Re: [GHC] #9581: Parse error in multiline case expression inside let inside do block

11 Sep 2014


      #9581: Parse error in multiline case expression inside let inside do block
-------------------------------------+-------------------------------------
              Reporter:  mpopov      |            Owner:
                  Type:  bug         |           Status:  closed
              Priority:  normal      |        Milestone:
             Component:  Compiler    |          Version:  7.8.3
            Resolution:  invalid     |         Keywords:
      Operating System:  Linux       |     Architecture:  Unknown/Multiple
       Type of failure:  GHC         |       Difficulty:  Unknown
  rejects valid program              |       Blocked By:
             Test Case:              |  Related Tickets:
              Blocking:              |
Differential Revisions:              |
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Changes (by rwbarton):

 * status:  new => closed
 * resolution:   => invalid


Comment:

 This program isn't valid. `let` introduces layout, so because line 3's
 first non-whitespace character is in the same column as the first non-
 whitespace character after the `let`, lines 2-4 desugar to
 {{{
 let { x = case 1 of {};
       0 -> False;
       _ -> True
     };
 }}}
 Lines 3 and 4 need to be indented by at least one more space for the
 intended meaning.

 (It may help to recall that
 {{{
 main = do
     let x = 1
         y = 2
     print x
 }}}
 is valid syntax.)

--
Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9581#comment:1
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