Merge #1786

1786: Various minor trait improvements r=matklad a=flodiebold

 - lower bounds on trait definition, i.e. super traits
 - use super traits for associated types
 - use traits from where clauses and their super traits for method resolution
 - lower fn-like paths (i.e. `Fn(X, Y) -> Z`)
 - pass the environment to Chalk in the correct way to make elaboration work, i.e. inferring things like `T: Clone` from `T: Copy`. The clauses need to be wrapped in `FromEnv` clauses for that to work, which I didn't do before.
 - add some tests for closure inference already

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

1 files changed, 7 insertions, 1 deletions

diff --git a/crates/ra_hir/src/ty/method_resolution.rs b/crates/ra_hir/src/ty/method_resolution.rs
index 9873a0440..cf787bdaa 100644
--- a/crates/ra_hir/src/ty/method_resolution.rs
+++ b/crates/ra_hir/src/ty/method_resolution.rs
@@ -212,7 +212,13 @@ fn iterate_trait_method_candidates<T>(
     // FIXME: maybe put the trait_env behind a query (need to figure out good input parameters for that)
     let env = lower::trait_env(db, resolver);
     // if ty is `impl Trait` or `dyn Trait`, the trait doesn't need to be in scope
-    let traits = ty.value.inherent_trait().into_iter().chain(resolver.traits_in_scope(db));
+    let inherent_trait = ty.value.inherent_trait().into_iter();
+    // if we have `T: Trait` in the param env, the trait doesn't need to be in scope
+    let traits_from_env = env
+        .trait_predicates_for_self_ty(&ty.value)
+        .map(|tr| tr.trait_)
+        .flat_map(|t| t.all_super_traits(db));
+    let traits = inherent_trait.chain(traits_from_env).chain(resolver.traits_in_scope(db));
     'traits: for t in traits {
         let data = t.trait_data(db);