_nested_goals); let (var_values, mut external_constraints) = (self.var_values, external_constraints) diff --git a/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/mod.rs b/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/mod.rs index 3f2f34d3255..15b123ebdf9 100644 --- a/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/mod.rs +++ b/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/mod.rs @@ -17,7 +17,7 @@ use crate::delegate::SolverDelegate; use crate::solve::inspect::{self, ProofTreeBuilder}; use crate::solve::search_graph::SearchGraph; use crate::solve::{ - CanonicalInput, CanonicalResponse, Certainty, Goal, GoalEvaluationKind, GoalSource, MaybeCause, + CanonicalInput, CanonicalResponse, Certainty, Goal, GoalEvaluationKind, GoalSource, NestedNormalizationGoals, NoSolution, PredefinedOpaquesData, QueryResult, SolverMode, FIXPOINT_STEP_LIMIT, }; @@ -370,7 +370,7 @@ where canonical_goal, &mut goal_evaluation, ); - let canonical_response = match canonical_response { + let response = match canonical_response { Err(e) => { self.inspect.goal_evaluation(goal_evaluation); return Err(e); @@ -378,12 +378,11 @@ where Ok(response) => response, }; - let (normalization_nested_goals, certainty, has_changed) = self - .instantiate_response_discarding_overflow( - goal.param_env, - orig_values, - canonical_response, - ); + let has_changed = !response.value.var_values.is_identity_modulo_regions() + || !response.value.external_constraints.opaque_types.is_empty(); + + let (normalization_nested_goals, certainty) = + self.instantiate_and_apply_query_response(goal.param_env, orig_values, response); self.inspect.goal_evaluation(goal_evaluation); // FIXME: We previously had an assert here that checked that recomputing // a goal after applying its constraints did not change its response. @@ -398,24 +397,6 @@ where Ok((normalization_nested_goals, has_changed, certainty)) } - fn instantiate_response_discarding_overflow( - &mut self, - param_env: I::ParamEnv, - original_values: Vec<I::GenericArg>, - response: CanonicalResponse<I>, - ) -> (NestedNormalizationGoals<I>, Certainty, bool) { - if let Certainty::Maybe(MaybeCause::Overflow { .. }) = response.value.certainty { - return (NestedNormalizationGoals::empty(), response.value.certainty, false); - } - - let has_changed = !response.value.var_values.is_identity_modulo_regions() - || !response.value.external_constraints.opaque_types.is_empty(); - - let (normalization_nested_goals, certainty) = - self.instantiate_and_apply_query_response(param_env, original_values, response); - (normalization_nested_goals, certainty, has_changed) - } - fn compute_goal(&mut self, goal: Goal<I, I::Predicate>) -> QueryResult<I> { let Goal { param_env, predicate } = goal; let kind = predicate.kind(); diff --git a/compiler/rustc_trait_selection/src/solve/fulfill.rs b/compiler/rustc_trait_selection/src/solve/fulfill.rs index f5f36f40f7e..cfc73e2e47e 100644 --- a/compiler/rustc_trait_selection/src/solve/fulfill.rs +++ b/compiler/rustc_trait_selection/src/solve/fulfill.rs @@ -302,7 +302,7 @@ fn fulfillment_error_for_stalled<'tcx>( Ok((_, Certainty::Maybe(MaybeCause::Overflow { suggest_increasing_limit }))) => ( FulfillmentErrorCode::Ambiguity { overflow: Some(suggest_increasing_limit) }, // Don't look into overflows because we treat overflows weirdly anyways. - // In `instantiate_response_discarding_overflow` we set `has_changed = false`, + // We discard the inference constraints from overflowing goals, so // recomputing the goal again during `find_best_leaf_obligation` may apply // inference guidance that makes other goals go from ambig -> pass, for example. // diff --git a/compiler/rustc_type_ir/src/solve/mod.rs b/compiler/rustc_type_ir/src/solve/mod.rs index 96998d2ec9f..a0f7658212f 100644 --- a/compiler/rustc_type_ir/src/solve/mod.rs +++ b/compiler/rustc_type_ir/src/solve/mod.rs @@ -117,7 +117,8 @@ impl<I: Interner, P> Goal<I, P> { /// Why a specific goal has to be proven. /// /// This is necessary as we treat nested goals different depending on -/// their source. +/// their source. This is currently mostly used by proof tree visitors +/// but will be used by cycle handling in the future. #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash)] #[cfg_attr(feature = "nightly", derive(HashStable_NoContext))] pub enum GoalSource { @@ -126,13 +127,6 @@ pub enum GoalSource { /// /// FIXME(-Znext-solver=coinductive): Explain how and why this /// changes whether cycles are coinductive. - /// - /// This also impacts whether we erase constraints on overflow. - /// Erasing constraints is generally very useful for perf and also - /// results in better error messages by avoiding spurious errors. - /// We do not erase overflow constraints in `normalizes-to` goals unless - /// they are from an impl where-clause. This is necessary due to - /// backwards compatibility, cc trait-system-refactor-initiatitive#70. ImplWhereBound, /// Instantiating a higher-ranked goal and re-proving it. InstantiateHigherRanked, |