diff options
| -rw-r--r-- | src/librustc/infer/equate.rs | 10 | ||||
| -rw-r--r-- | src/librustc/infer/nll_relate/mod.rs | 11 | ||||
| -rw-r--r-- | src/test/ui/closures/deeply-nested_closures.rs | 23 |
3 files changed, 42 insertions, 2 deletions
diff --git a/src/librustc/infer/equate.rs b/src/librustc/infer/equate.rs index 4a41cdb1407..f192295c1aa 100644 --- a/src/librustc/infer/equate.rs +++ b/src/librustc/infer/equate.rs @@ -125,7 +125,13 @@ impl TypeRelation<'tcx> for Equate<'combine, 'infcx, 'tcx> { where T: Relate<'tcx>, { - self.fields.higher_ranked_sub(a, b, self.a_is_expected)?; - self.fields.higher_ranked_sub(b, a, self.a_is_expected) + if a.skip_binder().has_escaping_bound_vars() || b.skip_binder().has_escaping_bound_vars() { + self.fields.higher_ranked_sub(a, b, self.a_is_expected)?; + self.fields.higher_ranked_sub(b, a, self.a_is_expected) + } else { + // Fast path for the common case. + self.relate(a.skip_binder(), b.skip_binder())?; + return Ok(a.clone()); + } } } diff --git a/src/librustc/infer/nll_relate/mod.rs b/src/librustc/infer/nll_relate/mod.rs index 6b53871b9e2..6af004f7776 100644 --- a/src/librustc/infer/nll_relate/mod.rs +++ b/src/librustc/infer/nll_relate/mod.rs @@ -529,6 +529,10 @@ where b = self.infcx.shallow_resolve(b); } + if a == b { + return Ok(a); + } + match (&a.kind, &b.kind) { (_, &ty::Infer(ty::TyVar(vid))) => { if D::forbid_inference_vars() { @@ -638,6 +642,13 @@ where debug!("binders({:?}: {:?}, ambient_variance={:?})", a, b, self.ambient_variance); + if !a.skip_binder().has_escaping_bound_vars() && !b.skip_binder().has_escaping_bound_vars() + { + // Fast path for the common case. + self.relate(a.skip_binder(), b.skip_binder())?; + return Ok(a.clone()); + } + if self.ambient_covariance() { // Covariance, so we want `for<..> A <: for<..> B` -- // therefore we compare any instantiation of A (i.e., A diff --git a/src/test/ui/closures/deeply-nested_closures.rs b/src/test/ui/closures/deeply-nested_closures.rs new file mode 100644 index 00000000000..a02684ee1de --- /dev/null +++ b/src/test/ui/closures/deeply-nested_closures.rs @@ -0,0 +1,23 @@ +// Check that this can be compiled in a reasonable time. + +// build-pass + +fn main() { + // 96 nested closures + let x = (); + || || || || || || || || + || || || || || || || || + || || || || || || || || + || || || || || || || || + + || || || || || || || || + || || || || || || || || + || || || || || || || || + || || || || || || || || + + || || || || || || || || + || || || || || || || || + || || || || || || || || + || || || || || || || || + [&(), &x]; +} |