debug print reasons more verbosely

Summary:
^

We need this to match up with oxidized's debug printing for validating that the DDP port to oxidized doesn't change anything

Reviewed By: andrewjkennedy

Differential Revision: D68492271

fbshipit-source-id: a23514155dc1285cbef6313d045f25cd225c6424

Author: Scott Owens

hphp/hack/src/oxidized_by_ref/manual/typing_reason_impl.rs

@@ -156,7 +156,7 @@ impl<'a> std::fmt::Debug for T_<'a> {
             NoReason => f.debug_tuple("Rnone").finish(),
             MissingField => f.debug_tuple("RmissingField").finish(),
             FromWitnessLocl(witness) => witness.fmt(f),
-            FromWitnessDecl(witness) => witness.fmt(f),
+            FromWitnessDecl(witness) => f.debug_tuple("FromWitnessDecl").field(witness).finish(),
             Idx((p, t)) => f.debug_tuple("Ridx").field(p).field(t).finish(),
             ArithRetFloat((p, t, ap)) => f
                 .debug_tuple("RarithRetFloat")