Merge #8133

8133: Ignore type bindings in generic_predicates_for_param (fix panic on ena and crates depending on it) r=flodiebold a=flodiebold

This allows us to handle more cases without a query cycle, which includes certain cases that rustc accepted. That in turn means we avoid triggering salsa-rs/salsa#257 on valid code (it will still happen if the user writes an actual cycle).

We actually accept more definitions than rustc now; that's because rustc only ignores bindings when looking up super traits, whereas we now also ignore them when looking for predicates to disambiguate associated type shorthand. We could introduce a separate query for super traits if necessary, but for now I think this should be fine.

Co-authored-by: Florian Diebold <[email protected]>

1 files changed, 15 insertions, 2 deletions

diff --git a/crates/hir_ty/src/lib.rs b/crates/hir_ty/src/lib.rs
index c46529879..ad908f957 100644
--- a/crates/hir_ty/src/lib.rs
+++ b/crates/hir_ty/src/lib.rs
@@ -106,6 +106,10 @@ impl ProjectionTy {
         }
     }
 
+    pub fn self_type_parameter(&self) -> &Ty {
+        &self.substitution[0]
+    }
+
     fn trait_(&self, db: &dyn HirDatabase) -> TraitId {
         match from_assoc_type_id(self.associated_ty_id).lookup(db.upcast()).container {
             AssocContainerId::TraitId(it) => it,
@@ -936,10 +940,19 @@ impl Ty {
                 let param_data = &generic_params.types[id.local_id];
                 match param_data.provenance {
                     hir_def::generics::TypeParamProvenance::ArgumentImplTrait => {
+                        let substs = Substitution::type_params(db, id.parent);
                         let predicates = db
-                            .generic_predicates_for_param(id)
+                            .generic_predicates(id.parent)
                             .into_iter()
-                            .map(|pred| pred.value.clone())
+                            .map(|pred| pred.clone().subst(&substs))
+                            .filter(|wc| match &wc {
+                                WhereClause::Implemented(tr) => tr.self_type_parameter() == self,
+                                WhereClause::AliasEq(AliasEq {
+                                    alias: AliasTy::Projection(proj),
+                                    ty: _,
+                                }) => proj.self_type_parameter() == self,
+                                _ => false,
+                            })
                             .collect_vec();
 
                         Some(predicates)