• Alan Zimmerman's avatar
    Refactor ConDecl · 51a5e68d
    Alan Zimmerman authored
    The ConDecl type in HsDecls is an uneasy compromise. For the most part,
    HsSyn directly reflects the syntax written by the programmer; and that
    gives just the right "pegs" on which to hang Alan's API annotations. But
    ConDecl doesn't properly reflect the syntax of Haskell-98 and GADT-style
    data type declarations.
    
    To be concrete, here's a draft new data type
    
    ```lang=hs
    data ConDecl name
      | ConDeclGADT
          { con_names   :: [Located name]
          , con_type    :: LHsSigType name  -- The type after the ‘::’
          , con_doc     :: Maybe LHsDocString }
    
      | ConDeclH98
          { con_name    :: Located name
    
          , con_qvars     :: Maybe (LHsQTyVars name)
            -- User-written forall (if any), and its implicit
            -- kind variables
            -- Non-Nothing needs -XExistentialQuantification
    
          , con_cxt       :: Maybe (LHsContext name)
            -- ^ User-written context (if any)
    
          , con_details   :: HsConDeclDetails name
              -- ^ Arguments
    
          , con_doc       :: Maybe LHsDocString
              -- ^ A possible Haddock comment.
          } deriving (Typeable)
    ```
    
    Note that
    
        For GADTs, just keep a type. That's what the user writes.
        NB:HsType can represent records on the LHS of an arrow:
    
          { x:Int,y:Bool} -> T
    
        con_qvars and con_cxt are both Maybe because they are both
        optional (the forall and the context of an existential data type
    
        For ConDeclGADT the type variables of the data type do not scope
        over the con_type; whereas for ConDeclH98 they do scope over con_cxt
        and con_details.
    
    Updates haddock submodule.
    
    Test Plan: ./validate
    
    Reviewers: simonpj, erikd, hvr, goldfire, austin, bgamari
    
    Subscribers: erikd, goldfire, thomie, mpickering
    
    Differential Revision: https://phabricator.haskell.org/D1558
    
    GHC Trac Issues: #11028
    51a5e68d
HsTypes.hs 45.1 KB