GHC-NOTES

Parse tree of

-------------------------------------
module B where
-- Test for refactor of if to case

foo x = if (odd x) then "Odd" else "Even"

foo' x = case (odd x) of
  True -> "Odd"
  False -> "Even"

main = do
  putStrLn $ show $ foo 5

mary = [1,2,3]
------------------------------------
getStuff
tokens=[
(RealSrcSpan (SrcSpanOneLine {srcSpanFile = "./B.hs", srcSpanLine = 1, srcSpanSCol = 1, srcSpanECol = 7}),"module"),
(RealSrcSpan (SrcSpanOneLine {srcSpanFile = "./B.hs", srcSpanLine = 1, srcSpanSCol = 8, srcSpanECol = 9}),"B"),
(RealSrcSpan (SrcSpanOneLine {srcSpanFile = "./B.hs", srcSpanLine = 1, srcSpanSCol = 10, srcSpanECol = 15}),"where"),
(RealSrcSpan (SrcSpanOneLine {srcSpanFile = "./B.hs", srcSpanLine = 2, srcSpanSCol = 1, srcSpanECol = 35}),"-- Test for refactor of if to case"),
(RealSrcSpan (SrcSpanPoint {srcSpanFile = "./B.hs", srcSpanLine = 4, srcSpanCol = 1}),""),
(RealSrcSpan (SrcSpanOneLine {srcSpanFile = "./B.hs", srcSpanLine = 4, srcSpanSCol = 1, srcSpanECol = 4}),"foo"),
(RealSrcSpan (SrcSpanOneLine {srcSpanFile = "./B.hs", srcSpanLine = 4, srcSpanSCol = 5, srcSpanECol = 6}),"x"),
(RealSrcSpan (SrcSpanOneLine {srcSpanFile = "./B.hs", srcSpanLine = 4, srcSpanSCol = 7, srcSpanECol = 8}),"="),
(RealSrcSpan (SrcSpanOneLine {srcSpanFile = "./B.hs", srcSpanLine = 4, srcSpanSCol = 9, srcSpanECol = 11}),"if"),
(RealSrcSpan (SrcSpanOneLine {srcSpanFile = "./B.hs", srcSpanLine = 4, srcSpanSCol = 12, srcSpanECol = 13}),"("),
(RealSrcSpan (SrcSpanOneLine {srcSpanFile = "./B.hs", srcSpanLine = 4, srcSpanSCol = 13, srcSpanECol = 16}),"odd"),
(RealSrcSpan (SrcSpanOneLine {srcSpanFile = "./B.hs", srcSpanLine = 4, srcSpanSCol = 17, srcSpanECol = 18}),"x"),
(RealSrcSpan (SrcSpanOneLine {srcSpanFile = "./B.hs", srcSpanLine = 4, srcSpanSCol = 18, srcSpanECol = 19}),")"),
(RealSrcSpan (SrcSpanOneLine {srcSpanFile = "./B.hs", srcSpanLine = 4, srcSpanSCol = 20, srcSpanECol = 24}),"then"),
(RealSrcSpan (SrcSpanOneLine {srcSpanFile = "./B.hs", srcSpanLine = 4, srcSpanSCol = 25, srcSpanECol = 30}),"\"Odd\""),
(RealSrcSpan (SrcSpanOneLine {srcSpanFile = "./B.hs", srcSpanLine = 4, srcSpanSCol = 31, srcSpanECol = 35}),"else"),
(RealSrcSpan (SrcSpanOneLine {srcSpanFile = "./B.hs", srcSpanLine = 4, srcSpanSCol = 36, srcSpanECol = 42}),"\"Even\""),
(RealSrcSpan (SrcSpanPoint {srcSpanFile = "./B.hs", srcSpanLine = 6, srcSpanCol = 1}),""),
(RealSrcSpan (SrcSpanOneLine {srcSpanFile = "./B.hs", srcSpanLine = 6, srcSpanSCol = 1, srcSpanECol = 5}),"foo'"),
(RealSrcSpan (SrcSpanOneLine {srcSpanFile = "./B.hs", srcSpanLine = 6, srcSpanSCol = 6, srcSpanECol = 7}),"x"),
(RealSrcSpan (SrcSpanOneLine {srcSpanFile = "./B.hs", srcSpanLine = 6, srcSpanSCol = 8, srcSpanECol = 9}),"="),
(RealSrcSpan (SrcSpanOneLine {srcSpanFile = "./B.hs", srcSpanLine = 6, srcSpanSCol = 10, srcSpanECol = 14}),"case"),
(RealSrcSpan (SrcSpanOneLine {srcSpanFile = "./B.hs", srcSpanLine = 6, srcSpanSCol = 15, srcSpanECol = 16}),"("),
...
-------------------------------------

(L {B.hs:1:1} 
 (HsModule 
  (Just 
   (L {B.hs:1:8} {ModuleName: B})) 
  (Nothing) 
  [] 
  [
   (L {B.hs:4:1-41} 
    (ValD 
     (FunBind 
      (L {B.hs:4:1-3} 
       (Unqual {OccName: foo})) 
      (False) 
      (MatchGroup 
       [
        (L {B.hs:4:1-41} 
         (Match 
          [
           (L {B.hs:4:5} 
            (VarPat 
             (Unqual {OccName: x})))] 
          (Nothing) 
          (GRHSs 
           [
            (L {B.hs:4:9-41} 
             (GRHS 
              [] 
              (L {B.hs:4:9-41} 
               (HsIf 
                (Just 
                 (HsLit 
                  (HsString {FastString: "noSyntaxExpr"}))) 
                (L {B.hs:4:12-18} 
                 (HsPar 
                  (L {B.hs:4:13-17} 
                   (HsApp 
                    (L {B.hs:4:13-15} 
                     (HsVar 
                      (Unqual {OccName: odd}))) 
                    (L {B.hs:4:17} 
                     (HsVar 
                      (Unqual {OccName: x}))))))) 
                (L {B.hs:4:25-29} 
                 (HsLit 
                  (HsString {FastString: "Odd"}))) 
                (L {B.hs:4:36-41} 
                 (HsLit 
                  (HsString {FastString: "Even"})))))))] 
           (EmptyLocalBinds))))] {!type placeholder here?!}) 
      (WpHole) {!NameSet placeholder here!} 
      (Nothing)))),
   (L {B.hs:(6,1)-(8,17)} 
    (ValD 
     (FunBind 
      (L {B.hs:6:1-4} 
       (Unqual {OccName: foo'})) 
      (False) 
      (MatchGroup 
       [
        (L {B.hs:(6,1)-(8,17)} 
         (Match 
          [
           (L {B.hs:6:6} 
            (VarPat 
             (Unqual {OccName: x})))] 
          (Nothing) 
          (GRHSs 
           [
            (L {B.hs:(6,10)-(8,17)} 
             (GRHS 
              [] 
              (L {B.hs:(6,10)-(8,17)} 
               (HsCase 
                (L {B.hs:6:15-21} 
                 (HsPar 
                  (L {B.hs:6:16-20} 
                   (HsApp 
                    (L {B.hs:6:16-18} 
                     (HsVar 
                      (Unqual {OccName: odd}))) 
                    (L {B.hs:6:20} 
                     (HsVar 
                      (Unqual {OccName: x}))))))) 
                (MatchGroup 
                 [
                  (L {B.hs:7:3-15} 
                   (Match 
                    [
                     (L {B.hs:7:3-6} 
                      (ConPatIn 
                       (L {B.hs:7:3-6} 
                        (Unqual {OccName: True})) 
                       (PrefixCon 
                        [])))] 
                    (Nothing) 
                    (GRHSs 
                     [
                      (L {B.hs:7:11-15} 
                       (GRHS 
                        [] 
                        (L {B.hs:7:11-15} 
                         (HsLit 
                          (HsString {FastString: "Odd"})))))] 
                     (EmptyLocalBinds)))),
                  (L {B.hs:8:3-17} 
                   (Match 
                    [
                     (L {B.hs:8:3-7} 
                      (ConPatIn 
                       (L {B.hs:8:3-7} 
                        (Unqual {OccName: False})) 
                       (PrefixCon 
                        [])))] 
                    (Nothing) 
                    (GRHSs 
                     [
                      (L {B.hs:8:12-17} 
                       (GRHS 
                        [] 
                        (L {B.hs:8:12-17} 
                         (HsLit 
                          (HsString {FastString: "Even"})))))] 
                     (EmptyLocalBinds))))] {!type placeholder here?!})))))] 
           (EmptyLocalBinds))))] {!type placeholder here?!}) 
      (WpHole) {!NameSet placeholder here!} 
      (Nothing)))),
   (L {B.hs:(10,1)-(11,25)} 
    (ValD 
     (FunBind 
      (L {B.hs:10:1-4} 
       (Unqual {OccName: main})) 
      (False) 
      (MatchGroup 
       [
        (L {B.hs:(10,1)-(11,25)} 
         (Match 
          [] 
          (Nothing) 
          (GRHSs 
           [
            (L {B.hs:(10,8)-(11,25)} 
             (GRHS 
              [] 
              (L {B.hs:(10,8)-(11,25)} 
               (HsDo 
                (DoExpr) 
                [
                 (L {B.hs:11:3-25} 
                  (ExprStmt 
                   (L {B.hs:11:3-25} 
                    (OpApp 
                     (L {B.hs:11:3-17} 
                      (OpApp 
                       (L {B.hs:11:3-10} 
                        (HsVar 
                         (Unqual {OccName: putStrLn}))) 
                       (L {B.hs:11:12} 
                        (HsVar 
                         (Unqual {OccName: $}))) {!fixity placeholder here?!} 
                       (L {B.hs:11:14-17} 
                        (HsVar 
                         (Unqual {OccName: show}))))) 
                     (L {B.hs:11:19} 
                      (HsVar 
                       (Unqual {OccName: $}))) {!fixity placeholder here?!} 
                     (L {B.hs:11:21-25} 
                      (HsApp 
                       (L {B.hs:11:21-23} 
                        (HsVar 
                         (Unqual {OccName: foo}))) 
                       (L {B.hs:11:25} 
                        (HsOverLit 
                         (OverLit 
                          (HsIntegral 
                           (5)) 
                          (<interactive>: panic! (the 'impossible' happened)
  (GHC version 7.4.1 for i386-unknown-linux):
	noRebindableInfo


-- ---------------------------------------------------------------------

Detailed tokens
--------------------
module FreeAndDeclared.Declare where

toplevel :: Integer -> Integer
toplevel x = c * x
 
c,d :: Integer
c = 7
d = 9

-- Pattern bind
tup :: (Int, Int)
h :: Int
t :: Int
tup@(h,t) = head $ zip [1..10] [3..15]

data D = A | B String | C

unD (B y) = y

-- Infix data constructor, see http://stackoverflow.com/a/6420943/595714
data F = G | (:|) String String

unF (a :| b) = (a,b)

main = do
  a <- getChar
  putStrLn "foo"

--------------------
[(((1,1),(1,7)),ITmodule,"module"),
(((1,8),(1,31)),ITqconid ("FreeAndDeclared","Declare"),"FreeAndDeclared.Declare"),
(((1,32),(1,37)),ITwhere,"where"),
(((3,1),(3,1)),ITvocurly,""),
(((3,1),(3,9)),ITvarid "toplevel","toplevel"),
(((3,10),(3,12)),ITdcolon,"::"),
(((3,13),(3,20)),ITconid "Integer","Integer"),
(((3,21),(3,23)),ITrarrow,"->"),
(((3,24),(3,31)),ITconid "Integer","Integer"),
(((4,1),(4,1)),ITsemi,""),
(((4,1),(4,9)),ITvarid "toplevel","toplevel"),
(((4,10),(4,11)),ITvarid "x","x"),
(((4,12),(4,13)),ITequal,"="),
(((4,14),(4,15)),ITvarid "c","c"),
(((4,16),(4,17)),ITstar,"*"),
(((4,18),(4,19)),ITvarid "x","x"),
(((6,1),(6,1)),ITsemi,""),
(((6,1),(6,2)),ITvarid "c","c"),
(((6,2),(6,3)),ITcomma,","),
(((6,3),(6,4)),ITvarid "d","d"),
(((6,5),(6,7)),ITdcolon,"::"),
(((6,8),(6,15)),ITconid "Integer","Integer"),
(((7,1),(7,1)),ITsemi,""),
(((7,1),(7,2)),ITvarid "c","c"),
(((7,3),(7,4)),ITequal,"="),
(((7,5),(7,6)),ITinteger 7,"7"),
(((8,1),(8,1)),ITsemi,""),
(((8,1),(8,2)),ITvarid "d","d"),
(((8,3),(8,4)),ITequal,"="),
(((8,5),(8,6)),ITinteger 9,"9"),
(((10,1),(10,16)),ITlineComment "-- Pattern bind","-- Pattern bind"),
(((11,1),(11,1)),ITsemi,""),
(((11,1),(11,4)),ITvarid "tup","tup"),
(((11,5),(11,7)),ITdcolon,"::"),
(((11,8),(11,9)),IToparen,"("),
(((11,9),(11,12)),ITconid "Int","Int"),
(((11,12),(11,13)),ITcomma,","),
(((11,14),(11,17)),ITconid "Int","Int"),
(((11,17),(11,18)),ITcparen,")"),
(((12,1),(12,1)),ITsemi,""),(((12,1),(12,2)),ITvarid "h","h"),(((12,3),(12,5)),ITdcolon,"::"),(((12,6),(12,9)),ITconid "Int","Int"),(((13,1),(13,1)),ITsemi,""),(((13,1),(13,2)),ITvarid "t","t"),(((13,3),(13,5)),ITdcolon,"::"),(((13,6),(13,9)),ITconid "Int","Int"),(((14,1),(14,1)),ITsemi,""),(((14,1),(14,4)),ITvarid "tup","tup"),(((14,4),(14,5)),ITat,"@"),(((14,5),(14,6)),IToparen,"("),(((14,6),(14,7)),ITvarid "h","h"),(((14,7),(14,8)),ITcomma,","),(((14,8),(14,9)),ITvarid "t","t"),(((14,9),(14,10)),ITcparen,")"),(((14,11),(14,12)),ITequal,"="),(((14,13),(14,17)),ITvarid "head","head"),(((14,18),(14,19)),ITvarsym "$","$"),(((14,20),(14,23)),ITvarid "zip","zip"),(((14,24),(14,25)),ITobrack,"["),(((14,25),(14,26)),ITinteger 1,"1"),(((14,26),(14,28)),ITdotdot,".."),(((14,28),(14,30)),ITinteger 10,"10"),(((14,30),(14,31)),ITcbrack,"]"),(((14,32),(14,33)),ITobrack,"["),(((14,33),(14,34)),ITinteger 3,"3"),(((14,34),(14,36)),ITdotdot,".."),(((14,36),(14,38)),ITinteger 15,"15"),(((14,38),(14,39)),ITcbrack,"]"),(((16,1),(16,1)),ITsemi,""),(((16,1),(16,5)),ITdata,"data"),(((16,6),(16,7)),ITconid "D","D"),(((16,8),(16,9)),ITequal,"="),(((16,10),(16,11)),ITconid "A","A"),(((16,12),(16,13)),ITvbar,"|"),(((16,14),(16,15)),ITconid "B","B"),(((16,16),(16,22)),ITconid "String","String"),(((16,23),(16,24)),ITvbar,"|"),(((16,25),(16,26)),ITconid "C","C"),(((18,1),(18,1)),ITsemi,""),(((18,1),(18,4)),ITvarid "unD","unD"),(((18,5),(18,6)),IToparen,"("),(((18,6),(18,7)),ITconid "B","B"),(((18,8),(18,9)),ITvarid "y","y"),(((18,9),(18,10)),ITcparen,")"),(((18,11),(18,12)),ITequal,"="),(((18,13),(18,14)),ITvarid "y","y"),(((20,1),(20,73)),ITlineComment "-- Infix data constructor, see http://stackoverflow.com/a/6420943/595714","-- Infix data constructor, see http://stackoverflow.com/a/6420943/595714"),(((21,1),(21,1)),ITsemi,""),(((21,1),(21,5)),ITdata,"data"),(((21,6),(21,7)),ITconid "F","F"),(((21,8),(21,9)),ITequal,"="),(((21,10),(21,11)),ITconid "G","G"),(((21,12),(21,13)),ITvbar,"|"),(((21,14),(21,15)),IToparen,"("),(((21,15),(21,17)),ITconsym ":|",":|"),(((21,17),(21,18)),ITcparen,")"),(((21,19),(21,25)),ITconid "String","String"),(((21,26),(21,32)),ITconid "String","String"),(((23,1),(23,1)),ITsemi,""),(((23,1),(23,4)),ITvarid "unF","unF"),(((23,5),(23,6)),IToparen,"("),(((23,6),(23,7)),ITvarid "a","a"),(((23,8),(23,10)),ITconsym ":|",":|"),(((23,11),(23,12)),ITvarid "b","b"),(((23,12),(23,13)),ITcparen,")"),(((23,14),(23,15)),ITequal,"="),(((23,16),(23,17)),IToparen,"("),(((23,17),(23,18)),ITvarid "a","a"),(((23,18),(23,19)),ITcomma,","),(((23,19),(23,20)),ITvarid "b","b"),(((23,20),(23,21)),ITcparen,")"),(((25,1),(25,1)),ITsemi,""),(((25,1),(25,5)),ITvarid "main","main"),(((25,6),(25,7)),ITequal,"="),(((25,8),(25,10)),ITdo,"do"),(((26,3),(26,3)),ITvocurly,""),(((26,3),(26,4)),ITvarid "a","a"),(((26,5),(26,7)),ITlarrow,"<-"),(((26,8),(26,15)),ITvarid "getChar","getChar"),(((27,3),(27,3)),ITsemi,""),(((27,3),(27,11)),ITvarid "putStrLn","putStrLn"),(((27,12),(27,17)),ITstring "foo","\"foo\""),(((29,1),(29,1)),ITvccurly,""),(((29,1),(29,1)),ITsemi,"")]

--------------------
GHC Lexer token insertion / layout rules

When in layout mode
  If first token of a line is to the left of prior line
   - insert ITvccurly

  If first token of a line is same as prior
   - insert ITsemi

In layout mode
  -- Insert ITvocurly if line to the right of prior
  -- Insert ITvccurly if line to the left of prior


---------------------

MatchGroup
----------

Although matches only ever occur on a FunBind in the original
http://hackage.haskell.org/packages/archive/haskell-src/1.0.1.4/doc/html/Language-Haskell-Syntax.html#t:HsMatch, in GHC they appear as follows

HsBinds
  FunBind

HsExpr
 HsLam
 HsCase
 
[original has (HsLambda .. [HsPat] ..)
          and (HsCase HsExp [HsAlt])
]

------------------------------------------------

2014-02-06

Scratching through the GHC source, looking for hsVisiblePN options.
Must be in the renamer somewhere.

module TxRnTypes.lhs has a TcGlbEnv structure which is returned as one
of the fields of TypecheckedModule.

-- ----------------------------
data TcGblEnv
  = TcGblEnv {
	tcg_mod     :: Module,         -- ^ Module being compiled
	tcg_src     :: HscSource,
          -- ^ What kind of module (regular Haskell, hs-boot, ext-core)

	tcg_rdr_env :: GlobalRdrEnv,   -- ^ Top level envt; used during renaming
	tcg_default :: Maybe [Type],
          -- ^ Types used for defaulting. @Nothing@ => no @default@ decl

	tcg_fix_env   :: FixityEnv,	-- ^ Just for things in this module
	tcg_field_env :: RecFieldEnv,	-- ^ Just for things in this module

	tcg_type_env :: TypeEnv,
          -- ^ Global type env for the module we are compiling now.  All
	  -- TyCons and Classes (for this module) end up in here right away,
	  -- along with their derived constructors, selectors.
	  --
	  -- (Ids defined in this module start in the local envt, though they
	  --  move to the global envt during zonking)

	tcg_type_env_var :: TcRef TypeEnv,
		-- Used only to initialise the interface-file
		-- typechecker in initIfaceTcRn, so that it can see stuff
		-- bound in this module when dealing with hi-boot recursions
		-- Updated at intervals (e.g. after dealing with types and classes)
	....
        ....
-- -------------------------------------

The GlobalRdrEnv has



---------------------

       ; let bound_names = collectHsValBinders binds'
       ; envs <- getRdrEnvs
       ; checkDupAndShadowedNames envs bound_names

-- ---------------------------------------------------------------------

Name and RdrName [2015-01-25]
-----------------------------

The RenamedSource is parameterised with Name, ParsedSource with RdrName.

The ParsedSource is closer to the original, so we want to output it
via ghc-exactprint, and manipulate the ParsedSource AST.

Critical to this is a way to map a RdrName to the Name applied by the
renamer.

Inside the renamer, the following happens for localvars


    newLocalBndrRn :: Located RdrName -> RnM Name
    -- Used for non-top-level binders.  These should
    -- never be qualified.
    newLocalBndrRn (L loc rdr_name)
      | Just name <- isExact_maybe rdr_name
      = return name -- This happens in code generated by Template Haskell
                    -- See Note [Binders in Template Haskell] in Convert.lhs
      | otherwise
      = do { unless (isUnqual rdr_name)
                    (addErrAt loc (badQualBndrErr rdr_name))
           ; uniq <- newUnique
           ; return (mkInternalName uniq (rdrNameOcc rdr_name) loc) }

In turn, mkInternalName is

    -- | Create a name which is (for now at least) local to the current module and hence
    -- does not need a 'Module' to disambiguate it from other 'Name's
    mkInternalName :: Unique -> OccName -> SrcSpan -> Name
    mkInternalName uniq occ loc = Name { n_uniq = getKeyFastInt uniq
                                       , n_sort = Internal
                                       , n_occ = occ
                                       , n_loc = loc }
            -- NB: You might worry that after lots of huffing and
            -- puffing we might end up with two local names with distinct
            -- uniques, but the same OccName.  Indeed we can, but that's ok
            --      * the insides of the compiler don't care: they use the Unique
            --      * when printing for -ddump-xxx you can switch on -dppr-debug to get the
            --        uniques if you get confused
            --      * for interface files we tidyCore first, which makes
            --        the OccNames distinct when they need to be

The thing we care about is the uniq inside the Name. So the only
viable path is to match up the rdrNameOcc and location to the one in
the Name.

This can happen in one of two ways

1. Use the location to find the equivalent Name in the RenamedSource,
and use that

2. Pre-generate a table of Name/Location -> RdrName and look up in that.

This is a later performance question, for now we go with the first.