Add type outlives constraints to fhir

crates/flux-fhir-analysis/src/conv.rs

@@ -409,6 +409,16 @@ impl<'a, 'genv, 'tcx> ConvCtxt<'a, 'genv, 'tcx> {
                         )?;
                     }
                 }
+                fhir::GenericBound::Outlives(lft) => {
+                    let re = self.conv_lifetime(env, *lft);
+                    clauses.push(rty::Clause::new(
+                        List::empty(),
+                        rty::ClauseKind::TypeOutlives(rty::OutlivesPredicate(
+                            bounded_ty.clone(),
+                            re,
+                        )),
+                    ));
+                }
                 // Maybe bounds are only supported for `?Sized`. The effect of the maybe bound is to
                 // relax the default which is `Sized` to not have the `Sized` bound, so we just skip
                 // it here.

crates/flux-middle/src/fhir.rs

@@ -309,6 +309,7 @@ pub type GenericBounds<'fhir> = &'fhir [GenericBound<'fhir>];
 #[derive(Debug, Clone, Copy)]
 pub enum GenericBound<'fhir> {
     Trait(PolyTraitRef<'fhir>, TraitBoundModifier),
+    Outlives(Lifetime),
 }
 
 #[derive(Debug, Clone, Copy)]

crates/flux-middle/src/fhir/lift.rs

@@ -212,6 +212,10 @@ impl<'a, 'genv, 'tcx> LiftCtxt<'a, 'genv, 'tcx> {
                     fhir::TraitBoundModifier::Maybe,
                 ))
             }
+            hir::GenericBound::Outlives(lft) => {
+                let lft = self.lift_lifetime(lft)?;
+                Ok(fhir::GenericBound::Outlives(lft))
+            }
             _ => self.emit_unsupported(&format!("unsupported generic bound: `{bound:?}`")),
         }
     }

crates/flux-middle/src/fhir/visit.rs

@@ -230,6 +230,7 @@ pub fn walk_opaque_ty<'v, V: Visitor<'v>>(vis: &mut V, opaque_ty: &OpaqueTy<'v>)
 pub fn walk_generic_bound<'v, V: Visitor<'v>>(vis: &mut V, bound: &GenericBound<'v>) {
     match bound {
         GenericBound::Trait(trait_ref, _) => vis.visit_poly_trait_ref(trait_ref),
+        GenericBound::Outlives(_) => {}
     }
 }
 

tests/tests/pos/surface/type-outlives.rs

@@ -0,0 +1,4 @@
+struct S<'a, T: 'a> {
+    x: T,
+    y: &'a i32,
+}