[GHC] #14588: GHC 8.2.1 allows bang patterns in let-bindings without -XBangPatterns

[GHC]

#14588: GHC 8.2.1 allows bang patterns in let-bindings without -XBangPatterns
-------------------------------------+-------------------------------------
           Reporter:  kmiyazato      |             Owner:  (none)
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Compiler       |           Version:  8.2.1
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  GHC accepts
  Unknown/Multiple                   |  invalid program
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
-------------------------------------+-------------------------------------
 Bang patterns occurring in let-bindings are allowed even if -XBangPatterns
 extension is not enabled.

 {{{#!hs
 -- Compile error in 8.0.2
 -- Compiles in 8.2.1 and 8.2.2
 main = print (let !x = 1 + 2 in x)
 }}}

 {{{#!hs
 -- Compile error in all of 8.0.2, 8.2.1, and 8.2.2
 main = print (let f !x !y = x + y in f 1 2)
 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14588>
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