Remove needless dedup from projection

Author: ishitatsuyuki

src/librustc/traits/project.rs

@@ -835,16 +835,6 @@ fn project_type<'cx, 'gcx, 'tcx>(
         return Err(ProjectionTyError::TooManyCandidates);
     }
 
-    // Drop duplicates.
-    //
-    // Note: `candidates.vec` seems to be on the critical path of the
-    // compiler. Replacing it with an HashSet was also tried, which would
-    // render the following dedup unnecessary. The original comment indicated
-    // that it was 9% slower, but that data is now obsolete and a new
-    // benchmark should be performed.
-    candidates.vec.sort_unstable();
-    candidates.vec.dedup();
-
     // Prefer where-clauses. As in select, if there are multiple
     // candidates, we prefer where-clause candidates over impls.  This
     // may seem a bit surprising, since impls are the source of