/compiler/typecheck/TcRnDriver.lhs

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%
% (c) The University of Glasgow 2006
% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
%
\section[TcMovectle]{Typechecking a whole module}

\begin{code}
module TcRnDriver (
#ifdef GHCI
        tcRnStmt, tcRnExpr, tcRnType,
        tcRnImportDecls,
        tcRnLookupRdrName,
        getModuleInterface,
        tcRnDeclsi,
        isGHCiMonad,
#endif
        tcRnLookupName,
        tcRnGetInfo,
        tcRnModule,
        tcTopSrcDecls,
        tcRnExtCore
    ) where

#ifdef GHCI
import {-# SOURCE #-} TcSplice ( tcSpliceDecls )
#endif

import DynFlags
import StaticFlags
import HsSyn
import PrelNames
import RdrName
import TcHsSyn
import TcExpr
import TcRnMonad
import TcEvidence
import Coercion( pprCoAxiom, pprCoAxBranch )
import FamInst
import InstEnv
import FamInstEnv
import TcAnnotations
import TcBinds
import HeaderInfo       ( mkPrelImports )
import TcDefaults
import TcEnv
import TcRules
import TcForeign
import TcInstDcls
import TcIface
import TcMType
import MkIface
import TcSimplify
import TcTyClsDecls
import LoadIface
import RnNames
import RnEnv
import RnSource
import PprCore
import CoreSyn
import ErrUtils
import Id
import VarEnv
import Module
import UniqFM
import Name
import NameEnv
import NameSet
import Avail
import TyCon
import SrcLoc
import HscTypes
import ListSetOps
import Outputable
import DataCon
import Type
import Class
import CoAxiom
import Inst     ( tcGetInstEnvs )
import Data.List ( sortBy )
import Data.IORef ( readIORef )
import Data.Ord

#ifdef GHCI
import TcType   ( isUnitTy, isTauTy )
import TcHsType
import TcMatches
import RnTypes
import RnExpr
import MkId
import BasicTypes
import TidyPgm    ( globaliseAndTidyId )
import TysWiredIn ( unitTy, mkListTy )
#endif

import FastString
import Maybes
import Util
import Bag

import Control.Monad

#include "HsVersions.h"
\end{code}

%************************************************************************
%*                                                                      *
        Typecheck and rename a module
%*                                                                      *
%************************************************************************


\begin{code}
-- | Top level entry point for typechecker and renamer
tcRnModule :: HscEnv
           -> HscSource
           -> Bool              -- True <=> save renamed syntax
           -> HsParsedModule
           -> IO (Messages, Maybe TcGblEnv)

tcRnModule hsc_env hsc_src save_rn_syntax
   HsParsedModule {
      hpm_module =
         (L loc (HsModule maybe_mod export_ies
                          import_decls local_decls mod_deprec
                          maybe_doc_hdr)),
      hpm_src_files =
         src_files
   }
 = do { showPass (hsc_dflags hsc_env) "Renamer/typechecker" ;

   let { this_pkg = thisPackage (hsc_dflags hsc_env) ;
         (this_mod, prel_imp_loc)
            = case maybe_mod of
                Nothing -- 'module M where' is omitted
                    ->  (mAIN, srcLocSpan (srcSpanStart loc))

                Just (L mod_loc mod)  -- The normal case
                    -> (mkModule this_pkg mod, mod_loc) } ;

   initTc hsc_env hsc_src save_rn_syntax this_mod $
   setSrcSpan loc $
   do {         -- Deal with imports; first add implicit prelude
        implicit_prelude <- xoptM Opt_ImplicitPrelude;
        let { prel_imports = mkPrelImports (moduleName this_mod) prel_imp_loc
                                         implicit_prelude import_decls } ;

        whenWOptM Opt_WarnImplicitPrelude $
             when (notNull prel_imports) $ addWarn (implicitPreludeWarn) ;

        tcg_env <- {-# SCC "tcRnImports" #-}
                   tcRnImports hsc_env this_mod (prel_imports ++ import_decls) ;

          -- If the whole module is warned about or deprecated 
          -- (via mod_deprec) record that in tcg_warns. If we do thereby add
          -- a WarnAll, it will override any subseqent depracations added to tcg_warns
        let { tcg_env1 = case mod_deprec of 
                         Just txt -> tcg_env { tcg_warns = WarnAll txt } 
                         Nothing  -> tcg_env 
            } ;
 
        setGblEnv tcg_env1 $ do {

                -- Load the hi-boot interface for this module, if any
                -- We do this now so that the boot_names can be passed
                -- to tcTyAndClassDecls, because the boot_names are
                -- automatically considered to be loop breakers
                --
                -- Do this *after* tcRnImports, so that we know whether
                -- a module that we import imports us; and hence whether to
                -- look for a hi-boot file
        boot_iface <- tcHiBootIface hsc_src this_mod ;

                -- Rename and type check the declarations
        traceRn (text "rn1a") ;
        tcg_env <- if isHsBoot hsc_src then
                        tcRnHsBootDecls local_decls
                   else
                        {-# SCC "tcRnSrcDecls" #-}
                        tcRnSrcDecls boot_iface local_decls ;
        setGblEnv tcg_env               $ do {

                -- Process the export list
        traceRn (text "rn4a: before exports");
        tcg_env <- rnExports (isJust maybe_mod) export_ies tcg_env ;
        traceRn (text "rn4b: after exports") ;

                -- Check that main is exported (must be after rnExports)
        checkMainExported tcg_env ;

        -- Compare the hi-boot iface (if any) with the real thing
        -- Must be done after processing the exports
        tcg_env <- checkHiBootIface tcg_env boot_iface ;

        -- The new type env is already available to stuff slurped from
        -- interface files, via TcEnv.updateGlobalTypeEnv
        -- It's important that this includes the stuff in checkHiBootIface,
        -- because the latter might add new bindings for boot_dfuns,
        -- which may be mentioned in imported unfoldings

                -- Don't need to rename the Haddock documentation,
                -- it's not parsed by GHC anymore.
        tcg_env <- return (tcg_env { tcg_doc_hdr = maybe_doc_hdr }) ;

                -- Report unused names
        reportUnusedNames export_ies tcg_env ;

                -- add extra source files to tcg_dependent_files
        addDependentFiles src_files ;

                -- Dump output and return
        tcDump tcg_env ;
        return tcg_env
    }}}}


implicitPreludeWarn :: SDoc
implicitPreludeWarn
  = ptext (sLit "Module `Prelude' implicitly imported")
\end{code}


%************************************************************************
%*                                                                      *
                Import declarations
%*                                                                      *
%************************************************************************

\begin{code}
tcRnImports :: HscEnv -> Module
            -> [LImportDecl RdrName] -> TcM TcGblEnv
tcRnImports hsc_env this_mod import_decls
  = do  { (rn_imports, rdr_env, imports,hpc_info) <- rnImports import_decls ;

        ; let { dep_mods :: ModuleNameEnv (ModuleName, IsBootInterface)
                -- Make sure we record the dependencies from the DynFlags in the EPS or we
                -- end up hitting the sanity check in LoadIface.loadInterface that
                -- checks for unknown home-package modules being loaded. We put
                -- these dependencies on the left so their (non-source) imports
                -- take precedence over the (possibly-source) imports on the right.
                -- We don't add them to any other field (e.g. the imp_dep_mods of
                -- imports) because we don't want to load their instances etc.
              ; dep_mods = listToUFM [(mod_nm, (mod_nm, False)) | mod_nm <- dynFlagDependencies (hsc_dflags hsc_env)]
                                `plusUFM` imp_dep_mods imports

                -- We want instance declarations from all home-package
                -- modules below this one, including boot modules, except
                -- ourselves.  The 'except ourselves' is so that we don't
                -- get the instances from this module's hs-boot file
              ; want_instances :: ModuleName -> Bool
              ; want_instances mod = mod `elemUFM` dep_mods
                                   && mod /= moduleName this_mod
              ; (home_insts, home_fam_insts) = hptInstances hsc_env
                                                            want_instances
              } ;

                -- Record boot-file info in the EPS, so that it's
                -- visible to loadHiBootInterface in tcRnSrcDecls,
                -- and any other incrementally-performed imports
        ; updateEps_ (\eps -> eps { eps_is_boot = dep_mods }) ;

                -- Update the gbl env
        ; updGblEnv ( \ gbl ->
            gbl {
              tcg_rdr_env      = plusOccEnv (tcg_rdr_env gbl) rdr_env,
              tcg_imports      = tcg_imports gbl `plusImportAvails` imports,
              tcg_rn_imports   = rn_imports,
              tcg_inst_env     = extendInstEnvList (tcg_inst_env gbl) home_insts,
              tcg_fam_inst_env = extendFamInstEnvList (tcg_fam_inst_env gbl)
                                                      home_fam_insts,
              tcg_hpc          = hpc_info
            }) $ do {

        ; traceRn (text "rn1" <+> ppr (imp_dep_mods imports))
                -- Fail if there are any errors so far
                -- The error printing (if needed) takes advantage
                -- of the tcg_env we have now set
--      ; traceIf (text "rdr_env: " <+> ppr rdr_env)
        ; failIfErrsM

                -- Load any orphan-module and family instance-module
                -- interfaces, so that their rules and instance decls will be
                -- found.
        ; loadModuleInterfaces (ptext (sLit "Loading orphan modules"))
                               (imp_orphs imports)

                -- Check type-family consistency
        ; traceRn (text "rn1: checking family instance consistency")
        ; let { dir_imp_mods = moduleEnvKeys
                             . imp_mods
                             $ imports }
        ; checkFamInstConsistency (imp_finsts imports) dir_imp_mods ;

        ; getGblEnv } }
\end{code}


%************************************************************************
%*                                                                      *
        Type-checking external-core modules
%*                                                                      *
%************************************************************************

\begin{code}
tcRnExtCore :: HscEnv
            -> HsExtCore RdrName
            -> IO (Messages, Maybe ModGuts)
        -- Nothing => some error occurred

tcRnExtCore hsc_env (HsExtCore this_mod decls src_binds)
        -- The decls are IfaceDecls; all names are original names
 = do { showPass (hsc_dflags hsc_env) "Renamer/typechecker" ;

   initTc hsc_env ExtCoreFile False this_mod $ do {

   let { ldecls  = map noLoc decls } ;

       -- Bring the type and class decls into scope
       -- ToDo: check that this doesn't need to extract the val binds.
       --       It seems that only the type and class decls need to be in scope below because
       --          (a) tcTyAndClassDecls doesn't need the val binds, and
       --          (b) tcExtCoreBindings doesn't need anything
       --              (in fact, it might not even need to be in the scope of
       --               this tcg_env at all)
   (tc_envs, _bndrs) <- getLocalNonValBinders emptyFsEnv {- no fixity decls -}
                                              (mkFakeGroup ldecls) ;
   setEnvs tc_envs $ do {

   (rn_decls, _fvs) <- checkNoErrs $ rnTyClDecls [] [ldecls] ;
   -- The empty list is for extra dependencies coming from .hs-boot files
   -- See Note [Extra dependencies from .hs-boot files] in RnSource

        -- Dump trace of renaming part
   rnDump (ppr rn_decls) ;

        -- Typecheck them all together so that
        -- any mutually recursive types are done right
        -- Just discard the auxiliary bindings; they are generated
        -- only for Haskell source code, and should already be in Core
   tcg_env   <- tcTyAndClassDecls emptyModDetails rn_decls ;
   safe_mode <- liftIO $ finalSafeMode (hsc_dflags hsc_env) tcg_env ;
   dep_files <- liftIO $ readIORef (tcg_dependent_files tcg_env) ;

   setGblEnv tcg_env $ do {
        -- Make the new type env available to stuff slurped from interface files

        -- Now the core bindings
   core_binds <- initIfaceExtCore (tcExtCoreBindings src_binds) ;


        -- Wrap up
   let {
        bndrs      = bindersOfBinds core_binds ;
        my_exports = map (Avail . idName) bndrs ;
                -- ToDo: export the data types also?

        mod_guts = ModGuts {    mg_module    = this_mod,
                                mg_boot      = False,
                                mg_used_names = emptyNameSet, -- ToDo: compute usage
                                mg_used_th   = False,
                                mg_dir_imps  = emptyModuleEnv, -- ??
                                mg_deps      = noDependencies,  -- ??
                                mg_exports   = my_exports,
                                mg_tcs       = tcg_tcs tcg_env,
                                mg_insts     = tcg_insts tcg_env,
                                mg_fam_insts = tcg_fam_insts tcg_env,
                                mg_inst_env  = tcg_inst_env tcg_env,
                                mg_fam_inst_env = tcg_fam_inst_env tcg_env,
                                mg_rules        = [],
                                mg_vect_decls   = [],
                                mg_anns         = [],
                                mg_binds        = core_binds,

                                -- Stubs
                                mg_rdr_env      = emptyGlobalRdrEnv,
                                mg_fix_env      = emptyFixityEnv,
                                mg_warns        = NoWarnings,
                                mg_foreign      = NoStubs,
                                mg_hpc_info     = emptyHpcInfo False,
                                mg_modBreaks    = emptyModBreaks,
                                mg_vect_info    = noVectInfo,
                                mg_safe_haskell = safe_mode,
                                mg_trust_pkg    = False,
                                mg_dependent_files = dep_files
                            } } ;

   tcCoreDump mod_guts ;

   return mod_guts
   }}}}

mkFakeGroup :: [LTyClDecl a] -> HsGroup a
mkFakeGroup decls -- Rather clumsy; lots of unused fields
  = emptyRdrGroup { hs_tyclds = [decls] }
\end{code}


%************************************************************************
%*                                                                      *
        Type-checking the top level of a module
%*                                                                      *
%************************************************************************

\begin{code}
tcRnSrcDecls :: ModDetails -> [LHsDecl RdrName] -> TcM TcGblEnv
        -- Returns the variables free in the decls
        -- Reason: solely to report unused imports and bindings
tcRnSrcDecls boot_iface decls
 = do {         -- Do all the declarations
        ((tcg_env, tcl_env), lie) <- captureConstraints $ tc_rn_src_decls boot_iface decls ;
      ; traceTc "Tc8" empty ;
      ; setEnvs (tcg_env, tcl_env) $
   do {

             --         Finish simplifying class constraints
             --
             -- simplifyTop deals with constant or ambiguous InstIds.
             -- How could there be ambiguous ones?  They can only arise if a
             -- top-level decl falls under the monomorphism restriction
             -- and no subsequent decl instantiates its type.
             --
             -- We do this after checkMain, so that we use the type info
             -- that checkMain adds
             --
             -- We do it with both global and local env in scope:
             --  * the global env exposes the instances to simplifyTop
             --  * the local env exposes the local Ids to simplifyTop,
             --    so that we get better error messages (monomorphism restriction)
        new_ev_binds <- {-# SCC "simplifyTop" #-}
                        simplifyTop lie ;
        traceTc "Tc9" empty ;

        failIfErrsM ;   -- Don't zonk if there have been errors
                        -- It's a waste of time; and we may get debug warnings
                        -- about strangely-typed TyCons!

        -- Zonk the final code.  This must be done last.
        -- Even simplifyTop may do some unification.
        -- This pass also warns about missing type signatures
        let { TcGblEnv { tcg_type_env  = type_env,
                         tcg_binds     = binds,
                         tcg_sigs      = sig_ns,
                         tcg_ev_binds  = cur_ev_binds,
                         tcg_imp_specs = imp_specs,
                         tcg_rules     = rules,
                         tcg_vects     = vects,
                         tcg_fords     = fords } = tcg_env
            ; all_ev_binds = cur_ev_binds `unionBags` new_ev_binds } ;

        (bind_ids, ev_binds', binds', fords', imp_specs', rules', vects')
            <- {-# SCC "zonkTopDecls" #-}
               zonkTopDecls all_ev_binds binds sig_ns rules vects imp_specs fords ;

        let { final_type_env = extendTypeEnvWithIds type_env bind_ids
            ; tcg_env' = tcg_env { tcg_binds    = binds',
                                   tcg_ev_binds = ev_binds',
                                   tcg_imp_specs = imp_specs',
                                   tcg_rules    = rules',
                                   tcg_vects    = vects',
                                   tcg_fords    = fords' } } ;

        setGlobalTypeEnv tcg_env' final_type_env
       
   } }

tc_rn_src_decls :: ModDetails
                    -> [LHsDecl RdrName]
                    -> TcM (TcGblEnv, TcLclEnv)
-- Loops around dealing with each top level inter-splice group
-- in turn, until it's dealt with the entire module
tc_rn_src_decls boot_details ds
 = {-# SCC "tc_rn_src_decls" #-}
   do { (first_group, group_tail) <- findSplice ds  ;
                -- If ds is [] we get ([], Nothing)

        -- The extra_deps are needed while renaming type and class declarations
        -- See Note [Extra dependencies from .hs-boot files] in RnSource
        let { extra_deps = map tyConName (typeEnvTyCons (md_types boot_details)) } ;
        -- Deal with decls up to, but not including, the first splice
        (tcg_env, rn_decls) <- rnTopSrcDecls extra_deps first_group ;
                -- rnTopSrcDecls fails if there are any errors

        (tcg_env, tcl_env) <- setGblEnv tcg_env $
                              tcTopSrcDecls boot_details rn_decls ;

        -- If there is no splice, we're nearly done
        setEnvs (tcg_env, tcl_env) $
        case group_tail of {
           Nothing -> do { tcg_env <- checkMain ;       -- Check for `main'
                           traceTc "returning from tc_rn_src_decls: " $
                             ppr $ nameEnvElts $ tcg_type_env tcg_env ;
                           return (tcg_env, tcl_env)
                      } ;

#ifndef GHCI
        -- There shouldn't be a splice
           Just (SpliceDecl {}, _) -> do {
        failWithTc (text "Can't do a top-level splice; need a bootstrapped compiler")
#else
        -- If there's a splice, we must carry on
           Just (SpliceDecl splice_expr _, rest_ds) -> do {

        -- Rename the splice expression, and get its supporting decls
        (rn_splice_expr, splice_fvs) <- checkNoErrs (rnLExpr splice_expr) ;
                -- checkNoErrs: don't typecheck if renaming failed
        rnDump (ppr rn_splice_expr) ;

        -- Execute the splice
        spliced_decls <- tcSpliceDecls rn_splice_expr ;

        -- Glue them on the front of the remaining decls and loop
        setGblEnv (tcg_env `addTcgDUs` usesOnly splice_fvs) $
        tc_rn_src_decls boot_details (spliced_decls ++ rest_ds)
#endif /* GHCI */
    } } }
\end{code}

%************************************************************************
%*                                                                      *
        Compiling hs-boot source files, and
        comparing the hi-boot interface with the real thing
%*                                                                      *
%************************************************************************

\begin{code}
tcRnHsBootDecls :: [LHsDecl RdrName] -> TcM TcGblEnv
tcRnHsBootDecls decls
   = do { (first_group, group_tail) <- findSplice decls

                -- Rename the declarations
        ; (tcg_env, HsGroup {
                   hs_tyclds = tycl_decls,
                   hs_instds = inst_decls,
                   hs_derivds = deriv_decls,
                   hs_fords  = for_decls,
                   hs_defds  = def_decls,
                   hs_ruleds = rule_decls,
                   hs_vects  = vect_decls,
                   hs_annds  = _,
                   hs_valds  = val_binds }) <- rnTopSrcDecls [] first_group
        -- The empty list is for extra dependencies coming from .hs-boot files
        -- See Note [Extra dependencies from .hs-boot files] in RnSource
        ; (gbl_env, lie) <- captureConstraints $ setGblEnv tcg_env $ do {


                -- Check for illegal declarations
        ; case group_tail of
             Just (SpliceDecl d _, _) -> badBootDecl "splice" d
             Nothing                  -> return ()
        ; mapM_ (badBootDecl "foreign") for_decls
        ; mapM_ (badBootDecl "default") def_decls
        ; mapM_ (badBootDecl "rule")    rule_decls
        ; mapM_ (badBootDecl "vect")    vect_decls

                -- Typecheck type/class/isntance decls
        ; traceTc "Tc2 (boot)" empty
        ; (tcg_env, inst_infos, _deriv_binds)
             <- tcTyClsInstDecls emptyModDetails tycl_decls inst_decls deriv_decls
        ; setGblEnv tcg_env     $ do {

                -- Typecheck value declarations
        ; traceTc "Tc5" empty
        ; val_ids <- tcHsBootSigs val_binds

                -- Wrap up
                -- No simplification or zonking to do
        ; traceTc "Tc7a" empty
        ; gbl_env <- getGblEnv

                -- Make the final type-env
                -- Include the dfun_ids so that their type sigs
                -- are written into the interface file.
        ; let { type_env0 = tcg_type_env gbl_env
              ; type_env1 = extendTypeEnvWithIds type_env0 val_ids
              ; type_env2 = extendTypeEnvWithIds type_env1 dfun_ids
              ; dfun_ids = map iDFunId inst_infos
              }

        ; setGlobalTypeEnv gbl_env type_env2
   }}
   ; traceTc "boot" (ppr lie); return gbl_env }

badBootDecl :: String -> Located decl -> TcM ()
badBootDecl what (L loc _)
  = addErrAt loc (char 'A' <+> text what
      <+> ptext (sLit "declaration is not (currently) allowed in a hs-boot file"))
\end{code}

Once we've typechecked the body of the module, we want to compare what
we've found (gathered in a TypeEnv) with the hi-boot details (if any).

\begin{code}
checkHiBootIface :: TcGblEnv -> ModDetails -> TcM TcGblEnv
-- Compare the hi-boot file for this module (if there is one)
-- with the type environment we've just come up with
-- In the common case where there is no hi-boot file, the list
-- of boot_names is empty.
--
-- The bindings we return give bindings for the dfuns defined in the
-- hs-boot file, such as        $fbEqT = $fEqT

checkHiBootIface
        tcg_env@(TcGblEnv { tcg_src = hs_src, tcg_binds = binds,
                            tcg_insts = local_insts,
                            tcg_type_env = local_type_env, tcg_exports = local_exports })
        (ModDetails { md_insts = boot_insts, md_fam_insts = boot_fam_insts,
                      md_types = boot_type_env, md_exports = boot_exports })
  | isHsBoot hs_src     -- Current module is already a hs-boot file!
  = return tcg_env

  | otherwise
  = do  { traceTc "checkHiBootIface" $ vcat
             [ ppr boot_type_env, ppr boot_insts, ppr boot_exports]

                -- Check the exports of the boot module, one by one
        ; mapM_ check_export boot_exports

                -- Check for no family instances
        ; unless (null boot_fam_insts) $
            panic ("TcRnDriver.checkHiBootIface: Cannot handle family " ++
                   "instances in boot files yet...")
            -- FIXME: Why?  The actual comparison is not hard, but what would
            --        be the equivalent to the dfun bindings returned for class
            --        instances?  We can't easily equate tycons...

                -- Check instance declarations
        ; mb_dfun_prs <- mapM check_inst boot_insts
        ; let dfun_prs   = catMaybes mb_dfun_prs
              boot_dfuns = map fst dfun_prs
              dfun_binds = listToBag [ mkVarBind boot_dfun (nlHsVar dfun)
                                     | (boot_dfun, dfun) <- dfun_prs ]
              type_env'  = extendTypeEnvWithIds local_type_env boot_dfuns
              tcg_env'   = tcg_env { tcg_binds = binds `unionBags` dfun_binds }

        ; failIfErrsM
        ; setGlobalTypeEnv tcg_env' type_env' }
             -- Update the global type env *including* the knot-tied one
             -- so that if the source module reads in an interface unfolding
             -- mentioning one of the dfuns from the boot module, then it
             -- can "see" that boot dfun.   See Trac #4003
  where
    check_export boot_avail     -- boot_avail is exported by the boot iface
      | name `elem` dfun_names = return ()
      | isWiredInName name     = return ()      -- No checking for wired-in names.  In particular,
                                                -- 'error' is handled by a rather gross hack
                                                -- (see comments in GHC.Err.hs-boot)

        -- Check that the actual module exports the same thing
      | not (null missing_names)
      = addErrAt (nameSrcSpan (head missing_names))
                 (missingBootThing (head missing_names) "exported by")

        -- If the boot module does not *define* the thing, we are done
        -- (it simply re-exports it, and names match, so nothing further to do)
      | isNothing mb_boot_thing = return ()

        -- Check that the actual module also defines the thing, and
        -- then compare the definitions
      | Just real_thing <- lookupTypeEnv local_type_env name,
        Just boot_thing <- mb_boot_thing
      = when (not (checkBootDecl boot_thing real_thing))
            $ addErrAt (nameSrcSpan (getName boot_thing))
                       (bootMisMatch real_thing boot_thing)

      | otherwise
      = addErrTc (missingBootThing name "defined in")
      where
        name          = availName boot_avail
        mb_boot_thing = lookupTypeEnv boot_type_env name
        missing_names = case lookupNameEnv local_export_env name of
                          Nothing    -> [name]
                          Just avail -> availNames boot_avail `minusList` availNames avail

    dfun_names = map getName boot_insts

    local_export_env :: NameEnv AvailInfo
    local_export_env = availsToNameEnv local_exports

    check_inst :: ClsInst -> TcM (Maybe (Id, Id))
        -- Returns a pair of the boot dfun in terms of the equivalent real dfun
    check_inst boot_inst
        = case [dfun | inst <- local_insts,
                       let dfun = instanceDFunId inst,
                       idType dfun `eqType` boot_inst_ty ] of
            [] -> do { traceTc "check_inst" (vcat [ text "local_insts" <+> vcat (map (ppr . idType . instanceDFunId) local_insts)
                                                  , text "boot_inst"   <+> ppr boot_inst
                                                  , text "boot_inst_ty" <+> ppr boot_inst_ty
                                                  ])
                     ; addErrTc (instMisMatch boot_inst); return Nothing }
            (dfun:_) -> return (Just (local_boot_dfun, dfun))
        where
          boot_dfun = instanceDFunId boot_inst
          boot_inst_ty = idType boot_dfun
          local_boot_dfun = Id.mkExportedLocalId (idName boot_dfun) boot_inst_ty


-- This has to compare the TyThing from the .hi-boot file to the TyThing
-- in the current source file.  We must be careful to allow alpha-renaming
-- where appropriate, and also the boot declaration is allowed to omit
-- constructors and class methods.
--
-- See rnfail055 for a good test of this stuff.

checkBootDecl :: TyThing -> TyThing -> Bool

checkBootDecl (AnId id1) (AnId id2)
  = ASSERT(id1 == id2)
    (idType id1 `eqType` idType id2)

checkBootDecl (ATyCon tc1) (ATyCon tc2)
  = checkBootTyCon tc1 tc2

checkBootDecl (ADataCon dc1) (ADataCon _)
  = pprPanic "checkBootDecl" (ppr dc1)

checkBootDecl _ _ = False -- probably shouldn't happen

----------------
checkBootTyCon :: TyCon -> TyCon -> Bool
checkBootTyCon tc1 tc2
  | not (eqKind (tyConKind tc1) (tyConKind tc2))
  = False       -- First off, check the kind

  | Just c1 <- tyConClass_maybe tc1
  , Just c2 <- tyConClass_maybe tc2
  , let (clas_tvs1, clas_fds1, sc_theta1, _, ats1, op_stuff1)
          = classExtraBigSig c1
        (clas_tvs2, clas_fds2, sc_theta2, _, ats2, op_stuff2)
          = classExtraBigSig c2
  , Just env <- eqTyVarBndrs emptyRnEnv2 clas_tvs1 clas_tvs2
  = let
       eqSig (id1, def_meth1) (id2, def_meth2)
         = idName id1 == idName id2 &&
           eqTypeX env op_ty1 op_ty2 &&
           def_meth1 == def_meth2
         where
          (_, rho_ty1) = splitForAllTys (idType id1)
          op_ty1 = funResultTy rho_ty1
          (_, rho_ty2) = splitForAllTys (idType id2)
          op_ty2 = funResultTy rho_ty2

       eqAT (tc1, def_ats1) (tc2, def_ats2)
         = checkBootTyCon tc1 tc2 &&
           eqListBy eqATDef def_ats1 def_ats2

       -- Ignore the location of the defaults
       eqATDef (CoAxBranch { cab_tvs = tvs1, cab_lhs =  ty_pats1, cab_rhs = ty1 })
               (CoAxBranch { cab_tvs = tvs2, cab_lhs =  ty_pats2, cab_rhs = ty2 })
         | Just env <- eqTyVarBndrs emptyRnEnv2 tvs1 tvs2
         = eqListBy (eqTypeX env) ty_pats1 ty_pats2 &&
           eqTypeX env ty1 ty2
         | otherwise = False

       eqFD (as1,bs1) (as2,bs2) =
         eqListBy (eqTypeX env) (mkTyVarTys as1) (mkTyVarTys as2) &&
         eqListBy (eqTypeX env) (mkTyVarTys bs1) (mkTyVarTys bs2)
    in
       roles1 == roles2 &&
             -- Checks kind of class
       eqListBy eqFD clas_fds1 clas_fds2 &&
       (null sc_theta1 && null op_stuff1 && null ats1
        ||   -- Above tests for an "abstract" class
        eqListBy (eqPredX env) sc_theta1 sc_theta2 &&
        eqListBy eqSig op_stuff1 op_stuff2 &&
        eqListBy eqAT ats1 ats2)

  | Just syn_rhs1 <- synTyConRhs_maybe tc1
  , Just syn_rhs2 <- synTyConRhs_maybe tc2
  , Just env <- eqTyVarBndrs emptyRnEnv2 (tyConTyVars tc1) (tyConTyVars tc2)
  = ASSERT(tc1 == tc2)
    let eqSynRhs OpenSynFamilyTyCon OpenSynFamilyTyCon = True
        eqSynRhs AbstractClosedSynFamilyTyCon (ClosedSynFamilyTyCon {}) = True
        eqSynRhs (ClosedSynFamilyTyCon {}) AbstractClosedSynFamilyTyCon = True
        eqSynRhs (ClosedSynFamilyTyCon ax1) (ClosedSynFamilyTyCon ax2)
            = eqClosedFamilyAx ax1 ax2
        eqSynRhs (SynonymTyCon t1) (SynonymTyCon t2)
            = eqTypeX env t1 t2
        eqSynRhs _ _ = False
    in
    roles1 == roles2 &&
    eqSynRhs syn_rhs1 syn_rhs2

  | isAlgTyCon tc1 && isAlgTyCon tc2
  , Just env <- eqTyVarBndrs emptyRnEnv2 (tyConTyVars tc1) (tyConTyVars tc2)
  = ASSERT(tc1 == tc2)
    roles1 == roles2 &&
    eqListBy (eqPredX env) (tyConStupidTheta tc1) (tyConStupidTheta tc2) &&
    eqAlgRhs (algTyConRhs tc1) (algTyConRhs tc2)

  | isForeignTyCon tc1 && isForeignTyCon tc2
  = eqKind (tyConKind tc1) (tyConKind tc2) &&
    tyConExtName tc1 == tyConExtName tc2

  | otherwise = False
  where
    roles1 = tyConRoles tc1
    roles2 = tyConRoles tc2

    eqAlgRhs (AbstractTyCon dis1) rhs2
      | dis1      = isDistinctAlgRhs rhs2   --Check compatibility
      | otherwise = True
    eqAlgRhs DataFamilyTyCon{} DataFamilyTyCon{} = True
    eqAlgRhs tc1@DataTyCon{} tc2@DataTyCon{} =
        eqListBy eqCon (data_cons tc1) (data_cons tc2)
    eqAlgRhs tc1@NewTyCon{} tc2@NewTyCon{} =
        eqCon (data_con tc1) (data_con tc2)
    eqAlgRhs _ _ = False

    eqCon c1 c2
      =  dataConName c1 == dataConName c2
      && dataConIsInfix c1 == dataConIsInfix c2
      && eqListBy eqHsBang (dataConStrictMarks c1) (dataConStrictMarks c2)
      && dataConFieldLabels c1 == dataConFieldLabels c2
      && eqType (dataConUserType c1) (dataConUserType c2)

    eqClosedFamilyAx (CoAxiom { co_ax_branches = branches1 })
                     (CoAxiom { co_ax_branches = branches2 })
      =  brListLength branches1 == brListLength branches2
      && (and $ brListZipWith eqClosedFamilyBranch branches1 branches2)

    eqClosedFamilyBranch (CoAxBranch { cab_tvs = tvs1, cab_lhs = lhs1, cab_rhs = rhs1 })
                         (CoAxBranch { cab_tvs = tvs2, cab_lhs = lhs2, cab_rhs = rhs2 })
      | Just env <- eqTyVarBndrs emptyRnEnv2 tvs1 tvs2
      = eqListBy (eqTypeX env) lhs1 lhs2 &&
        eqTypeX env rhs1 rhs2

      | otherwise = False

emptyRnEnv2 :: RnEnv2
emptyRnEnv2 = mkRnEnv2 emptyInScopeSet

----------------
missingBootThing :: Name -> String -> SDoc
missingBootThing name what
  = ppr name <+> ptext (sLit "is exported by the hs-boot file, but not")
              <+> text what <+> ptext (sLit "the module")

bootMisMatch :: TyThing -> TyThing -> SDoc
bootMisMatch real_thing boot_thing
  = vcat [ppr real_thing <+>
          ptext (sLit "has conflicting definitions in the module"),
          ptext (sLit "and its hs-boot file"),
          ptext (sLit "Main module:") <+> ppr_mismatch real_thing,
          ptext (sLit "Boot file:  ") <+> ppr_mismatch boot_thing]
  where
      -- closed type families need special treatment, because they might differ
      -- in their equations, which are not stored in the corresponding IfaceDecl
    ppr_mismatch thing
      | ATyCon tc <- thing
      , Just (ClosedSynFamilyTyCon ax) <- synTyConRhs_maybe tc
      = hang (ppr iface_decl <+> ptext (sLit "where"))
           2 (vcat $ brListMap (pprCoAxBranch tc) (coAxiomBranches ax))
      
      | otherwise
      = ppr iface_decl
      where iface_decl = tyThingToIfaceDecl thing

instMisMatch :: ClsInst -> SDoc
instMisMatch inst
  = hang (ppr inst)
       2 (ptext (sLit "is defined in the hs-boot file, but not in the module itself"))
\end{code}


%************************************************************************
%*                                                                      *
        Type-checking the top level of a module
%*                                                                      *
%************************************************************************

tcRnGroup takes a bunch of top-level source-code declarations, and
 * renames them
 * gets supporting declarations from interface files
 * typechecks them
 * zonks them
 * and augments the TcGblEnv with the results

In Template Haskell it may be called repeatedly for each group of
declarations.  It expects there to be an incoming TcGblEnv in the
monad; it augments it and returns the new TcGblEnv.

\begin{code}
------------------------------------------------
rnTopSrcDecls :: [Name] -> HsGroup RdrName -> TcM (TcGblEnv, HsGroup Name)
-- Fails if there are any errors
rnTopSrcDecls extra_deps group
 = do { -- Rename the source decls
        traceTc "rn12" empty ;
        (tcg_env, rn_decls) <- checkNoErrs $ rnSrcDecls extra_deps group ;
        traceTc "rn13" empty ;

        -- save the renamed syntax, if we want it
        let { tcg_env'
                | Just grp <- tcg_rn_decls tcg_env
                  = tcg_env{ tcg_rn_decls = Just (appendGroups grp rn_decls) }
                | otherwise
                   = tcg_env };

                -- Dump trace of renaming part
        rnDump (ppr rn_decls) ;

        return (tcg_env', rn_decls)
   }

------------------------------------------------
tcTopSrcDecls :: ModDetails -> HsGroup Name -> TcM (TcGblEnv, TcLclEnv)
tcTopSrcDecls boot_details
        (HsGroup { hs_tyclds = tycl_decls,
                   hs_instds = inst_decls,
                   hs_derivds = deriv_decls,
                   hs_fords  = foreign_decls,
                   hs_defds  = default_decls,
                   hs_annds  = annotation_decls,
                   hs_ruleds = rule_decls,
                   hs_vects  = vect_decls,
                   hs_valds  = val_binds })
 = do {         -- Type-check the type and class decls, and all imported decls
                -- The latter come in via tycl_decls
        traceTc "Tc2 (src)" empty ;

                -- Source-language instances, including derivings,
                -- and import the supporting declarations
        traceTc "Tc3" empty ;
        (tcg_env, inst_infos, deriv_binds)
            <- tcTyClsInstDecls boot_details tycl_decls inst_decls deriv_decls ;
        setGblEnv tcg_env       $ do {

                -- Foreign import declarations next.
        traceTc "Tc4" empty ;
        (fi_ids, fi_decls, fi_gres) <- tcForeignImports foreign_decls ;
        tcExtendGlobalValEnv fi_ids     $ do {

                -- Default declarations
        traceTc "Tc4a" empty ;
        default_tys <- tcDefaults default_decls ;
        updGblEnv (\gbl -> gbl { tcg_default = default_tys }) $ do {

                -- Now GHC-generated derived bindings, generics, and selectors
                -- Do not generate warnings from compiler-generated code;
                -- hence the use of discardWarnings
        tc_envs <- discardWarnings (tcTopBinds deriv_binds) ;
        setEnvs tc_envs $ do {

                -- Value declarations next
        traceTc "Tc5" empty ;
        tc_envs@(tcg_env, tcl_env) <- tcTopBinds val_binds;
        setEnvs tc_envs $ do {  -- Environment doesn't change now

                -- Second pass over class and instance declarations,
                -- now using the kind-checked decls
        traceTc "Tc6" empty ;
        inst_binds <- tcInstDecls2 (concat tycl_decls) inst_infos ;

                -- Foreign exports
        traceTc "Tc7" empty ;
        (foe_binds, foe_decls, foe_gres) <- tcForeignExports foreign_decls ;

                -- Annotations
        annotations <- tcAnnotations annotation_decls ;

                -- Rules
        rules <- tcRules rule_decls ;

                -- Vectorisation declarations
        vects <- tcVectDecls vect_decls ;

                -- Wrap up
        traceTc "Tc7a" empty ;
        let { all_binds = inst_binds     `unionBags`
                          foe_binds

            ; fo_gres = fi_gres `unionBags` foe_gres
            ; fo_fvs = foldrBag (\gre fvs -> fvs `addOneFV` gre_name gre) 
                                emptyFVs fo_gres
            ; fo_rdr_names :: [RdrName]
            ; fo_rdr_names = foldrBag gre_to_rdr_name [] fo_gres

            ; sig_names = mkNameSet (collectHsValBinders val_binds)
                          `minusNameSet` getTypeSigNames val_binds

                -- Extend the GblEnv with the (as yet un-zonked)
                -- bindings, rules, foreign decls
            ; tcg_env' = tcg_env { tcg_binds = tcg_binds tcg_env `unionBags` all_binds
                                 , tcg_sigs  = tcg_sigs tcg_env `unionNameSets` sig_names
                                 , tcg_rules = tcg_rules tcg_env ++ rules
                                 , tcg_vects = tcg_vects tcg_env ++ vects
                                 , tcg_anns  = tcg_anns tcg_env ++ annotations
                                 , tcg_fords = tcg_fords tcg_env ++ foe_decls ++ fi_decls
                                 , tcg_dus   = tcg_dus tcg_env `plusDU` usesOnly fo_fvs } } ;
                                 -- tcg_dus: see Note [Newtype constructor usage in foreign declarations]

        addUsedRdrNames fo_rdr_names ;
        return (tcg_env', tcl_env)
    }}}}}}
  where
    gre_to_rdr_name :: GlobalRdrElt -> [RdrName] -> [RdrName]
        -- For *imported* newtype data constructors, we want to
        -- make sure that at least one of the imports for them is used
        -- See Note [Newtype constructor usage in foreign declarations]
    gre_to_rdr_name gre rdrs
      = case gre_prov gre of
           LocalDef          -> rdrs
           Imported []       -> panic "gre_to_rdr_name: Imported []"
           Imported (is : _) -> mkRdrQual modName occName : rdrs
              where
                modName = is_as (is_decl is)
                occName = nameOccName (gre_name gre)

---------------------------
tcTyClsInstDecls :: ModDetails 
                 -> [TyClGroup Name] 
                 -> [LInstDecl Name]
                 -> [LDerivDecl Name]
                 -> TcM (TcGblEnv,            -- The full inst env
                         [InstInfo Name],     -- Source-code instance decls to process;
                                              -- contains all dfuns for this module
                          HsValBinds Name)    -- Supporting bindings for derived instances

tcTyClsInstDecls boot_details tycl_decls inst_decls deriv_decls
 = tcExtendTcTyThingEnv [(con, APromotionErr FamDataConPE) 
                        | lid <- inst_decls, con <- get_cons lid ] $
      -- Note [AFamDataCon: not promoting data family constructors]
   do { tcg_env <- tcTyAndClassDecls boot_details tycl_decls ;
      ; setGblEnv tcg_env $
        tcInstDecls1 (concat tycl_decls) inst_decls deriv_decls }
  where
    -- get_cons extracts the *constructor* bindings of the declaration
    get_cons :: LInstDecl Name -> [Name]
    get_cons (L _ (TyFamInstD {}))                     = []
    get_cons (L _ (DataFamInstD { dfid_inst = fid }))  = get_fi_cons fid
    get_cons (L _ (ClsInstD { cid_inst = ClsInstDecl { cid_datafam_insts = fids } }))
      = concatMap (get_fi_cons . unLoc) fids

    get_fi_cons :: DataFamInstDecl Name -> [Name]
    get_fi_cons (DataFamInstDecl { dfid_defn = HsDataDefn { dd_cons = cons } }) 
      = map (unLoc . con_name . unLoc) cons
\end{code}

Note [AFamDataCon: not promoting data family constructors]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Consider
  data family T a
  data instance T Int = MkT
  data Proxy (a :: k)
  data S = MkS (Proxy 'MkT)

Is it ok to use the promoted data family instance constructor 'MkT' in
the data declaration for S?  No, we don't allow this. It *might* make
sense, but at least it would mean that we'd have to interleave
typechecking instances and data types, whereas at present we do data
types *then* instances.

So to check for this we put in the TcLclEnv a binding for all the family
constructors, bound to AFamDataCon, so that if we trip over 'MkT' when
type checking 'S' we'll produce a decent error message.


%************************************************************************
%*                                                                      *
        Checking for 'main'
%*                                                                      *
%************************************************************************

\begin{code}
checkMain :: TcM TcGblEnv
-- If we are in module Main, check that 'main' is defined.
checkMain
  = do { tcg_env   <- getGblEnv ;
         dflags    <- getDynFlags ;
         check_main dflags tcg_env
    }

check_main :: DynFlags -> TcGblEnv -> TcM TcGblEnv
check_main dflags tcg_env
 | mod /= main_mod
 = traceTc "checkMain not" (ppr main_mod <+> ppr mod) >>
   return tcg_env

 | otherwise
 = do   { mb_main <- lookupGlobalOccRn_maybe main_fn
                -- Check that 'main' is in scope
                -- It might be imported from another module!
        ; case mb_main of {
             Nothing -> do { traceTc "checkMain fail" (ppr main_mod <+> ppr main_fn)
                           ; complain_no_main
                           ; return tcg_env } ;
             Just main_name -> do

        { traceTc "checkMain found" (ppr main_mod <+> ppr main_fn)
        ; let loc = srcLocSpan (getSrcLoc main_name)
        ; ioTyCon <- tcLookupTyCon ioTyConName
        ; res_ty <- newFlexiTyVarTy liftedTypeKind
        ; main_expr
                <- addErrCtxt mainCtxt    $
                   tcMonoExpr (L loc (HsVar main_name)) (mkTyConApp ioTyCon [res_ty])

                -- See Note [Root-main Id]
                -- Construct the binding
                --      :Main.main :: IO res_ty = runMainIO res_ty main
        ; run_main_id <- tcLookupId runMainIOName
        ; let { root_main_name =  mkExternalName rootMainKey rOOT_MAIN
                                   (mkVarOccFS (fsLit "main"))
                                   (getSrcSpan main_name)
              ; root_main_id = Id.mkExportedLocalId root_main_name
                                                    (mkTyConApp ioTyCon [res_ty])
              ; co  = mkWpTyApps [res_ty]
              ; rhs = nlHsApp (mkLHsWrap co (nlHsVar run_main_id)) main_expr
              ; main_bind = mkVarBind root_main_id rhs }

        ; return (tcg_env { tcg_main  = Just main_name,
                            tcg_binds = tcg_binds tcg_env
                                        `snocBag` main_bind,
                            tcg_dus   = tcg_dus tcg_env
                                        `plusDU` usesOnly (unitFV main_name)
                        -- Record the use of 'main', so that we don't
                        -- complain about it being defined but not used
                 })
    }}}
  where
    mod          = tcg_mod tcg_env
    main_mod     = mainModIs dflags
    main_fn      = getMainFun dflags

    complain_no_main | ghcLink dflags == LinkInMemory = return ()
                     | otherwise = failWithTc noMainMsg
        -- In interactive mode, don't worry about the absence of 'main'
        -- In other modes, fail altogether, so that we don't go on
        -- and complain a second time when processing the export list.

    mainCtxt  = ptext (sLit "When checking the type of the") <+> pp_main_fn
    noMainMsg = ptext (sLit "The") <+> pp_main_fn
                <+> ptext (sLit "is not defined in module") <+> quotes (ppr main_mod)
    pp_main_fn = ppMainFn main_fn

-- | Get the unqualified name of the function to use as the \"main\" for the main module.
-- Either returns the default name or the one configured on the command line with -main-is
getMainFun :: DynFlags -> RdrName
getMainFun dflags = case mainFunIs dflags of
                      Just fn -> mkRdrUnqual (mkVarOccFS (mkFastString fn))
                      Nothing -> main_RDR_Unqual

checkMainExported :: TcGblEnv -> TcM ()
checkMainExported tcg_env
  = case tcg_main tcg_env of
      Nothing -> return () -- not the main module
      Just main_name -> 
         do { dflags <- getDynFlags
            ; let main_mod = mainModIs dflags
            ; checkTc (main_name `elem` concatMap availNames (tcg_exports tcg_env)) $
                ptext (sLit "The") <+> ppMainFn (nameRdrName main_name) <+>
                ptext (sLit "is not exported by module") <+> quotes (ppr main_mod) }

ppMainFn :: RdrName -> SDoc
ppMainFn main_fn
  | rdrNameOcc main_fn == mainOcc
  = ptext (sLit "IO action") <+> quotes (ppr main_fn)
  | otherwise
  = ptext (sLit "main IO action") <+> quotes (ppr main_fn)

mainOcc :: OccName
mainOcc = mkVarOccFS (fsLit "main")
\end{code}


Note [Root-main Id]
~~~~~~~~~~~~~~~~~~~
The function that the RTS invokes is always :Main.main, which we call
root_main_id.  (Because GHC allows the user to have a module not
called Main as the main module, we can't rely on the main function
being called "Main.main".  That's why root_main_id has a fixed module
":Main".)

This is unusual: it's a LocalId whose Name has a Module from another
module.  Tiresomely, we must filter it out again in MkIface, les we
get two defns for 'main' in the interface file!


%*********************************************************
%*                                                       *
                GHCi stuff
%*                                                       *
%*********************************************************

\begin{code}
setInteractiveContext :: HscEnv -> InteractiveContext -> TcRn a -> TcRn a
setInteractiveContext hsc_env icxt thing_inside
  = let -- Initialise the tcg_inst_env with instances from all home modules.
        -- This mimics the more selective call to hptInstances in tcRnImports
        (home_insts, home_fam_insts) = hptInstances hsc_env (\_ -> True)
        (ic_insts, ic_finsts) = ic_instances icxt

        -- Note [GHCi temporary Ids]
        -- Ideally we would just make a type_env from ic_tythings
        -- and ic_sys_vars, adding in implicit things.  However, Ids
        -- bound interactively might have some free type variables
        -- (RuntimeUnk things), and if we don't register these free
        -- TyVars as global TyVars then the typechecker will try to
        -- quantify over them and fall over in zonkQuantifiedTyVar.
        --
        -- So we must add any free TyVars to the typechecker's global
        -- TyVar set.  This is what happens when the local environment
        -- is extended, so we use tcExtendGhciEnv below which extends
        -- the local environment with the Ids.
        --
        -- However, any Ids bound this way will shadow other Ids in
        -- the GlobalRdrEnv, so we have to be careful to only add Ids
        -- which are visible in the GlobalRdrEnv.
        --
        -- Perhaps it would be better to just extend the global TyVar
        -- list from the free tyvars in the Ids here?  Anyway, at least
        -- this hack is lo…

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