implement transitive relation type that can compute transitive

closures, upper bounds, and other fun things

Author: nikomatsakis

src/librustc_data_structures/lib.rs

@@ -37,6 +37,7 @@ pub mod bitvec;
 pub mod graph;
 pub mod ivar;
 pub mod snapshot_vec;
+pub mod transitive_relation;
 pub mod unify;
 
 // See comments in src/librustc/lib.rs