Add HIR Expr machinery

crates/ra_hir/src/path.rs

@@ -65,6 +65,14 @@ impl Path {
         }
     }
 
+    /// Converts an `ast::NameRef` into a single-identifier `Path`.
+    pub fn from_name_ref(name_ref: ast::NameRef) -> Path {
+        Path {
+            kind: PathKind::Plain,
+            segments: vec![name_ref.as_name()],
+        }
+    }
+
     /// `true` is this path is a single identifier, like `foo`
     pub fn is_ident(&self) -> bool {
         self.kind == PathKind::Plain && self.segments.len() == 1