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normalizes-to disable infer var check

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lcnr 2024-10-21 16:25:42 +02:00
parent 3e33bda032
commit b64b25b99e
4 changed files with 74 additions and 14 deletions
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23
compiler/rustc_next_trait_solver/src/solve/eval_ctxt/canonical.rs
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@ -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 +165,21 @@ 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()).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)