Merge #1266

1266: Chalk integration / method resolution fixes r=matklad a=flodiebold

 - fix impl blocks with unresolved target trait being treated as inherent impls
 - add traits from prelude for method resolution, and deduplicate them
 - blacklist some traits from being considered in where clauses, namely `Send`, `Sync`, `Sized`, and the `Fn` traits. We don't handle these correctly yet for several reasons, and this makes us much less likely to run into cases where Chalk gets very slow (because these usually only happen if there is no solution, and that's more likely to happen for these traits).
 - when there's an errored where clause, return just that one (since it will be always false anyway). This also makes things easier on Chalk ;)

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

1 files changed, 28 insertions, 1 deletions

diff --git a/crates/ra_hir/src/ty/traits/chalk.rs b/crates/ra_hir/src/ty/traits/chalk.rs
index 027c5ec4c..78440b258 100644
--- a/crates/ra_hir/src/ty/traits/chalk.rs
+++ b/crates/ra_hir/src/ty/traits/chalk.rs
@@ -190,6 +190,14 @@ fn make_binders<T>(value: T, num_vars: usize) -> chalk_ir::Binders<T> {
     }
 }
 
+fn blacklisted_trait(db: &impl HirDatabase, trait_: Trait) -> bool {
+    let name = trait_.name(db).unwrap_or_else(crate::Name::missing).to_string();
+    match &*name {
+        "Send" | "Sync" | "Sized" | "Fn" | "FnMut" | "FnOnce" => true,
+        _ => false,
+    }
+}
+
 fn convert_where_clauses(
     db: &impl HirDatabase,
     def: GenericDef,
@@ -198,6 +206,19 @@ fn convert_where_clauses(
     let generic_predicates = db.generic_predicates(def);
     let mut result = Vec::with_capacity(generic_predicates.len());
     for pred in generic_predicates.iter() {
+        if pred.is_error() {
+            // HACK: Return just the single predicate (which is always false
+            // anyway), otherwise Chalk can easily get into slow situations
+            return vec![pred.clone().subst(substs).to_chalk(db)];
+        }
+        match pred {
+            GenericPredicate::Implemented(trait_ref) => {
+                if blacklisted_trait(db, trait_ref.trait_) {
+                    continue;
+                }
+            }
+            _ => {}
+        }
         result.push(pred.clone().subst(substs).to_chalk(db));
     }
     result
@@ -230,6 +251,7 @@ where
             return Arc::new(TraitDatum { binders: make_binders(trait_datum_bound, 1) });
         }
         let trait_: Trait = from_chalk(self.db, trait_id);
+        debug!("trait {:?} = {:?}", trait_id, trait_.name(self.db));
         let generic_params = trait_.generic_params(self.db);
         let bound_vars = Substs::bound_vars(&generic_params);
         let trait_ref = trait_.trait_ref(self.db).subst(&bound_vars).to_chalk(self.db);
@@ -250,6 +272,7 @@ where
     fn struct_datum(&self, struct_id: chalk_ir::StructId) -> Arc<StructDatum> {
         debug!("struct_datum {:?}", struct_id);
         let type_ctor = from_chalk(self.db, struct_id);
+        debug!("struct {:?} = {:?}", struct_id, type_ctor);
         // FIXME might be nicer if we can create a fake GenericParams for the TypeCtor
         // FIXME extract this to a method on Ty
         let (num_params, where_clauses, upstream) = match type_ctor {
@@ -358,7 +381,11 @@ where
         if trait_id == UNKNOWN_TRAIT {
             return Vec::new();
         }
-        let trait_ = from_chalk(self.db, trait_id);
+        let trait_: Trait = from_chalk(self.db, trait_id);
+        let blacklisted = blacklisted_trait(self.db, trait_);
+        if blacklisted {
+            return Vec::new();
+        }
         let result: Vec<_> = self
             .db
             .impls_for_trait(self.krate, trait_)