indexmap: add another previously-failing assert.

Author: Dirbaio

CHANGELOG.md

@@ -43,6 +43,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 ### Fixed
 
 - Fixed a `dropping_references` warning in `LinearMap`.
+- Fixed IndexMap entry API returning wrong slot after an insert on vacant entry. (#360)
 
 ### Removed
 

src/indexmap.rs

@@ -1469,7 +1469,7 @@ mod tests {
                     panic!("Entry found before insert");
                 }
                 Entry::Vacant(v) => {
-                    v.insert(i).unwrap();
+                    assert_eq!(i, *v.insert(i).unwrap());
                 }
             }
         }