Store renamings as (ModuleName, ModuleName) pairs.

Authored by ezyang.

Description

Store renamings as (ModuleName, ModuleName) pairs.

Summary: Signed-off-by: Edward Z. Yang <ezyang@cs.stanford.edu>

Test Plan: validate

Reviewers: austin, simonpj

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D710

Details