Refactoring & documenting the Term pprinter used by :print
[ghc.git] / compiler / ghci / Debugger.hs
1 -----------------------------------------------------------------------------
2 --
3 -- GHCi Interactive debugging commands
4 --
5 -- Pepe Iborra (supported by Google SoC) 2006
6 --
7 -- ToDo: lots of violation of layering here. This module should
8 -- decide whether it is above the GHC API (import GHC and nothing
9 -- else) or below it.
10 --
11 -----------------------------------------------------------------------------
12
13 module Debugger (pprintClosureCommand, showTerm) where
14
15 import Linker
16 import RtClosureInspect
17
18 import HscTypes
19 import IdInfo
20 --import Id
21 import Name
22 import Var hiding ( varName )
23 import VarSet
24 import Name
25 import UniqSupply
26 import TcType
27 import GHC
28 import InteractiveEval
29 import Outputable
30 import Pretty ( Mode(..), showDocWith )
31 import SrcLoc
32
33 import Control.Exception
34 import Control.Monad
35 import Data.List
36 import Data.Maybe
37 import Data.IORef
38
39 import System.IO
40 import GHC.Exts
41
42 -------------------------------------
43 -- | The :print & friends commands
44 -------------------------------------
45 pprintClosureCommand :: Session -> Bool -> Bool -> String -> IO ()
46 pprintClosureCommand session bindThings force str = do
47 tythings <- (catMaybes . concat) `liftM`
48 mapM (\w -> GHC.parseName session w >>=
49 mapM (GHC.lookupName session))
50 (words str)
51 let ids = [id | AnId id <- tythings]
52
53 -- Obtain the terms and the recovered type information
54 (terms, substs) <- unzip `liftM` mapM (go session) ids
55
56 -- Apply the substitutions obtained after recovering the types
57 modifySession session $ \hsc_env ->
58 hsc_env{hsc_IC = foldr (flip substInteractiveContext)
59 (hsc_IC hsc_env)
60 (map skolemiseSubst substs)}
61 -- Finally, print the Terms
62 unqual <- GHC.getPrintUnqual session
63 let showSDocForUserOneLine unqual doc =
64 showDocWith LeftMode (doc (mkErrStyle unqual))
65 docterms <- mapM (showTerm session) terms
66 (putStrLn . showSDocForUserOneLine unqual . vcat)
67 (zipWith (\id docterm -> ppr id <+> char '=' <+> docterm)
68 ids
69 docterms)
70 where
71
72 -- Do the obtainTerm--bindSuspensions-computeSubstitution dance
73 go :: Session -> Id -> IO (Term, TvSubst)
74 go cms id = do
75 term_ <- GHC.obtainTerm cms force id
76 term <- tidyTermTyVars cms term_
77 term' <- if not bindThings then return term
78 else bindSuspensions cms term
79 -- Before leaving, we compare the type obtained to see if it's more specific
80 -- Then, we extract a substitution,
81 -- mapping the old tyvars to the reconstructed types.
82 let Just reconstructed_type = termType term
83 Just subst = computeRTTIsubst (idType id) (reconstructed_type)
84 return (term',subst)
85
86 tidyTermTyVars :: Session -> Term -> IO Term
87 tidyTermTyVars (Session ref) t = do
88 hsc_env <- readIORef ref
89 let env_tvs = ic_tyvars (hsc_IC hsc_env)
90 my_tvs = termTyVars t
91 tvs = env_tvs `minusVarSet` my_tvs
92 tyvarOccName = nameOccName . tyVarName
93 tidyEnv = (initTidyOccEnv (map tyvarOccName (varSetElems tvs))
94 , env_tvs `intersectVarSet` my_tvs)
95 return$ mapTermType (snd . tidyOpenType tidyEnv) t
96
97 -- | Give names, and bind in the interactive environment, to all the suspensions
98 -- included (inductively) in a term
99 bindSuspensions :: Session -> Term -> IO Term
100 bindSuspensions cms@(Session ref) t = do
101 hsc_env <- readIORef ref
102 inScope <- GHC.getBindings cms
103 let ictxt = hsc_IC hsc_env
104 prefix = "_t"
105 alreadyUsedNames = map (occNameString . nameOccName . getName) inScope
106 availNames = map ((prefix++) . show) [(1::Int)..] \\ alreadyUsedNames
107 availNames_var <- newIORef availNames
108 (t', stuff) <- foldTerm (nameSuspensionsAndGetInfos availNames_var) t
109 let (names, tys, hvals) = unzip3 stuff
110 let tys' = map (fst.skolemiseTy) tys
111 let ids = [ mkGlobalId VanillaGlobal name ty vanillaIdInfo
112 | (name,ty) <- zip names tys']
113 new_tyvars = tyVarsOfTypes tys'
114 new_ic = extendInteractiveContext ictxt ids new_tyvars
115 extendLinkEnv (zip names hvals)
116 writeIORef ref (hsc_env {hsc_IC = new_ic })
117 return t'
118 where
119
120 -- Processing suspensions. Give names and recopilate info
121 nameSuspensionsAndGetInfos :: IORef [String] ->
122 TermFold (IO (Term, [(Name,Type,HValue)]))
123 nameSuspensionsAndGetInfos freeNames = TermFold
124 {
125 fSuspension = doSuspension freeNames
126 , fTerm = \ty dc v tt -> do
127 tt' <- sequence tt
128 let (terms,names) = unzip tt'
129 return (Term ty dc v terms, concat names)
130 , fPrim = \ty n ->return (Prim ty n,[])
131 }
132 doSuspension freeNames ct mb_ty hval _name = do
133 name <- atomicModifyIORef freeNames (\x->(tail x, head x))
134 n <- newGrimName name
135 let ty' = fromMaybe (error "unexpected") mb_ty
136 return (Suspension ct mb_ty hval (Just n), [(n,ty',hval)])
137
138
139 -- A custom Term printer to enable the use of Show instances
140 showTerm :: Session -> Term -> IO SDoc
141 showTerm cms@(Session ref) = cPprTerm (liftM2 (++) cPprShowable cPprTermBase)
142 where
143 cPprShowable _y = [\prec ty _ val tt ->
144 if not (all isFullyEvaluatedTerm tt)
145 then return Nothing
146 else do
147 hsc_env <- readIORef ref
148 dflags <- GHC.getSessionDynFlags cms
149 do
150 (new_env, bname) <- bindToFreshName hsc_env ty "showme"
151 writeIORef ref (new_env)
152 let noop_log _ _ _ _ = return ()
153 expr = "show " ++ showSDoc (ppr bname)
154 GHC.setSessionDynFlags cms dflags{log_action=noop_log}
155 mb_txt <- withExtendedLinkEnv [(bname, val)]
156 (GHC.compileExpr cms expr)
157 let myprec = 10 -- application precedence. TODO Infix constructors
158 case mb_txt of
159 Just txt_ | txt <- unsafeCoerce# txt_, not (null txt)
160 -> return $ Just$ cparen (prec >= myprec &&
161 needsParens txt)
162 (text txt)
163 _ -> return Nothing
164 `finally` do
165 writeIORef ref hsc_env
166 GHC.setSessionDynFlags cms dflags]
167 needsParens ('"':_) = False -- some simple heuristics to see whether parens
168 -- are redundant in an arbitrary Show output
169 needsParens ('(':_) = False
170 needsParens txt = ' ' `elem` txt
171
172
173 bindToFreshName hsc_env ty userName = do
174 name <- newGrimName userName
175 let ictxt = hsc_IC hsc_env
176 tmp_ids = ic_tmp_ids ictxt
177 id = mkGlobalId VanillaGlobal name (sigmaType ty) vanillaIdInfo
178 new_ic = ictxt { ic_tmp_ids = id : tmp_ids }
179 return (hsc_env {hsc_IC = new_ic }, name)
180
181 -- Create new uniques and give them sequentially numbered names
182 newGrimName :: String -> IO Name
183 newGrimName userName = do
184 us <- mkSplitUniqSupply 'b'
185 let unique = uniqFromSupply us
186 occname = mkOccName varName userName
187 name = mkInternalName unique occname noSrcSpan
188 return name