[GHC] #15320: Save the types in the typechecked syntax tree

[GHC]

#15320: Save the types in the typechecked syntax tree
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           Reporter:  nboldi         |             Owner:  (none)
               Type:  feature        |            Status:  new
  request                            |
           Priority:  normal         |         Milestone:  8.6.1
          Component:  Compiler       |           Version:  8.4.3
           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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 When working on development tools that use the GHC API as a backend, it is
 useful to have information on the types (or kinds) of the elements of the
 syntax tree (expressions, patterns, types).

 I found that the lack of this semantic information is limiting in some
 cases of refactoring transformations (for example to generate the type
 signature or extract a subexpression to a binding with type signature),
 and is necessary for tools that try to fix common programmer errors. But
 there should be other kind of tools that this little change may help.

 The type is currently saved for some expressions and most patterns but it
 would be useful if it would be available uniformly.

 It could be implemented nicely by adding type information to the `X*
 GhcTc` type families.

 I plan to implement these changes, I'm just asking the opinion of the
 developers about a change in this direction.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15320>
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