[GHC] #14296: Add `Lift Exp` instance to `Language.Haskell.TH.Syntax`

[GHC]

#14296: Add `Lift Exp` instance to `Language.Haskell.TH.Syntax`
-------------------------------------+-------------------------------------
        Reporter:  heisenbug         |                Owner:  (none)
            Type:  feature request   |               Status:  closed
        Priority:  normal            |            Milestone:
       Component:  Template Haskell  |              Version:  8.2.1
      Resolution:  duplicate         |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Poor/confusing    |  Unknown/Multiple
  error message                      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #14030            |  Differential Rev(s):
       Wiki Page:                    |
-------------------------------------+-------------------------------------

Comment (by Ben Gamari <ben@…>):

 In [changeset:"626f0454ef1ca8f40c38064197dba97a36d52dbb/ghc" 626f045/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="626f0454ef1ca8f40c38064197dba97a36d52dbb"
 Document a law for TH's Lift class

 Inspired by the discussion in #14296, I've decided to
 document a law which is usually in the back of my mind when I'm using
 Template Haskell's `Lift` class, but isn't formally stated anywhere.
 That is, every `Lift` instance should satisfy (for all `x`):

 ```lang=haskell
 $(lift x) == x
 ```

 Test Plan: Read it

 Reviewers: austin, goldfire, bgamari

 Subscribers: rwbarton, thomie

 Differential Revision: https://phabricator.haskell.org/D4050
 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14296#comment:8>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler