AbsSyntax.hs

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

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

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

import Paths_idris

import System.Console.Haskeline

import Control.Monad.State

import Data.List
import Data.Char
import Data.Either

import Debug.Trace

import Util.Pretty
import Util.System

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

getObjectFiles :: Idris [FilePath]
getObjectFiles = do i <- getIState; return (idris_objs i)

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

getLibs :: Idris [String]
getLibs = do i <- getIState; return (idris_libs i)

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

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

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

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

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

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) }

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

addDocStr :: Name -> String -> Idris ()
addDocStr n doc 
   = do i <- getIState
        putIState $ i { idris_docstrings = addDef n doc (idris_docstrings i) }

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 ins] ->
                     do let cs = addDef n (CI a b c d (addI i ins)) (idris_classes ist)
                        putIState $ ist { idris_classes = cs }
                _ -> do let cs = addDef n (CI (MN 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 ('@':'@':_)) = 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 = [] }

getHdrs :: Idris [String]
getHdrs = do i <- getIState; return (idris_hdrs i)

setErrLine :: Int -> Idris ()
setErrLine x = do i <- getIState;
                  case (errLine i) of
                      Nothing -> putIState $ i { errLine = Just x }
                      Just _ -> return ()

clearErr :: Idris ()
clearErr = do i <- getIState
              putIState $ i { errLine = 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

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

checkUndefined :: FC -> Name -> Idris ()
checkUndefined fc n 
    = do i <- getContext
         case lookupTy n i of
             (_:_)  -> fail $ 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, Type)] -> Idris ()
addDeferred' nt ns 
  = do mapM_ (\(n, t) -> updateContext (addTyDecl n nt (tidyNames [] t))) ns
       i <- getIState
       putIState $ i { idris_metavars = map fst 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 = idris_metavars i \\ [n] }

iResult :: String -> Idris ()
iResult s = do i <- getIState
               case idris_outputmode i of
                 RawOutput -> case s of
                                   "" -> return ()
                                   s  -> liftIO $ putStrLn s
                 IdeSlave n ->
                   let good = SexpList [SymbolAtom "ok", toSExp s] in
                       liftIO $ putStrLn $ convSExp "return" good n

iFail :: String -> Idris ()
iFail s = do i <- getIState
             case idris_outputmode i of
               RawOutput -> case s of
                                 "" -> return ()
                                 s  -> liftIO $ putStrLn s
               IdeSlave n ->
                 let good = SexpList [SymbolAtom "error", toSExp s] in
                     liftIO $ putStrLn $ convSExp "return" good n

iputStrLn :: String -> Idris ()
iputStrLn s = do i <- getIState
                 case idris_outputmode i of
                   RawOutput -> liftIO $ putStrLn s
                   IdeSlave n ->
                     case span (/=':') s of
                       (fn, ':':rest) -> case span isDigit rest of
                         ([], ':':msg) -> write
                         ([], msg) -> write
                         (num, ':':msg) -> iWarn (FC fn (read num)) msg
                       _  -> write
                     where write = liftIO $ putStrLn $ convSExp "write-string" s n

iWarn :: FC -> String -> Idris ()
iWarn fc err = do i <- getIState
                  case idris_outputmode i of
                    RawOutput -> liftIO $ putStrLn (show fc ++ ":" ++ err)
                    IdeSlave n -> liftIO $ putStrLn $ convSExp "warning" (fc_fname fc, fc_line fc, err) 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 } }

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' }

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

setTarget :: Target -> Idris ()
setTarget t = do i <- getIState
                 let opts = idris_options i
                 let opt' = opts { opt_target = t }
                 putIState $ i { idris_options = opt' }

target :: Idris Target
target = do i <- getIState
            return (opt_target (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) }
setIdeSlave False = return ()

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

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' }

logLvl :: Int -> String -> Idris ()
logLvl l str = do i <- getIState
                  let lvl = opt_logLevel (idris_options i)
                  when (lvl >= l)
                      $ do liftIO (putStrLn str)
                           putIState $ i { idris_log = idris_log i ++ str ++ "\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 errLine 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' }


-- For inferring types of things

bi = FC "builtin" 0

inferTy   = MN 0 "__Infer"
inferCon  = MN 0 "__infer"
inferDecl = PDatadecl inferTy 
                      PType
                      [("", inferCon, PPi impl (MN 0 "A") PType (
                                  PPi expl (MN 0 "a") (PRef bi (MN 0 "A"))
                                  (PRef bi inferTy)), bi)]

infTerm t = PApp bi (PRef bi inferCon) [pimp (MN 0 "A") Placeholder, pexp t]
infP = P (TCon 6 0) inferTy (TType (UVal 0))

getInferTerm, getInferType :: Term -> Term
getInferTerm (Bind n b sc) = Bind n b $ getInferTerm sc
getInferTerm (App (App _ _) tm) = tm
getInferTerm tm = tm -- error ("getInferTerm " ++ show tm)

getInferType (Bind n b sc) = Bind n b $ getInferType sc
getInferType (App (App _ ty) _) = ty

-- Handy primitives: Unit, False, Pair, MkPair, =, mkForeign

primNames = [unitTy, unitCon,
             falseTy, pairTy, pairCon,
             eqTy, eqCon, inferTy, inferCon]

unitTy   = MN 0 "__Unit"
unitCon  = MN 0 "__II"
unitDecl = PDatadecl unitTy PType
                     [("", unitCon, PRef bi unitTy, bi)]

falseTy   = MN 0 "__False"
falseDecl = PDatadecl falseTy PType []

pairTy    = MN 0 "__Pair"
pairCon   = MN 0 "__MkPair"
pairDecl  = PDatadecl pairTy (piBind [(n "A", PType), (n "B", PType)] PType)
            [("", pairCon, PPi impl (n "A") PType (
                       PPi impl (n "B") PType (
                       PPi expl (n "a") (PRef bi (n "A")) (
                       PPi expl (n "b") (PRef bi (n "B"))  
                           (PApp bi (PRef bi pairTy) [pexp (PRef bi (n "A")),
                                                pexp (PRef bi (n "B"))])))), bi)]
    where n a = MN 0 a

eqTy = UN "="
eqCon = UN "refl"
eqDecl = PDatadecl eqTy (piBind [(n "a", PType), (n "b", PType),
                                 (n "x", PRef bi (n "a")), (n "y", PRef bi (n "b"))]
                                 PType)
                [("", eqCon, PPi impl (n "a") PType (
                         PPi impl (n "x") (PRef bi (n "a"))
                           (PApp bi (PRef bi eqTy) [pimp (n "a") Placeholder,
                                                    pimp (n "b") Placeholder,
                                                    pexp (PRef bi (n "x")),
                                                    pexp (PRef bi (n "x"))])), bi)]
    where n a = MN 0 a

-- Defined in builtins.idr
sigmaTy   = UN "Exists"
existsCon = UN "Ex_intro"

piBind :: [(Name, PTerm)] -> PTerm -> PTerm
piBind = piBindp expl

piBindp :: Plicity -> [(Name, PTerm)] -> PTerm -> PTerm
piBindp p [] t = t
piBindp p ((n, ty):ns) t = PPi p n ty (piBind ns t)
    
-- 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
               = 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
               = 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
               = 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)
    en (PEq f l r) = PEq f (en l) (en r)
    en (PRewrite f l r) = PRewrite f (en l) (en r)
    en (PTyped l r) = PTyped (en l) (en r)
    en (PPair f l r) = PPair f (en l) (en r)
    en (PDPair f l t r) = PDPair f (en l) (en t) (en r)
    en (PAlternative a as) = PAlternative a (map en as)
    en (PHidden t) = PHidden (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 (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 (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 syn fc o n ty) 
    = if n `elem` ns && (not rhsonly)
         then -- trace (show (n, expandParams dec ps ns ty)) $
              PTy doc syn fc o (dec n) (piBind ps (expandParams dec ps ns [] ty))
         else --trace (show (n, expandParams dec ps ns ty)) $ 
              PTy doc 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 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 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 = (MN i (show n ++ "_u"), t) : updateps yn nm as
expandParamsD rhs ist dec ps ns (PData doc syn fc co pd) 
    = PData doc 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, n, t, fc) 
       = (doc, dec n, piBindp expl ps (expandParams dec ps ns [] t), fc)
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 (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 freeNames (map snd statics)
       let dnames = nub $ concatMap freeNames (map snd dynamics)
       when (not (null statics)) $
          logLvl 7 $ show n ++ " " ++ show statics ++ "\n" ++ show dynamics
                        ++ "\n" ++ show stnames ++ "\n" ++ show dnames
       let statics' = nub $ map fst statics ++ 
                              filter (\x -> not (elem x dnames)) stnames
       let stpos = staticList statics' tm
       i <- getIState
       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 (static, (n, ty) : dynamic)
    initStatics t pt = ([], [])

    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 False Dynamic "") (MN 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 False (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
    = 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) in
          if null ns 
            then (tm, reverse declimps) 
            else implicitise syn ignore ist (pibind uvars ns tm)
  where
    uvars = map ipair (filter uimplicit (using syn))
    pvars = syn_params syn

    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 = []

    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 _ doc) n ty sc) 
        = do let isn = nub (namesIn uvars ist ty) `dropAll` [n]
             (decls , ns) <- get
             put (PImp (getPriority ist ty) l n ty doc : decls, 
                  nub (ns ++ (isn `dropAll` (env ++ map fst (getImps decls)))))
             imps True (n:env) sc
    imps top env (PPi (Exp l _ doc) n ty sc) 
        = do let isn = nub (namesIn uvars ist 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 ty doc : decls, 
                  nub (ns ++ (isn `dropAll` (env ++ map fst (getImps decls)))))
             imps True (n:env) sc
    imps top env (PPi (Constraint l _ doc) n ty sc)
        = do let isn = nub (namesIn uvars ist ty ++ case sc of
                            (PRef _ x) -> namesIn uvars ist sc `dropAll` [n]
                            _ -> [])
             (decls, ns) <- get -- ignore decls in HO types
             put (PConstraint 10 l ty doc : decls, 
                  nub (ns ++ (isn `dropAll` (env ++ map fst (getImps decls)))))
             imps True (n:env) sc
    imps top env (PPi (TacImp l _ scr doc) n ty sc)
        = do let isn = nub (namesIn uvars ist 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 ty doc : 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 _               = return ()

    pibind using []     sc = sc
    pibind using (n:ns) sc 
      = case lookup n using of
            Just ty -> PPi (Imp False Dynamic "") n ty (pibind using ns sc)
            Nothing -> PPi (Imp False Dynamic "") 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 = ai (zip env (repeat Nothing)) ptm
  where
    ai env (PRef fc f)    
        | f `elem` infns = PInferRef fc f
        | not (f `elem` map fst env) = handleErr $ aiFn inpat inpat ist fc f []
    ai env (PHidden (PRef fc f))
        | not (f `elem` map fst env) = handleErr $ aiFn inpat False ist fc f []
    ai env (PEq fc l r)   = let l' = ai env l
                                r' = ai env r in
                                PEq fc l' r'
    ai env (PRewrite fc l r)   = let l' = ai env l
                                     r' = ai env r in
                                     PRewrite fc l' r'
    ai env (PTyped l r) = let l' = ai env l
                              r' = ai env r in
                              PTyped l' r'
    ai env (PPair fc l r) = let l' = ai env l
                                r' = ai env r in
                                PPair fc l' r'
    ai env (PDPair fc l t r) = let l' = ai env l
                                   t' = ai env t
                                   r' = ai env r in
                                   PDPair fc l' t' r'
    ai env (PAlternative a as) = let as' = map (ai env) as in
                                     PAlternative a as'
    ai env (PApp fc (PInferRef _ f) as) 
        = let as' = map (fmap (ai env)) as in
              PApp fc (PInferRef fc f) as'  
    ai env (PApp fc ftm@(PRef _ f) as) 
        | f `elem` infns = ai env (PApp fc (PInferRef fc f) as)
        | not (f `elem` map fst env)
                          = let as' = map (fmap (ai env)) as in
                                handleErr $ aiFn inpat False ist fc f as'
        | Just (Just ty) <- lookup f env
                          = let as' = map (fmap (ai env)) as 
                                arity = getPArity ty in
                                mkPApp fc arity ftm as'
    ai env (PApp fc f as) = let f' = ai env f
                                as' = map (fmap (ai env)) as in
                                mkPApp fc 1 f' as'
    ai env (PCase fc c os) = let c' = ai env c
                                 os' = map (pmap (ai env)) os in
                                 PCase fc c' os'
    ai env (PLam n ty sc) = let ty' = ai env ty
                                sc' = ai ((n, Just ty):env) sc in
                                PLam n ty' sc'
    ai env (PLet n ty val sc)
                          = let ty' = ai env ty
                                val' = ai env val
                                sc' = ai ((n, Just ty):env) sc in
                                PLet n ty' val' sc'
    ai env (PPi p n ty sc) = let ty' = ai env ty
                                 sc' = ai ((n, Just ty):env) sc in
                                 PPi p n ty' sc'
    ai env (PHidden tm) = PHidden (ai env tm)
    ai env (PProof ts) = PProof (map (fmap (ai env)) ts)
    ai env (PTactics ts) = PTactics (map (fmap (ai env)) ts)
    ai env 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 -> [PArg] -> Either Err PTerm
aiFn inpat True ist fc f []
  = case lookupDef f (tt_ctxt ist) of
        [] -> Right $ PPatvar fc f
        alts -> let ialts = lookupCtxt 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 constructor alts || any allImp ialts)
                        then aiFn inpat False ist fc f [] -- 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

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

aiFn inpat expat ist fc f as
    | f `elem` primNames = Right $ PApp fc (PRef fc f) as
aiFn inpat expat ist fc f as
          -- This is where namespaces get resolved by adding PAlternative
        = case lookupCtxtName f (idris_implicits ist) of
            [(f',ns)] -> Right $ mkPApp fc (length ns) (PRef fc f') (insertImpl ns as)
            [] -> if f `elem` 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
    insertImpl :: [PArg] -> [PArg] -> [PArg]
    insertImpl (PExp p l ty _ : ps) (PExp _ _ tm d : given) =
                                 PExp p l tm d : insertImpl ps given
    insertImpl (PConstraint p l ty _ : ps) (PConstraint _ _ tm d : given) =
                                 PConstraint p l tm d : insertImpl ps given
    insertImpl (PConstraint p l ty d : ps) given =
                 PConstraint p l (PResolveTC fc) d : insertImpl ps given
    insertImpl (PImp p l n ty d : ps) given =
        case find n given [] of
            Just (tm, given') -> PImp p l n tm "" : insertImpl ps given'
            Nothing ->           PImp p l n Placeholder "" : insertImpl ps given
    insertImpl (PTacImplicit p l n sc ty d : ps) given =
        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 (PApp fc fn args) = do fn' <- sl fn
                              args' <- mapM slA args
                              return $ PApp fc fn' args'
       where slA (PImp p l n t d) = do t' <- sl t
                                       return $ PImp p l n t' d
             slA (PExp p l t d) = do t' <- sl t
                                     return $ PExp p l t' d
             slA (PConstraint p l t d) 
                                = do t' <- sl t
                                     return $ PConstraint p l t' d
             slA (PTacImplicit p l n sc t d) 
                                = do t' <- sl t
                                     return $ PTacImplicit p l n sc t' d
    sl x = return x

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 (showImp True 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

-- Debugging/logging stuff

dumpDecls :: [PDecl] -> String
dumpDecls [] = ""
dumpDecls (d:ds) = dumpDecl d ++ "\n" ++ dumpDecls ds

dumpDecl (PFix _ f ops) = show f ++ " " ++ showSep ", " ops 
dumpDecl (PTy _ _ _ _ n t) = "tydecl " ++ show n ++ " : " ++ showImp True t
dumpDecl (PClauses _ _ n cs) = "pat " ++ show n ++ "\t" ++ showSep "\n\t" (map (showCImp True) cs)
dumpDecl (PData _ _ _ _ d) = showDImp True d
dumpDecl (PParams _ ns ps) = "params {" ++ show ns ++ "\n" ++ dumpDecls ps ++ "}\n"
dumpDecl (PNamespace n ps) = "namespace {" ++ n ++ "\n" ++ dumpDecls ps ++ "}\n"
dumpDecl (PSyntax _ syn) = "syntax " ++ show syn
dumpDecl (PClass _ _ _ cs n ps ds) 
    = "class " ++ show cs ++ " " ++ show n ++ " " ++ show ps ++ "\n" ++ dumpDecls ds
dumpDecl (PInstance _ _ cs n _ t _ ds) 
    = "instance " ++ show cs ++ " " ++ show n ++ " " ++ show t ++ "\n" ++ dumpDecls ds
dumpDecl _ = "..."
-- dumpDecl (PImport i) = "import " ++ i

-- 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 "fromInteger") ["builtins"])) [_,_,x]) x' 
        | PConstant (I _) <- getTm x = match (getTm x) x'
    match x' (PApp _ (PRef _ (NS (UN "fromInteger") ["builtins"])) [_,_,x])
        | PConstant (I _) <- getTm x = match (getTm x) x'
    match (PApp _ (PRef _ (UN "lazy")) [_,x]) x' = match (getTm x) x'
    match x (PApp _ (PRef _ (UN "lazy")) [_,x']) = 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 _ n) (PRef _ n') | n == n' = return []
--                                  | otherwise = Nothing
    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)) || tm == Placeholder)
            = return [(n, tm)]
        | n == n' = return []
    match (PRef _ n) tm 
        | not names && (not (isConName 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 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 (FC "" 0) x') t)) 
                            (sm (x':xs) (substMatch x (PRef (FC "" 0) x') sc))
         | otherwise = PPi p x (sm xs t) (sm (x : xs) sc)
    sm xs (PApp f x as) = 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) = PRewrite f (sm xs x) (sm xs y)
    sm xs (PTyped x y) = PTyped (sm xs x) (sm xs y)
    sm xs (PPair f x y) = PPair f (sm xs x) (sm xs y)
    sm xs (PDPair f x t y) = PDPair f (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 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) = PLam x (sm t) (sm sc)
    sm (PPi p x t sc) = PPi p x (sm t) (sm sc)
    sm (PApp f x as) = PApp 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) = PRewrite f (sm x) (sm y)
    sm (PTyped x y) = PTyped (sm x) (sm y)
    sm (PPair f x y) = PPair f (sm x) (sm y)
    sm (PDPair f x t y) = PDPair f (sm x) (sm t) (sm y)
    sm (PAlternative a as) = PAlternative a (map sm as)
    sm (PHidden x) = PHidden (sm x)
    sm x = x