[GHC] #11270: "Unusable UNPACK pragma" warnings should be printed even without -O

[GHC]

#11270: "Unusable UNPACK pragma" warnings should be printed even without -O
-------------------------------------+-------------------------------------
           Reporter:  osa1           |             Owner:
               Type:  feature        |            Status:  new
  request                            |
           Priority:  normal         |         Milestone:
          Component:  Compiler       |           Version:  7.11
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
-------------------------------------+-------------------------------------
 UNPACK pragmas are ignored when -O is not used, and this is very annoying
 when developing inside GHCi. Example:

 {{{
 ➜  unpack_warning  ghc-stage2 Main.hs -Wall -fforce-recomp --make
 [1 of 1] Compiling Main             ( Main.hs, Main.o )
 Linking Main ...
 }}}

 No warning printed even though I used {{{-Wall}}}. If I add {{{-O}}}:

 {{{
 ➜  unpack_warning  ghc-stage2 Main.hs -Wall -fforce-recomp --make -O
 [1 of 1] Compiling Main             ( Main.hs, Main.o )

 Main.hs:5:13: warning:
     • Ignoring unusable UNPACK pragma on the first argument of ‘Blah’
     • In the definition of data constructor ‘Blah’
       In the data type declaration for ‘Blah’
 Linking Main ...
 }}}

 This is very annoying, because {{{-O}}} is ignored in GHCi:

 {{{
 ➜  unpack_warning  ghc-stage2 Main.hs -Wall -fforce-recomp  -O
 --interactive

 when making flags consistent: warning:
     -O conflicts with --interactive; -O ignored.
 GHCi, version 7.11.20151220: http://www.haskell.org/ghc/  :? for help
 [1 of 1] Compiling Main             ( Main.hs, interpreted )
 Ok, modules loaded: Main.
 }}}

 So basically there's no way to get these warning in GHCi.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11270>
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