{-# LANGUAGE MultiParamTypeClasses, FlexibleInstances, DeriveFunctor,
             TypeSynonymInstances, PatternGuards #-}

module Idris.AbsSyntax(module Idris.AbsSyntax, module Idris.AbsSyntaxTree) where

import Idris.Core.TT
import Idris.Core.Evaluate
import Idris.Core.Elaborate hiding (Tactic(..))
import Idris.Core.Typecheck
import Idris.AbsSyntaxTree
import Idris.Colours
import Idris.Docstrings
import Idris.IdeSlave hiding (Opt(..))
import IRTS.CodegenCommon
import Util.DynamicLinker

import Paths_idris

import System.Console.Haskeline
import System.IO

import Control.Monad.State
import Control.Monad.Error(throwError)

import Data.List
import Data.Char
import qualified Data.Text as T
import Data.Either
import qualified Data.Map as M
import Data.Maybe
import qualified Data.Set as S
import Data.Word (Word)

import Debug.Trace

import Control.Monad.Error (throwError, catchError)
import System.IO.Error(isUserError, ioeGetErrorString, tryIOError)

import Util.Pretty
import Util.ScreenSize
import Util.System

getContext :: Idris Context
getContext = do i <- getIState; return (tt_ctxt i)

forCodegen :: Codegen -> [(Codegen, a)] -> [a]
forCodegen tgt xs = [x | (tgt', x) <- xs, tgt == tgt']

getObjectFiles :: Codegen -> Idris [FilePath]
getObjectFiles tgt = do i <- getIState; return (forCodegen tgt $ idris_objs i)

addObjectFile :: Codegen -> FilePath -> Idris ()
addObjectFile tgt f = do i <- getIState; putIState $ i { idris_objs = nub $ (tgt, f) : idris_objs i }

getLibs :: Codegen -> Idris [String]
getLibs tgt = do i <- getIState; return (forCodegen tgt $ idris_libs i)

addLib :: Codegen -> String -> Idris ()
addLib tgt f = do i <- getIState; putIState $ i { idris_libs = nub $ (tgt, f) : idris_libs i }

getFlags :: Codegen -> Idris [String]
getFlags tgt = do i <- getIState; return (forCodegen tgt $ idris_cgflags i)

addFlag :: Codegen -> String -> Idris ()
addFlag tgt f = do i <- getIState; putIState $ i { idris_cgflags = nub $ (tgt, f) : idris_cgflags i }

addDyLib :: [String] -> Idris (Either DynamicLib String)
addDyLib libs = do i <- getIState
                   let ls = idris_dynamic_libs i
                   let importdirs = opt_importdirs (idris_options i)
                   case mapMaybe (findDyLib ls) libs of
                     x:_ -> return (Left x)
                     [] -> do
                       handle <- lift . lift .
                                 mapM (\l -> catchIO (tryLoadLib importdirs l)
                                                     (\_ -> return Nothing)) $ libs
                       case msum handle of
                         Nothing -> return (Right $ "Could not load dynamic alternatives \"" ++
                                                    concat (intersperse "," libs) ++ "\"")
                         Just x -> do putIState $ i { idris_dynamic_libs = x:ls }
                                      return (Left x)
    where findDyLib :: [DynamicLib] -> String -> Maybe DynamicLib
          findDyLib []         l                     = Nothing
          findDyLib (lib:libs) l | l == lib_name lib = Just lib
                                 | otherwise         = findDyLib libs l


addHdr :: Codegen -> String -> Idris ()
addHdr tgt f = do i <- getIState; putIState $ i { idris_hdrs = nub $ (tgt, f) : idris_hdrs i }

addImported :: FilePath -> Idris ()
addImported f = do i <- getIState
                   putIState $ i { idris_imported = nub $ f : idris_imported i }

addLangExt :: LanguageExt -> Idris ()
addLangExt TypeProviders = do i <- getIState
                              putIState $ i {
                                idris_language_extensions = TypeProviders : idris_language_extensions i
                              }
addLangExt ErrorReflection = do i <- getIState
                                putIState $ i {
                                  idris_language_extensions = ErrorReflection : idris_language_extensions i
                                }

addTrans :: (Term, Term) -> Idris ()
addTrans t = do i <- getIState
                putIState $ i { idris_transforms = t : idris_transforms i }

addErrRev :: (Term, Term) -> Idris ()
addErrRev t = do i <- getIState
                 putIState $ i { idris_errRev = t : idris_errRev i }

totcheck :: (FC, Name) -> Idris ()
totcheck n = do i <- getIState; putIState $ i { idris_totcheck = idris_totcheck i ++ [n] }

defer_totcheck :: (FC, Name) -> Idris ()
defer_totcheck n 
   = do i <- getIState; 
        putIState $ i { idris_defertotcheck = nub (idris_defertotcheck i ++ [n]) }

clear_totcheck :: Idris ()
clear_totcheck  = do i <- getIState; putIState $ i { idris_totcheck = [] }

setFlags :: Name -> [FnOpt] -> Idris ()
setFlags n fs = do i <- getIState; putIState $ i { idris_flags = addDef n fs (idris_flags i) }

setAccessibility :: Name -> Accessibility -> Idris ()
setAccessibility n a
         = do i <- getIState
              let ctxt = setAccess n a (tt_ctxt i)
              putIState $ i { tt_ctxt = ctxt }

setTotality :: Name -> Totality -> Idris ()
setTotality n a
         = do i <- getIState
              let ctxt = setTotal n a (tt_ctxt i)
              putIState $ i { tt_ctxt = ctxt }

getTotality :: Name -> Idris Totality
getTotality n
         = do i <- getIState
              case lookupTotal n (tt_ctxt i) of
                [t] -> return t
                _ -> return (Total [])

-- Get coercions which might return the required type
getCoercionsTo :: IState -> Type -> [Name]
getCoercionsTo i ty =
    let cs = idris_coercions i
        (fn,_) = unApply (getRetTy ty) in
        findCoercions fn cs
    where findCoercions t [] = []
          findCoercions t (n : ns) =
             let ps = case lookupTy n (tt_ctxt i) of
                        [ty'] -> case unApply (getRetTy ty') of
                                   (t', _) ->
                                      if t == t' then [n] else []
                        _ -> [] in
                 ps ++ findCoercions t ns

addToCG :: Name -> CGInfo -> Idris ()
addToCG n cg
   = do i <- getIState
        putIState $ i { idris_callgraph = addDef n cg (idris_callgraph i) }

addTyInferred :: Name -> Idris ()
addTyInferred n 
   = do i <- getIState
        putIState $ i { idris_tyinfodata =
                        addDef n TIPartial (idris_tyinfodata i) }

addTyInfConstraints :: FC -> [(Term, Term)] -> Idris ()
addTyInfConstraints fc ts = do logLvl 2 $ "TI missing: " ++ show ts
                               mapM_ addConstraint ts
                               return ()
    where addConstraint (x, y) = findMVApps x y

          findMVApps x y
             = do let (fx, argsx) = unApply x
                  let (fy, argsy) = unApply y
                  if (not (fx == fy)) 
                     then do
                       tryAddMV fx y
                       tryAddMV fy x
                     else mapM_ addConstraint (zip argsx argsy)

          tryAddMV (P _ mv _) y =
               do ist <- get
                  case lookup mv (idris_metavars ist) of
                       Just _ -> addConstraintRule mv y
                       _ -> return ()
          tryAddMV _ _ = return ()

          addConstraintRule :: Name -> Term -> Idris ()
          addConstraintRule n t 
             = do ist <- get
                  logLvl 1 $ "TI constraint: " ++ show (n, t)
                  case lookupCtxt n (idris_tyinfodata ist) of
                     [TISolution ts] -> 
                         do mapM_ (checkConsistent t) ts
                            let ti' = addDef n (TISolution (t : ts)) 
                                               (idris_tyinfodata ist)
                            put $ ist { idris_tyinfodata = ti' }
                     _ ->  
                         do let ti' = addDef n (TISolution [t]) 
                                               (idris_tyinfodata ist)
                            put $ ist { idris_tyinfodata = ti' }

          -- Check a solution is consistent with previous solutions
          -- Meaning: If heads are both data types, they had better be the
          -- same.
          checkConsistent :: Term -> Term -> Idris ()
          checkConsistent x y =
              do let (fx, _) = unApply x
                 let (fy, _) = unApply y
                 case (fx, fy) of
                      (P (TCon _ _) n _, P (TCon _ _) n' _) -> errWhen (n/=n) 
                      (P (TCon _ _) n _, Constant _) -> errWhen True
                      (Constant _, P (TCon _ _) n' _) -> errWhen True
                      (P (DCon _ _) n _, P (DCon _ _) n' _) -> errWhen (n/=n) 
                      _ -> return ()

              where errWhen True 
                       = throwError (At fc 
                            (CantUnify False x y (Msg "") [] 0))
                    errWhen False = return ()

isTyInferred :: Name -> Idris Bool
isTyInferred n
   = do i <- getIState
        case lookupCtxt n (idris_tyinfodata i) of
             [TIPartial] -> return True
             _ -> return False

-- | Adds error handlers for a particular function and argument. If names are
-- ambiguous, all matching handlers are updated.
addFunctionErrorHandlers :: Name -> Name -> [Name] -> Idris ()
addFunctionErrorHandlers f arg hs =
 do i <- getIState
    let oldHandlers = idris_function_errorhandlers i
    let newHandlers = flip (addDef f) oldHandlers $
                      case lookupCtxtExact f oldHandlers of
                        Nothing            -> M.singleton arg (S.fromList hs)
                        Just (oldHandlers) -> M.insertWith S.union arg (S.fromList hs) oldHandlers
                        -- will always be one of those two, thus no extra case
    putIState $ i { idris_function_errorhandlers = newHandlers }

getFunctionErrorHandlers :: Name -> Name -> Idris [Name]
getFunctionErrorHandlers f arg = do i <- getIState
                                    return . maybe [] S.toList $
                                     undefined --lookup arg =<< lookupCtxtExact f (idris_function_errorhandlers i)


-- Trace all the names in a call graph starting at the given name
getAllNames :: Name -> Idris [Name]
getAllNames n = allNames [] n

allNames :: [Name] -> Name -> Idris [Name]
allNames ns n | n `elem` ns = return []
allNames ns n = do i <- getIState
                   case lookupCtxtExact n (idris_callgraph i) of
                      Just ns' -> do more <- mapM (allNames (n:ns)) (map fst (calls ns'))
                                     return (nub (n : concat more))
                      _ -> return [n]

addCoercion :: Name -> Idris ()
addCoercion n = do i <- getIState
                   putIState $ i { idris_coercions = nub $ n : idris_coercions i }

addDocStr :: Name -> Docstring -> [(Name, Docstring)] -> Idris ()
addDocStr n doc args
   = do i <- getIState
        putIState $ i { idris_docstrings = addDef n (doc, args) (idris_docstrings i) }

addNameHint :: Name -> Name -> Idris ()
addNameHint ty n
   = do i <- getIState
        ty' <- case lookupCtxtName ty (idris_implicits i) of
                       [(tyn, _)] -> return tyn
                       [] -> throwError (NoSuchVariable ty)
                       tyns -> throwError (CantResolveAlts (map show (map fst tyns)))
        let ns' = case lookupCtxt ty' (idris_namehints i) of
                       [ns] -> ns ++ [n]
                       _ -> [n]
        putIState $ i { idris_namehints = addDef ty' ns' (idris_namehints i) }

getNameHints :: IState -> Name -> [Name]
getNameHints i (UN arr) | arr == txt "->" = [sUN "f",sUN "g"]
getNameHints i n =
        case lookupCtxt n (idris_namehints i) of
             [ns] -> ns
             _ -> []

addToCalledG :: Name -> [Name] -> Idris ()
addToCalledG n ns = return () -- TODO

-- Add a class instance function. Dodgy hack: Put integer instances first in the
-- list so they are resolved by default.
-- Dodgy hack 2: put constraint chasers (@@) last

addInstance :: Bool -> Name -> Name -> Idris ()
addInstance int n i
    = do ist <- getIState
         case lookupCtxt n (idris_classes ist) of
                [CI a b c d e ins] ->
                     do let cs = addDef n (CI a b c d e (addI i ins)) (idris_classes ist)
                        putIState $ ist { idris_classes = cs }
                _ -> do let cs = addDef n (CI (sMN 0 "none") [] [] [] [] [i]) (idris_classes ist)
                        putIState $ ist { idris_classes = cs }
  where addI i ins | int = i : ins
                   | chaser n = ins ++ [i]
                   | otherwise = insI i ins
        insI i [] = [i]
        insI i (n : ns) | chaser n = i : n : ns
                        | otherwise = n : insI i ns

        chaser (UN nm) 
             | ('@':'@':_) <- str nm = True
        chaser (NS n _) = chaser n
        chaser _ = False

addClass :: Name -> ClassInfo -> Idris ()
addClass n i
   = do ist <- getIState
        let i' = case lookupCtxt n (idris_classes ist) of
                      [c] -> c { class_instances = class_instances i }
                      _ -> i
        putIState $ ist { idris_classes = addDef n i' (idris_classes ist) }

addIBC :: IBCWrite -> Idris ()
addIBC ibc@(IBCDef n)
           = do i <- getIState
                when (notDef (ibc_write i)) $
                  putIState $ i { ibc_write = ibc : ibc_write i }
   where notDef [] = True
         notDef (IBCDef n': is) | n == n' = False
         notDef (_ : is) = notDef is
addIBC ibc = do i <- getIState; putIState $ i { ibc_write = ibc : ibc_write i }

clearIBC :: Idris ()
clearIBC = do i <- getIState; putIState $ i { ibc_write = [] }

resetNameIdx :: Idris ()
resetNameIdx = do i <- getIState
                  put (i { idris_nameIdx = (0, emptyContext) })

-- Used to preserve sharing of names
addNameIdx :: Name -> Idris (Int, Name)
addNameIdx n = do i <- getIState
                  let (i', x) = addNameIdx' i n
                  return x

addNameIdx' :: IState -> Name -> (IState, (Int, Name))
addNameIdx' i n
   = let idxs = snd (idris_nameIdx i) in
         case lookupCtxt n idxs of
            [x] -> (i, x)
            _ -> let i' = fst (idris_nameIdx i) + 1 in
                    (i { idris_nameIdx = (i', addDef n (i', n) idxs) }, (i', n))

getHdrs :: Codegen -> Idris [String]
getHdrs tgt = do i <- getIState; return (forCodegen tgt $ idris_hdrs i)

getImported ::  Idris [FilePath]
getImported = do i <- getIState; return (idris_imported i)

setErrSpan :: FC -> Idris ()
setErrSpan x = do i <- getIState;
                  case (errSpan i) of
                      Nothing -> putIState $ i { errSpan = Just x }
                      Just _ -> return ()

clearErr :: Idris ()
clearErr = do i <- getIState
              putIState $ i { errSpan = Nothing }

getSO :: Idris (Maybe String)
getSO = do i <- getIState
           return (compiled_so i)

setSO :: Maybe String -> Idris ()
setSO s = do i <- getIState
             putIState $ (i { compiled_so = s })

getIState :: Idris IState
getIState = get

putIState :: IState -> Idris ()
putIState = put

-- | A version of liftIO that puts errors into the exception type of the Idris monad
runIO :: IO a -> Idris a
runIO x = liftIO (tryIOError x) >>= either (throwError . Msg . show) return
-- TODO: create specific Idris exceptions for specific IO errors such as "openFile: does not exist"

getName :: Idris Int
getName = do i <- getIState;
             let idx = idris_name i;
             putIState $ (i { idris_name = idx + 1 })
             return idx

-- InternalApp keeps track of the real function application for making case splits from, not the application the
-- programmer wrote, which doesn't have the whole context in any case other than top level definitions
addInternalApp :: FilePath -> Int -> PTerm -> Idris ()
addInternalApp fp l t
    = do i <- getIState
         putIState (i { idris_lineapps = ((fp, l), t) : idris_lineapps i })

getInternalApp :: FilePath -> Int -> Idris PTerm
getInternalApp fp l = do i <- getIState
                         case lookup (fp, l) (idris_lineapps i) of
                              Just n' -> return n'
                              Nothing -> return Placeholder
                              -- TODO: What if it's not there?

-- Pattern definitions are only used for coverage checking, so erase them
-- when we're done
clearOrigPats :: Idris ()
clearOrigPats = do i <- get
                   let ps = idris_patdefs i
                   let ps' = mapCtxt (\ (_,miss) -> ([], miss)) ps
                   put (i { idris_patdefs = ps' })

-- Erase types from Ps in the context (basically ending up with what's in
-- the .ibc, which is all we need after all the analysis is done)
clearPTypes :: Idris ()
clearPTypes = do i <- get
                 let ctxt = tt_ctxt i 
                 put (i { tt_ctxt = mapDefCtxt pErase ctxt })
   where pErase (CaseOp c t tys orig tot cds) 
            = CaseOp c t tys orig [] (pErase' cds)
         pErase x = x
         pErase' (CaseDefs _ (cs, c) _ rs)
             = let c' = (cs, fmap pEraseType c) in
                   CaseDefs c' c' c' rs

checkUndefined :: FC -> Name -> Idris ()
checkUndefined fc n
    = do i <- getContext
         case lookupTy n i of
             (_:_)  -> throwError . Msg $ show fc ++ ":" ++
                                          show n ++ " already defined"
             _ -> return ()

isUndefined :: FC -> Name -> Idris Bool
isUndefined fc n
    = do i <- getContext
         case lookupTy n i of
             (_:_)  -> return False
             _ -> return True

setContext :: Context -> Idris ()
setContext ctxt = do i <- getIState; putIState $ (i { tt_ctxt = ctxt } )

updateContext :: (Context -> Context) -> Idris ()
updateContext f = do i <- getIState; putIState $ (i { tt_ctxt = f (tt_ctxt i) } )

addConstraints :: FC -> (Int, [UConstraint]) -> Idris ()
addConstraints fc (v, cs)
    = do i <- getIState
         let ctxt = tt_ctxt i
         let ctxt' = ctxt { uconstraints = cs ++ uconstraints ctxt,
                            next_tvar = v }
         let ics = zip cs (repeat fc) ++ idris_constraints i
         putIState $ i { tt_ctxt = ctxt', idris_constraints = ics }

addDeferred = addDeferred' Ref
addDeferredTyCon = addDeferred' (TCon 0 0)

addDeferred' :: NameType -> [(Name, (Int, Maybe Name, Type, Bool))] -> Idris ()
addDeferred' nt ns
  = do mapM_ (\(n, (i, _, t, _)) -> updateContext (addTyDecl n nt (tidyNames [] t))) ns
       mapM_ (\(n, _) -> when (not (n `elem` primDefs)) $ addIBC (IBCMetavar n)) ns
       i <- getIState
       putIState $ i { idris_metavars = map (\(n, (i, top, _, isTopLevel)) -> (n, (top, i, isTopLevel))) ns ++
                                            idris_metavars i }
  where tidyNames used (Bind (MN i x) b sc)
            = let n' = uniqueName (UN x) used in
                  Bind n' b $ tidyNames (n':used) sc
        tidyNames used (Bind n b sc)
            = let n' = uniqueName n used in
                  Bind n' b $ tidyNames (n':used) sc
        tidyNames used b = b

solveDeferred :: Name -> Idris ()
solveDeferred n = do i <- getIState
                     putIState $ i { idris_metavars =
                                       filter (\(n', _) -> n/=n')
                                          (idris_metavars i),
                                     ibc_write =
                                       filter (notMV n) (ibc_write i)
                                          }
    where notMV n (IBCMetavar n') = not (n == n')
          notMV n _ = True

getUndefined :: Idris [Name]
getUndefined = do i <- getIState
                  return (map fst (idris_metavars i) \\ primDefs)

isMetavarName :: Name -> IState -> Bool
isMetavarName n ist
     = case lookupNames n (tt_ctxt ist) of
            (t:_) -> isJust $ lookup t (idris_metavars ist)
            _     -> False

getWidth :: Idris ConsoleWidth
getWidth = fmap idris_consolewidth getIState

setWidth :: ConsoleWidth -> Idris ()
setWidth w = do ist <- getIState
                put ist { idris_consolewidth = w }

renderWidth :: Idris Int
renderWidth = do iw <- getWidth
                 case iw of
                   InfinitelyWide -> return 100000000
                   ColsWide n -> return (max n 1)
                   AutomaticWidth -> runIO getScreenWidth



type1Doc :: Doc OutputAnnotation
type1Doc = (annotate AnnConstType $ text "Type 1")


isetPrompt :: String -> Idris ()
isetPrompt p = do i <- getIState
                  case idris_outputmode i of
                    IdeSlave n -> runIO . putStrLn $ convSExp "set-prompt" p n

setLogLevel :: Int -> Idris ()
setLogLevel l = do i <- getIState
                   let opts = idris_options i
                   let opt' = opts { opt_logLevel = l }
                   putIState $ i { idris_options = opt' }

setCmdLine :: [Opt] -> Idris ()
setCmdLine opts = do i <- getIState
                     let iopts = idris_options i
                     putIState $ i { idris_options = iopts { opt_cmdline = opts } }

getCmdLine :: Idris [Opt]
getCmdLine = do i <- getIState
                return (opt_cmdline (idris_options i))

getDumpDefun :: Idris (Maybe FilePath)
getDumpDefun = do i <- getIState
                  return $ findC (opt_cmdline (idris_options i))
    where findC [] = Nothing
          findC (DumpDefun x : _) = Just x
          findC (_ : xs) = findC xs

getDumpCases :: Idris (Maybe FilePath)
getDumpCases = do i <- getIState
                  return $ findC (opt_cmdline (idris_options i))
    where findC [] = Nothing
          findC (DumpCases x : _) = Just x
          findC (_ : xs) = findC xs

logLevel :: Idris Int
logLevel = do i <- getIState
              return (opt_logLevel (idris_options i))

setErrContext :: Bool -> Idris ()
setErrContext t = do i <- getIState
                     let opts = idris_options i
                     let opt' = opts { opt_errContext = t }
                     putIState $ i { idris_options = opt' }

errContext :: Idris Bool
errContext = do i <- getIState
                return (opt_errContext (idris_options i))

useREPL :: Idris Bool
useREPL = do i <- getIState
             return (opt_repl (idris_options i))

setREPL :: Bool -> Idris ()
setREPL t = do i <- getIState
               let opts = idris_options i
               let opt' = opts { opt_repl = t }
               putIState $ i { idris_options = opt' }

showOrigErr :: Idris Bool
showOrigErr = do i <- getIState
                 return (opt_origerr (idris_options i))

setShowOrigErr :: Bool -> Idris ()
setShowOrigErr b = do i <- getIState
                      let opts = idris_options i
                      let opt' = opts { opt_origerr = b }
                      putIState $ i { idris_options = opt' }

setAutoSolve :: Bool -> Idris ()
setAutoSolve b = do i <- getIState
                    let opts = idris_options i
                    let opt' = opts { opt_autoSolve = b }
                    putIState $ i { idris_options = opt' }

setNoBanner :: Bool -> Idris ()
setNoBanner n = do i <- getIState
                   let opts = idris_options i
                   let opt' = opts { opt_nobanner = n }
                   putIState $ i { idris_options = opt' }

getNoBanner :: Idris Bool
getNoBanner = do i <- getIState
                 let opts = idris_options i
                 return (opt_nobanner opts)

setQuiet :: Bool -> Idris ()
setQuiet q = do i <- getIState
                let opts = idris_options i
                let opt' = opts { opt_quiet = q }
                putIState $ i { idris_options = opt' }

getQuiet :: Idris Bool
getQuiet = do i <- getIState
              let opts = idris_options i
              return (opt_quiet opts)

setCodegen :: Codegen -> Idris ()
setCodegen t = do i <- getIState
                  let opts = idris_options i
                  let opt' = opts { opt_codegen = t }
                  putIState $ i { idris_options = opt' }

codegen :: Idris Codegen
codegen = do i <- getIState
             return (opt_codegen (idris_options i))

setOutputTy :: OutputType -> Idris ()
setOutputTy t = do i <- getIState
                   let opts = idris_options i
                   let opt' = opts { opt_outputTy = t }
                   putIState $ i { idris_options = opt' }

outputTy :: Idris OutputType
outputTy = do i <- getIState
              return $ opt_outputTy $ idris_options i

setIdeSlave :: Bool -> Idris ()
setIdeSlave True  = do i <- getIState
                       putIState $ i { idris_outputmode = (IdeSlave 0), idris_colourRepl = False }
setIdeSlave False = return ()

setTargetTriple :: String -> Idris ()
setTargetTriple t = do i <- getIState
                       let opts = idris_options i
                           opt' = opts { opt_triple = t }
                       putIState $ i { idris_options = opt' }

targetTriple :: Idris String
targetTriple = do i <- getIState
                  return (opt_triple (idris_options i))

setTargetCPU :: String -> Idris ()
setTargetCPU t = do i <- getIState
                    let opts = idris_options i
                        opt' = opts { opt_cpu = t }
                    putIState $ i { idris_options = opt' }

targetCPU :: Idris String
targetCPU = do i <- getIState
               return (opt_cpu (idris_options i))

setOptLevel :: Word -> Idris ()
setOptLevel t = do i <- getIState
                   let opts = idris_options i
                       opt' = opts { opt_optLevel = t }
                   putIState $ i { idris_options = opt' }

optLevel :: Idris Word
optLevel = do i <- getIState
              return (opt_optLevel (idris_options i))

verbose :: Idris Bool
verbose = do i <- getIState
             return (opt_verbose (idris_options i))

setVerbose :: Bool -> Idris ()
setVerbose t = do i <- getIState
                  let opts = idris_options i
                  let opt' = opts { opt_verbose = t }
                  putIState $ i { idris_options = opt' }

typeInType :: Idris Bool
typeInType = do i <- getIState
                return (opt_typeintype (idris_options i))

setTypeInType :: Bool -> Idris ()
setTypeInType t = do i <- getIState
                     let opts = idris_options i
                     let opt' = opts { opt_typeintype = t }
                     putIState $ i { idris_options = opt' }

coverage :: Idris Bool
coverage = do i <- getIState
              return (opt_coverage (idris_options i))

setCoverage :: Bool -> Idris ()
setCoverage t = do i <- getIState
                   let opts = idris_options i
                   let opt' = opts { opt_coverage = t }
                   putIState $ i { idris_options = opt' }

setIBCSubDir :: FilePath -> Idris ()
setIBCSubDir fp = do i <- getIState
                     let opts = idris_options i
                     let opt' = opts { opt_ibcsubdir = fp }
                     putIState $ i { idris_options = opt' }

valIBCSubDir :: IState -> Idris FilePath
valIBCSubDir i = return (opt_ibcsubdir (idris_options i))

addImportDir :: FilePath -> Idris ()
addImportDir fp = do i <- getIState
                     let opts = idris_options i
                     let opt' = opts { opt_importdirs = fp : opt_importdirs opts }
                     putIState $ i { idris_options = opt' }

setImportDirs :: [FilePath] -> Idris ()
setImportDirs fps = do i <- getIState
                       let opts = idris_options i
                       let opt' = opts { opt_importdirs = fps }
                       putIState $ i { idris_options = opt' }

allImportDirs :: Idris [FilePath]
allImportDirs = do i <- getIState
                   let optdirs = opt_importdirs (idris_options i)
                   return ("." : reverse optdirs)

colourise :: Idris Bool
colourise = do i <- getIState
               return $ idris_colourRepl i

setColourise :: Bool -> Idris ()
setColourise b = do i <- getIState
                    putIState $ i { idris_colourRepl = b }

setOutH :: Handle -> Idris ()
setOutH h = do i <- getIState
               putIState $ i { idris_outh = h }

impShow :: Idris Bool
impShow = do i <- getIState
             return (opt_showimp (idris_options i))

setImpShow :: Bool -> Idris ()
setImpShow t = do i <- getIState
                  let opts = idris_options i
                  let opt' = opts { opt_showimp = t }
                  putIState $ i { idris_options = opt' }

setColour :: ColourType -> IdrisColour -> Idris ()
setColour ct c = do i <- getIState
                    let newTheme = setColour' ct c (idris_colourTheme i)
                    putIState $ i { idris_colourTheme = newTheme }
    where setColour' KeywordColour  c t = t { keywordColour = c }
          setColour' BoundVarColour c t = t { boundVarColour = c }
          setColour' ImplicitColour c t = t { implicitColour = c }
          setColour' FunctionColour c t = t { functionColour = c }
          setColour' TypeColour     c t = t { typeColour = c }
          setColour' DataColour     c t = t { dataColour = c }
          setColour' PromptColour   c t = t { promptColour = c }

logLvl :: Int -> String -> Idris ()
logLvl l str = do i <- getIState
                  let lvl = opt_logLevel (idris_options i)
                  when (lvl >= l) $
                    case idris_outputmode i of
                      RawOutput -> do runIO $ putStrLn str
                      IdeSlave n ->
                        do let good = SexpList [IntegerAtom (toInteger l), toSExp str]
                           runIO $ putStrLn $ convSExp "log" good n

cmdOptType :: Opt -> Idris Bool
cmdOptType x = do i <- getIState
                  return $ x `elem` opt_cmdline (idris_options i)

iLOG :: String -> Idris ()
iLOG = logLvl 1

noErrors :: Idris Bool
noErrors = do i <- getIState
              case errSpan i of
                Nothing -> return True
                _       -> return False

setTypeCase :: Bool -> Idris ()
setTypeCase t = do i <- getIState
                   let opts = idris_options i
                   let opt' = opts { opt_typecase = t }
                   putIState $ i { idris_options = opt' }


-- Dealing with parameters

expandParams :: (Name -> Name) -> [(Name, PTerm)] ->
                [Name] -> -- all names
                [Name] -> -- names with no declaration
                PTerm -> PTerm
expandParams dec ps ns infs tm = en tm
  where
    -- if we shadow a name (say in a lambda binding) that is used in a call to
    -- a lifted function, we need access to both names - once in the scope of the
    -- binding and once to call the lifted functions. So we'll explicitly shadow
    -- it. (Yes, it's a hack. The alternative would be to resolve names earlier
    -- but we didn't...)

    mkShadow (UN n) = MN 0 n
    mkShadow (MN i n) = MN (i+1) n
    mkShadow (NS x s) = NS (mkShadow x) s

    en (PLam n t s)
       | n `elem` (map fst ps ++ ns)
               = let n' = mkShadow n in
                     PLam n' (en t) (en (shadow n n' s))
       | otherwise = PLam n (en t) (en s)
    en (PPi p n t s)
       | n `elem` (map fst ps ++ ns)
               = let n' = mkShadow n in
                     PPi p n' (en t) (en (shadow n n' s))
       | otherwise = PPi p n (en t) (en s)
    en (PLet n ty v s)
       | n `elem` (map fst ps ++ ns)
               = let n' = mkShadow n in
                     PLet n' (en ty) (en v) (en (shadow n n' s))
       | otherwise = PLet n (en ty) (en v) (en s)
    -- FIXME: Should only do this in a type signature!
    en (PDPair f p (PRef f' n) t r)
       | n `elem` (map fst ps ++ ns) && t /= Placeholder
           = let n' = mkShadow n in
                 PDPair f p (PRef f' n') (en t) (en (shadow n n' r))
    en (PEq f l r) = PEq f (en l) (en r)
    en (PRewrite f l r g) = PRewrite f (en l) (en r) (fmap en g)
    en (PTyped l r) = PTyped (en l) (en r)
    en (PPair f p l r) = PPair f p (en l) (en r)
    en (PDPair f p l t r) = PDPair f p (en l) (en t) (en r)
    en (PAlternative a as) = PAlternative a (map en as)
    en (PHidden t) = PHidden (en t)
    en (PUnifyLog t) = PUnifyLog (en t)
    en (PDisamb ds t) = PDisamb ds (en t)
    en (PNoImplicits t) = PNoImplicits (en t)
    en (PDoBlock ds) = PDoBlock (map (fmap en) ds)
    en (PProof ts)   = PProof (map (fmap en) ts)
    en (PTactics ts) = PTactics (map (fmap en) ts)

    en (PQuote (Var n))
        | n `nselem` ns = PQuote (Var (dec n))
    en (PApp fc (PInferRef fc' n) as)
        | n `nselem` ns = PApp fc (PInferRef fc' (dec n))
                           (map (pexp . (PRef fc)) (map fst ps) ++ (map (fmap en) as))
    en (PApp fc (PRef fc' n) as)
        | n `elem` infs = PApp fc (PInferRef fc' (dec n))
                           (map (pexp . (PRef fc)) (map fst ps) ++ (map (fmap en) as))
        | n `nselem` ns = PApp fc (PRef fc' (dec n))
                           (map (pexp . (PRef fc)) (map fst ps) ++ (map (fmap en) as))
    en (PAppBind fc (PRef fc' n) as)
        | n `elem` infs = PAppBind fc (PInferRef fc' (dec n))
                           (map (pexp . (PRef fc)) (map fst ps) ++ (map (fmap en) as))
        | n `nselem` ns = PAppBind fc (PRef fc' (dec n))
                           (map (pexp . (PRef fc)) (map fst ps) ++ (map (fmap en) as))
    en (PRef fc n)
        | n `elem` infs = PApp fc (PInferRef fc (dec n))
                           (map (pexp . (PRef fc)) (map fst ps))
        | n `nselem` ns = PApp fc (PRef fc (dec n))
                           (map (pexp . (PRef fc)) (map fst ps))
    en (PInferRef fc n)
        | n `nselem` ns = PApp fc (PInferRef fc (dec n))
                           (map (pexp . (PRef fc)) (map fst ps))
    en (PApp fc f as) = PApp fc (en f) (map (fmap en) as)
    en (PAppBind fc f as) = PAppBind fc (en f) (map (fmap en) as)
    en (PCase fc c os) = PCase fc (en c) (map (pmap en) os)
    en t = t

    nselem x [] = False
    nselem x (y : xs) | nseq x y = True
                      | otherwise = nselem x xs

    nseq x y = nsroot x == nsroot y

expandParamsD :: Bool -> -- True = RHS only
                 IState ->
                 (Name -> Name) -> [(Name, PTerm)] -> [Name] -> PDecl -> PDecl
expandParamsD rhsonly ist dec ps ns (PTy doc argdocs syn fc o n ty)
    = if n `elem` ns && (not rhsonly)
         then -- trace (show (n, expandParams dec ps ns ty)) $
              PTy doc argdocs syn fc o (dec n) (piBindp expl_param ps (expandParams dec ps ns [] ty))
         else --trace (show (n, expandParams dec ps ns ty)) $
              PTy doc argdocs syn fc o n (expandParams dec ps ns [] ty)
expandParamsD rhsonly ist dec ps ns (PPostulate doc syn fc o n ty)
    = if n `elem` ns && (not rhsonly)
         then -- trace (show (n, expandParams dec ps ns ty)) $
              PPostulate doc syn fc o (dec n) (piBind ps
                            (expandParams dec ps ns [] ty))
         else --trace (show (n, expandParams dec ps ns ty)) $
              PPostulate doc syn fc o n (expandParams dec ps ns [] ty)
expandParamsD rhsonly ist dec ps ns (PClauses fc opts n cs)
    = let n' = if n `elem` ns then dec n else n in
          PClauses fc opts n' (map expandParamsC cs)
  where
    expandParamsC (PClause fc n lhs ws rhs ds)
        = let -- ps' = updateps True (namesIn ist rhs) (zip ps [0..])
              ps'' = updateps False (namesIn [] ist lhs) (zip ps [0..])
              lhs' = if rhsonly then lhs else (expandParams dec ps'' ns [] lhs)
              n' = if n `elem` ns then dec n else n
              -- names bound on the lhs should not be expanded on the rhs
              ns' = removeBound lhs ns in
              PClause fc n' lhs'
                            (map (expandParams dec ps'' ns' []) ws)
                            (expandParams dec ps'' ns' [] rhs)
                            (map (expandParamsD True ist dec ps'' ns') ds)
    expandParamsC (PWith fc n lhs ws wval ds)
        = let -- ps' = updateps True (namesIn ist wval) (zip ps [0..])
              ps'' = updateps False (namesIn [] ist lhs) (zip ps [0..])
              lhs' = if rhsonly then lhs else (expandParams dec ps'' ns [] lhs)
              n' = if n `elem` ns then dec n else n
              ns' = removeBound lhs ns in
              PWith fc n' lhs'
                          (map (expandParams dec ps'' ns' []) ws)
                          (expandParams dec ps'' ns' [] wval)
                          (map (expandParamsD rhsonly ist dec ps'' ns') ds)
    updateps yn nm [] = []
    updateps yn nm (((a, t), i):as)
        | (a `elem` nm) == yn = (a, t) : updateps yn nm as
        | otherwise = (sMN i (show n ++ "_u"), t) : updateps yn nm as

    removeBound lhs ns = ns \\ nub (bnames lhs)

    bnames (PRef _ n) = [n]
    bnames (PApp _ _ args) = concatMap bnames (map getTm args)
    bnames (PPair _ _ l r) = bnames l ++ bnames r
    bnames (PDPair _ _ l Placeholder r) = bnames l ++ bnames r
    bnames _ = []

expandParamsD rhs ist dec ps ns (PData doc argDocs syn fc co pd)
    = PData doc argDocs syn fc co (expandPData pd)
  where
    -- just do the type decl, leave constructors alone (parameters will be
    -- added implicitly)
    expandPData (PDatadecl n ty cons)
       = if n `elem` ns
            then PDatadecl (dec n) (piBind ps (expandParams dec ps ns [] ty))
                           (map econ cons)
            else PDatadecl n (expandParams dec ps ns [] ty) (map econ cons)
    econ (doc, argDocs, n, t, fc, fs)
       = (doc, argDocs, dec n, piBindp expl ps (expandParams dec ps ns [] t), fc, fs)
expandParamsD rhs ist dec ps ns (PRecord doc syn fc tn tty cdoc cn cty)
   = if tn `elem` ns
        then PRecord doc syn fc (dec tn) (piBind ps (expandParams dec ps ns [] tty))
                     cdoc (dec cn) conty
        else PRecord doc syn fc (dec tn) (expandParams dec ps ns [] tty)
                     cdoc (dec cn) conty
   where conty = piBindp expl ps (expandParams dec ps ns [] cty)
expandParamsD rhs ist dec ps ns (PParams f params pds)
   = PParams f (ps ++ map (mapsnd (expandParams dec ps ns [])) params)
               (map (expandParamsD True ist dec ps ns) pds)
--                (map (expandParamsD ist dec ps ns) pds)
expandParamsD rhs ist dec ps ns (PMutual f pds)
   = PMutual f (map (expandParamsD rhs ist dec ps ns) pds)
expandParamsD rhs ist dec ps ns (PClass doc info f cs n params decls)
   = PClass doc info f
           (map (expandParams dec ps ns []) cs)
           n
           (map (mapsnd (expandParams dec ps ns [])) params)
           (map (expandParamsD rhs ist dec ps ns) decls)
expandParamsD rhs ist dec ps ns (PInstance info f cs n params ty cn decls)
   = PInstance info f
           (map (expandParams dec ps ns []) cs)
           n
           (map (expandParams dec ps ns []) params)
           (expandParams dec ps ns [] ty)
           cn
           (map (expandParamsD rhs ist dec ps ns) decls)
expandParamsD rhs ist dec ps ns d = d

mapsnd f (x, t) = (x, f t)

-- Calculate a priority for a type, for deciding elaboration order
-- * if it's just a type variable or concrete type, do it early (0)
-- * if there's only type variables and injective constructors, do it next (1)
-- * if there's a function type, next (2)
-- * finally, everything else (3)

getPriority :: IState -> PTerm -> Int
getPriority i tm = 1 -- pri tm
  where
    pri (PRef _ n) =
        case lookupP n (tt_ctxt i) of
            ((P (DCon _ _) _ _):_) -> 1
            ((P (TCon _ _) _ _):_) -> 1
            ((P Ref _ _):_) -> 1
            [] -> 0 -- must be locally bound, if it's not an error...
    pri (PPi _ _ x y) = max 5 (max (pri x) (pri y))
    pri (PTrue _ _) = 0
    pri (PFalse _) = 0
    pri (PRefl _ _) = 1
    pri (PEq _ l r) = max 1 (max (pri l) (pri r))
    pri (PRewrite _ l r _) = max 1 (max (pri l) (pri r))
    pri (PApp _ f as) = max 1 (max (pri f) (foldr max 0 (map (pri.getTm) as)))
    pri (PAppBind _ f as) = max 1 (max (pri f) (foldr max 0 (map (pri.getTm) as)))
    pri (PCase _ f as) = max 1 (max (pri f) (foldr max 0 (map (pri.snd) as)))
    pri (PTyped l r) = pri l
    pri (PPair _ _ l r) = max 1 (max (pri l) (pri r))
    pri (PDPair _ _ l t r) = max 1 (max (pri l) (max (pri t) (pri r)))
    pri (PAlternative a as) = maximum (map pri as)
    pri (PConstant _) = 0
    pri Placeholder = 1
    pri _ = 3


addStatics :: Name -> Term -> PTerm -> Idris ()
addStatics n tm ptm =
    do let (statics, dynamics) = initStatics tm ptm
       let stnames = nub $ concatMap freeArgNames (map snd statics)
       let dnames = nub $ concatMap freeArgNames (map snd dynamics)
       -- also get the arguments which are 'uniquely inferrable' from
       -- statics (see sec 4.2 of "Scrapping Your Inefficient Engine")
       let statics' = nub $ map fst statics ++
                              filter (\x -> not (elem x dnames)) stnames
       let stpos = staticList statics' tm
       i <- getIState
       when (not (null statics)) $
          logLvl 5 $ show n ++ " " ++ show statics' ++ "\n" ++ show dynamics
                        ++ "\n" ++ show stnames ++ "\n" ++ show dnames
       putIState $ i { idris_statics = addDef n stpos (idris_statics i) }
       addIBC (IBCStatic n)
  where
    initStatics (Bind n (Pi ty) sc) (PPi p _ _ s)
            = let (static, dynamic) = initStatics (instantiate (P Bound n ty) sc) s in
                  if pstatic p == Static then ((n, ty) : static, dynamic)
                    else if (not (searchArg p)) 
                            then (static, (n, ty) : dynamic)
                            else (static, dynamic)
    initStatics t pt = ([], [])

    freeArgNames (Bind n (Pi ty) sc) 
          = nub $ freeArgNames ty 
    freeArgNames tm = let (_, args) = unApply tm in
                          concatMap freeNames args

    -- if a name appears in a type class or tactic implicit index, it doesn't
    -- affect its 'uniquely inferrable' from a static status since these are
    -- resolved by searching.
    searchArg (Constraint _ _) = True
    searchArg (TacImp _ _ _) = True
    searchArg _ = False

    staticList sts (Bind n (Pi _) sc) = (n `elem` sts) : staticList sts sc
    staticList _ _ = []

-- Dealing with implicit arguments

-- Add constraint bindings from using block

addUsingConstraints :: SyntaxInfo -> FC -> PTerm -> Idris PTerm
addUsingConstraints syn fc t
   = do ist <- get
        let ns = namesIn [] ist t
        let cs = getConstraints t -- check declared constraints
        let addconsts = uconsts \\ cs
        -- if all names in the arguments of addconsts appear in ns,
        -- add the constraint implicitly
        return (doAdd addconsts ns t)
   where uconsts = filter uconst (using syn)
         uconst (UConstraint _ _) = True
         uconst _ = False

         doAdd [] _ t = t
         -- if all of args in ns, then add it
         doAdd (UConstraint c args : cs) ns t
             | all (\n -> elem n ns) args
                   = PPi (Constraint [] Dynamic) (sMN 0 "cu")
                         (mkConst c args) (doAdd cs ns t)
             | otherwise = doAdd cs ns t

         mkConst c args = PApp fc (PRef fc c)
                             (map (\n -> PExp 0 [] (PRef fc n)) args)

         getConstraints (PPi (Constraint _ _) _ c sc)
             = getcapp c ++ getConstraints sc
         getConstraints (PPi _ _ c sc) = getConstraints sc
         getConstraints _ = []

         getcapp (PApp _ (PRef _ c) args)
             = do ns <- mapM getName args
                  return (UConstraint c ns)
         getcapp _ = []

         getName (PExp _ _ (PRef _ n)) = return n
         getName _ = []

-- Add implicit Pi bindings for any names in the term which appear in an
-- argument position.

-- This has become a right mess already. Better redo it some time...

implicit :: SyntaxInfo -> Name -> PTerm -> Idris PTerm
implicit syn n ptm = implicit' syn [] n ptm

implicit' :: SyntaxInfo -> [Name] -> Name -> PTerm -> Idris PTerm
implicit' syn ignore n ptm
    = do i <- getIState
         let (tm', impdata) = implicitise syn ignore i ptm
--          let (tm'', spos) = findStatics i tm'
         putIState $ i { idris_implicits = addDef n impdata (idris_implicits i) }
         addIBC (IBCImp n)
         logLvl 5 ("Implicit " ++ show n ++ " " ++ show impdata)
--          i <- get
--          putIState $ i { idris_statics = addDef n spos (idris_statics i) }
         return tm'

implicitise :: SyntaxInfo -> [Name] -> IState -> PTerm -> (PTerm, [PArg])
implicitise syn ignore ist tm = -- trace ("INCOMING " ++ showImp True tm) $
      let (declimps, ns') = execState (imps True [] tm) ([], [])
          ns = filter (\n -> implicitable n || elem n (map fst uvars)) $
                  ns' \\ (map fst pvars ++ no_imp syn ++ ignore)
          nsOrder = filter (not . inUsing) ns ++ filter inUsing ns in
          if null ns
            then (tm, reverse declimps)
            else implicitise syn ignore ist (pibind uvars nsOrder tm)
  where
    uvars = map ipair (filter uimplicit (using syn))
    pvars = syn_params syn

    inUsing n = n `elem` map fst uvars

    ipair (UImplicit x y) = (x, y)
    uimplicit (UImplicit _ _) = True
    uimplicit _ = False

    dropAll (x:xs) ys | x `elem` ys = dropAll xs ys
                      | otherwise   = x : dropAll xs ys
    dropAll [] ys = []

    -- Find names in argument position in a type, suitable for implicit
    -- binding
    -- Not the function position, but do everything else...
    implNamesIn uv (PApp fc f args) = concatMap (implNamesIn uv) (map getTm args)
    implNamesIn uv t = namesIn uv ist t

    imps top env (PApp _ f as)
       = do (decls, ns) <- get
            let isn = concatMap (namesIn uvars ist) (map getTm as)
            put (decls, nub (ns ++ (isn `dropAll` (env ++ map fst (getImps decls)))))
    imps top env (PPi (Imp l _ _) n ty sc)
        = do let isn = nub (implNamesIn uvars ty) `dropAll` [n]
             (decls , ns) <- get
             put (PImp (getPriority ist ty) True l n Placeholder : decls,
                  nub (ns ++ (isn `dropAll` (env ++ map fst (getImps decls)))))
             imps True (n:env) sc
    imps top env (PPi (Exp l _ _) n ty sc)
        = do let isn = nub (implNamesIn uvars ty ++ case sc of
                            (PRef _ x) -> namesIn uvars ist sc `dropAll` [n]
                            _ -> [])
             (decls, ns) <- get -- ignore decls in HO types
             put (PExp (getPriority ist ty) l Placeholder : decls,
                  nub (ns ++ (isn `dropAll` (env ++ map fst (getImps decls)))))
             imps True (n:env) sc
    imps top env (PPi (Constraint l _) n ty sc)
        = do let isn = nub (implNamesIn uvars ty ++ case sc of
                            (PRef _ x) -> namesIn uvars ist sc `dropAll` [n]
                            _ -> [])
             (decls, ns) <- get -- ignore decls in HO types
             put (PConstraint 10 l Placeholder : decls,
                  nub (ns ++ (isn `dropAll` (env ++ map fst (getImps decls)))))
             imps True (n:env) sc
    imps top env (PPi (TacImp l _ scr) n ty sc)
        = do let isn = nub (implNamesIn uvars ty ++ case sc of
                            (PRef _ x) -> namesIn uvars ist sc `dropAll` [n]
                            _ -> [])
             (decls, ns) <- get -- ignore decls in HO types
             put (PTacImplicit 10 l n scr Placeholder : decls,
                  nub (ns ++ (isn `dropAll` (env ++ map fst (getImps decls)))))
             imps True (n:env) sc
    imps top env (PEq _ l r)
        = do (decls, ns) <- get
             let isn = namesIn uvars ist l ++ namesIn uvars ist r
             put (decls, nub (ns ++ (isn `dropAll` (env ++ map fst (getImps decls)))))
    imps top env (PRewrite _ l r _)
        = do (decls, ns) <- get
             let isn = namesIn uvars ist l ++ namesIn uvars ist r
             put (decls, nub (ns ++ (isn `dropAll` (env ++ map fst (getImps decls)))))
    imps top env (PTyped l r)
        = imps top env l
    imps top env (PPair _ _ l r)
        = do (decls, ns) <- get
             let isn = namesIn uvars ist l ++ namesIn uvars ist r
             put (decls, nub (ns ++ (isn `dropAll` (env ++ map fst (getImps decls)))))
    imps top env (PDPair _ _ (PRef _ n) t r)
        = do (decls, ns) <- get
             let isn = nub (namesIn uvars ist t ++ namesIn uvars ist r) \\ [n]
             put (decls, nub (ns ++ (isn \\ (env ++ map fst (getImps decls)))))
    imps top env (PDPair _ _ l t r)
        = do (decls, ns) <- get
             let isn = namesIn uvars ist l ++ namesIn uvars ist t ++
                       namesIn uvars ist r
             put (decls, nub (ns ++ (isn \\ (env ++ map fst (getImps decls)))))
    imps top env (PAlternative a as)
        = do (decls, ns) <- get
             let isn = concatMap (namesIn uvars ist) as
             put (decls, nub (ns ++ (isn `dropAll` (env ++ map fst (getImps decls)))))
    imps top env (PLam n ty sc)
        = do imps False env ty
             imps False (n:env) sc
    imps top env (PHidden tm)    = imps False env tm
    imps top env (PUnifyLog tm)  = imps False env tm
    imps top env (PNoImplicits tm)  = imps False env tm
    imps top env _               = return ()

    pibind using []     sc = sc
    pibind using (n:ns) sc
      = case lookup n using of
            Just ty -> PPi (Imp [] Dynamic False) n ty (pibind using ns sc)
            Nothing -> PPi (Imp [] Dynamic False) n Placeholder
                                   (pibind using ns sc)

-- Add implicit arguments in function calls
addImplPat :: IState -> PTerm -> PTerm
addImplPat = addImpl' True [] []

addImplBound :: IState -> [Name] -> PTerm -> PTerm
addImplBound ist ns = addImpl' False ns [] ist

addImplBoundInf :: IState -> [Name] -> [Name] -> PTerm -> PTerm
addImplBoundInf ist ns inf = addImpl' False ns inf ist

addImpl :: IState -> PTerm -> PTerm
addImpl = addImpl' False [] []

-- TODO: in patterns, don't add implicits to function names guarded by constructors
-- and *not* inside a PHidden

addImpl' :: Bool -> [Name] -> [Name] -> IState -> PTerm -> PTerm
addImpl' inpat env infns ist ptm 
         = mkUniqueNames env (ai (zip env (repeat Nothing)) [] ptm)
  where
    ai env ds (PRef fc f)
        | f `elem` infns = PInferRef fc f
        | not (f `elem` map fst env) = handleErr $ aiFn inpat inpat ist fc f ds []
    ai env ds (PHidden (PRef fc f))
        | not (f `elem` map fst env) = handleErr $ aiFn inpat False ist fc f ds []
    ai env ds (PEq fc l r)   
      = let l' = ai env ds l
            r' = ai env ds r in
            PEq fc l' r'
    ai env ds (PRewrite fc l r g)   
       = let l' = ai env ds l
             r' = ai env ds r
             g' = fmap (ai env ds) g in
         PRewrite fc l' r' g'
    ai env ds (PTyped l r) 
      = let l' = ai env ds l
            r' = ai env ds r in
            PTyped l' r'
    ai env ds (PPair fc p l r) 
      = let l' = ai env ds l
            r' = ai env ds r in
            PPair fc p l' r'
    ai env ds (PDPair fc p l t r)
         = let l' = ai env ds l
               t' = ai env ds t
               r' = ai env ds r in
           PDPair fc p l' t' r'
    ai env ds (PAlternative a as) 
           = let as' = map (ai env ds) as in
                 PAlternative a as'
    ai env _ (PDisamb ds' as) = ai env ds' as
    ai env ds (PApp fc (PInferRef _ f) as)
        = let as' = map (fmap (ai env ds)) as in
              PApp fc (PInferRef fc f) as'
    ai env ds (PApp fc ftm@(PRef _ f) as)
        | f `elem` infns = ai env ds (PApp fc (PInferRef fc f) as)
        | not (f `elem` map fst env)
                          = let as' = map (fmap (ai env ds)) as in
                                handleErr $ aiFn inpat False ist fc f ds as'
        | Just (Just ty) <- lookup f env =
             let as' = map (fmap (ai env ds)) as
                 arity = getPArity ty in
              mkPApp fc arity ftm as'
    ai env ds (PApp fc f as) 
      = let f' = ai env ds f
            as' = map (fmap (ai env ds)) as in
         mkPApp fc 1 f' as'
    ai env ds (PCase fc c os) 
      = let c' = ai env ds c
            os' = map (pmap (ai env ds)) os in
            PCase fc c' os'
    ai env ds (PLam n ty sc) 
      = let ty' = ai env ds ty
            sc' = ai ((n, Just ty):env) ds sc in
            PLam n ty' sc'
    ai env ds (PLet n ty val sc)
      = let ty' = ai env ds ty
            val' = ai env ds val
            sc' = ai ((n, Just ty):env) ds sc in
            PLet n ty' val' sc'
    ai env ds (PPi p n ty sc) 
      = let ty' = ai env ds ty
            sc' = ai ((n, Just ty):env) ds sc in
            PPi p n ty' sc'
    ai env ds (PGoal fc r n sc) 
      = let r' = ai env ds r
            sc' = ai ((n, Nothing):env) ds sc in
            PGoal fc r' n sc'
    ai env ds (PHidden tm) = PHidden (ai env ds tm)
    ai env ds (PProof ts) = PProof (map (fmap (ai env ds)) ts)
    ai env ds (PTactics ts) = PTactics (map (fmap (ai env ds)) ts)
    ai env ds (PRefl fc tm) = PRefl fc (ai env ds tm)
    ai env ds (PUnifyLog tm) = PUnifyLog (ai env ds tm)
    ai env ds (PNoImplicits tm) = PNoImplicits (ai env ds tm)
    ai env ds tm = tm

    handleErr (Left err) = PElabError err
    handleErr (Right x) = x

-- if in a pattern, and there are no arguments, and there's no possible
-- names with zero explicit arguments, don't add implicits.

aiFn :: Bool -> Bool -> IState -> FC -> Name -> [[T.Text]] -> [PArg] -> Either Err PTerm
aiFn inpat True ist fc f ds []
  = case lookupDef f (tt_ctxt ist) of
        [] -> Right $ PPatvar fc f
        alts -> let ialts = lookupCtxtName f (idris_implicits ist) in
                    -- trace (show f ++ " " ++ show (fc, any (all imp) ialts, ialts, any constructor alts)) $
                    if (not (vname f) || tcname f
                           || any (conCaf (tt_ctxt ist)) ialts)
--                            any constructor alts || any allImp ialts))
                        then aiFn inpat False ist fc f ds [] -- use it as a constructor
                        else Right $ PPatvar fc f
    where imp (PExp _ _ _) = False
          imp _ = True
--           allImp [] = False
          allImp xs = all imp xs
          constructor (TyDecl (DCon _ _) _) = True
          constructor _ = False

          conCaf ctxt (n, cia) = isDConName n ctxt && allImp cia

          vname (UN n) = True -- non qualified
          vname _ = False

aiFn inpat expat ist fc f ds as
    | f `elem` primNames = Right $ PApp fc (PRef fc f) as
aiFn inpat expat ist fc f ds as
          -- This is where namespaces get resolved by adding PAlternative
     = do let ns = lookupCtxtName f (idris_implicits ist)
          let nh = filter (\(n, _) -> notHidden n) ns
          let ns' = case trimAlts ds nh of
                         [] -> nh
                         x -> x 
          case ns' of
            [(f',ns)] -> Right $ mkPApp fc (length ns) (PRef fc f') (insertImpl ns as)
            [] -> if f `elem` (map fst (idris_metavars ist))
                    then Right $ PApp fc (PRef fc f) as
                    else Right $ mkPApp fc (length as) (PRef fc f) as
            alts -> Right $
                         PAlternative True $
                           map (\(f', ns) -> mkPApp fc (length ns) (PRef fc f')
                                                  (insertImpl ns as)) alts
  where
    trimAlts [] alts = alts
    trimAlts ns alts 
        = filter (\(x, _) -> any (\d -> d `isPrefixOf` nspace x) ns) alts

    nspace (NS _ s) = s
    nspace _ = []

    notHidden n = case getAccessibility n of
                        Hidden -> False
                        _ -> True

    getAccessibility n
             = case lookupDefAcc n False (tt_ctxt ist) of
                    [(n,t)] -> t
                    _ -> Public


    insertImpl :: [PArg] -> [PArg] -> [PArg]
    insertImpl (PExp p l ty : ps) (PExp _ _ tm : given) =
                                 PExp p l tm : insertImpl ps given
    insertImpl (PConstraint p l ty : ps) (PConstraint _ _ tm : given) =
                                 PConstraint p l tm : insertImpl ps given
    insertImpl (PConstraint p l ty : ps) given =
                 PConstraint p l (PResolveTC fc) : insertImpl ps given
    insertImpl (PImp p _ l n ty : ps) given =
        case find n given [] of
            Just (tm, given') -> PImp p False l n tm : insertImpl ps given'
            Nothing ->           PImp p True l n Placeholder : insertImpl ps given
    insertImpl (PTacImplicit p l n sc' ty : ps) given =
      let sc = addImpl ist sc' in
        case find n given [] of
            Just (tm, given') -> PTacImplicit p l n sc tm : insertImpl ps given'
            Nothing -> if inpat
                          then PTacImplicit p l n sc Placeholder : insertImpl ps given
                          else PTacImplicit p l n sc sc : insertImpl ps given
    insertImpl expected [] = []
    insertImpl _        given  = given

    find n []               acc = Nothing
    find n (PImp _ _ _ n' t : gs) acc
         | n == n' = Just (t, reverse acc ++ gs)
    find n (PTacImplicit _ _ n' _ t : gs) acc
         | n == n' = Just (t, reverse acc ++ gs)
    find n (g : gs) acc = find n gs (g : acc)

-- replace non-linear occurrences with _
-- ASSUMPTION: This is called before adding 'alternatives' because otherwise
-- it is hard to get right!

stripLinear :: IState -> PTerm -> PTerm
stripLinear i tm = evalState (sl tm) [] where
    sl :: PTerm -> State [Name] PTerm
    sl (PRef fc f)
         | (_:_) <- lookupTy f (tt_ctxt i)
              = return $ PRef fc f
         | otherwise = do ns <- get
                          if (f `elem` ns)
                             then return Placeholder
                             else do put (f : ns)
                                     return (PRef fc f)
    sl (PPatvar fc f)
                     = do ns <- get
                          if (f `elem` ns)
                             then return Placeholder
                             else do put (f : ns)
                                     return (PPatvar fc f)
    sl t@(PAlternative _ (a : as)) = do sl a
                                        return t
    sl (PApp fc fn args) = do -- Just the args, fn isn't matchable as a var 
                              args' <- mapM slA args
                              return $ PApp fc fn args'
       where slA (PImp p m l n t) = do t' <- sl t
                                       return $ PImp p m l n t'
             slA (PExp p l t) = do t' <- sl t
                                   return $ PExp p l t'
             slA (PConstraint p l t)
                                = do t' <- sl t
                                     return $ PConstraint p l t'
             slA (PTacImplicit p l n sc t)
                                = do t' <- sl t
                                     return $ PTacImplicit p l n sc t'
    sl x = return x

-- Remove functions which aren't applied to anything, which must then
-- be resolved by unification. Assume names resolved and alternatives
-- filled in (so no ambiguity).

stripUnmatchable :: IState -> PTerm -> PTerm
stripUnmatchable i (PApp fc fn args) = PApp fc fn (fmap (fmap su) args) where
    su :: PTerm -> PTerm
    su (PRef fc f)
       | (Bind n (Pi t) sc :_) <- lookupTy f (tt_ctxt i) 
          = Placeholder
    su (PApp fc fn args) 
       = PApp fc fn (fmap (fmap su) args)
    su (PAlternative b alts) 
       = let alts' = filter (/= Placeholder) (map su alts) in
             if null alts' then Placeholder
                           else PAlternative b alts'
    su (PPair fc p l r) = PPair fc p (su l) (su r)
    su (PDPair fc p l t r) = PDPair fc p (su l) (su t) (su r)
    su t = t
stripUnmatchable i tm = tm

mkPApp fc a f [] = f
mkPApp fc a f as = let rest = drop a as in
                       appRest fc (PApp fc f (take a as)) rest
  where
    appRest fc f [] = f
    appRest fc f (a : as) = appRest fc (PApp fc f [a]) as

-- Find 'static' argument positions
-- (the declared ones, plus any names in argument position in the declared
-- statics)
-- FIXME: It's possible that this really has to happen after elaboration

findStatics :: IState -> PTerm -> (PTerm, [Bool])
findStatics ist tm = trace (show tm) $
                      let (ns, ss) = fs tm in
                         runState (pos ns ss tm) []
  where fs (PPi p n t sc)
            | Static <- pstatic p
                        = let (ns, ss) = fs sc in
                              (namesIn [] ist t : ns, n : ss)
            | otherwise = let (ns, ss) = fs sc in
                              (ns, ss)
        fs _ = ([], [])

        inOne n ns = length (filter id (map (elem n) ns)) == 1

        pos ns ss (PPi p n t sc)
            | elem n ss = do sc' <- pos ns ss sc
                             spos <- get
                             put (True : spos)
                             return (PPi (p { pstatic = Static }) n t sc')
            | otherwise = do sc' <- pos ns ss sc
                             spos <- get
                             put (False : spos)
                             return (PPi p n t sc')
        pos ns ss t = return t

-- for 6.12/7 compatibility
data EitherErr a b = LeftErr a | RightOK b

instance Monad (EitherErr a) where
    return = RightOK

    (LeftErr e) >>= k = LeftErr e
    RightOK v   >>= k = k v

toEither (LeftErr e)  = Left e
toEither (RightOK ho) = Right ho

-- syntactic match of a against b, returning pair of variables in a
-- and what they match. Returns the pair that failed if not a match.

matchClause :: IState -> PTerm -> PTerm -> Either (PTerm, PTerm) [(Name, PTerm)]
matchClause = matchClause' False

matchClause' :: Bool -> IState -> PTerm -> PTerm -> Either (PTerm, PTerm) [(Name, PTerm)]
matchClause' names i x y = checkRpts $ match (fullApp x) (fullApp y) where
    matchArg x y = match (fullApp (getTm x)) (fullApp (getTm y))

    fullApp (PApp _ (PApp fc f args) xs) = fullApp (PApp fc f (args ++ xs))
    fullApp x = x

    match' x y = match (fullApp x) (fullApp y)
    match (PApp _ (PRef _ (NS (UN fi) [b])) [_,_,x]) x'
        | fi == txt "fromInteger" && b == txt "builtins",
          PConstant (I _) <- getTm x = match (getTm x) x'
    match x' (PApp _ (PRef _ (NS (UN fi) [b])) [_,_,x])
        | fi == txt "fromInteger" && b == txt "builtins",
          PConstant (I _) <- getTm x = match (getTm x) x'
    match (PApp _ (PRef _ (UN l)) [_,x]) x' | l == txt "lazy" = match (getTm x) x'
    match x (PApp _ (PRef _ (UN l)) [_,x']) | l == txt "lazy" = match x (getTm x')
    match (PApp _ f args) (PApp _ f' args')
        | length args == length args'
            = do mf <- match' f f'
                 ms <- zipWithM matchArg args args'
                 return (mf ++ concat ms)
    match (PRef f n) (PApp _ x []) = match (PRef f n) x
    match (PPatvar f n) xr = match (PRef f n) xr
    match xr (PPatvar f n) = match xr (PRef f n)
    match (PApp _ x []) (PRef f n) = match x (PRef f n)
    match (PRef _ n) tm@(PRef _ n')
        | n == n' && not names &&
          (not (isConName n (tt_ctxt i) || isFnName n (tt_ctxt i)) 
                || tm == Placeholder)
            = return [(n, tm)]
        -- if one namespace is missing, drop the other
        | n == n' || n == dropNS n' || dropNS n == n' = return []
       where dropNS (NS n _) = n
             dropNS n = n
    match (PRef _ n) tm
        | not names && (not (isConName n (tt_ctxt i) ||
                             isFnName n (tt_ctxt i)) || tm == Placeholder)
            = return [(n, tm)]
    match (PEq _ l r) (PEq _ l' r') = do ml <- match' l l'
                                         mr <- match' r r'
                                         return (ml ++ mr)
    match (PRewrite _ l r _) (PRewrite _ l' r' _)
                                    = do ml <- match' l l'
                                         mr <- match' r r'
                                         return (ml ++ mr)
    match (PTyped l r) (PTyped l' r') = do ml <- match l l'
                                           mr <- match r r'
                                           return (ml ++ mr)
    match (PTyped l r) x = match l x
    match x (PTyped l r) = match x l
    match (PPair _ _ l r) (PPair _ _ l' r') = do ml <- match' l l'
                                                 mr <- match' r r'
                                                 return (ml ++ mr)
    match (PDPair _ _ l t r) (PDPair _ _ l' t' r') = do ml <- match' l l'
                                                        mt <- match' t t'
                                                        mr <- match' r r'
                                                        return (ml ++ mt ++ mr)
    match (PAlternative a as) (PAlternative a' as')
        = do ms <- zipWithM match' as as'
             return (concat ms)
    match a@(PAlternative _ as) b
        = do let ms = zipWith match' as (repeat b)
             case (rights (map toEither ms)) of
                (x: _) -> return x
                _ -> LeftErr (a, b)
    match (PCase _ _ _) _ = return [] -- lifted out
    match (PMetavar _) _ = return [] -- modified
    match (PInferRef _ _) _ = return [] -- modified
    match (PQuote _) _ = return []
    match (PProof _) _ = return []
    match (PTactics _) _ = return []
    match (PRefl _ _) (PRefl _ _) = return []
    match (PResolveTC _) (PResolveTC _) = return []
    match (PTrue _ _) (PTrue _ _) = return []
    match (PFalse _) (PFalse _) = return []
    match (PReturn _) (PReturn _) = return []
    match (PPi _ _ t s) (PPi _ _ t' s') = do mt <- match' t t'
                                             ms <- match' s s'
                                             return (mt ++ ms)
    match (PLam _ t s) (PLam _ t' s') = do mt <- match' t t'
                                           ms <- match' s s'
                                           return (mt ++ ms)
    match (PLet _ t ty s) (PLet _ t' ty' s') = do mt <- match' t t'
                                                  mty <- match' ty ty'
                                                  ms <- match' s s'
                                                  return (mt ++ mty ++ ms)
    match (PHidden x) (PHidden y) = match' x y
    match (PUnifyLog x) y = match' x y
    match x (PUnifyLog y) = match' x y
    match (PNoImplicits x) y = match' x y
    match x (PNoImplicits y) = match' x y
    match Placeholder _ = return []
    match _ Placeholder = return []
    match (PResolveTC _) _ = return []
    match a b | a == b = return []
              | otherwise = LeftErr (a, b)

    checkRpts (RightOK ms) = check ms where
        check ((n,t):xs)
            | Just t' <- lookup n xs = if t/=t' && t/=Placeholder && t'/=Placeholder
                                                then Left (t, t')
                                                else check xs
        check (_:xs) = check xs
        check [] = Right ms
    checkRpts (LeftErr x) = Left x

substMatches :: [(Name, PTerm)] -> PTerm -> PTerm
substMatches ms = substMatchesShadow ms []

substMatchesShadow :: [(Name, PTerm)] -> [Name] -> PTerm -> PTerm
substMatchesShadow [] shs t = t
substMatchesShadow ((n,tm):ns) shs t
   = substMatchShadow n shs tm (substMatchesShadow ns shs t)

substMatch :: Name -> PTerm -> PTerm -> PTerm
substMatch n = substMatchShadow n []

substMatchShadow :: Name -> [Name] -> PTerm -> PTerm -> PTerm
substMatchShadow n shs tm t = sm shs t where
    sm xs (PRef _ n') | n == n' = tm
    sm xs (PLam x t sc) = PLam x (sm xs t) (sm xs sc)
    sm xs (PPi p x t sc)
         | x `elem` xs
             = let x' = nextName x in
                   PPi p x' (sm (x':xs) (substMatch x (PRef emptyFC x') t))
                            (sm (x':xs) (substMatch x (PRef emptyFC x') sc))
         | otherwise = PPi p x (sm xs t) (sm (x : xs) sc)
    sm xs (PApp f x as) = fullApp $ PApp f (sm xs x) (map (fmap (sm xs)) as)
    sm xs (PCase f x as) = PCase f (sm xs x) (map (pmap (sm xs)) as)
    sm xs (PEq f x y) = PEq f (sm xs x) (sm xs y)
    sm xs (PRewrite f x y tm) = PRewrite f (sm xs x) (sm xs y)
                                           (fmap (sm xs) tm)
    sm xs (PTyped x y) = PTyped (sm xs x) (sm xs y)
    sm xs (PPair f p x y) = PPair f p (sm xs x) (sm xs y)
    sm xs (PDPair f p x t y) = PDPair f p (sm xs x) (sm xs t) (sm xs y)
    sm xs (PAlternative a as) = PAlternative a (map (sm xs) as)
    sm xs (PHidden x) = PHidden (sm xs x)
    sm xs (PUnifyLog x) = PUnifyLog (sm xs x)
    sm xs (PNoImplicits x) = PNoImplicits (sm xs x)
    sm xs x = x

    fullApp (PApp _ (PApp fc f args) xs) = fullApp (PApp fc f (args ++ xs))
    fullApp x = x

shadow :: Name -> Name -> PTerm -> PTerm
shadow n n' t = sm t where
    sm (PRef fc x) | n == x = PRef fc n'
    sm (PLam x t sc) | n /= x = PLam x (sm t) (sm sc)
    sm (PPi p x t sc) | n /=x = PPi p x (sm t) (sm sc)
    sm (PLet x t v sc) | n /= x = PLet x (sm t) (sm v) (sm sc)
    sm (PApp f x as) = PApp f (sm x) (map (fmap sm) as)
    sm (PAppBind f x as) = PAppBind f (sm x) (map (fmap sm) as)
    sm (PCase f x as) = PCase f (sm x) (map (pmap sm) as)
    sm (PEq f x y) = PEq f (sm x) (sm y)
    sm (PRewrite f x y tm) = PRewrite f (sm x) (sm y) (fmap sm tm)
    sm (PTyped x y) = PTyped (sm x) (sm y)
    sm (PPair f p x y) = PPair f p (sm x) (sm y)
    sm (PDPair f p x t y) = PDPair f p (sm x) (sm t) (sm y)
    sm (PAlternative a as) = PAlternative a (map sm as)
    sm (PTactics ts) = PTactics (map (fmap sm) ts)
    sm (PProof ts) = PProof (map (fmap sm) ts)
    sm (PHidden x) = PHidden (sm x)
    sm (PUnifyLog x) = PUnifyLog (sm x)
    sm (PNoImplicits x) = PNoImplicits (sm x)
    sm x = x

-- Rename any binders which are repeated (so that we don't have to mess
-- about with shadowing anywhere else).

mkUniqueNames :: [Name] -> PTerm -> PTerm
mkUniqueNames env tm = evalState (mkUniq tm) env where
  inScope = boundNamesIn tm

  mkUniqA arg = do t' <- mkUniq (getTm arg)
                   return (arg { getTm = t' })

  -- Initialise the unique name with the environment length (so we're not
  -- looking for too long...)
  initN (UN n) l = UN $ txt (str n ++ show l)
  initN (MN i s) l = MN (i+l) s
  initN n l = n

  -- FIXME: Probably ought to do this for completeness! It's fine as
  -- long as there are no bindings inside tactics though.
  mkUniqT tac = return tac

  mkUniq :: PTerm -> State [Name] PTerm
  mkUniq (PLam n ty sc)
         = do env <- get
              (n', sc') <-
                    if n `elem` env
                       then do let n' = uniqueName (initN n (length env))
                                                   (env ++ inScope)
                               return (n', shadow n n' sc)
                       else return (n, sc)
              put (n' : env)
              ty' <- mkUniq ty
              sc'' <- mkUniq sc'
              return $! PLam n' ty' sc''
  mkUniq (PPi p n ty sc)
         = do env <- get
              (n', sc') <-
                    if n `elem` env
                       then do let n' = uniqueName (initN n (length env))
                                                   (env ++ inScope)
                               return (n', shadow n n' sc)
                       else return (n, sc)
              put (n' : env)
              ty' <- mkUniq ty
              sc'' <- mkUniq sc'
              return $! PPi p n' ty' sc''
  mkUniq (PLet n ty val sc)
         = do env <- get
              (n', sc') <-
                    if n `elem` env
                       then do let n' = uniqueName (initN n (length env))
                                                   (env ++ inScope)
                               return (n', shadow n n' sc)
                       else return (n, sc)
              put (n' : env)
              ty' <- mkUniq ty; val' <- mkUniq val
              sc'' <- mkUniq sc'
              return $! PLet n' ty' val' sc''
  mkUniq (PApp fc t args)
         = do t' <- mkUniq t
              args' <- mapM mkUniqA args
              return $! PApp fc t' args'
  mkUniq (PAppBind fc t args)
         = do t' <- mkUniq t
              args' <- mapM mkUniqA args
              return $! PAppBind fc t' args'
  mkUniq (PCase fc t alts)
         = do t' <- mkUniq t
              alts' <- mapM (\(x,y)-> do x' <- mkUniq x; y' <- mkUniq y
                                         return (x', y')) alts
              return $! PCase fc t' alts'
  mkUniq (PPair fc p l r)
         = do l' <- mkUniq l; r' <- mkUniq r
              return $! PPair fc p l' r'
  mkUniq (PDPair fc p (PRef fc' n) t sc)
      | t /= Placeholder
         = do env <- get
              (n', sc') <- if n `elem` env
                              then do let n' = uniqueName n (env ++ inScope)
                                      return (n', shadow n n' sc)
                              else return (n, sc)
              put (n' : env)
              t' <- mkUniq t
              sc'' <- mkUniq sc'
              return $! PDPair fc p (PRef fc' n') t' sc''
  mkUniq (PDPair fc p l t r)
         = do l' <- mkUniq l; t' <- mkUniq t; r' <- mkUniq r
              return $! PDPair fc p l' t' r'
  mkUniq (PAlternative b as)
         = liftM (PAlternative b) (mapM mkUniq as)
  mkUniq (PHidden t) = liftM PHidden (mkUniq t)
  mkUniq (PUnifyLog t) = liftM PUnifyLog (mkUniq t)
  mkUniq (PDisamb n t) = liftM (PDisamb n) (mkUniq t)
  mkUniq (PNoImplicits t) = liftM PNoImplicits (mkUniq t)
  mkUniq (PProof ts) = liftM PProof (mapM mkUniqT ts)
  mkUniq (PTactics ts) = liftM PTactics (mapM mkUniqT ts)
  mkUniq t = return t