GHC.SYB.Utils

GHC.Syb.Utils provides common utilities for the Ghc Api, either based on Data/Typeable or for use with Data.Generics over Ghc Api types.

example output of showData on parsedSource, renamedSource, and typecheckedSource for a trivial HelloWorld module, compared with ppr output:

------------------------- pretty-printed parsedSource
module HelloWorld where
main = putStrLn "Hello, World!"
------------------------- pretty-printed renamedSource
Just (HelloWorld.main = System.IO.putStrLn "Hello, World!",
      [import Prelude],
      Nothing,
      Nothing,

(HaddockModInfo
 (Nothing)
 (Nothing)
 (Nothing)
 (Nothing)))
------------------------- pretty-printed typecheckedSource
Just <AbsBinds [] [] [HelloWorld.main <= [] main]
        HelloWorld.main :: GHC.IOBase.IO ()
        []
        { main = System.IO.putStrLn "Hello, World!" }>
------------------------- shown parsedSource

(L {HelloWorld.hs:1:0}
 (HsModule
  (Just
   (L {HelloWorld.hs:1:7-16} {ModuleName: HelloWorld}))
  (Nothing)
  []
  [
   (L {HelloWorld.hs:2:0-30}
    (ValD
     (FunBind
      (L {HelloWorld.hs:2:0-3}
       (Unqual {OccName: main}))
      (False)
      (MatchGroup
       [
        (L {HelloWorld.hs:2:0-30}
         (Match
          []
          (Nothing)
          (GRHSs
           [
            (L {HelloWorld.hs:2:7-30}
             (GRHS
              []
              (L {HelloWorld.hs:2:7-30}
               (HsApp
                (L {HelloWorld.hs:2:7-14}
                 (HsVar
                  (Unqual {OccName: putStrLn})))
                (L {HelloWorld.hs:2:16-30}
                 (HsLit
                  (HsString {FastString: "Hello, World!"})))))))]
           (EmptyLocalBinds))))] {!type placeholder here?!})
      (WpHole) {!NameSet placeholder here!}
      (Nothing))))]
  (Nothing)
  (HaddockModInfo
   (Nothing)
   (Nothing)
   (Nothing)
   (Nothing))
  (Nothing)))
------------------------- shown renamedSource

((,,,,)
 (HsGroup
  (ValBindsOut
   [
    ((,)
     (NonRecursive) {Bag(Located (HsBind Name)):
     [
      (L {HelloWorld.hs:2:0-30}
       (FunBind
        (L {HelloWorld.hs:2:0-3} {Name: HelloWorld.main})
        (False)
        (MatchGroup
         [
          (L {HelloWorld.hs:2:0-30}
           (Match
            []
            (Nothing)
            (GRHSs
             [
              (L {HelloWorld.hs:2:7-30}
               (GRHS
                []
                (L {HelloWorld.hs:2:7-30}
                 (HsApp
                  (L {HelloWorld.hs:2:7-14}
                   (HsVar {Name: System.IO.putStrLn}))
                  (L {HelloWorld.hs:2:16-30}
                   (HsLit
                    (HsString {FastString: "Hello, World!"})))))))]
             (EmptyLocalBinds))))] {!type placeholder here?!})
        (WpHole) {NameSet:
        [{Name: System.IO.putStrLn}]}
        (Nothing)))]})]
   [])
  []
  []
  []
  []
  []
  []
  []
  []
  [])
 [
  (L {Implicit import declaration}
   (ImportDecl
    (L {Implicit import declaration} {ModuleName: Prelude})
    (False)
    (False)
    (Nothing)
    (Nothing)))]
 (Nothing)
 (Nothing)
 (HaddockModInfo
  (Nothing)
  (Nothing)
  (Nothing)
  (Nothing)))
------------------------- shown typecheckedSource
{Bag(Located (HsBind Var)):
[
 (L {HelloWorld.hs:2:0-30}
  (AbsBinds
   []
   []
   [
    ((,,,)
     [] {Var: HelloWorld.main} {Var: main}
     [])] {Bag(Located (HsBind Var)):
   [
    (L {HelloWorld.hs:2:0-30}
     (FunBind
      (L {HelloWorld.hs:2:0-3} {Var: main})
      (False)
      (MatchGroup
       [
        (L {HelloWorld.hs:2:0-30}
         (Match
          []
          (Nothing)
          (GRHSs
           [
            (L {HelloWorld.hs:2:7-30}
             (GRHS
              []
              (L {HelloWorld.hs:2:7-30}
               (HsApp
                (L {HelloWorld.hs:2:7-14}
                 (HsVar {Var: System.IO.putStrLn}))
                (L {HelloWorld.hs:2:16-30}
                 (HsLit
                  (HsString {FastString: "Hello, World!"})))))))]
           (EmptyLocalBinds))))] GHC.IOBase.IO ())
      (WpHole) {!NameSet placeholder here!}
      (Nothing)))]}))]}

Documentation

nameSetElems :: NameSet -> [Name]

showSDoc_ :: SDoc -> String

data Stage

Ghc Ast types tend to have undefined holes, to be filled by later compiler phases. We tag Asts with their source, so that we can avoid such holes based on who generated the Asts.

Constructors

Parser

Renamer

TypeChecker

Instances

Eq Stage

Ord Stage

Show Stage

showData :: Data a => Stage -> Int -> a -> String

Generic Data-based show, with special cases for GHC Ast types, and simplistic indentation-based layout (the Int parameter); showing abstract types abstractly and avoiding known potholes (based on the Stage that generated the Ast)

everythingStaged :: Stage -> (r -> r -> r) -> r -> GenericQ r -> GenericQ r

Like everything, but avoid known potholes, based on the Stage that generated the Ast.

everythingButStaged :: Stage -> (r -> r -> r) -> r -> GenericQ (r, Bool) -> GenericQ r

A variation of everything, using a 'GenericQ Bool' to skip parts of the input Data. everythingBut :: GenericQ Bool -> (r -> r -> r) -> r -> GenericQ r -> GenericQ r everythingBut q k z f x | q x = z | otherwise = foldl k (f x) (gmapQ (everythingBut q k z f) x)

somethingStaged :: Stage -> Maybe u -> GenericQ (Maybe u) -> GenericQ (Maybe u)

Look up a subterm by means of a maybe-typed filter.

somewhereStaged :: MonadPlus m => Stage -> GenericM m -> GenericM m

Apply a monadic transformation at least somewhere.

The transformation is tried in a top-down manner and descends down if it fails to apply at the root of the term. If the transformation fails to apply anywhere within the the term, the whole operation fails.

everywhereMStaged :: Monad m => Stage -> GenericM m -> GenericM m

Monadic variation on everywhere