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]>

2 files changed, 7 insertions, 1 deletions

diff --git a/crates/ra_syntax/src/ast/generated.rs b/crates/ra_syntax/src/ast/generated.rs
index bcf753f78..d274b6fbc 100644
--- a/crates/ra_syntax/src/ast/generated.rs
+++ b/crates/ra_syntax/src/ast/generated.rs
@@ -2312,6 +2312,12 @@ impl PathSegment {
     pub fn type_arg_list(&self) -> Option<TypeArgList> {
         AstChildren::new(&self.syntax).next()
     }
+    pub fn param_list(&self) -> Option<ParamList> {
+        AstChildren::new(&self.syntax).next()
+    }
+    pub fn ret_type(&self) -> Option<RetType> {
+        AstChildren::new(&self.syntax).next()
+    }
 }
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
 pub struct PathType {
diff --git a/crates/ra_syntax/src/grammar.ron b/crates/ra_syntax/src/grammar.ron
index 3e6c2d3f3..993e58e64 100644
--- a/crates/ra_syntax/src/grammar.ron
+++ b/crates/ra_syntax/src/grammar.ron
@@ -684,7 +684,7 @@ Grammar(
             ]
         ),
         "PathSegment": (
-            options: [ "NameRef", "TypeArgList" ]
+            options: [ "NameRef", "TypeArgList", "ParamList", "RetType" ]
         ),
         "TypeArgList": (collections: [
             ("type_args", "TypeArg"),