fix: inline predicate_may_hold_fatal

Author: bvanjoi

compiler/rustc_trait_selection/src/traits/coherence.rs

@@ -292,7 +292,12 @@ fn impl_intersection_has_impossible_obligation<'cx, 'tcx>(
             Obligation::new(infcx.tcx, ObligationCause::dummy(), param_env, predicate)
         })
         .chain(obligations)
-        .find(|o| !selcx.predicate_may_hold_fatal(o));
+        .find(|o| {
+            selcx.evaluate_root_obligation(o).map_or(
+                false, // Overflow has occurred, and treat the obligation as possibly holding.
+                |result| !result.may_apply(),
+            )
+        });
 
     if let Some(failing_obligation) = opt_failing_obligation {
         debug!("overlap: obligation unsatisfiable {:?}", failing_obligation);

compiler/rustc_trait_selection/src/traits/select/mod.rs

@@ -518,19 +518,6 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
     // The result is "true" if the obligation *may* hold and "false" if
     // we can be sure it does not.
 
-    /// Evaluates whether the obligation `obligation` can be satisfied (by any means).
-    pub fn predicate_may_hold_fatal(&mut self, obligation: &PredicateObligation<'tcx>) -> bool {
-        debug!(?obligation, "predicate_may_hold_fatal");
-
-        // This fatal query is a stopgap that should only be used in standard mode,
-        // where we do not expect overflow to be propagated.
-        assert!(self.query_mode == TraitQueryMode::Standard);
-
-        self.evaluate_root_obligation(obligation)
-            .expect("Overflow should be caught earlier in standard query mode")
-            .may_apply()
-    }
-
     /// Evaluates whether the obligation `obligation` can be satisfied
     /// and returns an `EvaluationResult`. This is meant for the
     /// *initial* call.

tests/ui/traits/issue-105231.rs

@@ -0,0 +1,9 @@
+//~ ERROR overflow evaluating the requirement `A<A<A<A<A<A<A<...>>>>>>>: Send`
+struct A<T>(B<T>);
+//~^ ERROR recursive types `A` and `B` have infinite size
+struct B<T>(A<A<T>>);
+trait Foo {}
+impl<T> Foo for T where T: Send {}
+impl Foo for B<u8> {}
+
+fn main() {}

tests/ui/traits/issue-105231.stderr

@@ -0,0 +1,29 @@
+error[E0072]: recursive types `A` and `B` have infinite size
+  --> $DIR/issue-105231.rs:2:1
+   |
+LL | struct A<T>(B<T>);
+   | ^^^^^^^^^^^ ---- recursive without indirection
+LL |
+LL | struct B<T>(A<A<T>>);
+   | ^^^^^^^^^^^ ------- recursive without indirection
+   |
+help: insert some indirection (e.g., a `Box`, `Rc`, or `&`) to break the cycle
+   |
+LL ~ struct A<T>(Box<B<T>>);
+LL |
+LL ~ struct B<T>(Box<A<A<T>>>);
+   |
+
+error[E0275]: overflow evaluating the requirement `A<A<A<A<A<A<A<...>>>>>>>: Send`
+   |
+   = help: consider increasing the recursion limit by adding a `#![recursion_limit = "256"]` attribute to your crate (`issue_105231`)
+note: required because it appears within the type `B<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<u8>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>`
+  --> $DIR/issue-105231.rs:4:8
+   |
+LL | struct B<T>(A<A<T>>);
+   |        ^
+
+error: aborting due to 2 previous errors
+
+Some errors have detailed explanations: E0072, E0275.
+For more information about an error, try `rustc --explain E0072`.