[GHC] #14659: assertions are turned off if -O2 comes after -fno-ignore-asserts

[GHC]

#14659: assertions are turned off if -O2 comes after -fno-ignore-asserts
-------------------------------------+-------------------------------------
           Reporter:  mwotton        |             Owner:  (none)
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Compiler       |           Version:  8.2.2
           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:
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 test.hs:

 {{{#!hs
 import Control.Exception

 main = assert False (return ())
 }}}

 ➜  ~ rm test; rm test.o; stack ghc -- -fno-ignore-asserts -O2 test.hs;
 ./test && echo $?
 [1 of 1] Compiling Main             ( test.hs, test.o )
 Linking test ...
 0
 ➜  ~ rm test; rm test.o; stack ghc -- -O2 -fno-ignore-asserts  test.hs;
 ./test && echo $?
 [1 of 1] Compiling Main             ( test.hs, test.o )
 Linking test ...
 test: Assertion failed
 CallStack (from HasCallStack):
   assert, called at test.hs:3:8 in main:Main
 ```

 tested with ghc 8.0.2 and 8.2.2.

 would have expected -fno-ignore-asserts to override -O2, no matter where
 it is in the options list.
 https://twitter.com/AlecMuffett/status/950699975767482370 shows how
 dangerous this could be.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14659>
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