module GHC.Runtime.Context
   ( InteractiveContext (..)
   , InteractiveImport (..)
   , emptyInteractiveContext
   , extendInteractiveContext
   , extendInteractiveContextWithIds
   , setInteractivePrintName
   , substInteractiveContext
   , icExtendGblRdrEnv
   , icInteractiveModule
   , icInScopeTTs
   , icPrintUnqual
   )
where

import GHC.Prelude

import GHC.Hs

import GHC.Driver.Session
import {-# SOURCE #-} GHC.Driver.Plugins

import GHC.Runtime.Eval.Types ( Resume )

import GHC.Unit
import GHC.Unit.Env

import GHC.Core.FamInstEnv
import GHC.Core.InstEnv ( ClsInst, identicalClsInstHead )
import GHC.Core.Type

import GHC.Types.Avail
import GHC.Types.Fixity.Env
import GHC.Types.Id ( isRecordSelector )
import GHC.Types.Id.Info ( IdDetails(..) )
import GHC.Types.Name
import GHC.Types.Name.Env
import GHC.Types.Name.Reader
import GHC.Types.Name.Ppr
import GHC.Types.TyThing
import GHC.Types.Var

import GHC.Builtin.Names ( ioTyConName, printName, mkInteractiveModule )

import GHC.Utils.Outputable
import GHC.Utils.Misc

{-
Note [The interactive package]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Type, class, and value declarations at the command prompt are treated
as if they were defined in modules
   interactive:Ghci1
   interactive:Ghci2
   ...etc...
with each bunch of declarations using a new module, all sharing a
common package 'interactive' (see Module.interactiveUnitId, and
GHC.Builtin.Names.mkInteractiveModule).

This scheme deals well with shadowing.  For example:

   ghci> data T = A
   ghci> data T = B
   ghci> :i A
   data Ghci1.T = A  -- Defined at <interactive>:2:10

Here we must display info about constructor A, but its type T has been
shadowed by the second declaration.  But it has a respectable
qualified name (Ghci1.T), and its source location says where it was
defined.

So the main invariant continues to hold, that in any session an
original name M.T only refers to one unique thing.  (In a previous
iteration both the T's above were called :Interactive.T, albeit with
different uniques, which gave rise to all sorts of trouble.)

The details are a bit tricky though:

 * The field ic_mod_index counts which Ghci module we've got up to.
   It is incremented when extending ic_tythings

 * ic_tythings contains only things from the 'interactive' package.

 * Module from the 'interactive' package (Ghci1, Ghci2 etc) never go
   in the Home Package Table (HPT).  When you say :load, that's when we
   extend the HPT.

 * The 'homeUnitId' field of DynFlags is *not* set to 'interactive'.
   It stays as 'main' (or whatever -this-unit-id says), and is the
   package to which :load'ed modules are added to.

 * So how do we arrange that declarations at the command prompt get to
   be in the 'interactive' package?  Simply by setting the tcg_mod
   field of the TcGblEnv to "interactive:Ghci1".  This is done by the
   call to initTc in initTcInteractive, which in turn get the module
   from it 'icInteractiveModule' field of the interactive context.

   The 'homeUnitId' field stays as 'main' (or whatever -this-unit-id says.

 * The main trickiness is that the type environment (tcg_type_env) and
   fixity envt (tcg_fix_env), now contain entities from all the
   interactive-package modules (Ghci1, Ghci2, ...) together, rather
   than just a single module as is usually the case.  So you can't use
   "nameIsLocalOrFrom" to decide whether to look in the TcGblEnv vs
   the HPT/PTE.  This is a change, but not a problem provided you
   know.

* However, the tcg_binds, tcg_sigs, tcg_insts, tcg_fam_insts, etc fields
  of the TcGblEnv, which collect "things defined in this module", all
  refer to stuff define in a single GHCi command, *not* all the commands
  so far.

  In contrast, tcg_inst_env, tcg_fam_inst_env, have instances from
  all GhciN modules, which makes sense -- they are all "home package"
  modules.


Note [Interactively-bound Ids in GHCi]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The Ids bound by previous Stmts in GHCi are currently
        a) GlobalIds, with
        b) An External Name, like Ghci4.foo
           See Note [The interactive package] above
        c) A tidied type

 (a) They must be GlobalIds (not LocalIds) otherwise when we come to
     compile an expression using these ids later, the byte code
     generator will consider the occurrences to be free rather than
     global.

 (b) Having an External Name is important because of Note
     [GlobalRdrEnv shadowing] in GHC.Types.Names.RdrName

 (c) Their types are tidied. This is important, because :info may ask
     to look at them, and :info expects the things it looks up to have
     tidy types

Where do interactively-bound Ids come from?

  - GHCi REPL Stmts   e.g.
         ghci> let foo x = x+1
    These start with an Internal Name because a Stmt is a local
    construct, so the renamer naturally builds an Internal name for
    each of its binders.  Then in tcRnStmt they are externalised via
    GHC.Tc.Module.externaliseAndTidyId, so they get Names like Ghic4.foo.

  - Ids bound by the debugger etc have Names constructed by
    GHC.Iface.Env.newInteractiveBinder; at the call sites it is followed by
    mkVanillaGlobal or mkVanillaGlobalWithInfo.  So again, they are
    all Global, External.

  - TyCons, Classes, and Ids bound by other top-level declarations in
    GHCi (eg foreign import, record selectors) also get External
    Names, with Ghci9 (or 8, or 7, etc) as the module name.


Note [ic_tythings]
~~~~~~~~~~~~~~~~~~
The ic_tythings field contains
  * The TyThings declared by the user at the command prompt
    (eg Ids, TyCons, Classes)

  * The user-visible Ids that arise from such things, which
    *don't* come from 'implicitTyThings', notably:
       - record selectors
       - class ops
    The implicitTyThings are readily obtained from the TyThings
    but record selectors etc are not

It does *not* contain
  * DFunIds (they can be gotten from ic_instances)
  * CoAxioms (ditto)

See also Note [Interactively-bound Ids in GHCi]

Note [Override identical instances in GHCi]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
If you declare a new instance in GHCi that is identical to a previous one,
we simply override the previous one; we don't regard it as overlapping.
e.g.    Prelude> data T = A | B
        Prelude> instance Eq T where ...
        Prelude> instance Eq T where ...   -- This one overrides

It's exactly the same for type-family instances.  See #7102
-}

-- | Interactive context, recording information about the state of the
-- context in which statements are executed in a GHCi session.
data InteractiveContext
  = InteractiveContext {
         InteractiveContext -> DynFlags
ic_dflags     :: DynFlags,
             -- ^ The 'DynFlags' used to evaluate interactive expressions
             -- and statements.

         InteractiveContext -> Int
ic_mod_index :: Int,
             -- ^ Each GHCi stmt or declaration brings some new things into
             -- scope. We give them names like interactive:Ghci9.T,
             -- where the ic_index is the '9'.  The ic_mod_index is
             -- incremented whenever we add something to ic_tythings
             -- See Note [The interactive package]

         InteractiveContext -> [InteractiveImport]
ic_imports :: [InteractiveImport],
             -- ^ The GHCi top-level scope (ic_rn_gbl_env) is extended with
             -- these imports
             --
             -- This field is only stored here so that the client
             -- can retrieve it with GHC.getContext. GHC itself doesn't
             -- use it, but does reset it to empty sometimes (such
             -- as before a GHC.load). The context is set with GHC.setContext.

         InteractiveContext -> [TyThing]
ic_tythings   :: [TyThing],
             -- ^ TyThings defined by the user, in reverse order of
             -- definition (ie most recent at the front)
             -- See Note [ic_tythings]

         InteractiveContext -> GlobalRdrEnv
ic_rn_gbl_env :: GlobalRdrEnv,
             -- ^ The cached 'GlobalRdrEnv', built by
             -- 'GHC.Runtime.Eval.setContext' and updated regularly
             -- It contains everything in scope at the command line,
             -- including everything in ic_tythings

         InteractiveContext -> ([ClsInst], [FamInst])
ic_instances  :: ([ClsInst], [FamInst]),
             -- ^ All instances and family instances created during
             -- this session.  These are grabbed en masse after each
             -- update to be sure that proper overlapping is retained.
             -- That is, rather than re-check the overlapping each
             -- time we update the context, we just take the results
             -- from the instance code that already does that.

         InteractiveContext -> FixityEnv
ic_fix_env :: FixityEnv,
            -- ^ Fixities declared in let statements

         InteractiveContext -> Maybe [Type]
ic_default :: Maybe [Type],
             -- ^ The current default types, set by a 'default' declaration

          InteractiveContext -> [Resume]
ic_resume :: [Resume],
             -- ^ The stack of breakpoint contexts

         InteractiveContext -> Name
ic_monad      :: Name,
             -- ^ The monad that GHCi is executing in

         InteractiveContext -> Name
ic_int_print  :: Name,
             -- ^ The function that is used for printing results
             -- of expressions in ghci and -e mode.

         InteractiveContext -> Maybe FilePath
ic_cwd :: Maybe FilePath,
             -- ^ virtual CWD of the program

         InteractiveContext -> [LoadedPlugin]
ic_plugins :: ![LoadedPlugin]
             -- ^ Cache of loaded plugins. We store them here to avoid having to
             -- load them everytime we switch to the interctive context.
    }

data InteractiveImport
  = IIDecl (ImportDecl GhcPs)
      -- ^ Bring the exports of a particular module
      -- (filtered by an import decl) into scope

  | IIModule ModuleName
      -- ^ Bring into scope the entire top-level envt of
      -- of this module, including the things imported
      -- into it.


-- | Constructs an empty InteractiveContext.
emptyInteractiveContext :: DynFlags -> InteractiveContext
emptyInteractiveContext :: DynFlags -> InteractiveContext
emptyInteractiveContext DynFlags
dflags
  = InteractiveContext {
       ic_dflags :: DynFlags
ic_dflags     = DynFlags
dflags,
       ic_imports :: [InteractiveImport]
ic_imports    = [],
       ic_rn_gbl_env :: GlobalRdrEnv
ic_rn_gbl_env = GlobalRdrEnv
emptyGlobalRdrEnv,
       ic_mod_index :: Int
ic_mod_index  = Int
1,
       ic_tythings :: [TyThing]
ic_tythings   = [],
       ic_instances :: ([ClsInst], [FamInst])
ic_instances  = ([],[]),
       ic_fix_env :: FixityEnv
ic_fix_env    = FixityEnv
forall a. NameEnv a
emptyNameEnv,
       ic_monad :: Name
ic_monad      = Name
ioTyConName,  -- IO monad by default
       ic_int_print :: Name
ic_int_print  = Name
printName,    -- System.IO.print by default
       ic_default :: Maybe [Type]
ic_default    = Maybe [Type]
forall a. Maybe a
Nothing,
       ic_resume :: [Resume]
ic_resume     = [],
       ic_cwd :: Maybe FilePath
ic_cwd        = Maybe FilePath
forall a. Maybe a
Nothing,
       ic_plugins :: [LoadedPlugin]
ic_plugins    = []
       }

icInteractiveModule :: InteractiveContext -> Module
icInteractiveModule :: InteractiveContext -> Module
icInteractiveModule (InteractiveContext { ic_mod_index :: InteractiveContext -> Int
ic_mod_index = Int
index })
  = Int -> Module
mkInteractiveModule Int
index

-- | This function returns the list of visible TyThings (useful for
-- e.g. showBindings)
icInScopeTTs :: InteractiveContext -> [TyThing]
icInScopeTTs :: InteractiveContext -> [TyThing]
icInScopeTTs = InteractiveContext -> [TyThing]
ic_tythings

-- | Get the PrintUnqualified function based on the flags and this InteractiveContext
icPrintUnqual :: UnitEnv -> InteractiveContext -> PrintUnqualified
icPrintUnqual :: UnitEnv -> InteractiveContext -> PrintUnqualified
icPrintUnqual UnitEnv
unit_env InteractiveContext{ ic_rn_gbl_env :: InteractiveContext -> GlobalRdrEnv
ic_rn_gbl_env = GlobalRdrEnv
grenv } =
    UnitEnv -> GlobalRdrEnv -> PrintUnqualified
mkPrintUnqualified UnitEnv
unit_env GlobalRdrEnv
grenv

-- | extendInteractiveContext is called with new TyThings recently defined to update the
-- InteractiveContext to include them.  Ids are easily removed when shadowed,
-- but Classes and TyCons are not.  Some work could be done to determine
-- whether they are entirely shadowed, but as you could still have references
-- to them (e.g. instances for classes or values of the type for TyCons), it's
-- not clear whether removing them is even the appropriate behavior.
extendInteractiveContext :: InteractiveContext
                         -> [TyThing]
                         -> [ClsInst] -> [FamInst]
                         -> Maybe [Type]
                         -> FixityEnv
                         -> InteractiveContext
extendInteractiveContext :: InteractiveContext
-> [TyThing]
-> [ClsInst]
-> [FamInst]
-> Maybe [Type]
-> FixityEnv
-> InteractiveContext
extendInteractiveContext InteractiveContext
ictxt [TyThing]
new_tythings [ClsInst]
new_cls_insts [FamInst]
new_fam_insts Maybe [Type]
defaults FixityEnv
fix_env
  = InteractiveContext
ictxt { ic_mod_index :: Int
ic_mod_index  = InteractiveContext -> Int
ic_mod_index InteractiveContext
ictxt Int -> Int -> Int
forall a. Num a => a -> a -> a
+ Int
1
                            -- Always bump this; even instances should create
                            -- a new mod_index (#9426)
          , ic_tythings :: [TyThing]
ic_tythings   = [TyThing]
new_tythings [TyThing] -> [TyThing] -> [TyThing]
forall a. [a] -> [a] -> [a]
++ [TyThing]
old_tythings
          , ic_rn_gbl_env :: GlobalRdrEnv
ic_rn_gbl_env = InteractiveContext -> GlobalRdrEnv
ic_rn_gbl_env InteractiveContext
ictxt GlobalRdrEnv -> [TyThing] -> GlobalRdrEnv
`icExtendGblRdrEnv` [TyThing]
new_tythings
          , ic_instances :: ([ClsInst], [FamInst])
ic_instances  = ( [ClsInst]
new_cls_insts [ClsInst] -> [ClsInst] -> [ClsInst]
forall a. [a] -> [a] -> [a]
++ [ClsInst]
old_cls_insts
                            , [FamInst]
new_fam_insts [FamInst] -> [FamInst] -> [FamInst]
forall a. [a] -> [a] -> [a]
++ [FamInst]
fam_insts )
                            -- we don't shadow old family instances (#7102),
                            -- so don't need to remove them here
          , ic_default :: Maybe [Type]
ic_default    = Maybe [Type]
defaults
          , ic_fix_env :: FixityEnv
ic_fix_env    = FixityEnv
fix_env  -- See Note [Fixity declarations in GHCi]
          }
  where
    new_ids :: [Id]
new_ids = [Id
id | AnId Id
id <- [TyThing]
new_tythings]
    old_tythings :: [TyThing]
old_tythings = (TyThing -> Bool) -> [TyThing] -> [TyThing]
forall a. (a -> Bool) -> [a] -> [a]
filterOut ([Id] -> TyThing -> Bool
shadowed_by [Id]
new_ids) (InteractiveContext -> [TyThing]
ic_tythings InteractiveContext
ictxt)

    -- Discard old instances that have been fully overridden
    -- See Note [Override identical instances in GHCi]
    ([ClsInst]
cls_insts, [FamInst]
fam_insts) = InteractiveContext -> ([ClsInst], [FamInst])
ic_instances InteractiveContext
ictxt
    old_cls_insts :: [ClsInst]
old_cls_insts = (ClsInst -> Bool) -> [ClsInst] -> [ClsInst]
forall a. (a -> Bool) -> [a] -> [a]
filterOut (\ClsInst
i -> (ClsInst -> Bool) -> [ClsInst] -> Bool
forall (t :: * -> *) a. Foldable t => (a -> Bool) -> t a -> Bool
any (ClsInst -> ClsInst -> Bool
identicalClsInstHead ClsInst
i) [ClsInst]
new_cls_insts) [ClsInst]
cls_insts

extendInteractiveContextWithIds :: InteractiveContext -> [Id] -> InteractiveContext
-- Just a specialised version
extendInteractiveContextWithIds :: InteractiveContext -> [Id] -> InteractiveContext
extendInteractiveContextWithIds InteractiveContext
ictxt [Id]
new_ids
  | [Id] -> Bool
forall (t :: * -> *) a. Foldable t => t a -> Bool
null [Id]
new_ids = InteractiveContext
ictxt
  | Bool
otherwise    = InteractiveContext
ictxt { ic_mod_index :: Int
ic_mod_index  = InteractiveContext -> Int
ic_mod_index InteractiveContext
ictxt Int -> Int -> Int
forall a. Num a => a -> a -> a
+ Int
1
                         , ic_tythings :: [TyThing]
ic_tythings   = [TyThing]
new_tythings [TyThing] -> [TyThing] -> [TyThing]
forall a. [a] -> [a] -> [a]
++ [TyThing]
old_tythings
                         , ic_rn_gbl_env :: GlobalRdrEnv
ic_rn_gbl_env = InteractiveContext -> GlobalRdrEnv
ic_rn_gbl_env InteractiveContext
ictxt GlobalRdrEnv -> [TyThing] -> GlobalRdrEnv
`icExtendGblRdrEnv` [TyThing]
new_tythings }
  where
    new_tythings :: [TyThing]
new_tythings = (Id -> TyThing) -> [Id] -> [TyThing]
forall a b. (a -> b) -> [a] -> [b]
map Id -> TyThing
AnId [Id]
new_ids
    old_tythings :: [TyThing]
old_tythings = (TyThing -> Bool) -> [TyThing] -> [TyThing]
forall a. (a -> Bool) -> [a] -> [a]
filterOut ([Id] -> TyThing -> Bool
shadowed_by [Id]
new_ids) (InteractiveContext -> [TyThing]
ic_tythings InteractiveContext
ictxt)

shadowed_by :: [Id] -> TyThing -> Bool
shadowed_by :: [Id] -> TyThing -> Bool
shadowed_by [Id]
ids = TyThing -> Bool
shadowed
  where
    -- Keep record selectors because they might be needed by HasField (#19322)
    shadowed :: TyThing -> Bool
shadowed (AnId Id
id) | Id -> Bool
isRecordSelector Id
id = Bool
False
    shadowed TyThing
tything = TyThing -> OccName
forall a. NamedThing a => a -> OccName
getOccName TyThing
tything OccName -> OccSet -> Bool
`elemOccSet` OccSet
new_occs
    new_occs :: OccSet
new_occs = [OccName] -> OccSet
mkOccSet ((Id -> OccName) -> [Id] -> [OccName]
forall a b. (a -> b) -> [a] -> [b]
map Id -> OccName
forall a. NamedThing a => a -> OccName
getOccName [Id]
ids)

setInteractivePrintName :: InteractiveContext -> Name -> InteractiveContext
setInteractivePrintName :: InteractiveContext -> Name -> InteractiveContext
setInteractivePrintName InteractiveContext
ic Name
n = InteractiveContext
ic{ic_int_print :: Name
ic_int_print = Name
n}

    -- ToDo: should not add Ids to the gbl env here

-- | Add TyThings to the GlobalRdrEnv, earlier ones in the list shadowing
-- later ones, and shadowing existing entries in the GlobalRdrEnv.
icExtendGblRdrEnv :: GlobalRdrEnv -> [TyThing] -> GlobalRdrEnv
icExtendGblRdrEnv :: GlobalRdrEnv -> [TyThing] -> GlobalRdrEnv
icExtendGblRdrEnv GlobalRdrEnv
env [TyThing]
tythings
  = (TyThing -> GlobalRdrEnv -> GlobalRdrEnv)
-> GlobalRdrEnv -> [TyThing] -> GlobalRdrEnv
forall (t :: * -> *) a b.
Foldable t =>
(a -> b -> b) -> b -> t a -> b
foldr TyThing -> GlobalRdrEnv -> GlobalRdrEnv
add GlobalRdrEnv
env [TyThing]
tythings  -- Foldr makes things in the front of
                            -- the list shadow things at the back
  where
    -- One at a time, to ensure each shadows the previous ones
    add :: TyThing -> GlobalRdrEnv -> GlobalRdrEnv
add TyThing
thing GlobalRdrEnv
env
       | TyThing -> Bool
is_sub_bndr TyThing
thing
       = GlobalRdrEnv
env
       | Bool
otherwise
       = (GlobalRdrEnv -> GlobalRdrElt -> GlobalRdrEnv)
-> GlobalRdrEnv -> [GlobalRdrElt] -> GlobalRdrEnv
forall (t :: * -> *) b a.
Foldable t =>
(b -> a -> b) -> b -> t a -> b
foldl' GlobalRdrEnv -> GlobalRdrElt -> GlobalRdrEnv
extendGlobalRdrEnv GlobalRdrEnv
env1 ((AvailInfo -> [GlobalRdrElt]) -> [AvailInfo] -> [GlobalRdrElt]
forall (t :: * -> *) a b. Foldable t => (a -> [b]) -> t a -> [b]
concatMap AvailInfo -> [GlobalRdrElt]
localGREsFromAvail [AvailInfo]
avail)
       where
          env1 :: GlobalRdrEnv
env1  = GlobalRdrEnv -> [GreName] -> GlobalRdrEnv
shadowNames GlobalRdrEnv
env ((AvailInfo -> [GreName]) -> [AvailInfo] -> [GreName]
forall (t :: * -> *) a b. Foldable t => (a -> [b]) -> t a -> [b]
concatMap AvailInfo -> [GreName]
availGreNames [AvailInfo]
avail)
          avail :: [AvailInfo]
avail = TyThing -> [AvailInfo]
tyThingAvailInfo TyThing
thing

    -- Ugh! The new_tythings may include record selectors, since they
    -- are not implicit-ids, and must appear in the TypeEnv.  But they
    -- will also be brought into scope by the corresponding (ATyCon
    -- tc).  And we want the latter, because that has the correct
    -- parent (#10520)
    is_sub_bndr :: TyThing -> Bool
is_sub_bndr (AnId Id
f) = case Id -> IdDetails
idDetails Id
f of
                             RecSelId {}  -> Bool
True
                             ClassOpId {} -> Bool
True
                             IdDetails
_            -> Bool
False
    is_sub_bndr TyThing
_ = Bool
False

substInteractiveContext :: InteractiveContext -> TCvSubst -> InteractiveContext
substInteractiveContext :: InteractiveContext -> TCvSubst -> InteractiveContext
substInteractiveContext ictxt :: InteractiveContext
ictxt@InteractiveContext{ ic_tythings :: InteractiveContext -> [TyThing]
ic_tythings = [TyThing]
tts } TCvSubst
subst
  | TCvSubst -> Bool
isEmptyTCvSubst TCvSubst
subst = InteractiveContext
ictxt
  | Bool
otherwise             = InteractiveContext
ictxt { ic_tythings :: [TyThing]
ic_tythings = (TyThing -> TyThing) -> [TyThing] -> [TyThing]
forall a b. (a -> b) -> [a] -> [b]
map TyThing -> TyThing
subst_ty [TyThing]
tts }
  where
    subst_ty :: TyThing -> TyThing
subst_ty (AnId Id
id)
      = Id -> TyThing
AnId (Id -> TyThing) -> Id -> TyThing
forall a b. (a -> b) -> a -> b
$ (Type -> Type) -> Id -> Id
updateIdTypeAndMult (TCvSubst -> Type -> Type
substTyAddInScope TCvSubst
subst) Id
id
      -- Variables in the interactive context *can* mention free type variables
      -- because of the runtime debugger. Otherwise you'd expect all
      -- variables bound in the interactive context to be closed.
    subst_ty TyThing
tt
      = TyThing
tt

instance Outputable InteractiveImport where
  ppr :: InteractiveImport -> SDoc
ppr (IIModule ModuleName
m) = Char -> SDoc
char Char
'*' SDoc -> SDoc -> SDoc
<> ModuleName -> SDoc
forall a. Outputable a => a -> SDoc
ppr ModuleName
m
  ppr (IIDecl ImportDecl GhcPs
d)   = ImportDecl GhcPs -> SDoc
forall a. Outputable a => a -> SDoc
ppr ImportDecl GhcPs
d