Skip to content

Commit

Permalink
Unrolled build for rust-lang#130617
Browse files Browse the repository at this point in the history
Rollup merge of rust-lang#130617 - lcnr:nalgebra-hang-3, r=compiler-errors

bail if there are too many non-region infer vars in the query response

A minimal fix for the hang in nalgebra. If the query response would result in too many distinct non-region inference variables, simply overwrite the result with overflow. This should either happen if the result already has too many distinct type inference variables, or if evaluating the query encountered a lot of ambiguous associated types. In both cases it's straightforward to wait until the aliases are no longer ambiguous and then try again.

r? `@compiler-errors`
  • Loading branch information
rust-timer authored Sep 20, 2024
2 parents 5ba6db1 + a6aeba8 commit ebd9a0f
Show file tree
Hide file tree
Showing 5 changed files with 27 additions and 1 deletion.
11 changes: 11 additions & 0 deletions compiler/rustc_next_trait_solver/src/solve/eval_ctxt/canonical.rs
Original file line number Diff line number Diff line change
Expand Up @@ -157,6 +157,17 @@ 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,
}));
}

Ok(canonical)
}

Expand Down
2 changes: 2 additions & 0 deletions tests/ui/traits/coherence-alias-hang.rs
Original file line number Diff line number Diff line change
@@ -1,4 +1,6 @@
//@ check-pass
//@ revisions: current next
//[next]@ compile-flags: -Znext-solver

// Regression test for nalgebra hang <https://github.com/rust-lang/rust/issues/130056>.

Expand Down
Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,7 @@ error[E0275]: overflow evaluating the requirement `W<_>: Trait`
LL | impls::<W<_>>();
| ^^^^
|
= help: consider increasing the recursion limit by adding a `#![recursion_limit = "256"]` attribute to your crate (`fixpoint_exponential_growth`)
note: required by a bound in `impls`
--> $DIR/fixpoint-exponential-growth.rs:30:13
|
Expand Down
Original file line number Diff line number Diff line change
@@ -1,6 +1,7 @@
//~ ERROR overflow evaluating the requirement `Self: Trait`
//~^ ERROR overflow evaluating the requirement `Self well-formed`
// This is a non-regression test for issue #115351, where a recursion limit of 0 caused an ICE.
//@ compile-flags: -Znext-solver --crate-type=lib
//@ check-pass

#![recursion_limit = "0"]
trait Trait {}
Expand Down
Original file line number Diff line number Diff line change
@@ -0,0 +1,11 @@
error[E0275]: overflow evaluating the requirement `Self: Trait`
|
= help: consider increasing the recursion limit by adding a `#![recursion_limit = "2"]` attribute to your crate (`recursion_limit_zero_issue_115351`)

error[E0275]: overflow evaluating the requirement `Self well-formed`
|
= help: consider increasing the recursion limit by adding a `#![recursion_limit = "2"]` attribute to your crate (`recursion_limit_zero_issue_115351`)

error: aborting due to 2 previous errors

For more information about this error, try `rustc --explain E0275`.

0 comments on commit ebd9a0f

Please sign in to comment.