{-
(c) The University of Glasgow 2006
(c) The GRASP/AQUA Project, Glasgow University, 1992-1998


Utility functions on @Core@ syntax
-}

module GHC.Core.Subst (
        -- * Main data types
        Subst(..), -- Implementation exported for supercompiler's Renaming.hs only
        TvSubstEnv, IdSubstEnv, InScopeSet,

        -- ** Substituting into expressions and related types
        deShadowBinds, substRuleInfo, substRulesForImportedIds,
        substTyUnchecked, substCo, substExpr, substExprSC, substBind, substBindSC,
        substUnfolding, substUnfoldingSC,
        lookupIdSubst, lookupIdSubst_maybe, substIdType, substIdOcc,
        substTickish, substDVarSet, substIdInfo,

        -- ** Operations on substitutions
        emptySubst, mkEmptySubst, mkSubst, mkOpenSubst, isEmptySubst,
        extendIdSubst, extendIdSubstList, extendTCvSubst, extendTvSubstList,
        extendIdSubstWithClone,
        extendSubst, extendSubstList, extendSubstWithVar,
        extendSubstInScope, extendSubstInScopeList, extendSubstInScopeSet,
        isInScope, setInScope, getSubstInScope,
        extendTvSubst, extendCvSubst,
        delBndr, delBndrs, zapSubst,

        -- ** Substituting and cloning binders
        substBndr, substBndrs, substRecBndrs, substTyVarBndr, substCoVarBndr,
        cloneBndr, cloneBndrs, cloneIdBndr, cloneIdBndrs, cloneRecIdBndrs,

    ) where

import GHC.Prelude

import GHC.Core
import GHC.Core.FVs
import GHC.Core.Seq
import GHC.Core.Utils

        -- We are defining local versions
import GHC.Core.Type hiding ( substTy )
import GHC.Core.Coercion
    ( tyCoFVsOfCo, mkCoVarCo, substCoVarBndr )

import GHC.Types.Var.Set
import GHC.Types.Var.Env as InScopeSet
import GHC.Types.Id
import GHC.Types.Name     ( Name )
import GHC.Types.Var
import GHC.Types.Tickish
import GHC.Types.Id.Info
import GHC.Types.Unique.Supply

import GHC.Builtin.Names
import GHC.Data.Maybe

import GHC.Utils.Misc
import GHC.Utils.Outputable
import GHC.Utils.Panic
import GHC.Utils.Panic.Plain

import Data.Functor.Identity (Identity (..))
import Data.List (mapAccumL)

{-
************************************************************************
*                                                                      *
\subsection{Substitutions}
*                                                                      *
************************************************************************
-}

{-
Note [Extending the IdSubstEnv]
~~~~~~~~~~~~~~~~~~~~~~~~~~
We make a different choice for Ids than we do for TyVars.

For TyVars, see Note [Extending the TvSubstEnv and CvSubstEnv] in GHC.Core.TyCo.Subst.

For Ids, we have a different invariant
        The IdSubstEnv is extended *only* when the Unique on an Id changes
        Otherwise, we just extend the InScopeSet

In consequence:

* If all subst envs are empty, substExpr would be a
  no-op, so substExprSC ("short cut") does nothing.

  However, substExpr still goes ahead and substitutes.  Reason: we may
  want to replace existing Ids with new ones from the in-scope set, to
  avoid space leaks.

* In substIdBndr, we extend the IdSubstEnv only when the unique changes

* If the CvSubstEnv, TvSubstEnv and IdSubstEnv are all empty,
  substExpr does nothing (Note that the above rule for substIdBndr
  maintains this property.  If the incoming envts are both empty, then
  substituting the type and IdInfo can't change anything.)

* In lookupIdSubst, we *must* look up the Id in the in-scope set, because
  it may contain non-trivial changes.  Example:
        (/\a. \x:a. ...x...) Int
  We extend the TvSubstEnv with [a |-> Int]; but x's unique does not change
  so we only extend the in-scope set.  Then we must look up in the in-scope
  set when we find the occurrence of x.

* The requirement to look up the Id in the in-scope set means that we
  must NOT take no-op short cut when the IdSubst is empty.
  We must still look up every Id in the in-scope set.

* (However, we don't need to do so for expressions found in the IdSubst
  itself, whose range is assumed to be correct wrt the in-scope set.)

Why do we make a different choice for the IdSubstEnv than the
TvSubstEnv and CvSubstEnv?

* For Ids, we change the IdInfo all the time (e.g. deleting the
  unfolding), and adding it back later, so using the TyVar convention
  would entail extending the substitution almost all the time

* The simplifier wants to look up in the in-scope set anyway, in case it
  can see a better unfolding from an enclosing case expression

* For TyVars, only coercion variables can possibly change, and they are
  easy to spot
-}

----------------------------

-- We keep GHC.Core.Subst separate from GHC.Core.TyCo.Subst to avoid creating
-- circular dependencies. Functions in this file that don't depend on
-- the definition of CoreExpr can be moved to GHC.Core.TyCo.Subst, as long
-- as it does not require importing too many additional hs-boot files and
-- cause a significant drop in performance.

-- | Add a substitution for an 'Id' to the 'Subst': you must ensure that the in-scope set is
-- such that TyCoSubst Note [The substitution invariant]
-- holds after extending the substitution like this
extendIdSubst :: Subst -> Id -> CoreExpr -> Subst
-- ToDo: add an ASSERT that fvs(subst-result) is already in the in-scope set
extendIdSubst :: Subst -> Id -> CoreExpr -> Subst
extendIdSubst (Subst InScopeSet
in_scope IdSubstEnv
ids TvSubstEnv
tvs CvSubstEnv
cvs) Id
v CoreExpr
r
  = Bool -> SDoc -> Subst -> Subst
forall a. HasCallStack => Bool -> SDoc -> a -> a
assertPpr (Id -> Bool
isNonCoVarId Id
v) (Id -> SDoc
forall a. Outputable a => a -> SDoc
ppr Id
v SDoc -> SDoc -> SDoc
forall doc. IsDoc doc => doc -> doc -> doc
$$ CoreExpr -> SDoc
forall a. Outputable a => a -> SDoc
ppr CoreExpr
r) (Subst -> Subst) -> Subst -> Subst
forall a b. (a -> b) -> a -> b
$
    InScopeSet -> IdSubstEnv -> TvSubstEnv -> CvSubstEnv -> Subst
Subst InScopeSet
in_scope (IdSubstEnv -> Id -> CoreExpr -> IdSubstEnv
forall a. VarEnv a -> Id -> a -> VarEnv a
extendVarEnv IdSubstEnv
ids Id
v CoreExpr
r) TvSubstEnv
tvs CvSubstEnv
cvs

extendIdSubstWithClone :: Subst -> Id -> Id -> Subst
extendIdSubstWithClone :: Subst -> Id -> Id -> Subst
extendIdSubstWithClone (Subst InScopeSet
in_scope IdSubstEnv
ids TvSubstEnv
tvs CvSubstEnv
cvs) Id
v Id
v'
  = Bool -> SDoc -> Subst -> Subst
forall a. HasCallStack => Bool -> SDoc -> a -> a
assertPpr (Id -> Bool
isNonCoVarId Id
v) (Id -> SDoc
forall a. Outputable a => a -> SDoc
ppr Id
v SDoc -> SDoc -> SDoc
forall doc. IsDoc doc => doc -> doc -> doc
$$ Id -> SDoc
forall a. Outputable a => a -> SDoc
ppr Id
v') (Subst -> Subst) -> Subst -> Subst
forall a b. (a -> b) -> a -> b
$
    InScopeSet -> IdSubstEnv -> TvSubstEnv -> CvSubstEnv -> Subst
Subst (InScopeSet -> VarSet -> InScopeSet
extendInScopeSetSet InScopeSet
in_scope VarSet
new_in_scope)
          (IdSubstEnv -> Id -> CoreExpr -> IdSubstEnv
forall a. VarEnv a -> Id -> a -> VarEnv a
extendVarEnv IdSubstEnv
ids Id
v (Id -> CoreExpr
forall b. Id -> Expr b
varToCoreExpr Id
v')) TvSubstEnv
tvs CvSubstEnv
cvs
    where
      new_in_scope :: VarSet
new_in_scope = Type -> VarSet
tyCoVarsOfType (Id -> Type
varType Id
v') VarSet -> Id -> VarSet
`extendVarSet` Id
v'

-- | Adds multiple 'Id' substitutions to the 'Subst': see also 'extendIdSubst'
extendIdSubstList :: Subst -> [(Id, CoreExpr)] -> Subst
extendIdSubstList :: Subst -> [(Id, CoreExpr)] -> Subst
extendIdSubstList (Subst InScopeSet
in_scope IdSubstEnv
ids TvSubstEnv
tvs CvSubstEnv
cvs) [(Id, CoreExpr)]
prs
  = Bool -> Subst -> Subst
forall a. HasCallStack => Bool -> a -> a
assert (((Id, CoreExpr) -> Bool) -> [(Id, CoreExpr)] -> Bool
forall (t :: * -> *) a. Foldable t => (a -> Bool) -> t a -> Bool
all (Id -> Bool
isNonCoVarId (Id -> Bool) -> ((Id, CoreExpr) -> Id) -> (Id, CoreExpr) -> Bool
forall b c a. (b -> c) -> (a -> b) -> a -> c
. (Id, CoreExpr) -> Id
forall a b. (a, b) -> a
fst) [(Id, CoreExpr)]
prs) (Subst -> Subst) -> Subst -> Subst
forall a b. (a -> b) -> a -> b
$
    InScopeSet -> IdSubstEnv -> TvSubstEnv -> CvSubstEnv -> Subst
Subst InScopeSet
in_scope (IdSubstEnv -> [(Id, CoreExpr)] -> IdSubstEnv
forall a. VarEnv a -> [(Id, a)] -> VarEnv a
extendVarEnvList IdSubstEnv
ids [(Id, CoreExpr)]
prs) TvSubstEnv
tvs CvSubstEnv
cvs

-- | Add a substitution appropriate to the thing being substituted
--   (whether an expression, type, or coercion). See also
--   'extendIdSubst', 'extendTvSubst', 'extendCvSubst'
extendSubst :: Subst -> Var -> CoreArg -> Subst
extendSubst :: Subst -> Id -> CoreExpr -> Subst
extendSubst Subst
subst Id
var CoreExpr
arg
  = case CoreExpr
arg of
      Type Type
ty     -> Bool -> Subst -> Subst
forall a. HasCallStack => Bool -> a -> a
assert (Id -> Bool
isTyVar Id
var) (Subst -> Subst) -> Subst -> Subst
forall a b. (a -> b) -> a -> b
$ Subst -> Id -> Type -> Subst
extendTvSubst Subst
subst Id
var Type
ty
      Coercion Coercion
co -> Bool -> Subst -> Subst
forall a. HasCallStack => Bool -> a -> a
assert (Id -> Bool
isCoVar Id
var) (Subst -> Subst) -> Subst -> Subst
forall a b. (a -> b) -> a -> b
$ Subst -> Id -> Coercion -> Subst
extendCvSubst Subst
subst Id
var Coercion
co
      CoreExpr
_           -> Bool -> Subst -> Subst
forall a. HasCallStack => Bool -> a -> a
assert (Id -> Bool
isId    Id
var) (Subst -> Subst) -> Subst -> Subst
forall a b. (a -> b) -> a -> b
$ Subst -> Id -> CoreExpr -> Subst
extendIdSubst Subst
subst Id
var CoreExpr
arg

extendSubstWithVar :: Subst -> Var -> Var -> Subst
extendSubstWithVar :: Subst -> Id -> Id -> Subst
extendSubstWithVar Subst
subst Id
v1 Id
v2
  | Id -> Bool
isTyVar Id
v1 = Bool -> Subst -> Subst
forall a. HasCallStack => Bool -> a -> a
assert (Id -> Bool
isTyVar Id
v2) (Subst -> Subst) -> Subst -> Subst
forall a b. (a -> b) -> a -> b
$ Subst -> Id -> Type -> Subst
extendTvSubst Subst
subst Id
v1 (Id -> Type
mkTyVarTy Id
v2)
  | Id -> Bool
isCoVar Id
v1 = Bool -> Subst -> Subst
forall a. HasCallStack => Bool -> a -> a
assert (Id -> Bool
isCoVar Id
v2) (Subst -> Subst) -> Subst -> Subst
forall a b. (a -> b) -> a -> b
$ Subst -> Id -> Coercion -> Subst
extendCvSubst Subst
subst Id
v1 (Id -> Coercion
mkCoVarCo Id
v2)
  | Bool
otherwise  = Bool -> Subst -> Subst
forall a. HasCallStack => Bool -> a -> a
assert (Id -> Bool
isId    Id
v2) (Subst -> Subst) -> Subst -> Subst
forall a b. (a -> b) -> a -> b
$ Subst -> Id -> CoreExpr -> Subst
extendIdSubst Subst
subst Id
v1 (Id -> CoreExpr
forall b. Id -> Expr b
Var Id
v2)

-- | Add a substitution as appropriate to each of the terms being
--   substituted (whether expressions, types, or coercions). See also
--   'extendSubst'.
extendSubstList :: Subst -> [(Var,CoreArg)] -> Subst
extendSubstList :: Subst -> [(Id, CoreExpr)] -> Subst
extendSubstList Subst
subst []              = Subst
subst
extendSubstList Subst
subst ((Id
var,CoreExpr
rhs):[(Id, CoreExpr)]
prs) = Subst -> [(Id, CoreExpr)] -> Subst
extendSubstList (Subst -> Id -> CoreExpr -> Subst
extendSubst Subst
subst Id
var CoreExpr
rhs) [(Id, CoreExpr)]
prs

-- | Find the substitution for an 'Id' in the 'Subst'
-- The Id should not be a CoVar
lookupIdSubst :: HasDebugCallStack => Subst -> Id -> CoreExpr
lookupIdSubst :: (() :: Constraint) => Subst -> Id -> CoreExpr
lookupIdSubst (Subst InScopeSet
in_scope IdSubstEnv
ids TvSubstEnv
_ CvSubstEnv
_) Id
v
  | Bool -> SDoc -> (Bool -> Bool) -> Bool -> Bool
forall a. HasCallStack => Bool -> SDoc -> a -> a
assertPpr (Id -> Bool
isId Id
v Bool -> Bool -> Bool
&& Bool -> Bool
not (Id -> Bool
isCoVar Id
v)) (Id -> SDoc
forall a. Outputable a => a -> SDoc
ppr Id
v)
    Bool -> Bool
not (Id -> Bool
isLocalId Id
v)                   = Id -> CoreExpr
forall b. Id -> Expr b
Var Id
v
  | Just CoreExpr
e  <- IdSubstEnv -> Id -> Maybe CoreExpr
forall a. VarEnv a -> Id -> Maybe a
lookupVarEnv IdSubstEnv
ids       Id
v = CoreExpr
e
  | Just Id
v' <- InScopeSet -> Id -> Maybe Id
lookupInScope InScopeSet
in_scope Id
v = Id -> CoreExpr
forall b. Id -> Expr b
Var Id
v'
        -- Vital! See Note [Extending the IdSubstEnv]
        -- If v isn't in the InScopeSet, we panic, because
        -- it's a bad bug and we really want to know
  | Bool
otherwise = String -> SDoc -> CoreExpr
forall a. HasCallStack => String -> SDoc -> a
pprPanic String
"lookupIdSubst" (Id -> SDoc
forall a. Outputable a => a -> SDoc
ppr Id
v SDoc -> SDoc -> SDoc
forall doc. IsDoc doc => doc -> doc -> doc
$$ InScopeSet -> SDoc
forall a. Outputable a => a -> SDoc
ppr InScopeSet
in_scope)

lookupIdSubst_maybe :: HasDebugCallStack => Subst -> Id -> Maybe CoreExpr
-- Just look up in the substitution; do not check the in-scope set
lookupIdSubst_maybe :: (() :: Constraint) => Subst -> Id -> Maybe CoreExpr
lookupIdSubst_maybe (Subst InScopeSet
_ IdSubstEnv
ids TvSubstEnv
_ CvSubstEnv
_) Id
v
  = Bool -> SDoc -> Maybe CoreExpr -> Maybe CoreExpr
forall a. HasCallStack => Bool -> SDoc -> a -> a
assertPpr (Id -> Bool
isId Id
v Bool -> Bool -> Bool
&& Bool -> Bool
not (Id -> Bool
isCoVar Id
v)) (Id -> SDoc
forall a. Outputable a => a -> SDoc
ppr Id
v) (Maybe CoreExpr -> Maybe CoreExpr)
-> Maybe CoreExpr -> Maybe CoreExpr
forall a b. (a -> b) -> a -> b
$
    IdSubstEnv -> Id -> Maybe CoreExpr
forall a. VarEnv a -> Id -> Maybe a
lookupVarEnv IdSubstEnv
ids Id
v

delBndr :: Subst -> Var -> Subst
delBndr :: Subst -> Id -> Subst
delBndr (Subst InScopeSet
in_scope IdSubstEnv
ids TvSubstEnv
tvs CvSubstEnv
cvs) Id
v
  | Id -> Bool
isCoVar Id
v = InScopeSet -> IdSubstEnv -> TvSubstEnv -> CvSubstEnv -> Subst
Subst InScopeSet
in_scope IdSubstEnv
ids TvSubstEnv
tvs (CvSubstEnv -> Id -> CvSubstEnv
forall a. VarEnv a -> Id -> VarEnv a
delVarEnv CvSubstEnv
cvs Id
v)
  | Id -> Bool
isTyVar Id
v = InScopeSet -> IdSubstEnv -> TvSubstEnv -> CvSubstEnv -> Subst
Subst InScopeSet
in_scope IdSubstEnv
ids (TvSubstEnv -> Id -> TvSubstEnv
forall a. VarEnv a -> Id -> VarEnv a
delVarEnv TvSubstEnv
tvs Id
v) CvSubstEnv
cvs
  | Bool
otherwise = InScopeSet -> IdSubstEnv -> TvSubstEnv -> CvSubstEnv -> Subst
Subst InScopeSet
in_scope (IdSubstEnv -> Id -> IdSubstEnv
forall a. VarEnv a -> Id -> VarEnv a
delVarEnv IdSubstEnv
ids Id
v) TvSubstEnv
tvs CvSubstEnv
cvs

delBndrs :: Subst -> [Var] -> Subst
delBndrs :: Subst -> [Id] -> Subst
delBndrs (Subst InScopeSet
in_scope IdSubstEnv
ids TvSubstEnv
tvs CvSubstEnv
cvs) [Id]
vs
  = InScopeSet -> IdSubstEnv -> TvSubstEnv -> CvSubstEnv -> Subst
Subst InScopeSet
in_scope (IdSubstEnv -> [Id] -> IdSubstEnv
forall a. VarEnv a -> [Id] -> VarEnv a
delVarEnvList IdSubstEnv
ids [Id]
vs) (TvSubstEnv -> [Id] -> TvSubstEnv
forall a. VarEnv a -> [Id] -> VarEnv a
delVarEnvList TvSubstEnv
tvs [Id]
vs) (CvSubstEnv -> [Id] -> CvSubstEnv
forall a. VarEnv a -> [Id] -> VarEnv a
delVarEnvList CvSubstEnv
cvs [Id]
vs)
      -- Easiest thing is just delete all from all!

-- | Simultaneously substitute for a bunch of variables
--   No left-right shadowing
--   ie the substitution for   (\x \y. e) a1 a2
--      so neither x nor y scope over a1 a2
mkOpenSubst :: InScopeSet -> [(Var,CoreArg)] -> Subst
mkOpenSubst :: InScopeSet -> [(Id, CoreExpr)] -> Subst
mkOpenSubst InScopeSet
in_scope [(Id, CoreExpr)]
pairs = InScopeSet -> IdSubstEnv -> TvSubstEnv -> CvSubstEnv -> Subst
Subst InScopeSet
in_scope
                                   ([(Id, CoreExpr)] -> IdSubstEnv
forall a. [(Id, a)] -> VarEnv a
mkVarEnv [(Id
id,CoreExpr
e)  | (Id
id, CoreExpr
e) <- [(Id, CoreExpr)]
pairs, Id -> Bool
isId Id
id])
                                   ([(Id, Type)] -> TvSubstEnv
forall a. [(Id, a)] -> VarEnv a
mkVarEnv [(Id
tv,Type
ty) | (Id
tv, Type Type
ty) <- [(Id, CoreExpr)]
pairs])
                                   ([(Id, Coercion)] -> CvSubstEnv
forall a. [(Id, a)] -> VarEnv a
mkVarEnv [(Id
v,Coercion
co)  | (Id
v, Coercion Coercion
co) <- [(Id, CoreExpr)]
pairs])

------------------------------

{-
************************************************************************
*                                                                      *
        Substituting expressions
*                                                                      *
************************************************************************
-}

substExprSC :: HasDebugCallStack => Subst -> CoreExpr -> CoreExpr
-- Just like substExpr, but a no-op if the substitution is empty
-- Note that this does /not/ replace occurrences of free vars with
-- their canonical representatives in the in-scope set
substExprSC :: (() :: Constraint) => Subst -> CoreExpr -> CoreExpr
substExprSC Subst
subst CoreExpr
orig_expr
  | Subst -> Bool
isEmptySubst Subst
subst = CoreExpr
orig_expr
  | Bool
otherwise          = -- pprTrace "enter subst-expr" (doc $$ ppr orig_expr) $
                         (() :: Constraint) => Subst -> CoreExpr -> CoreExpr
Subst -> CoreExpr -> CoreExpr
substExpr Subst
subst CoreExpr
orig_expr

-- | substExpr applies a substitution to an entire 'CoreExpr'. Remember,
-- you may only apply the substitution /once/:
-- See Note [Substitutions apply only once] in "GHC.Core.TyCo.Subst"
--
-- Do *not* attempt to short-cut in the case of an empty substitution!
-- See Note [Extending the IdSubstEnv]
substExpr :: HasDebugCallStack => Subst -> CoreExpr -> CoreExpr
   -- HasDebugCallStack so we can track failures in lookupIdSubst
substExpr :: (() :: Constraint) => Subst -> CoreExpr -> CoreExpr
substExpr Subst
subst CoreExpr
expr
  = CoreExpr -> CoreExpr
go CoreExpr
expr
  where
    go :: CoreExpr -> CoreExpr
go (Var Id
v)         = (() :: Constraint) => Subst -> Id -> CoreExpr
Subst -> Id -> CoreExpr
lookupIdSubst Subst
subst Id
v
    go (Type Type
ty)       = Type -> CoreExpr
forall b. Type -> Expr b
Type (Subst -> Type -> Type
substTyUnchecked Subst
subst Type
ty)
    go (Coercion Coercion
co)   = Coercion -> CoreExpr
forall b. Coercion -> Expr b
Coercion ((() :: Constraint) => Subst -> Coercion -> Coercion
Subst -> Coercion -> Coercion
substCo Subst
subst Coercion
co)
    go (Lit Literal
lit)       = Literal -> CoreExpr
forall b. Literal -> Expr b
Lit Literal
lit
    go (App CoreExpr
fun CoreExpr
arg)   = CoreExpr -> CoreExpr -> CoreExpr
forall b. Expr b -> Expr b -> Expr b
App (CoreExpr -> CoreExpr
go CoreExpr
fun) (CoreExpr -> CoreExpr
go CoreExpr
arg)
    go (Tick CoreTickish
tickish CoreExpr
e) = CoreTickish -> CoreExpr -> CoreExpr
mkTick (Subst -> CoreTickish -> CoreTickish
substTickish Subst
subst CoreTickish
tickish) (CoreExpr -> CoreExpr
go CoreExpr
e)
    go (Cast CoreExpr
e Coercion
co)     = CoreExpr -> Coercion -> CoreExpr
forall b. Expr b -> Coercion -> Expr b
Cast (CoreExpr -> CoreExpr
go CoreExpr
e) ((() :: Constraint) => Subst -> Coercion -> Coercion
Subst -> Coercion -> Coercion
substCo Subst
subst Coercion
co)
       -- Do not optimise even identity coercions
       -- Reason: substitution applies to the LHS of RULES, and
       --         if you "optimise" an identity coercion, you may
       --         lose a binder. We optimise the LHS of rules at
       --         construction time

    go (Lam Id
bndr CoreExpr
body) = Id -> CoreExpr -> CoreExpr
forall b. b -> Expr b -> Expr b
Lam Id
bndr' ((() :: Constraint) => Subst -> CoreExpr -> CoreExpr
Subst -> CoreExpr -> CoreExpr
substExpr Subst
subst' CoreExpr
body)
                       where
                         (Subst
subst', Id
bndr') = Subst -> Id -> (Subst, Id)
substBndr Subst
subst Id
bndr

    go (Let Bind Id
bind CoreExpr
body) = Bind Id -> CoreExpr -> CoreExpr
forall b. Bind b -> Expr b -> Expr b
Let Bind Id
bind' ((() :: Constraint) => Subst -> CoreExpr -> CoreExpr
Subst -> CoreExpr -> CoreExpr
substExpr Subst
subst' CoreExpr
body)
                       where
                         (Subst
subst', Bind Id
bind') = (() :: Constraint) => Subst -> Bind Id -> (Subst, Bind Id)
Subst -> Bind Id -> (Subst, Bind Id)
substBind Subst
subst Bind Id
bind

    go (Case CoreExpr
scrut Id
bndr Type
ty [Alt Id]
alts) = CoreExpr -> Id -> Type -> [Alt Id] -> CoreExpr
forall b. Expr b -> b -> Type -> [Alt b] -> Expr b
Case (CoreExpr -> CoreExpr
go CoreExpr
scrut) Id
bndr' (Subst -> Type -> Type
substTyUnchecked Subst
subst Type
ty) ((Alt Id -> Alt Id) -> [Alt Id] -> [Alt Id]
forall a b. (a -> b) -> [a] -> [b]
map (Subst -> Alt Id -> Alt Id
go_alt Subst
subst') [Alt Id]
alts)
                                 where
                                 (Subst
subst', Id
bndr') = Subst -> Id -> (Subst, Id)
substBndr Subst
subst Id
bndr

    go_alt :: Subst -> Alt Id -> Alt Id
go_alt Subst
subst (Alt AltCon
con [Id]
bndrs CoreExpr
rhs) = AltCon -> [Id] -> CoreExpr -> Alt Id
forall b. AltCon -> [b] -> Expr b -> Alt b
Alt AltCon
con [Id]
bndrs' ((() :: Constraint) => Subst -> CoreExpr -> CoreExpr
Subst -> CoreExpr -> CoreExpr
substExpr Subst
subst' CoreExpr
rhs)
                                 where
                                   (Subst
subst', [Id]
bndrs') = Subst -> [Id] -> (Subst, [Id])
forall (f :: * -> *).
Traversable f =>
Subst -> f Id -> (Subst, f Id)
substBndrs Subst
subst [Id]
bndrs

-- | Apply a substitution to an entire 'CoreBind', additionally returning an updated 'Subst'
-- that should be used by subsequent substitutions.
substBind, substBindSC :: HasDebugCallStack => Subst -> CoreBind -> (Subst, CoreBind)

substBindSC :: (() :: Constraint) => Subst -> Bind Id -> (Subst, Bind Id)
substBindSC Subst
subst Bind Id
bind    -- Short-cut if the substitution is empty
  | Bool -> Bool
not (Subst -> Bool
isEmptySubst Subst
subst)
  = (() :: Constraint) => Subst -> Bind Id -> (Subst, Bind Id)
Subst -> Bind Id -> (Subst, Bind Id)
substBind Subst
subst Bind Id
bind
  | Bool
otherwise
  = case Bind Id
bind of
       NonRec Id
bndr CoreExpr
rhs -> (Subst
subst', Id -> CoreExpr -> Bind Id
forall b. b -> Expr b -> Bind b
NonRec Id
bndr' CoreExpr
rhs)
          where
            (Subst
subst', Id
bndr') = Subst -> Id -> (Subst, Id)
substBndr Subst
subst Id
bndr
       Rec [(Id, CoreExpr)]
pairs -> (Subst
subst', [(Id, CoreExpr)] -> Bind Id
forall b. [(b, Expr b)] -> Bind b
Rec ([Id]
bndrs' [Id] -> [CoreExpr] -> [(Id, CoreExpr)]
forall a b. [a] -> [b] -> [(a, b)]
`zip` [CoreExpr]
rhss'))
          where
            ([Id]
bndrs, [CoreExpr]
rhss)    = [(Id, CoreExpr)] -> ([Id], [CoreExpr])
forall a b. [(a, b)] -> ([a], [b])
unzip [(Id, CoreExpr)]
pairs
            (Subst
subst', [Id]
bndrs') = Subst -> [Id] -> (Subst, [Id])
forall (f :: * -> *).
Traversable f =>
Subst -> f Id -> (Subst, f Id)
substRecBndrs Subst
subst [Id]
bndrs
            rhss' :: [CoreExpr]
rhss' | Subst -> Bool
isEmptySubst Subst
subst'
                  = [CoreExpr]
rhss
                  | Bool
otherwise
                  = (CoreExpr -> CoreExpr) -> [CoreExpr] -> [CoreExpr]
forall a b. (a -> b) -> [a] -> [b]
map ((() :: Constraint) => Subst -> CoreExpr -> CoreExpr
Subst -> CoreExpr -> CoreExpr
substExpr Subst
subst') [CoreExpr]
rhss

substBind :: (() :: Constraint) => Subst -> Bind Id -> (Subst, Bind Id)
substBind Subst
subst (NonRec Id
bndr CoreExpr
rhs)
  = (Subst
subst', Id -> CoreExpr -> Bind Id
forall b. b -> Expr b -> Bind b
NonRec Id
bndr' ((() :: Constraint) => Subst -> CoreExpr -> CoreExpr
Subst -> CoreExpr -> CoreExpr
substExpr Subst
subst CoreExpr
rhs))
  where
    (Subst
subst', Id
bndr') = Subst -> Id -> (Subst, Id)
substBndr Subst
subst Id
bndr

substBind Subst
subst (Rec [(Id, CoreExpr)]
pairs)
   = (Subst
subst', [(Id, CoreExpr)] -> Bind Id
forall b. [(b, Expr b)] -> Bind b
Rec ([Id]
bndrs' [Id] -> [CoreExpr] -> [(Id, CoreExpr)]
forall a b. [a] -> [b] -> [(a, b)]
`zip` [CoreExpr]
rhss'))
   where
       ([Id]
bndrs, [CoreExpr]
rhss)    = [(Id, CoreExpr)] -> ([Id], [CoreExpr])
forall a b. [(a, b)] -> ([a], [b])
unzip [(Id, CoreExpr)]
pairs
       (Subst
subst', [Id]
bndrs') = Subst -> [Id] -> (Subst, [Id])
forall (f :: * -> *).
Traversable f =>
Subst -> f Id -> (Subst, f Id)
substRecBndrs Subst
subst [Id]
bndrs
       rhss' :: [CoreExpr]
rhss' = (CoreExpr -> CoreExpr) -> [CoreExpr] -> [CoreExpr]
forall a b. (a -> b) -> [a] -> [b]
map ((() :: Constraint) => Subst -> CoreExpr -> CoreExpr
Subst -> CoreExpr -> CoreExpr
substExpr Subst
subst') [CoreExpr]
rhss

-- | De-shadowing the program is sometimes a useful pre-pass. It can be done simply
-- by running over the bindings with an empty substitution, because substitution
-- returns a result that has no-shadowing guaranteed.
--
-- (Actually, within a single /type/ there might still be shadowing, because
-- 'substTy' is a no-op for the empty substitution, but that's probably OK.)
--
-- [Aug 09] This function is not used in GHC at the moment, but seems so
--          short and simple that I'm going to leave it here
deShadowBinds :: CoreProgram -> CoreProgram
deShadowBinds :: CoreProgram -> CoreProgram
deShadowBinds CoreProgram
binds = (Subst, CoreProgram) -> CoreProgram
forall a b. (a, b) -> b
snd ((Subst -> Bind Id -> (Subst, Bind Id))
-> Subst -> CoreProgram -> (Subst, CoreProgram)
forall (t :: * -> *) s a b.
Traversable t =>
(s -> a -> (s, b)) -> s -> t a -> (s, t b)
mapAccumL (() :: Constraint) => Subst -> Bind Id -> (Subst, Bind Id)
Subst -> Bind Id -> (Subst, Bind Id)
substBind Subst
emptySubst CoreProgram
binds)

{-
************************************************************************
*                                                                      *
        Substituting binders
*                                                                      *
************************************************************************

Remember that substBndr and friends are used when doing expression
substitution only.  Their only business is substitution, so they
preserve all IdInfo (suitably substituted).  For example, we *want* to
preserve occ info in rules.
-}

-- | Substitutes a 'Var' for another one according to the 'Subst' given, returning
-- the result and an updated 'Subst' that should be used by subsequent substitutions.
-- 'IdInfo' is preserved by this process, although it is substituted into appropriately.
substBndr :: Subst -> Var -> (Subst, Var)
substBndr :: Subst -> Id -> (Subst, Id)
substBndr Subst
subst Id
bndr
  | Id -> Bool
isTyVar Id
bndr  = (() :: Constraint) => Subst -> Id -> (Subst, Id)
Subst -> Id -> (Subst, Id)
substTyVarBndr Subst
subst Id
bndr
  | Id -> Bool
isCoVar Id
bndr  = (() :: Constraint) => Subst -> Id -> (Subst, Id)
Subst -> Id -> (Subst, Id)
substCoVarBndr Subst
subst Id
bndr
  | Bool
otherwise     = SDoc -> Subst -> Subst -> Id -> (Subst, Id)
substIdBndr (String -> SDoc
forall doc. IsLine doc => String -> doc
text String
"var-bndr") Subst
subst Subst
subst Id
bndr

-- | Applies 'substBndr' to a number of 'Var's, accumulating a new 'Subst' left-to-right
substBndrs :: Traversable f => Subst -> f Var -> (Subst, f Var)
substBndrs :: forall (f :: * -> *).
Traversable f =>
Subst -> f Id -> (Subst, f Id)
substBndrs = (Subst -> Id -> (Subst, Id)) -> Subst -> f Id -> (Subst, f Id)
forall (t :: * -> *) s a b.
Traversable t =>
(s -> a -> (s, b)) -> s -> t a -> (s, t b)
mapAccumL Subst -> Id -> (Subst, Id)
substBndr
{-# INLINE substBndrs #-}

-- | Substitute in a mutually recursive group of 'Id's
substRecBndrs :: Traversable f => Subst -> f Id -> (Subst, f Id)
substRecBndrs :: forall (f :: * -> *).
Traversable f =>
Subst -> f Id -> (Subst, f Id)
substRecBndrs Subst
subst f Id
bndrs
  = (Subst
new_subst, f Id
new_bndrs)
  where         -- Here's the reason we need to pass rec_subst to subst_id
    (Subst
new_subst, f Id
new_bndrs) = (Subst -> Id -> (Subst, Id)) -> Subst -> f Id -> (Subst, f Id)
forall (t :: * -> *) s a b.
Traversable t =>
(s -> a -> (s, b)) -> s -> t a -> (s, t b)
mapAccumL (SDoc -> Subst -> Subst -> Id -> (Subst, Id)
substIdBndr (String -> SDoc
forall doc. IsLine doc => String -> doc
text String
"rec-bndr") Subst
new_subst) Subst
subst f Id
bndrs
{-# SPECIALIZE substRecBndrs :: Subst -> [Id] -> (Subst, [Id]) #-}
{-# SPECIALIZE substRecBndrs :: Subst -> Identity Id -> (Subst, Identity Id) #-}

substIdBndr :: SDoc
            -> Subst            -- ^ Substitution to use for the IdInfo
            -> Subst -> Id      -- ^ Substitution and Id to transform
            -> (Subst, Id)      -- ^ Transformed pair
                                -- NB: unfolding may be zapped

substIdBndr :: SDoc -> Subst -> Subst -> Id -> (Subst, Id)
substIdBndr SDoc
_doc Subst
rec_subst subst :: Subst
subst@(Subst InScopeSet
in_scope IdSubstEnv
env TvSubstEnv
tvs CvSubstEnv
cvs) Id
old_id
  = -- pprTrace "substIdBndr" (doc $$ ppr old_id $$ ppr in_scope) $
    (InScopeSet -> IdSubstEnv -> TvSubstEnv -> CvSubstEnv -> Subst
Subst (InScopeSet
in_scope InScopeSet -> Id -> InScopeSet
`InScopeSet.extendInScopeSet` Id
new_id) IdSubstEnv
new_env TvSubstEnv
tvs CvSubstEnv
cvs, Id
new_id)
  where
    id1 :: Id
id1 = InScopeSet -> Id -> Id
uniqAway InScopeSet
in_scope Id
old_id      -- id1 is cloned if necessary
    id2 :: Id
id2 | Bool
no_type_change = Id
id1
        | Bool
otherwise      = (Type -> Type) -> Id -> Id
updateIdTypeAndMult (Subst -> Type -> Type
substTyUnchecked Subst
subst) Id
id1

    old_ty :: Type
old_ty = Id -> Type
idType Id
old_id
    old_w :: Type
old_w = Id -> Type
idMult Id
old_id
    no_type_change :: Bool
no_type_change = (TvSubstEnv -> Bool
forall a. VarEnv a -> Bool
isEmptyVarEnv TvSubstEnv
tvs Bool -> Bool -> Bool
&& CvSubstEnv -> Bool
forall a. VarEnv a -> Bool
isEmptyVarEnv CvSubstEnv
cvs) Bool -> Bool -> Bool
||
                     (Type -> Bool
noFreeVarsOfType Type
old_ty Bool -> Bool -> Bool
&& Type -> Bool
noFreeVarsOfType Type
old_w)

        -- new_id has the right IdInfo
        -- The lazy-set is because we're in a loop here, with
        -- rec_subst, when dealing with a mutually-recursive group
    new_id :: Id
new_id = Maybe IdInfo -> Id -> Id
maybeModifyIdInfo Maybe IdInfo
mb_new_info Id
id2
    mb_new_info :: Maybe IdInfo
mb_new_info = Subst -> Id -> IdInfo -> Maybe IdInfo
substIdInfo Subst
rec_subst Id
id2 ((() :: Constraint) => Id -> IdInfo
Id -> IdInfo
idInfo Id
id2)
        -- NB: unfolding info may be zapped

        -- Extend the substitution if the unique has changed
        -- See the notes with substTyVarBndr for the delVarEnv
    new_env :: IdSubstEnv
new_env | Bool
no_change = IdSubstEnv -> Id -> IdSubstEnv
forall a. VarEnv a -> Id -> VarEnv a
delVarEnv IdSubstEnv
env Id
old_id
            | Bool
otherwise = IdSubstEnv -> Id -> CoreExpr -> IdSubstEnv
forall a. VarEnv a -> Id -> a -> VarEnv a
extendVarEnv IdSubstEnv
env Id
old_id (Id -> CoreExpr
forall b. Id -> Expr b
Var Id
new_id)

    no_change :: Bool
no_change = Id
id1 Id -> Id -> Bool
forall a. Eq a => a -> a -> Bool
== Id
old_id
        -- See Note [Extending the IdSubstEnv]
        -- it's /not/ necessary to check mb_new_info and no_type_change

{-
Now a variant that unconditionally allocates a new unique.
It also unconditionally zaps the OccInfo.
-}

-- | Very similar to 'substBndr', but it always allocates a new 'Unique' for
-- each variable in its output.  It substitutes the IdInfo though.
-- Discards non-Stable unfoldings
cloneIdBndr :: Subst -> UniqSupply -> Id -> (Subst, Id)
cloneIdBndr :: Subst -> UniqSupply -> Id -> (Subst, Id)
cloneIdBndr Subst
subst UniqSupply
us Id
old_id
  = Subst -> Subst -> (Id, Unique) -> (Subst, Id)
clone_id Subst
subst Subst
subst (Id
old_id, UniqSupply -> Unique
uniqFromSupply UniqSupply
us)

-- | Applies 'cloneIdBndr' to a number of 'Id's, accumulating a final
-- substitution from left to right
-- Discards non-Stable unfoldings
cloneIdBndrs :: Subst -> UniqSupply -> [Id] -> (Subst, [Id])
cloneIdBndrs :: Subst -> UniqSupply -> [Id] -> (Subst, [Id])
cloneIdBndrs Subst
subst UniqSupply
us [Id]
ids
  = (Subst -> (Id, Unique) -> (Subst, Id))
-> Subst -> [(Id, Unique)] -> (Subst, [Id])
forall (t :: * -> *) s a b.
Traversable t =>
(s -> a -> (s, b)) -> s -> t a -> (s, t b)
mapAccumL (Subst -> Subst -> (Id, Unique) -> (Subst, Id)
clone_id Subst
subst) Subst
subst ([Id]
ids [Id] -> [Unique] -> [(Id, Unique)]
forall a b. [a] -> [b] -> [(a, b)]
`zip` UniqSupply -> [Unique]
uniqsFromSupply UniqSupply
us)

cloneBndrs :: MonadUnique m => Subst -> [Var] -> m (Subst, [Var])
-- Works for all kinds of variables (typically case binders)
-- not just Ids
cloneBndrs :: forall (m :: * -> *).
MonadUnique m =>
Subst -> [Id] -> m (Subst, [Id])
cloneBndrs Subst
subst [Id]
vs
  = do [Unique]
us <- m [Unique]
forall (m :: * -> *). MonadUnique m => m [Unique]
getUniquesM
       (Subst, [Id]) -> m (Subst, [Id])
forall a. a -> m a
forall (f :: * -> *) a. Applicative f => a -> f a
pure ((Subst, [Id]) -> m (Subst, [Id]))
-> (Subst, [Id]) -> m (Subst, [Id])
forall a b. (a -> b) -> a -> b
$ (Subst -> (Id, Unique) -> (Subst, Id))
-> Subst -> [(Id, Unique)] -> (Subst, [Id])
forall (t :: * -> *) s a b.
Traversable t =>
(s -> a -> (s, b)) -> s -> t a -> (s, t b)
mapAccumL (\Subst
subst (Id
v, Unique
u) -> Subst -> Unique -> Id -> (Subst, Id)
cloneBndr Subst
subst Unique
u Id
v) Subst
subst ([Id]
vs [Id] -> [Unique] -> [(Id, Unique)]
forall a b. [a] -> [b] -> [(a, b)]
`zip` [Unique]
us)

cloneBndr :: Subst -> Unique -> Var -> (Subst, Var)
cloneBndr :: Subst -> Unique -> Id -> (Subst, Id)
cloneBndr Subst
subst Unique
uniq Id
v
  | Id -> Bool
isTyVar Id
v = Subst -> Id -> Unique -> (Subst, Id)
cloneTyVarBndr Subst
subst Id
v Unique
uniq
  | Bool
otherwise = Subst -> Subst -> (Id, Unique) -> (Subst, Id)
clone_id Subst
subst Subst
subst (Id
v,Unique
uniq)  -- Works for coercion variables too

-- | Clone a mutually recursive group of 'Id's
cloneRecIdBndrs :: MonadUnique m => Subst -> [Id] -> m (Subst, [Id])
cloneRecIdBndrs :: forall (m :: * -> *).
MonadUnique m =>
Subst -> [Id] -> m (Subst, [Id])
cloneRecIdBndrs Subst
subst [Id]
ids
  = do [Unique]
us <- m [Unique]
forall (m :: * -> *). MonadUnique m => m [Unique]
getUniquesM
       let (Subst
subst', [Id]
ids') = (Subst -> (Id, Unique) -> (Subst, Id))
-> Subst -> [(Id, Unique)] -> (Subst, [Id])
forall (t :: * -> *) s a b.
Traversable t =>
(s -> a -> (s, b)) -> s -> t a -> (s, t b)
mapAccumL (Subst -> Subst -> (Id, Unique) -> (Subst, Id)
clone_id Subst
subst') Subst
subst ([Id]
ids [Id] -> [Unique] -> [(Id, Unique)]
forall a b. [a] -> [b] -> [(a, b)]
`zip` [Unique]
us)
       (Subst, [Id]) -> m (Subst, [Id])
forall a. a -> m a
forall (f :: * -> *) a. Applicative f => a -> f a
pure (Subst
subst', [Id]
ids')

-- Just like substIdBndr, except that it always makes a new unique
-- It is given the unique to use
-- Discards non-Stable unfoldings
clone_id    :: Subst                    -- Substitution for the IdInfo
            -> Subst -> (Id, Unique)    -- Substitution and Id to transform
            -> (Subst, Id)              -- Transformed pair

clone_id :: Subst -> Subst -> (Id, Unique) -> (Subst, Id)
clone_id Subst
rec_subst subst :: Subst
subst@(Subst InScopeSet
in_scope IdSubstEnv
idvs TvSubstEnv
tvs CvSubstEnv
cvs) (Id
old_id, Unique
uniq)
  = (InScopeSet -> IdSubstEnv -> TvSubstEnv -> CvSubstEnv -> Subst
Subst (InScopeSet
in_scope InScopeSet -> Id -> InScopeSet
`InScopeSet.extendInScopeSet` Id
new_id) IdSubstEnv
new_idvs TvSubstEnv
tvs CvSubstEnv
new_cvs, Id
new_id)
  where
    id1 :: Id
id1     = Id -> Unique -> Id
setVarUnique Id
old_id Unique
uniq
    id2 :: Id
id2     = Subst -> Id -> Id
substIdType Subst
subst Id
id1
    new_id :: Id
new_id  = Maybe IdInfo -> Id -> Id
maybeModifyIdInfo (Subst -> Id -> IdInfo -> Maybe IdInfo
substIdInfo Subst
rec_subst Id
id2 ((() :: Constraint) => Id -> IdInfo
Id -> IdInfo
idInfo Id
old_id)) Id
id2
    (IdSubstEnv
new_idvs, CvSubstEnv
new_cvs) | Id -> Bool
isCoVar Id
old_id = (IdSubstEnv
idvs, CvSubstEnv -> Id -> Coercion -> CvSubstEnv
forall a. VarEnv a -> Id -> a -> VarEnv a
extendVarEnv CvSubstEnv
cvs Id
old_id (Id -> Coercion
mkCoVarCo Id
new_id))
                        | Bool
otherwise      = (IdSubstEnv -> Id -> CoreExpr -> IdSubstEnv
forall a. VarEnv a -> Id -> a -> VarEnv a
extendVarEnv IdSubstEnv
idvs Id
old_id (Id -> CoreExpr
forall b. Id -> Expr b
Var Id
new_id), CvSubstEnv
cvs)

{-
************************************************************************
*                                                                      *
                Types and Coercions
*                                                                      *
************************************************************************
-}

{-
************************************************************************
*                                                                      *
\section{IdInfo substitution}
*                                                                      *
************************************************************************
-}

substIdType :: Subst -> Id -> Id
substIdType :: Subst -> Id -> Id
substIdType subst :: Subst
subst@(Subst InScopeSet
_ IdSubstEnv
_ TvSubstEnv
tv_env CvSubstEnv
cv_env) Id
id
  | (TvSubstEnv -> Bool
forall a. VarEnv a -> Bool
isEmptyVarEnv TvSubstEnv
tv_env Bool -> Bool -> Bool
&& CvSubstEnv -> Bool
forall a. VarEnv a -> Bool
isEmptyVarEnv CvSubstEnv
cv_env)
    Bool -> Bool -> Bool
|| (Type -> Bool
noFreeVarsOfType Type
old_ty Bool -> Bool -> Bool
&& Type -> Bool
noFreeVarsOfType Type
old_w) = Id
id
  | Bool
otherwise   =
      (Type -> Type) -> Id -> Id
updateIdTypeAndMult (Subst -> Type -> Type
substTyUnchecked Subst
subst) Id
id
        -- The tyCoVarsOfType is cheaper than it looks
        -- because we cache the free tyvars of the type
        -- in a Note in the id's type itself
  where
    old_ty :: Type
old_ty = Id -> Type
idType Id
id
    old_w :: Type
old_w  = Id -> Type
varMult Id
id

------------------
-- | Substitute into some 'IdInfo' with regard to the supplied new 'Id'.
-- Discards unfoldings, unless they are Stable
substIdInfo :: Subst -> Id -> IdInfo -> Maybe IdInfo
substIdInfo :: Subst -> Id -> IdInfo -> Maybe IdInfo
substIdInfo Subst
subst Id
new_id IdInfo
info
  | Bool
nothing_to_do = Maybe IdInfo
forall a. Maybe a
Nothing
  | Bool
otherwise     = IdInfo -> Maybe IdInfo
forall a. a -> Maybe a
Just (IdInfo
info IdInfo -> RuleInfo -> IdInfo
`setRuleInfo`      Subst -> Id -> RuleInfo -> RuleInfo
substRuleInfo Subst
subst Id
new_id RuleInfo
old_rules
                               IdInfo -> Unfolding -> IdInfo
`setUnfoldingInfo` Subst -> Unfolding -> Unfolding
substUnfolding Subst
subst Unfolding
old_unf)
  where
    old_rules :: RuleInfo
old_rules     = IdInfo -> RuleInfo
ruleInfo IdInfo
info
    old_unf :: Unfolding
old_unf       = IdInfo -> Unfolding
realUnfoldingInfo IdInfo
info
    nothing_to_do :: Bool
nothing_to_do = RuleInfo -> Bool
isEmptyRuleInfo RuleInfo
old_rules Bool -> Bool -> Bool
&& Bool -> Bool
not (Unfolding -> Bool
hasCoreUnfolding Unfolding
old_unf)

------------------
-- | Substitutes for the 'Id's within an unfolding
-- NB: substUnfolding /discards/ any unfolding without
--     without a Stable source.  This is usually what we want,
--     but it may be a bit unexpected
substUnfolding, substUnfoldingSC :: Subst -> Unfolding -> Unfolding
        -- Seq'ing on the returned Unfolding is enough to cause
        -- all the substitutions to happen completely

substUnfoldingSC :: Subst -> Unfolding -> Unfolding
substUnfoldingSC Subst
subst Unfolding
unf       -- Short-cut version
  | Subst -> Bool
isEmptySubst Subst
subst = Unfolding
unf
  | Bool
otherwise          = Subst -> Unfolding -> Unfolding
substUnfolding Subst
subst Unfolding
unf

substUnfolding :: Subst -> Unfolding -> Unfolding
substUnfolding Subst
subst df :: Unfolding
df@(DFunUnfolding { df_bndrs :: Unfolding -> [Id]
df_bndrs = [Id]
bndrs, df_args :: Unfolding -> [CoreExpr]
df_args = [CoreExpr]
args })
  = Unfolding
df { df_bndrs = bndrs', df_args = args' }
  where
    (Subst
subst',[Id]
bndrs') = Subst -> [Id] -> (Subst, [Id])
forall (f :: * -> *).
Traversable f =>
Subst -> f Id -> (Subst, f Id)
substBndrs Subst
subst [Id]
bndrs
    args' :: [CoreExpr]
args'           = (CoreExpr -> CoreExpr) -> [CoreExpr] -> [CoreExpr]
forall a b. (a -> b) -> [a] -> [b]
map ((() :: Constraint) => Subst -> CoreExpr -> CoreExpr
Subst -> CoreExpr -> CoreExpr
substExpr Subst
subst') [CoreExpr]
args

substUnfolding Subst
subst unf :: Unfolding
unf@(CoreUnfolding { uf_tmpl :: Unfolding -> CoreExpr
uf_tmpl = CoreExpr
tmpl, uf_src :: Unfolding -> UnfoldingSource
uf_src = UnfoldingSource
src })
  -- Retain stable unfoldings
  | Bool -> Bool
not (UnfoldingSource -> Bool
isStableSource UnfoldingSource
src)  -- Zap an unstable unfolding, to save substitution work
  = Unfolding
NoUnfolding
  | Bool
otherwise                 -- But keep a stable one!
  = CoreExpr -> ()
seqExpr CoreExpr
new_tmpl () -> Unfolding -> Unfolding
forall a b. a -> b -> b
`seq`
    Unfolding
unf { uf_tmpl = new_tmpl }
  where
    new_tmpl :: CoreExpr
new_tmpl = (() :: Constraint) => Subst -> CoreExpr -> CoreExpr
Subst -> CoreExpr -> CoreExpr
substExpr Subst
subst CoreExpr
tmpl

substUnfolding Subst
_ Unfolding
unf = Unfolding
unf      -- NoUnfolding, OtherCon

------------------
substIdOcc :: Subst -> Id -> Id
-- These Ids should not be substituted to non-Ids
substIdOcc :: Subst -> Id -> Id
substIdOcc Subst
subst Id
v = case (() :: Constraint) => Subst -> Id -> CoreExpr
Subst -> Id -> CoreExpr
lookupIdSubst Subst
subst Id
v of
                        Var Id
v' -> Id
v'
                        CoreExpr
other  -> String -> SDoc -> Id
forall a. HasCallStack => String -> SDoc -> a
pprPanic String
"substIdOcc" ([SDoc] -> SDoc
forall doc. IsDoc doc => [doc] -> doc
vcat [Id -> SDoc
forall a. Outputable a => a -> SDoc
ppr Id
v SDoc -> SDoc -> SDoc
forall doc. IsLine doc => doc -> doc -> doc
<+> CoreExpr -> SDoc
forall a. Outputable a => a -> SDoc
ppr CoreExpr
other, Subst -> SDoc
forall a. Outputable a => a -> SDoc
ppr Subst
subst])

------------------
-- | Substitutes for the 'Id's within the 'RuleInfo' given the new function 'Id'
substRuleInfo :: Subst -> Id -> RuleInfo -> RuleInfo
substRuleInfo :: Subst -> Id -> RuleInfo -> RuleInfo
substRuleInfo Subst
subst Id
new_id (RuleInfo [CoreRule]
rules DVarSet
rhs_fvs)
  = [CoreRule] -> DVarSet -> RuleInfo
RuleInfo ((CoreRule -> CoreRule) -> [CoreRule] -> [CoreRule]
forall a b. (a -> b) -> [a] -> [b]
map (Subst -> (Name -> Name) -> CoreRule -> CoreRule
substRule Subst
subst Name -> Name
subst_ru_fn) [CoreRule]
rules)
                  ((() :: Constraint) => Subst -> DVarSet -> DVarSet
Subst -> DVarSet -> DVarSet
substDVarSet Subst
subst DVarSet
rhs_fvs)
  where
    subst_ru_fn :: Name -> Name
subst_ru_fn = Name -> Name -> Name
forall a b. a -> b -> a
const (Id -> Name
idName Id
new_id)

------------------
substRulesForImportedIds :: Subst -> [CoreRule] -> [CoreRule]
substRulesForImportedIds :: Subst -> [CoreRule] -> [CoreRule]
substRulesForImportedIds Subst
subst [CoreRule]
rules
  = (CoreRule -> CoreRule) -> [CoreRule] -> [CoreRule]
forall a b. (a -> b) -> [a] -> [b]
map (Subst -> (Name -> Name) -> CoreRule -> CoreRule
substRule Subst
subst Name -> Name
forall {a} {a}. Outputable a => a -> a
not_needed) [CoreRule]
rules
  where
    not_needed :: a -> a
not_needed a
name = String -> SDoc -> a
forall a. HasCallStack => String -> SDoc -> a
pprPanic String
"substRulesForImportedIds" (a -> SDoc
forall a. Outputable a => a -> SDoc
ppr a
name)

------------------
substRule :: Subst -> (Name -> Name) -> CoreRule -> CoreRule

-- The subst_ru_fn argument is applied to substitute the ru_fn field
-- of the rule:
--    - Rules for *imported* Ids never change ru_fn
--    - Rules for *local* Ids are in the IdInfo for that Id,
--      and the ru_fn field is simply replaced by the new name
--      of the Id
substRule :: Subst -> (Name -> Name) -> CoreRule -> CoreRule
substRule Subst
_ Name -> Name
_ rule :: CoreRule
rule@(BuiltinRule {}) = CoreRule
rule
substRule Subst
subst Name -> Name
subst_ru_fn rule :: CoreRule
rule@(Rule { ru_bndrs :: CoreRule -> [Id]
ru_bndrs = [Id]
bndrs, ru_args :: CoreRule -> [CoreExpr]
ru_args = [CoreExpr]
args
                                       , ru_fn :: CoreRule -> Name
ru_fn = Name
fn_name, ru_rhs :: CoreRule -> CoreExpr
ru_rhs = CoreExpr
rhs
                                       , ru_local :: CoreRule -> Bool
ru_local = Bool
is_local })
  = CoreRule
rule { ru_bndrs = bndrs'
         , ru_fn    = if is_local
                        then subst_ru_fn fn_name
                        else fn_name
         , ru_args  = map (substExpr subst') args
         , ru_rhs   = substExpr subst' rhs }
           -- Do NOT optimise the RHS (previously we did simplOptExpr here)
           -- See Note [Substitute lazily]
  where
    (Subst
subst', [Id]
bndrs') = Subst -> [Id] -> (Subst, [Id])
forall (f :: * -> *).
Traversable f =>
Subst -> f Id -> (Subst, f Id)
substBndrs Subst
subst [Id]
bndrs

------------------
substDVarSet :: HasDebugCallStack => Subst -> DVarSet -> DVarSet
substDVarSet :: (() :: Constraint) => Subst -> DVarSet -> DVarSet
substDVarSet subst :: Subst
subst@(Subst InScopeSet
_ IdSubstEnv
_ TvSubstEnv
tv_env CvSubstEnv
cv_env) DVarSet
fvs
  = [Id] -> DVarSet
mkDVarSet ([Id] -> DVarSet) -> [Id] -> DVarSet
forall a b. (a -> b) -> a -> b
$ ([Id], VarSet) -> [Id]
forall a b. (a, b) -> a
fst (([Id], VarSet) -> [Id]) -> ([Id], VarSet) -> [Id]
forall a b. (a -> b) -> a -> b
$ (Id -> ([Id], VarSet) -> ([Id], VarSet))
-> ([Id], VarSet) -> [Id] -> ([Id], VarSet)
forall a b. (a -> b -> b) -> b -> [a] -> b
forall (t :: * -> *) a b.
Foldable t =>
(a -> b -> b) -> b -> t a -> b
foldr Id -> ([Id], VarSet) -> ([Id], VarSet)
subst_fv ([], VarSet
emptyVarSet) ([Id] -> ([Id], VarSet)) -> [Id] -> ([Id], VarSet)
forall a b. (a -> b) -> a -> b
$ DVarSet -> [Id]
dVarSetElems DVarSet
fvs
  where
  subst_fv :: Var -> ([Var], VarSet) -> ([Var], VarSet)
  subst_fv :: Id -> ([Id], VarSet) -> ([Id], VarSet)
subst_fv Id
fv ([Id], VarSet)
acc
     | Id -> Bool
isTyVar Id
fv
     , let fv_ty :: Type
fv_ty = TvSubstEnv -> Id -> Maybe Type
forall a. VarEnv a -> Id -> Maybe a
lookupVarEnv TvSubstEnv
tv_env Id
fv Maybe Type -> Type -> Type
forall a. Maybe a -> a -> a
`orElse` Id -> Type
mkTyVarTy Id
fv
     = Type -> FV
tyCoFVsOfType Type
fv_ty (Bool -> Id -> Bool
forall a b. a -> b -> a
const Bool
True) VarSet
emptyVarSet (([Id], VarSet) -> ([Id], VarSet))
-> ([Id], VarSet) -> ([Id], VarSet)
forall a b. (a -> b) -> a -> b
$! ([Id], VarSet)
acc
     | Id -> Bool
isCoVar Id
fv
     , let fv_co :: Coercion
fv_co = CvSubstEnv -> Id -> Maybe Coercion
forall a. VarEnv a -> Id -> Maybe a
lookupVarEnv CvSubstEnv
cv_env Id
fv Maybe Coercion -> Coercion -> Coercion
forall a. Maybe a -> a -> a
`orElse` Id -> Coercion
mkCoVarCo Id
fv
     = Coercion -> FV
tyCoFVsOfCo Coercion
fv_co (Bool -> Id -> Bool
forall a b. a -> b -> a
const Bool
True) VarSet
emptyVarSet (([Id], VarSet) -> ([Id], VarSet))
-> ([Id], VarSet) -> ([Id], VarSet)
forall a b. (a -> b) -> a -> b
$! ([Id], VarSet)
acc
     | Bool
otherwise
     , let fv_expr :: CoreExpr
fv_expr = (() :: Constraint) => Subst -> Id -> CoreExpr
Subst -> Id -> CoreExpr
lookupIdSubst Subst
subst Id
fv
     = CoreExpr -> FV
exprFVs CoreExpr
fv_expr (Bool -> Id -> Bool
forall a b. a -> b -> a
const Bool
True) VarSet
emptyVarSet (([Id], VarSet) -> ([Id], VarSet))
-> ([Id], VarSet) -> ([Id], VarSet)
forall a b. (a -> b) -> a -> b
$! ([Id], VarSet)
acc

------------------
-- | Drop free vars from the breakpoint if they have a non-variable substitution.
substTickish :: Subst -> CoreTickish -> CoreTickish
substTickish :: Subst -> CoreTickish -> CoreTickish
substTickish Subst
subst (Breakpoint XBreakpoint 'TickishPassCore
ext Int
n [XTickishId 'TickishPassCore]
ids)
   = XBreakpoint 'TickishPassCore
-> Int -> [XTickishId 'TickishPassCore] -> CoreTickish
forall (pass :: TickishPass).
XBreakpoint pass -> Int -> [XTickishId pass] -> GenTickish pass
Breakpoint XBreakpoint 'TickishPassCore
ext Int
n ((Id -> Maybe Id) -> [Id] -> [Id]
forall a b. (a -> Maybe b) -> [a] -> [b]
mapMaybe Id -> Maybe Id
do_one [Id]
[XTickishId 'TickishPassCore]
ids)
 where
    do_one :: Id -> Maybe Id
do_one = CoreExpr -> Maybe Id
getIdFromTrivialExpr_maybe (CoreExpr -> Maybe Id) -> (Id -> CoreExpr) -> Id -> Maybe Id
forall b c a. (b -> c) -> (a -> b) -> a -> c
. (() :: Constraint) => Subst -> Id -> CoreExpr
Subst -> Id -> CoreExpr
lookupIdSubst Subst
subst

substTickish Subst
_subst CoreTickish
other = CoreTickish
other

{- Note [Substitute lazily]
~~~~~~~~~~~~~~~~~~~~~~~~~~~
The functions that substitute over IdInfo must be pretty lazy, because
they are knot-tied by substRecBndrs.

One case in point was #10627 in which a rule for a function 'f'
referred to 'f' (at a different type) on the RHS.  But instead of just
substituting in the rhs of the rule, we were calling simpleOptExpr, which
looked at the idInfo for 'f'; result <<loop>>.

In any case we don't need to optimise the RHS of rules, or unfoldings,
because the simplifier will do that.

Another place this went wrong was in `substRuleInfo`, which would immediately force
the lazy call to substExpr, which led to an infinite loop (as reported by #20112).

This time the call stack looked something like:

* `substRecBndrs`
* `substIdBndr`
* `substIdInfo`
* `substRuleInfo`
* `substRule`
* `substExpr`
* `mkTick`
* `isSaturatedConApp`
* Look at `IdInfo` for thing we are currently substituting because the rule is attached to `transpose` and mentions it in the `RHS` of the rule.

and the rule was

{-# RULES
"transpose/overlays1" forall xs. transpose (overlays1 xs) = overlays1 (fmap transpose xs) #-}

This rule was attached to `transpose`, but also mentions itself in the RHS so we have
to be careful to not force the `IdInfo` for transpose when dealing with the RHS of the rule.



Note [substTickish]
~~~~~~~~~~~~~~~~~~~~~~
A Breakpoint contains a list of Ids.  What happens if we ever want to
substitute an expression for one of these Ids?

First, we ensure that we only ever substitute trivial expressions for
these Ids, by marking them as NoOccInfo in the occurrence analyser.
Then, when substituting for the Id, we unwrap any type applications
and abstractions to get back to an Id, with getIdFromTrivialExpr.

Second, we have to ensure that we never try to substitute a literal
for an Id in a breakpoint.  We ensure this by never storing an Id with
an unlifted type in a Breakpoint - see GHC.HsToCore.Ticks.mkTickish.
Breakpoints can't handle free variables with unlifted types anyway.

These measures are only reliable with unoptimized code.
Since we can now enable optimizations for GHCi with
@-fno-unoptimized-core-for-interpreter -O@, nontrivial expressions can be
substituted, e.g. by specializations.
Therefore we resort to discarding free variables from breakpoints when this
situation occurs.
-}

{-
Note [Worker inlining]
~~~~~~~~~~~~~~~~~~~~~~
A worker can get substituted away entirely.
        - it might be trivial
        - it might simply be very small
We do not treat an InlWrapper as an 'occurrence' in the occurrence
analyser, so it's possible that the worker is not even in scope any more.

In all these cases we simply drop the special case, returning to
InlVanilla.  The WARN is just so I can see if it happens a lot.
-}