Merge #1515

1515: Trait environment r=matklad a=flodiebold

This adds the environment, i.e. the set of `where` clauses in scope, when solving trait goals. That means that e.g. in
```rust
fn foo<T: SomeTrait>(t: T) {}
```
, we are able to complete methods of `SomeTrait` on the `t`. This affects the trait APIs quite a bit (since every method that needs to be able to solve for some trait needs to get this environment somehow), so I thought I'd do it rather sooner than later ;)

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

1 files changed, 12 insertions, 0 deletions

diff --git a/crates/ra_hir/src/ty/lower.rs b/crates/ra_hir/src/ty/lower.rs
index b48ada760..ca47d6e96 100644
--- a/crates/ra_hir/src/ty/lower.rs
+++ b/crates/ra_hir/src/ty/lower.rs
@@ -317,6 +317,18 @@ pub(crate) fn type_for_field(db: &impl HirDatabase, field: StructField) -> Ty {
     Ty::from_hir(db, &resolver, type_ref)
 }
 
+pub(crate) fn trait_env(db: &impl HirDatabase, resolver: &Resolver) -> Arc<super::Environment> {
+    let predicates = resolver
+        .where_predicates_in_scope()
+        .map(|pred| {
+            TraitRef::for_where_predicate(db, &resolver, pred)
+                .map_or(GenericPredicate::Error, GenericPredicate::Implemented)
+        })
+        .collect::<Vec<_>>();
+
+    Arc::new(super::Environment { predicates })
+}
+
 /// Resolve the where clause(s) of an item with generics.
 pub(crate) fn generic_predicates_query(
     db: &impl HirDatabase,