arrow analogs of lambda case and multi-way if

GHC has now support for lambda case and multi-way if (see ticket #4359 (closed)). It would be good if arrow variants of these features would be implemented. There are three things that should be considered:

Lambda case expressions should have analog proc expressions where

proc case pat_1 -> cmd_1
          ...
          pat_n -> cmd_n

desugars to

proc fresh -> case fresh of
                  pat_1 -> cmd_1
                  ...
                  pat_n -> cmd_n

Lambda case expressions should also have analog arrow commands where

\ case pat_1 -> cmd_1
       ...
       pat_n -> cmd_n

desugars to

\ fresh -> case fresh of
               pat_1 -> cmd_1
               ...
               pat_n -> cmd_n

Multi-way if expressions should have analog arrow commands where

if | cond_1 -> cmd_1
     ...
     cond_n -> cmd_n

desugars to

case () of
    _ | cond_1 -> cmd_1
      ...
      | cond_n -> cmd_n

Identifiers pat_i, cond_i, and cmd_i denote patterns, boolean expressions, and arrow commands, respectively.

Bug #7071 (closed) has to be fixed before starting with this ticket.

Trac metadata

Trac field	Value
Version	7.5
Type	FeatureRequest
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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