diff options
Diffstat (limited to 'compiler')
| -rw-r--r-- | compiler/rustc_next_trait_solver/src/solve/eval_ctxt/canonical.rs | 24 | ||||
| -rw-r--r-- | compiler/rustc_trait_selection/src/traits/coherence.rs | 2 |
2 files changed, 19 insertions, 7 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 f49f3a1a3bf..71ce0cce772 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 @@ -16,7 +16,7 @@ use rustc_type_ir::fold::TypeFoldable; use rustc_type_ir::inherent::*; use rustc_type_ir::relate::solver_relating::RelateExt; use rustc_type_ir::{self as ty, Canonical, CanonicalVarValues, InferCtxtLike, Interner}; -use tracing::{instrument, trace}; +use tracing::{debug, instrument, trace}; use crate::canonicalizer::{CanonicalizeMode, Canonicalizer}; use crate::delegate::SolverDelegate; @@ -165,12 +165,22 @@ where // HACK: We bail with overflow if the response would have too many non-region // inference variables. This tends to only happen if we encounter a lot of // ambiguous alias types which get replaced with fresh inference variables - // during generalization. This prevents a hang in nalgebra. - let num_non_region_vars = canonical.variables.iter().filter(|c| !c.is_region()).count(); - if num_non_region_vars > self.cx().recursion_limit() { - return Ok(self.make_ambiguous_response_no_constraints(MaybeCause::Overflow { - suggest_increasing_limit: true, - })); + // during generalization. This prevents hangs caused by an exponential blowup, + // see tests/ui/traits/next-solver/coherence-alias-hang.rs. + // + // We don't do so for `NormalizesTo` goals as we erased the expected term and + // bailing with overflow here would prevent us from detecting a type-mismatch, + // causing a coherence error in diesel, see #131969. We still bail with verflow + // when later returning from the parent AliasRelate goal. + if !self.is_normalizes_to_goal { + let num_non_region_vars = + canonical.variables.iter().filter(|c| !c.is_region() && c.is_existential()).count(); + if num_non_region_vars > self.cx().recursion_limit() { + debug!(?num_non_region_vars, "too many inference variables -> overflow"); + return Ok(self.make_ambiguous_response_no_constraints(MaybeCause::Overflow { + suggest_increasing_limit: true, + })); + } } Ok(canonical) diff --git a/compiler/rustc_trait_selection/src/traits/coherence.rs b/compiler/rustc_trait_selection/src/traits/coherence.rs index f4a2483cebf..f8fb297e36c 100644 --- a/compiler/rustc_trait_selection/src/traits/coherence.rs +++ b/compiler/rustc_trait_selection/src/traits/coherence.rs @@ -298,6 +298,7 @@ fn equate_impl_headers<'tcx>( } /// The result of [fn impl_intersection_has_impossible_obligation]. +#[derive(Debug)] enum IntersectionHasImpossibleObligations<'tcx> { Yes, No { @@ -328,6 +329,7 @@ enum IntersectionHasImpossibleObligations<'tcx> { /// of the two impls above to be empty. /// /// Importantly, this works even if there isn't a `impl !Error for MyLocalType`. +#[instrument(level = "debug", skip(selcx), ret)] fn impl_intersection_has_impossible_obligation<'a, 'cx, 'tcx>( selcx: &mut SelectionContext<'cx, 'tcx>, obligations: &'a [PredicateObligation<'tcx>], |