{-# LANGUAGE DataKinds           #-}
{-# LANGUAGE FlexibleContexts    #-}
{-# LANGUAGE GADTs               #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE TupleSections       #-}
{-# LANGUAGE TypeFamilies        #-}
{-# LANGUAGE UndecidableInstances #-} -- Wrinkle in Note [Trees That Grow]
{-# LANGUAGE ViewPatterns        #-}
{-# LANGUAGE DisambiguateRecordFields #-}

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

module GHC.Tc.Gen.Head
       ( HsExprArg(..), EValArg(..), TcPass(..)
       , AppCtxt(..), appCtxtLoc, insideExpansion
       , splitHsApps, rebuildHsApps
       , addArgWrap, isHsValArg
       , leadingValArgs, isVisibleArg, pprHsExprArgTc

       , tcInferAppHead, tcInferAppHead_maybe
       , tcInferId, tcCheckId, obviousSig
       , tyConOf, tyConOfET, fieldNotInType
       , nonBidirectionalErr

       , addHeadCtxt, addExprCtxt, addStmtCtxt, addFunResCtxt ) where

import {-# SOURCE #-} GHC.Tc.Gen.Expr( tcExpr, tcCheckPolyExprNC, tcPolyLExprSig )
import {-# SOURCE #-} GHC.Tc.Gen.Splice( getUntypedSpliceBody )

import GHC.Prelude
import GHC.Hs
import GHC.Hs.Syn.Type

import GHC.Tc.Gen.HsType
import GHC.Rename.Unbound     ( unknownNameSuggestions, WhatLooking(..) )

import GHC.Tc.Gen.Bind( chooseInferredQuantifiers )
import GHC.Tc.Gen.Sig( tcUserTypeSig, tcInstSig )
import GHC.Tc.TyCl.PatSyn( patSynBuilderOcc )
import GHC.Tc.Utils.Monad
import GHC.Tc.Utils.Unify
import GHC.Tc.Utils.Concrete ( hasFixedRuntimeRep_syntactic )
import GHC.Tc.Utils.Instantiate
import GHC.Tc.Instance.Family ( tcLookupDataFamInst )
import GHC.Core.FamInstEnv    ( FamInstEnvs )
import GHC.Core.UsageEnv      ( singleUsageUE )
import GHC.Tc.Errors.Types
import GHC.Tc.Solver          ( InferMode(..), simplifyInfer )
import GHC.Tc.Utils.Env
import GHC.Tc.Utils.TcMType
import GHC.Tc.Types.Origin
import GHC.Tc.Utils.TcType as TcType
import GHC.Tc.Types.Evidence
import GHC.Tc.Zonk.TcType


import GHC.Core.PatSyn( PatSyn )
import GHC.Core.ConLike( ConLike(..) )
import GHC.Core.DataCon
import GHC.Core.TyCon
import GHC.Core.TyCo.Rep
import GHC.Core.Type

import GHC.Types.Id
import GHC.Types.Id.Info
import GHC.Types.Name
import GHC.Types.Name.Reader
import GHC.Types.SrcLoc
import GHC.Types.Basic
import GHC.Types.Error

import GHC.Builtin.Types( multiplicityTy )
import GHC.Builtin.Names
import GHC.Builtin.Names.TH( liftStringName, liftName )

import GHC.Driver.Env
import GHC.Driver.DynFlags
import GHC.Utils.Misc
import GHC.Utils.Outputable as Outputable
import GHC.Utils.Panic
import qualified GHC.LanguageExtensions as LangExt

import GHC.Data.Maybe
import Control.Monad



{- *********************************************************************
*                                                                      *
              HsExprArg: auxiliary data type
*                                                                      *
********************************************************************* -}

{- Note [HsExprArg]
~~~~~~~~~~~~~~~~~~~
The data type HsExprArg :: TcPass -> Type
is a very local type, used only within this module and GHC.Tc.Gen.App

* It's really a zipper for an application chain
  See Note [Application chains and heads] in GHC.Tc.Gen.App for
  what an "application chain" is.

* It's a GHC-specific type, so using TTG only where necessary

* It is indexed by TcPass, meaning
  - HsExprArg TcpRn:
      The result of splitHsApps, which decomposes a HsExpr GhcRn

  - HsExprArg TcpInst:
      The result of tcInstFun, which instantiates the function type
      Adds EWrap nodes, the argument type in EValArg,
      and the kind-checked type in ETypeArg

  - HsExprArg TcpTc:
      The result of tcArg, which typechecks the value args
      In EValArg we now have a (LHsExpr GhcTc)

* rebuildPrefixApps is dual to splitHsApps, and zips an application
  back into a HsExpr

Note [EValArg]
~~~~~~~~~~~~~~
The data type EValArg is the payload of the EValArg constructor of
HsExprArg; i.e. a value argument of the application.  EValArg has two
forms:

* ValArg: payload is just the expression itself. Simple.

* ValArgQL: captures the results of applying quickLookArg to the
  argument in a ValArg.  When we later want to typecheck that argument
  we can just carry on from where quick-look left off.  The fields of
  ValArgQL exactly capture what is needed to complete the job.

Invariants:

1. With QL switched off, all arguments are ValArg; no ValArgQL

2. With QL switched on, tcInstFun converts some ValArgs to ValArgQL,
   under the conditions when quick-look should happen (eg the argument
   type is guarded) -- see quickLookArg

Note [splitHsApps]
~~~~~~~~~~~~~~~~~~
The key function
  splitHsApps :: HsExpr GhcRn -> (HsExpr GhcRn, HsExpr GhcRn, [HsExprArg 'TcpRn])
takes apart either an HsApp, or an infix OpApp, returning

* The "head" of the application, an expression that is often a variable;
  this is used for typechecking

* The "user head" or "error head" of the application, to be reported to the
  user in case of an error.  Example:
         (`op` e)
  expands (via ExpandedThingRn) to
         (rightSection op e)
  but we don't want to see 'rightSection' in error messages. So we keep the
  innermost un-expanded head as the "error head".

* A list of HsExprArg, the arguments
-}

data TcPass = TcpRn     -- Arguments decomposed
            | TcpInst   -- Function instantiated
            | TcpTc     -- Typechecked

data HsExprArg (p :: TcPass)
  = -- See Note [HsExprArg]
    EValArg  { forall (p :: TcPass). HsExprArg p -> AppCtxt
eva_ctxt   :: AppCtxt
             , forall (p :: TcPass). HsExprArg p -> EValArg p
eva_arg    :: EValArg p
             , forall (p :: TcPass). HsExprArg p -> XEVAType p
eva_arg_ty :: !(XEVAType p) }

  | ETypeArg { eva_ctxt  :: AppCtxt
             , forall (p :: TcPass). HsExprArg p -> LHsWcType (GhcPass 'Renamed)
eva_hs_ty :: LHsWcType GhcRn  -- The type arg
             , forall (p :: TcPass). HsExprArg p -> XETAType p
eva_ty    :: !(XETAType p) }  -- Kind-checked type arg

  | EPrag    AppCtxt
             (HsPragE (GhcPass (XPass p)))

  | EWrap    EWrap

data EWrap = EPar    AppCtxt
           | EExpand HsThingRn
           | EHsWrap HsWrapper

data EValArg (p :: TcPass) where  -- See Note [EValArg]
  ValArg   :: LHsExpr (GhcPass (XPass p))
           -> EValArg p

  ValArgQL :: { EValArg 'TcpInst -> LHsExpr (GhcPass 'Renamed)
va_expr :: LHsExpr GhcRn        -- Original application
                                                -- For location and error msgs
              , EValArg 'TcpInst -> (HsExpr GhcTc, AppCtxt)
va_fun  :: (HsExpr GhcTc, AppCtxt) -- Function of the application,
                                                   -- typechecked, plus its context
              , EValArg 'TcpInst -> [HsExprArg 'TcpInst]
va_args :: [HsExprArg 'TcpInst] -- Args, instantiated
              , EValArg 'TcpInst -> TcSigmaType
va_ty   :: TcRhoType }          -- Result type
           -> EValArg 'TcpInst  -- Only exists in TcpInst phase

data AppCtxt
  = VAExpansion
       HsThingRn
       SrcSpan
       SrcSpan

  | VACall
       (HsExpr GhcRn) Int  -- In the third argument of function f
       SrcSpan             -- The SrcSpan of the application (f e1 e2 e3)
                         --    noSrcSpan if outermost; see Note [AppCtxt]

{- Note [AppCtxt]
~~~~~~~~~~~~~~~~~
In a call (f e1 ... en), we pair up each argument with an AppCtxt. For
example, the AppCtxt for e3 allows us to say
    "In the third argument of `f`"
See splitHsApps.

To do this we must take a quick look into the expression to find the
function at the head (`f` in this case) and how many arguments it
has. That is what the funcion top_ctxt does.

If the function part is an expansion, we don't want to look further.
For example, with rebindable syntax the expression
    (if e1 then e2 else e3) e4 e5
might expand to
    (ifThenElse e1 e2 e3) e4 e5
For e4 we an AppCtxt that says "In the first argument of (if ...)",
not "In the fourth argument of ifThenElse".  So top_ctxt stops
at expansions.

The SrcSpan in an AppCtxt describes the whole call.  We initialise
it to noSrcSpan, because splitHsApps deals in HsExpr not LHsExpr, so
we don't have a span for the whole call; and we use that noSrcSpan in
GHC.Tc.Gen.App.tcInstFun (set_fun_ctxt) to avoid pushing "In the expression `f`"
a second time.
-}

appCtxtLoc :: AppCtxt -> SrcSpan
appCtxtLoc :: AppCtxt -> SrcSpan
appCtxtLoc (VAExpansion HsThingRn
_ SrcSpan
l SrcSpan
_) = SrcSpan
l
appCtxtLoc (VACall HsExpr (GhcPass 'Renamed)
_ ThLevel
_ SrcSpan
l)    = SrcSpan
l

insideExpansion :: AppCtxt -> Bool
insideExpansion :: AppCtxt -> Bool
insideExpansion (VAExpansion {}) = Bool
True
insideExpansion (VACall {})      = Bool
False -- but what if the VACall has a generated context?

instance Outputable AppCtxt where
  ppr :: AppCtxt -> SDoc
ppr (VAExpansion HsThingRn
e SrcSpan
l SrcSpan
_) = String -> SDoc
forall doc. IsLine doc => String -> doc
text String
"VAExpansion" SDoc -> SDoc -> SDoc
forall doc. IsLine doc => doc -> doc -> doc
<+> HsThingRn -> SDoc
forall a. Outputable a => a -> SDoc
ppr HsThingRn
e SDoc -> SDoc -> SDoc
forall doc. IsLine doc => doc -> doc -> doc
<+> SrcSpan -> SDoc
forall a. Outputable a => a -> SDoc
ppr SrcSpan
l
  ppr (VACall HsExpr (GhcPass 'Renamed)
f ThLevel
n SrcSpan
l)    = String -> SDoc
forall doc. IsLine doc => String -> doc
text String
"VACall" SDoc -> SDoc -> SDoc
forall doc. IsLine doc => doc -> doc -> doc
<+> ThLevel -> SDoc
forall doc. IsLine doc => ThLevel -> doc
int ThLevel
n SDoc -> SDoc -> SDoc
forall doc. IsLine doc => doc -> doc -> doc
<+> HsExpr (GhcPass 'Renamed) -> SDoc
forall a. Outputable a => a -> SDoc
ppr HsExpr (GhcPass 'Renamed)
f  SDoc -> SDoc -> SDoc
forall doc. IsLine doc => doc -> doc -> doc
<+> SrcSpan -> SDoc
forall a. Outputable a => a -> SDoc
ppr SrcSpan
l

type family XPass p where
  XPass 'TcpRn   = 'Renamed
  XPass 'TcpInst = 'Renamed
  XPass 'TcpTc   = 'Typechecked

type family XETAType p where  -- Type arguments
  XETAType 'TcpRn = NoExtField
  XETAType _      = Type

type family XEVAType p where  -- Value arguments
  XEVAType 'TcpRn = NoExtField
  XEVAType _      = Scaled Type

mkEValArg :: AppCtxt -> LHsExpr GhcRn -> HsExprArg 'TcpRn
mkEValArg :: AppCtxt -> LHsExpr (GhcPass 'Renamed) -> HsExprArg 'TcpRn
mkEValArg AppCtxt
ctxt LHsExpr (GhcPass 'Renamed)
e = EValArg { eva_arg :: EValArg 'TcpRn
eva_arg = LHsExpr (GhcPass (XPass 'TcpRn)) -> EValArg 'TcpRn
forall (p :: TcPass). LHsExpr (GhcPass (XPass p)) -> EValArg p
ValArg LHsExpr (GhcPass 'Renamed)
LHsExpr (GhcPass (XPass 'TcpRn))
e, eva_ctxt :: AppCtxt
eva_ctxt = AppCtxt
ctxt
                           , eva_arg_ty :: XEVAType 'TcpRn
eva_arg_ty = NoExtField
XEVAType 'TcpRn
noExtField }

mkETypeArg :: AppCtxt -> LHsWcType GhcRn -> HsExprArg 'TcpRn
mkETypeArg :: AppCtxt -> LHsWcType (GhcPass 'Renamed) -> HsExprArg 'TcpRn
mkETypeArg AppCtxt
ctxt LHsWcType (GhcPass 'Renamed)
hs_ty =
  ETypeArg { eva_ctxt :: AppCtxt
eva_ctxt = AppCtxt
ctxt
           , eva_hs_ty :: LHsWcType (GhcPass 'Renamed)
eva_hs_ty = LHsWcType (GhcPass 'Renamed)
hs_ty
           , eva_ty :: XETAType 'TcpRn
eva_ty = NoExtField
XETAType 'TcpRn
noExtField }

addArgWrap :: HsWrapper -> [HsExprArg p] -> [HsExprArg p]
addArgWrap :: forall (p :: TcPass). HsWrapper -> [HsExprArg p] -> [HsExprArg p]
addArgWrap HsWrapper
wrap [HsExprArg p]
args
 | HsWrapper -> Bool
isIdHsWrapper HsWrapper
wrap = [HsExprArg p]
args
 | Bool
otherwise          = EWrap -> HsExprArg p
forall (p :: TcPass). EWrap -> HsExprArg p
EWrap (HsWrapper -> EWrap
EHsWrap HsWrapper
wrap) HsExprArg p -> [HsExprArg p] -> [HsExprArg p]
forall a. a -> [a] -> [a]
: [HsExprArg p]
args

splitHsApps :: HsExpr GhcRn
            -> TcM ( (HsExpr GhcRn, AppCtxt)  -- Head
                   , [HsExprArg 'TcpRn])      -- Args
-- See Note [splitHsApps].
--
-- This uses the TcM monad solely because we must run modFinalizers when looking
-- through HsUntypedSplices
-- (see Note [Looking through Template Haskell splices in splitHsApps]).
splitHsApps :: HsExpr (GhcPass 'Renamed)
-> TcM ((HsExpr (GhcPass 'Renamed), AppCtxt), [HsExprArg 'TcpRn])
splitHsApps HsExpr (GhcPass 'Renamed)
e = HsExpr (GhcPass 'Renamed)
-> AppCtxt
-> [HsExprArg 'TcpRn]
-> TcM ((HsExpr (GhcPass 'Renamed), AppCtxt), [HsExprArg 'TcpRn])
go HsExpr (GhcPass 'Renamed)
e (ThLevel -> HsExpr (GhcPass 'Renamed) -> AppCtxt
top_ctxt ThLevel
0 HsExpr (GhcPass 'Renamed)
e) []
  where
    top_ctxt :: Int -> HsExpr GhcRn -> AppCtxt
    -- Always returns VACall fun n_val_args noSrcSpan
    -- to initialise the argument splitting in 'go'
    -- See Note [AppCtxt]
    top_ctxt :: ThLevel -> HsExpr (GhcPass 'Renamed) -> AppCtxt
top_ctxt ThLevel
n (HsPar XPar (GhcPass 'Renamed)
_ LHsExpr (GhcPass 'Renamed)
fun)               = ThLevel
-> GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Renamed)) -> AppCtxt
forall {l}.
ThLevel -> GenLocated l (HsExpr (GhcPass 'Renamed)) -> AppCtxt
top_lctxt ThLevel
n LHsExpr (GhcPass 'Renamed)
GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Renamed))
fun
    top_ctxt ThLevel
n (HsPragE XPragE (GhcPass 'Renamed)
_ HsPragE (GhcPass 'Renamed)
_ LHsExpr (GhcPass 'Renamed)
fun)           = ThLevel
-> GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Renamed)) -> AppCtxt
forall {l}.
ThLevel -> GenLocated l (HsExpr (GhcPass 'Renamed)) -> AppCtxt
top_lctxt ThLevel
n LHsExpr (GhcPass 'Renamed)
GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Renamed))
fun
    top_ctxt ThLevel
n (HsAppType XAppTypeE (GhcPass 'Renamed)
_ LHsExpr (GhcPass 'Renamed)
fun LHsWcType (NoGhcTc (GhcPass 'Renamed))
_)         = ThLevel
-> GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Renamed)) -> AppCtxt
forall {l}.
ThLevel -> GenLocated l (HsExpr (GhcPass 'Renamed)) -> AppCtxt
top_lctxt (ThLevel
nThLevel -> ThLevel -> ThLevel
forall a. Num a => a -> a -> a
+ThLevel
1) LHsExpr (GhcPass 'Renamed)
GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Renamed))
fun
    top_ctxt ThLevel
n (HsApp XApp (GhcPass 'Renamed)
_ LHsExpr (GhcPass 'Renamed)
fun LHsExpr (GhcPass 'Renamed)
_)             = ThLevel
-> GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Renamed)) -> AppCtxt
forall {l}.
ThLevel -> GenLocated l (HsExpr (GhcPass 'Renamed)) -> AppCtxt
top_lctxt (ThLevel
nThLevel -> ThLevel -> ThLevel
forall a. Num a => a -> a -> a
+ThLevel
1) LHsExpr (GhcPass 'Renamed)
GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Renamed))
fun
    top_ctxt ThLevel
n (XExpr (ExpandedThingRn HsThingRn
o HsExpr (GhcPass 'Renamed)
_))
      | OrigExpr HsExpr (GhcPass 'Renamed)
fun <- HsThingRn
o                  = HsExpr (GhcPass 'Renamed) -> ThLevel -> SrcSpan -> AppCtxt
VACall HsExpr (GhcPass 'Renamed)
fun  ThLevel
n SrcSpan
noSrcSpan
    top_ctxt ThLevel
n HsExpr (GhcPass 'Renamed)
other_fun                   = HsExpr (GhcPass 'Renamed) -> ThLevel -> SrcSpan -> AppCtxt
VACall HsExpr (GhcPass 'Renamed)
other_fun ThLevel
n SrcSpan
noSrcSpan

    top_lctxt :: ThLevel -> GenLocated l (HsExpr (GhcPass 'Renamed)) -> AppCtxt
top_lctxt ThLevel
n (L l
_ HsExpr (GhcPass 'Renamed)
fun) = ThLevel -> HsExpr (GhcPass 'Renamed) -> AppCtxt
top_ctxt ThLevel
n HsExpr (GhcPass 'Renamed)
fun

    go :: HsExpr GhcRn -> AppCtxt -> [HsExprArg 'TcpRn]
       -> TcM ((HsExpr GhcRn, AppCtxt), [HsExprArg 'TcpRn])
    -- Modify the AppCtxt as we walk inwards, so it describes the next argument
    go :: HsExpr (GhcPass 'Renamed)
-> AppCtxt
-> [HsExprArg 'TcpRn]
-> TcM ((HsExpr (GhcPass 'Renamed), AppCtxt), [HsExprArg 'TcpRn])
go (HsPar XPar (GhcPass 'Renamed)
_ (L SrcSpanAnnA
l HsExpr (GhcPass 'Renamed)
fun))           AppCtxt
ctxt [HsExprArg 'TcpRn]
args = HsExpr (GhcPass 'Renamed)
-> AppCtxt
-> [HsExprArg 'TcpRn]
-> TcM ((HsExpr (GhcPass 'Renamed), AppCtxt), [HsExprArg 'TcpRn])
go HsExpr (GhcPass 'Renamed)
fun (SrcSpanAnnA -> AppCtxt -> AppCtxt
forall ann. EpAnn ann -> AppCtxt -> AppCtxt
set SrcSpanAnnA
l AppCtxt
ctxt) (EWrap -> HsExprArg 'TcpRn
forall (p :: TcPass). EWrap -> HsExprArg p
EWrap (AppCtxt -> EWrap
EPar AppCtxt
ctxt)     HsExprArg 'TcpRn -> [HsExprArg 'TcpRn] -> [HsExprArg 'TcpRn]
forall a. a -> [a] -> [a]
: [HsExprArg 'TcpRn]
args)
    go (HsPragE XPragE (GhcPass 'Renamed)
_ HsPragE (GhcPass 'Renamed)
p (L SrcSpanAnnA
l HsExpr (GhcPass 'Renamed)
fun))       AppCtxt
ctxt [HsExprArg 'TcpRn]
args = HsExpr (GhcPass 'Renamed)
-> AppCtxt
-> [HsExprArg 'TcpRn]
-> TcM ((HsExpr (GhcPass 'Renamed), AppCtxt), [HsExprArg 'TcpRn])
go HsExpr (GhcPass 'Renamed)
fun (SrcSpanAnnA -> AppCtxt -> AppCtxt
forall ann. EpAnn ann -> AppCtxt -> AppCtxt
set SrcSpanAnnA
l AppCtxt
ctxt) (AppCtxt -> HsPragE (GhcPass (XPass 'TcpRn)) -> HsExprArg 'TcpRn
forall (p :: TcPass).
AppCtxt -> HsPragE (GhcPass (XPass p)) -> HsExprArg p
EPrag      AppCtxt
ctxt HsPragE (GhcPass 'Renamed)
HsPragE (GhcPass (XPass 'TcpRn))
p     HsExprArg 'TcpRn -> [HsExprArg 'TcpRn] -> [HsExprArg 'TcpRn]
forall a. a -> [a] -> [a]
: [HsExprArg 'TcpRn]
args)
    go (HsAppType XAppTypeE (GhcPass 'Renamed)
_ (L SrcSpanAnnA
l HsExpr (GhcPass 'Renamed)
fun) LHsWcType (NoGhcTc (GhcPass 'Renamed))
ty)    AppCtxt
ctxt [HsExprArg 'TcpRn]
args = HsExpr (GhcPass 'Renamed)
-> AppCtxt
-> [HsExprArg 'TcpRn]
-> TcM ((HsExpr (GhcPass 'Renamed), AppCtxt), [HsExprArg 'TcpRn])
go HsExpr (GhcPass 'Renamed)
fun (SrcSpanAnnA -> AppCtxt -> AppCtxt
forall ann. EpAnn ann -> AppCtxt -> AppCtxt
dec SrcSpanAnnA
l AppCtxt
ctxt) (AppCtxt -> LHsWcType (GhcPass 'Renamed) -> HsExprArg 'TcpRn
mkETypeArg AppCtxt
ctxt LHsWcType (NoGhcTc (GhcPass 'Renamed))
LHsWcType (GhcPass 'Renamed)
ty    HsExprArg 'TcpRn -> [HsExprArg 'TcpRn] -> [HsExprArg 'TcpRn]
forall a. a -> [a] -> [a]
: [HsExprArg 'TcpRn]
args)
    go (HsApp XApp (GhcPass 'Renamed)
_ (L SrcSpanAnnA
l HsExpr (GhcPass 'Renamed)
fun) LHsExpr (GhcPass 'Renamed)
arg)       AppCtxt
ctxt [HsExprArg 'TcpRn]
args = HsExpr (GhcPass 'Renamed)
-> AppCtxt
-> [HsExprArg 'TcpRn]
-> TcM ((HsExpr (GhcPass 'Renamed), AppCtxt), [HsExprArg 'TcpRn])
go HsExpr (GhcPass 'Renamed)
fun (SrcSpanAnnA -> AppCtxt -> AppCtxt
forall ann. EpAnn ann -> AppCtxt -> AppCtxt
dec SrcSpanAnnA
l AppCtxt
ctxt) (AppCtxt -> LHsExpr (GhcPass 'Renamed) -> HsExprArg 'TcpRn
mkEValArg  AppCtxt
ctxt LHsExpr (GhcPass 'Renamed)
arg   HsExprArg 'TcpRn -> [HsExprArg 'TcpRn] -> [HsExprArg 'TcpRn]
forall a. a -> [a] -> [a]
: [HsExprArg 'TcpRn]
args)

    -- See Note [Looking through Template Haskell splices in splitHsApps]
    go e :: HsExpr (GhcPass 'Renamed)
e@(HsUntypedSplice XUntypedSplice (GhcPass 'Renamed)
splice_res HsUntypedSplice (GhcPass 'Renamed)
splice) AppCtxt
ctxt [HsExprArg 'TcpRn]
args
      = do { fun <- HsUntypedSpliceResult (HsExpr (GhcPass 'Renamed))
-> TcM (HsExpr (GhcPass 'Renamed))
getUntypedSpliceBody XUntypedSplice (GhcPass 'Renamed)
HsUntypedSpliceResult (HsExpr (GhcPass 'Renamed))
splice_res
           ; go fun ctxt' (EWrap (EExpand (OrigExpr e)) : args) }
      where
        ctxt' :: AppCtxt
        ctxt' :: AppCtxt
ctxt' = case HsUntypedSplice (GhcPass 'Renamed)
splice of
            HsUntypedSpliceExpr XUntypedSpliceExpr (GhcPass 'Renamed)
_ (L SrcSpanAnnA
l HsExpr (GhcPass 'Renamed)
_) -> SrcSpanAnnA -> AppCtxt -> AppCtxt
forall ann. EpAnn ann -> AppCtxt -> AppCtxt
set SrcSpanAnnA
l AppCtxt
ctxt -- l :: SrcAnn AnnListItem
            HsQuasiQuote XQuasiQuote (GhcPass 'Renamed)
_ IdP (GhcPass 'Renamed)
_ (L EpAnn NoEpAnns
l FastString
_)      -> EpAnn NoEpAnns -> AppCtxt -> AppCtxt
forall ann. EpAnn ann -> AppCtxt -> AppCtxt
set EpAnn NoEpAnns
l AppCtxt
ctxt -- l :: SrcAnn NoEpAnns

    -- See Note [Looking through ExpandedThingRn]
    go (XExpr (ExpandedThingRn HsThingRn
o HsExpr (GhcPass 'Renamed)
e)) AppCtxt
ctxt [HsExprArg 'TcpRn]
args
      | HsThingRn -> Bool
isHsThingRnExpr HsThingRn
o
      = HsExpr (GhcPass 'Renamed)
-> AppCtxt
-> [HsExprArg 'TcpRn]
-> TcM ((HsExpr (GhcPass 'Renamed), AppCtxt), [HsExprArg 'TcpRn])
go HsExpr (GhcPass 'Renamed)
e (HsThingRn -> SrcSpan -> SrcSpan -> AppCtxt
VAExpansion HsThingRn
o (AppCtxt -> SrcSpan
appCtxtLoc AppCtxt
ctxt) (AppCtxt -> SrcSpan
appCtxtLoc AppCtxt
ctxt))
               (EWrap -> HsExprArg 'TcpRn
forall (p :: TcPass). EWrap -> HsExprArg p
EWrap (HsThingRn -> EWrap
EExpand HsThingRn
o) HsExprArg 'TcpRn -> [HsExprArg 'TcpRn] -> [HsExprArg 'TcpRn]
forall a. a -> [a] -> [a]
: [HsExprArg 'TcpRn]
args)

      | OrigStmt (L SrcSpanAnnA
_ StmtLR
  (GhcPass 'Renamed)
  (GhcPass 'Renamed)
  (GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Renamed)))
stmt) <- HsThingRn
o                -- so that we set `(>>)` as generated
      , BodyStmt{} <- StmtLR
  (GhcPass 'Renamed)
  (GhcPass 'Renamed)
  (GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Renamed)))
stmt                      -- and get the right unused bind warnings
      = HsExpr (GhcPass 'Renamed)
-> AppCtxt
-> [HsExprArg 'TcpRn]
-> TcM ((HsExpr (GhcPass 'Renamed), AppCtxt), [HsExprArg 'TcpRn])
go HsExpr (GhcPass 'Renamed)
e (HsThingRn -> SrcSpan -> SrcSpan -> AppCtxt
VAExpansion HsThingRn
o SrcSpan
generatedSrcSpan SrcSpan
generatedSrcSpan)
                                                -- See Part 3. in Note [Expanding HsDo with XXExprGhcRn]
               (EWrap -> HsExprArg 'TcpRn
forall (p :: TcPass). EWrap -> HsExprArg p
EWrap (HsThingRn -> EWrap
EExpand HsThingRn
o) HsExprArg 'TcpRn -> [HsExprArg 'TcpRn] -> [HsExprArg 'TcpRn]
forall a. a -> [a] -> [a]
: [HsExprArg 'TcpRn]
args)       -- in `GHC.Tc.Gen.Do`


      | OrigPat (L SrcSpanAnnA
loc Pat (GhcPass 'Renamed)
_) <- HsThingRn
o                              -- so that we set the compiler generated fail context
      = HsExpr (GhcPass 'Renamed)
-> AppCtxt
-> [HsExprArg 'TcpRn]
-> TcM ((HsExpr (GhcPass 'Renamed), AppCtxt), [HsExprArg 'TcpRn])
go HsExpr (GhcPass 'Renamed)
e (HsThingRn -> SrcSpan -> SrcSpan -> AppCtxt
VAExpansion HsThingRn
o (SrcSpanAnnA -> SrcSpan
forall a. HasLoc a => a -> SrcSpan
locA SrcSpanAnnA
loc) (SrcSpanAnnA -> SrcSpan
forall a. HasLoc a => a -> SrcSpan
locA SrcSpanAnnA
loc))          -- to be originating from a failable pattern
                                                            -- See Part 1. Wrinkle 2. of
               (EWrap -> HsExprArg 'TcpRn
forall (p :: TcPass). EWrap -> HsExprArg p
EWrap (HsThingRn -> EWrap
EExpand HsThingRn
o) HsExprArg 'TcpRn -> [HsExprArg 'TcpRn] -> [HsExprArg 'TcpRn]
forall a. a -> [a] -> [a]
: [HsExprArg 'TcpRn]
args)                   -- Note [Expanding HsDo with XXExprGhcRn]
                                                            -- in `GHC.Tc.Gen.Do`

      | Bool
otherwise
      = HsExpr (GhcPass 'Renamed)
-> AppCtxt
-> [HsExprArg 'TcpRn]
-> TcM ((HsExpr (GhcPass 'Renamed), AppCtxt), [HsExprArg 'TcpRn])
go HsExpr (GhcPass 'Renamed)
e (HsThingRn -> SrcSpan -> SrcSpan -> AppCtxt
VAExpansion HsThingRn
o (AppCtxt -> SrcSpan
appCtxtLoc AppCtxt
ctxt) (AppCtxt -> SrcSpan
appCtxtLoc AppCtxt
ctxt))
               (EWrap -> HsExprArg 'TcpRn
forall (p :: TcPass). EWrap -> HsExprArg p
EWrap (HsThingRn -> EWrap
EExpand HsThingRn
o) HsExprArg 'TcpRn -> [HsExprArg 'TcpRn] -> [HsExprArg 'TcpRn]
forall a. a -> [a] -> [a]
: [HsExprArg 'TcpRn]
args)

    -- See Note [Desugar OpApp in the typechecker]
    go e :: HsExpr (GhcPass 'Renamed)
e@(OpApp XOpApp (GhcPass 'Renamed)
_ LHsExpr (GhcPass 'Renamed)
arg1 (L SrcSpanAnnA
l HsExpr (GhcPass 'Renamed)
op) LHsExpr (GhcPass 'Renamed)
arg2) AppCtxt
_ [HsExprArg 'TcpRn]
args
      = ((HsExpr (GhcPass 'Renamed), AppCtxt), [HsExprArg 'TcpRn])
-> TcM ((HsExpr (GhcPass 'Renamed), AppCtxt), [HsExprArg 'TcpRn])
forall a. a -> IOEnv (Env TcGblEnv TcLclEnv) a
forall (f :: * -> *) a. Applicative f => a -> f a
pure ( (HsExpr (GhcPass 'Renamed)
op, HsExpr (GhcPass 'Renamed) -> ThLevel -> SrcSpan -> AppCtxt
VACall HsExpr (GhcPass 'Renamed)
op ThLevel
0 (SrcSpanAnnA -> SrcSpan
forall a. HasLoc a => a -> SrcSpan
locA SrcSpanAnnA
l))
             ,   AppCtxt -> LHsExpr (GhcPass 'Renamed) -> HsExprArg 'TcpRn
mkEValArg (HsExpr (GhcPass 'Renamed) -> ThLevel -> SrcSpan -> AppCtxt
VACall HsExpr (GhcPass 'Renamed)
op ThLevel
1 SrcSpan
generatedSrcSpan) LHsExpr (GhcPass 'Renamed)
arg1
               HsExprArg 'TcpRn -> [HsExprArg 'TcpRn] -> [HsExprArg 'TcpRn]
forall a. a -> [a] -> [a]
: AppCtxt -> LHsExpr (GhcPass 'Renamed) -> HsExprArg 'TcpRn
mkEValArg (HsExpr (GhcPass 'Renamed) -> ThLevel -> SrcSpan -> AppCtxt
VACall HsExpr (GhcPass 'Renamed)
op ThLevel
2 SrcSpan
generatedSrcSpan) LHsExpr (GhcPass 'Renamed)
arg2
               HsExprArg 'TcpRn -> [HsExprArg 'TcpRn] -> [HsExprArg 'TcpRn]
forall a. a -> [a] -> [a]
: EWrap -> HsExprArg 'TcpRn
forall (p :: TcPass). EWrap -> HsExprArg p
EWrap (HsThingRn -> EWrap
EExpand (HsExpr (GhcPass 'Renamed) -> HsThingRn
OrigExpr HsExpr (GhcPass 'Renamed)
e))
               HsExprArg 'TcpRn -> [HsExprArg 'TcpRn] -> [HsExprArg 'TcpRn]
forall a. a -> [a] -> [a]
: [HsExprArg 'TcpRn]
args )

    go HsExpr (GhcPass 'Renamed)
e AppCtxt
ctxt [HsExprArg 'TcpRn]
args = ((HsExpr (GhcPass 'Renamed), AppCtxt), [HsExprArg 'TcpRn])
-> TcM ((HsExpr (GhcPass 'Renamed), AppCtxt), [HsExprArg 'TcpRn])
forall a. a -> IOEnv (Env TcGblEnv TcLclEnv) a
forall (f :: * -> *) a. Applicative f => a -> f a
pure ((HsExpr (GhcPass 'Renamed)
e,AppCtxt
ctxt), [HsExprArg 'TcpRn]
args)

    set :: EpAnn ann -> AppCtxt -> AppCtxt
    set :: forall ann. EpAnn ann -> AppCtxt -> AppCtxt
set EpAnn ann
l (VACall HsExpr (GhcPass 'Renamed)
f ThLevel
n SrcSpan
_)          = HsExpr (GhcPass 'Renamed) -> ThLevel -> SrcSpan -> AppCtxt
VACall HsExpr (GhcPass 'Renamed)
f ThLevel
n (EpAnn ann -> SrcSpan
forall a. HasLoc a => a -> SrcSpan
locA EpAnn ann
l)
    set EpAnn ann
l (VAExpansion HsThingRn
orig SrcSpan
ol SrcSpan
_) = HsThingRn -> SrcSpan -> SrcSpan -> AppCtxt
VAExpansion HsThingRn
orig SrcSpan
ol (EpAnn ann -> SrcSpan
forall a. HasLoc a => a -> SrcSpan
locA EpAnn ann
l)

    dec :: EpAnn ann -> AppCtxt -> AppCtxt
    dec :: forall ann. EpAnn ann -> AppCtxt -> AppCtxt
dec EpAnn ann
l (VACall HsExpr (GhcPass 'Renamed)
f ThLevel
n SrcSpan
_)          = HsExpr (GhcPass 'Renamed) -> ThLevel -> SrcSpan -> AppCtxt
VACall HsExpr (GhcPass 'Renamed)
f (ThLevel
nThLevel -> ThLevel -> ThLevel
forall a. Num a => a -> a -> a
-ThLevel
1) (EpAnn ann -> SrcSpan
forall a. HasLoc a => a -> SrcSpan
locA EpAnn ann
l)
    dec EpAnn ann
l (VAExpansion HsThingRn
orig SrcSpan
ol SrcSpan
_) = HsThingRn -> SrcSpan -> SrcSpan -> AppCtxt
VAExpansion HsThingRn
orig SrcSpan
ol (EpAnn ann -> SrcSpan
forall a. HasLoc a => a -> SrcSpan
locA EpAnn ann
l)

-- | Rebuild an application: takes a type-checked application head
-- expression together with arguments in the form of typechecked 'HsExprArg's
-- and returns a typechecked application of the head to the arguments.
--
-- This performs a representation-polymorphism check to ensure that
-- representation-polymorphic unlifted newtypes have been eta-expanded.
--
-- See Note [Eta-expanding rep-poly unlifted newtypes].
rebuildHsApps :: HsExpr GhcTc
                      -- ^ the function being applied
              -> AppCtxt
              -> [HsExprArg 'TcpTc]
                      -- ^ the arguments to the function
              -> TcRhoType
                      -- ^ result type of the application
              -> TcM (HsExpr GhcTc)
rebuildHsApps :: HsExpr GhcTc
-> AppCtxt
-> [HsExprArg 'TcpTc]
-> TcSigmaType
-> TcM (HsExpr GhcTc)
rebuildHsApps HsExpr GhcTc
fun AppCtxt
ctxt [HsExprArg 'TcpTc]
args TcSigmaType
app_res_rho
  = do { [HsExprArg 'TcpTc] -> TcSigmaType -> HsExpr GhcTc -> TcM ()
rejectRepPolyNewtypes [HsExprArg 'TcpTc]
args TcSigmaType
app_res_rho HsExpr GhcTc
fun
       ; HsExpr GhcTc -> TcM (HsExpr GhcTc)
forall a. a -> IOEnv (Env TcGblEnv TcLclEnv) a
forall (m :: * -> *) a. Monad m => a -> m a
return (HsExpr GhcTc -> TcM (HsExpr GhcTc))
-> HsExpr GhcTc -> TcM (HsExpr GhcTc)
forall a b. (a -> b) -> a -> b
$ HsExpr GhcTc -> AppCtxt -> [HsExprArg 'TcpTc] -> HsExpr GhcTc
rebuild_hs_apps HsExpr GhcTc
fun AppCtxt
ctxt [HsExprArg 'TcpTc]
args }

-- | The worker function for 'rebuildHsApps': simply rebuilds
-- an application chain in which arguments are specified as
-- typechecked 'HsExprArg's.
rebuild_hs_apps :: HsExpr GhcTc
                      -- ^ the function being applied
              -> AppCtxt
              -> [HsExprArg 'TcpTc]
                      -- ^ the arguments to the function
              -> HsExpr GhcTc
rebuild_hs_apps :: HsExpr GhcTc -> AppCtxt -> [HsExprArg 'TcpTc] -> HsExpr GhcTc
rebuild_hs_apps HsExpr GhcTc
fun AppCtxt
_ [] = HsExpr GhcTc
fun
rebuild_hs_apps HsExpr GhcTc
fun AppCtxt
ctxt (HsExprArg 'TcpTc
arg : [HsExprArg 'TcpTc]
args)
  = case HsExprArg 'TcpTc
arg of
      EValArg { eva_arg :: forall (p :: TcPass). HsExprArg p -> EValArg p
eva_arg = ValArg LHsExpr (GhcPass (XPass 'TcpTc))
arg, eva_ctxt :: forall (p :: TcPass). HsExprArg p -> AppCtxt
eva_ctxt = AppCtxt
ctxt' }
        -> HsExpr GhcTc -> AppCtxt -> [HsExprArg 'TcpTc] -> HsExpr GhcTc
rebuild_hs_apps (XApp GhcTc -> LHsExpr GhcTc -> LHsExpr GhcTc -> HsExpr GhcTc
forall p. XApp p -> LHsExpr p -> LHsExpr p -> HsExpr p
HsApp XApp GhcTc
NoExtField
noExtField LHsExpr GhcTc
GenLocated SrcSpanAnnA (HsExpr GhcTc)
lfun LHsExpr GhcTc
LHsExpr (GhcPass (XPass 'TcpTc))
arg) AppCtxt
ctxt' [HsExprArg 'TcpTc]
args
      ETypeArg { eva_hs_ty :: forall (p :: TcPass). HsExprArg p -> LHsWcType (GhcPass 'Renamed)
eva_hs_ty = LHsWcType (GhcPass 'Renamed)
hs_ty, eva_ty :: forall (p :: TcPass). HsExprArg p -> XETAType p
eva_ty = XETAType 'TcpTc
ty, eva_ctxt :: forall (p :: TcPass). HsExprArg p -> AppCtxt
eva_ctxt = AppCtxt
ctxt' }
        -> HsExpr GhcTc -> AppCtxt -> [HsExprArg 'TcpTc] -> HsExpr GhcTc
rebuild_hs_apps (XAppTypeE GhcTc
-> LHsExpr GhcTc -> LHsWcType (NoGhcTc GhcTc) -> HsExpr GhcTc
forall p.
XAppTypeE p -> LHsExpr p -> LHsWcType (NoGhcTc p) -> HsExpr p
HsAppType XAppTypeE GhcTc
XETAType 'TcpTc
ty LHsExpr GhcTc
GenLocated SrcSpanAnnA (HsExpr GhcTc)
lfun LHsWcType (NoGhcTc GhcTc)
LHsWcType (GhcPass 'Renamed)
hs_ty) AppCtxt
ctxt' [HsExprArg 'TcpTc]
args
      EPrag AppCtxt
ctxt' HsPragE (GhcPass (XPass 'TcpTc))
p
        -> HsExpr GhcTc -> AppCtxt -> [HsExprArg 'TcpTc] -> HsExpr GhcTc
rebuild_hs_apps (XPragE GhcTc -> HsPragE GhcTc -> LHsExpr GhcTc -> HsExpr GhcTc
forall p. XPragE p -> HsPragE p -> LHsExpr p -> HsExpr p
HsPragE XPragE GhcTc
NoExtField
noExtField HsPragE GhcTc
HsPragE (GhcPass (XPass 'TcpTc))
p LHsExpr GhcTc
GenLocated SrcSpanAnnA (HsExpr GhcTc)
lfun) AppCtxt
ctxt' [HsExprArg 'TcpTc]
args
      EWrap (EPar AppCtxt
ctxt')
        -> HsExpr GhcTc -> AppCtxt -> [HsExprArg 'TcpTc] -> HsExpr GhcTc
rebuild_hs_apps (LHsExpr GhcTc -> HsExpr GhcTc
forall (p :: Pass).
IsPass p =>
LHsExpr (GhcPass p) -> HsExpr (GhcPass p)
gHsPar LHsExpr GhcTc
GenLocated SrcSpanAnnA (HsExpr GhcTc)
lfun) AppCtxt
ctxt' [HsExprArg 'TcpTc]
args
      EWrap (EExpand HsThingRn
orig)
        | OrigExpr HsExpr (GhcPass 'Renamed)
oe <- HsThingRn
orig
        -> HsExpr GhcTc -> AppCtxt -> [HsExprArg 'TcpTc] -> HsExpr GhcTc
rebuild_hs_apps (HsExpr (GhcPass 'Renamed) -> HsExpr GhcTc -> HsExpr GhcTc
mkExpandedExprTc HsExpr (GhcPass 'Renamed)
oe HsExpr GhcTc
fun) AppCtxt
ctxt [HsExprArg 'TcpTc]
args
        | Bool
otherwise
        -> HsExpr GhcTc -> AppCtxt -> [HsExprArg 'TcpTc] -> HsExpr GhcTc
rebuild_hs_apps HsExpr GhcTc
fun AppCtxt
ctxt [HsExprArg 'TcpTc]
args
      EWrap (EHsWrap HsWrapper
wrap)
        -> HsExpr GhcTc -> AppCtxt -> [HsExprArg 'TcpTc] -> HsExpr GhcTc
rebuild_hs_apps (HsWrapper -> HsExpr GhcTc -> HsExpr GhcTc
mkHsWrap HsWrapper
wrap HsExpr GhcTc
fun) AppCtxt
ctxt [HsExprArg 'TcpTc]
args
  where
    lfun :: GenLocated SrcSpanAnnA (HsExpr GhcTc)
lfun = SrcSpanAnnA
-> HsExpr GhcTc -> GenLocated SrcSpanAnnA (HsExpr GhcTc)
forall l e. l -> e -> GenLocated l e
L (SrcSpan -> SrcSpanAnnA
forall e. HasAnnotation e => SrcSpan -> e
noAnnSrcSpan (SrcSpan -> SrcSpanAnnA) -> SrcSpan -> SrcSpanAnnA
forall a b. (a -> b) -> a -> b
$ AppCtxt -> SrcSpan
appCtxtLoc' AppCtxt
ctxt) HsExpr GhcTc
fun
    appCtxtLoc' :: AppCtxt -> SrcSpan
appCtxtLoc' (VAExpansion HsThingRn
_ SrcSpan
_ SrcSpan
l) = SrcSpan
l
    appCtxtLoc' AppCtxt
v = AppCtxt -> SrcSpan
appCtxtLoc AppCtxt
v

{- Note [Representation-polymorphic Ids with no binding]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We cannot have representation-polymorphic or levity-polymorphic
function arguments. See Note [Representation polymorphism invariants]
in GHC.Core.  That is checked in 'GHC.Tc.Gen.App.tcInstFun', see the call
to 'matchActualFunTy', which performs the representation-polymorphism
check.

However, some special Ids have representation-polymorphic argument
types. These are all GHC built-ins or data constructors. They have no binding;
instead they have compulsory unfoldings. Specifically, these Ids are:

1. Some wired-in Ids, such as coerce, oneShot and unsafeCoerce# (which is only
   partly wired-in),
2. Representation-polymorphic primops, such as raise#.
3. Representation-polymorphic data constructors: unboxed tuples
   and unboxed sums.
4. Newtype constructors with `UnliftedNewtypes` which have
   a representation-polymorphic argument.

For (1) consider
  badId :: forall r (a :: TYPE r). a -> a
  badId = unsafeCoerce# @r @r @a @a

The (partly) wired-in function
  unsafeCoerce# :: forall (r1 :: RuntimeRep) (r2 :: RuntimeRep)
                   (a :: TYPE r1) (b :: TYPE r2).
                   a -> b
has a convenient but representation-polymorphic type. It has no
binding; instead it has a compulsory unfolding, after which we
would have
  badId = /\r /\(a :: TYPE r). \(x::a). ...body of unsafeCorece#...
And this is no good because of that rep-poly \(x::a).  So we want
to reject this.

On the other hand
  goodId :: forall (a :: Type). a -> a
  goodId = unsafeCoerce# @LiftedRep @LiftedRep @a @a

is absolutely fine, because after we inline the unfolding, the \(x::a)
is representation-monomorphic.

Test cases: T14561, RepPolyWrappedVar2.

For primops (2) and unboxed tuples/sums (3), the situation is similar;
they are eta-expanded in CorePrep to be saturated, and that eta-expansion
must not add a representation-polymorphic lambda.

Test cases: T14561b, RepPolyWrappedVar, UnliftedNewtypesCoerceFail.

The Note [Representation-polymorphism checking built-ins] explains how we handle
cases (1) (2) and (3).

For (4), consider a representation-polymorphic newtype with
UnliftedNewtypes:

  type Id :: forall r. TYPE r -> TYPE r
  newtype Id a where { MkId :: a }

  bad :: forall r (a :: TYPE r). a -> Id a
  bad = MkId @r @a             -- Want to reject

  good :: forall (a :: Type). a -> Id a
  good = MkId @LiftedRep @a   -- Want to accept

Test cases: T18481, UnliftedNewtypesLevityBinder

(4) is handled differently than (1) (2) and (3);
see Note [Eta-expanding rep-poly unlifted newtypes].

Note [Representation-polymorphism checking built-ins]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Some primops and wired-in functions are representation-polymorphic, but must
only be instantiated at particular, concrete representations.
There are three cases, all for `hasNoBinding` Ids:

* Wired-in Ids.  For example, `seq`
  is a wired-in Id, defined in GHC.Types.Id.Make.seqId, with this type:

  seq :: forall {r} a (b :: TYPE r). a -> b -> b

  It is more like a macro than a regular Id: it has /compulsory/ unfolding, so
  we inline it at every call site.  At those call sites we should instantiate
  `r` with a concrete RuntimeRep, so that the lambda has a concrete representation.
  So somehow the type checker has to ensure that `seq` is called with a concrete
  instantiation for `r`.

  NB: unsafeCoerce# is not quite wired-in (see Note [Wiring in unsafeCoerce#] in GHC.HsToCore),
  but it gets a similar treatment.

* PrimOps. Some representation-polymorphic primops must be called at a concrete
  type.  For example:

  catch# :: forall {r} {l} (k :: TYPE r) (w :: TYPE (BoxedRep l)).
              (State# RealWorld -> (# State# RealWorld, k #) )
           -> (w -> State# RealWorld -> (# State# RealWorld, k #) )
           -> State# RealWorld -> (# State# RealWorld, k #)

  This primop pushes a "catch frame" on the stack, which must "know"
  the return convention of `k`.  So `k` must be concrete, so we know
  what kind of catch-frame to push. (See #21868 for more details.

  So again we want to ensure that `r` is instantiated with a concrete RuntimeRep.

* Unboxed-tuple data constructors.  Consider the unboxed pair data constructor:

  (#,#) :: forall {r1} {r2} (a :: TYPE r1) (b :: TYPE r2). a -> b -> (# a, b #)

  Again, we need concrete `r1` and `r2`. For example, we want to reject

    f :: forall r (a :: TYPE r). a -> (# Int, a #)
    f = (#,#) 3

As pointed out in #21906; we see here that it is not enough to simply check
the representation of the argument types, as for example "k :: TYPE r" in the
type of catch# occurs in negative position but not directly as the type of
an argument.

NB: we specifically *DO NOT* handle representation-polymorphic unlifted newtypes
with this mechanism. See Note [Eta-expanding rep-poly unlifted newtypes] for an
overview of representation-polymorphism checks for those.

To achieve this goal, for these these three kinds of `hasNoBinding` functions:

* We identify the quantified variable `r` as a "concrete quantifier"

* When instantiating a concrete quantifier, such as `r`, at a call site, we
  instantiate with a ConcreteTv meta-tyvar, `r0[conc]`.
  See Note [ConcreteTv] in GHC.Tc.Utils.Concrete.

Now the type checker will ensure that `r0` is instantiated with a concrete
RuntimeRep.

Here are the moving parts:

* In the IdDetails of an Id, we record a mapping from type variable name
  to concreteness information, in the form of a ConcreteTvOrigin.
  See 'idDetailsConcreteTvs'.

  The ConcreteTvOrigin is used to determine which error message to show
  to the user if the type variable gets instantiated to a non-concrete type;
  this is slightly more granular than simply storing a set of type variable names.

* The domain of this NameEnv is the outer forall'd TyVars of that
  Id's type.  (A bit yukky because it means that alpha-renaming that type
  would be invalid.  But we never do that.)  So `seq` has
    Type:       forall {r} a (b :: TYPE r). a -> b -> b
    IdDetails:  RepPolyId [ r :-> ConcreteFRR (FixedRuntimeRepOrigin b (..)) ]

* When instantiating the type of an Id at a call site, at the call to
  GHC.Tc.Utils.Instantiate.instantiateSigma in GHC.Tc.Gen.App.tcInstFun,
  create ConcreteTv metavariables (instead of TauTvs) based on the
  ConcreteTyVars stored in the IdDetails of the Id.

Note that the /only/ place that one of these restricted rep-poly Ids can enter
typechecking is in `tcInferId`, and all the interesting cases then land
in `tcInstFun` where we take care to instantantiate those concrete
type variables correctly.

  Design alternative: in some ways, it would be more kosher for the concrete-ness
  to be stored in the /type/, thus  forall (r[conc] :: RuntimeRep). ty.
  But that pollutes Type for a very narrow use-case; so instead we adopt the
  more ad-hoc solution described above.

Examples:

  ok :: forall (a :: Type) (b :: Type). a -> b -> b
  ok = seq

  bad :: forall s (b :: TYPE s). Int -> b -> b
  bad x = seq x

    Here we will instantiate the RuntimeRep skolem variable r from the type
    of seq to a concrete metavariable rr[conc].
    For 'ok' we will unify rr := LiftedRep, and for 'bad' we will fail to
    solve rr[conc] ~# s[sk] and report a representation-polymorphism error to
    the user.

  type RR :: RuntimeRep
  type family RR where { RR = IntRep }

  tricky1, tricky2 :: forall (b :: TYPE RR). Int -> b -> b
  tricky1 = seq
  tricky2 = seq @RR

    'tricky1' proceeds as above: we instantiate r |-> rr[conc], get a Wanted
    rr[conc] ~# RR, which we solve by rewriting the type family.

    For 'tricky2', we again create a fresh ConcreteTv metavariable rr[conc],
    and we then proceed as if the user had written "seq @rr", but adding an
    additional [W] rr ~ RR to the constraint solving context.

[Wrinkle: VTA]

  We must also handle the case when the user has instantiated the type variables
  themselves, with a visible type application. We do this in GHC.Tc.Gen.App.tcVTA.

  For example:

    type F :: Type -> RuntimeRep
    type family F a where { F Bool = IntRep }

    foo = (# , #) @(F Bool) @FloatRep

  We want to accept "foo" even though "F Bool" is not a concrete RuntimeRep.
  We proceed as follows (see tcVTA):

    - create a fresh concrete metavariable kappa,
    - emit [W] F Bool ~ kappa[conc]
    - pretend the user wrote (#,#) @kappa.

  The solver will then unify kappa := IntRep, after rewriting the type family
  application on the LHS of the Wanted.

  Note that this is a bit of a corner case: only a few built-ins, such as
  unsafeCoerce# and unboxed tuples, have specified (not inferred) RuntimeRep
  quantified variables which can be instantiated by the user with a
  visible type application.
  For example,

    coerce :: forall {r :: RuntimeRep} (a :: TYPE r) (b :: TYPE r)
           .  Coercible a b => a -> b

  does not allow the RuntimeRep argument to be specified by a visible type
  application.

Note [Eta-expanding rep-poly unlifted newtypes]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Any occurrence of a newtype constructor must appear at a known representation.
If the newtype is applied to an argument, then we are done: by (I2) in
Note [Representation polymorphism invariants], the argument has a known
representation, and we are done. So we are left with the situation of an
unapplied newtype constructor. For example:

  type N :: TYPE r -> TYPE r
  newtype N a = MkN a

  ok :: N Int# -> N Int#
  ok = MkN

  bad :: forall r (a :: TYPE r). N (# Int, r #) -> N (# Int, r #)
  bad = MkN

The difficulty is that, unlike the situation described in
Note [Representation-polymorphism checking built-ins],
it is not necessarily the case that we simply need to check the instantiation
of a single variable. Consider for example:

  type RR :: Type -> Type -> RuntimeRep
  type family RR a b where ...

  type T :: forall a -> forall b -> TYPE (RR a b)
  type family T a b where ...

  type M :: forall a -> forall b -> TYPE (RR a b)
  newtype M a b = MkM (T a b)

Now, suppose we instantiate MkM, say with two types X, Y from the environment:

  foo :: T X Y -> M X Y
  foo = MkM @X @Y

we need to check that we can eta-expand MkM, for which we need to know the
representation of its argument, which is "RR X Y".

To do this, in "rejectRepPolyNewtypes", we perform a syntactic representation-
polymorphism check on the instantiated argument of the newtype, and reject
the definition if the representation isn't concrete (in the sense of Note [Concrete types]
in GHC.Tc.Utils.Concrete).

For example, we would accept "ok" above, as "IntRep" is a concrete RuntimeRep.
However, we would reject "foo", because "RR X Y" is not a concrete RuntimeRep.
If we wanted to accept "foo" (performing a PHASE 2 check (in the sense of
Note [The Concrete mechanism] in GHC.Tc.Utils.Concrete), we would have to
significantly re-engineer unlifted newtypes in GHC. Currently, "MkM" has type:

  MkM :: forall a b. T a b %1 -> M a b

However, we should only be able to use MkM when we know the representation of
T a b (which is RR a b). This means that MkM should instead have type:

  MkM :: forall {must_be_conc} a b (co :: RR a b ~# must_be_conc)
      .  T a b |> GRefl Nominal (TYPE co) %1 -> M a b

where "must_be_conc" is a skolem type variable that must be instantiated to
a concrete type, just as in Note [Representation-polymorphism checking built-ins].
This means that any instantiation of "MkM", such as "MkM @X @Y" from "foo",
would create a fresh concrete metavariable "gamma[conc]" and emit a Wanted constraint

  [W] co :: RR X Y ~# gamma[conc]

However, this all seems like a lot of work for a feature that no one is asking for,
so we decided to keep the much simpler syntactic check. Note that one possible
advantage of this approach is that we should be able to stop skipping
representation-polymorphism checks in the output of the desugarer; see (C) in
Wrinkle [Representation-polymorphic lambdas] in Note [Typechecking data constructors].
-}

-- | Reject any unsaturated use of an unlifted newtype constructor
-- if the representation of its argument isn't known.
--
-- See Note [Eta-expanding rep-poly unlifted newtypes].
rejectRepPolyNewtypes :: [HsExprArg 'TcpTc]
                      -> TcRhoType
                      -> HsExpr GhcTc
                      -> TcM ()
rejectRepPolyNewtypes :: [HsExprArg 'TcpTc] -> TcSigmaType -> HsExpr GhcTc -> TcM ()
rejectRepPolyNewtypes [HsExprArg 'TcpTc]
_applied_args TcSigmaType
app_res_rho HsExpr GhcTc
fun = case HsExpr GhcTc
fun of

  XExpr (ConLikeTc (RealDataCon DataCon
con) [Var]
_ [Scaled TcSigmaType]
_)
    -- Check that this is an unsaturated occurrence of a
    -- representation-polymorphic newtype constructor.
    | DataCon -> Bool
isNewDataCon DataCon
con
    , Bool -> Bool
not (Bool -> Bool) -> Bool -> Bool
forall a b. (a -> b) -> a -> b
$ TyCon -> Bool
tcHasFixedRuntimeRep (TyCon -> Bool) -> TyCon -> Bool
forall a b. (a -> b) -> a -> b
$ DataCon -> TyCon
dataConTyCon DataCon
con
    , Just (FunTyFlag
_rem_arg_af, TcSigmaType
_rem_arg_mult, TcSigmaType
rem_arg_ty, TcSigmaType
_nt_res_ty)
        <- TcSigmaType
-> Maybe (FunTyFlag, TcSigmaType, TcSigmaType, TcSigmaType)
splitFunTy_maybe TcSigmaType
app_res_rho
    -> do { let frr_ctxt :: FixedRuntimeRepContext
frr_ctxt = DataCon -> FixedRuntimeRepContext
FRRRepPolyUnliftedNewtype DataCon
con
          ; HasDebugCallStack =>
FixedRuntimeRepContext -> TcSigmaType -> TcM ()
FixedRuntimeRepContext -> TcSigmaType -> TcM ()
hasFixedRuntimeRep_syntactic FixedRuntimeRepContext
frr_ctxt TcSigmaType
rem_arg_ty }

  HsExpr GhcTc
_ -> () -> TcM ()
forall a. a -> IOEnv (Env TcGblEnv TcLclEnv) a
forall (m :: * -> *) a. Monad m => a -> m a
return ()

isHsValArg :: HsExprArg id -> Bool
isHsValArg :: forall (id :: TcPass). HsExprArg id -> Bool
isHsValArg (EValArg {}) = Bool
True
isHsValArg HsExprArg id
_            = Bool
False

leadingValArgs :: [HsExprArg id] -> [EValArg id]
leadingValArgs :: forall (id :: TcPass). [HsExprArg id] -> [EValArg id]
leadingValArgs []                        = []
leadingValArgs (arg :: HsExprArg id
arg@(EValArg {}) : [HsExprArg id]
args) = HsExprArg id -> EValArg id
forall (p :: TcPass). HsExprArg p -> EValArg p
eva_arg HsExprArg id
arg EValArg id -> [EValArg id] -> [EValArg id]
forall a. a -> [a] -> [a]
: [HsExprArg id] -> [EValArg id]
forall (id :: TcPass). [HsExprArg id] -> [EValArg id]
leadingValArgs [HsExprArg id]
args
leadingValArgs (EWrap {}    : [HsExprArg id]
args)      = [HsExprArg id] -> [EValArg id]
forall (id :: TcPass). [HsExprArg id] -> [EValArg id]
leadingValArgs [HsExprArg id]
args
leadingValArgs (EPrag {}    : [HsExprArg id]
args)      = [HsExprArg id] -> [EValArg id]
forall (id :: TcPass). [HsExprArg id] -> [EValArg id]
leadingValArgs [HsExprArg id]
args
leadingValArgs (ETypeArg {} : [HsExprArg id]
_)         = []

isValArg :: HsExprArg id -> Bool
isValArg :: forall (id :: TcPass). HsExprArg id -> Bool
isValArg (EValArg {}) = Bool
True
isValArg HsExprArg id
_            = Bool
False

isVisibleArg :: HsExprArg id -> Bool
isVisibleArg :: forall (id :: TcPass). HsExprArg id -> Bool
isVisibleArg (EValArg {})  = Bool
True
isVisibleArg (ETypeArg {}) = Bool
True
isVisibleArg HsExprArg id
_             = Bool
False

instance OutputableBndrId (XPass p) => Outputable (HsExprArg p) where
  ppr :: HsExprArg p -> SDoc
ppr (EValArg { eva_arg :: forall (p :: TcPass). HsExprArg p -> EValArg p
eva_arg = EValArg p
arg })      = String -> SDoc
forall doc. IsLine doc => String -> doc
text String
"EValArg" SDoc -> SDoc -> SDoc
forall doc. IsLine doc => doc -> doc -> doc
<+> EValArg p -> SDoc
forall a. Outputable a => a -> SDoc
ppr EValArg p
arg
  ppr (EPrag AppCtxt
_ HsPragE (GhcPass (XPass p))
p)                      = String -> SDoc
forall doc. IsLine doc => String -> doc
text String
"EPrag" SDoc -> SDoc -> SDoc
forall doc. IsLine doc => doc -> doc -> doc
<+> HsPragE (GhcPass (XPass p)) -> SDoc
forall a. Outputable a => a -> SDoc
ppr HsPragE (GhcPass (XPass p))
p
  ppr (ETypeArg { eva_hs_ty :: forall (p :: TcPass). HsExprArg p -> LHsWcType (GhcPass 'Renamed)
eva_hs_ty = LHsWcType (GhcPass 'Renamed)
hs_ty }) = Char -> SDoc
forall doc. IsLine doc => Char -> doc
char Char
'@' SDoc -> SDoc -> SDoc
forall doc. IsLine doc => doc -> doc -> doc
<> HsWildCardBndrs
  (GhcPass 'Renamed)
  (GenLocated SrcSpanAnnA (HsType (GhcPass 'Renamed)))
-> SDoc
forall a. Outputable a => a -> SDoc
ppr LHsWcType (GhcPass 'Renamed)
HsWildCardBndrs
  (GhcPass 'Renamed)
  (GenLocated SrcSpanAnnA (HsType (GhcPass 'Renamed)))
hs_ty
  ppr (EWrap EWrap
wrap)                     = EWrap -> SDoc
forall a. Outputable a => a -> SDoc
ppr EWrap
wrap

instance Outputable EWrap where
  ppr :: EWrap -> SDoc
ppr (EPar AppCtxt
_)       = String -> SDoc
forall doc. IsLine doc => String -> doc
text String
"EPar"
  ppr (EHsWrap HsWrapper
w)    = String -> SDoc
forall doc. IsLine doc => String -> doc
text String
"EHsWrap" SDoc -> SDoc -> SDoc
forall doc. IsLine doc => doc -> doc -> doc
<+> HsWrapper -> SDoc
forall a. Outputable a => a -> SDoc
ppr HsWrapper
w
  ppr (EExpand HsThingRn
orig) = String -> SDoc
forall doc. IsLine doc => String -> doc
text String
"EExpand" SDoc -> SDoc -> SDoc
forall doc. IsLine doc => doc -> doc -> doc
<+> HsThingRn -> SDoc
forall a. Outputable a => a -> SDoc
ppr HsThingRn
orig

instance OutputableBndrId (XPass p) => Outputable (EValArg p) where
  ppr :: EValArg p -> SDoc
ppr (ValArg LHsExpr (GhcPass (XPass p))
e) = GenLocated SrcSpanAnnA (HsExpr (GhcPass (XPass p))) -> SDoc
forall a. Outputable a => a -> SDoc
ppr LHsExpr (GhcPass (XPass p))
GenLocated SrcSpanAnnA (HsExpr (GhcPass (XPass p)))
e
  ppr (ValArgQL { va_fun :: EValArg 'TcpInst -> (HsExpr GhcTc, AppCtxt)
va_fun = (HsExpr GhcTc, AppCtxt)
fun, va_args :: EValArg 'TcpInst -> [HsExprArg 'TcpInst]
va_args = [HsExprArg 'TcpInst]
args, va_ty :: EValArg 'TcpInst -> TcSigmaType
va_ty = TcSigmaType
ty})
    = SDoc -> ThLevel -> SDoc -> SDoc
hang (String -> SDoc
forall doc. IsLine doc => String -> doc
text String
"ValArgQL" SDoc -> SDoc -> SDoc
forall doc. IsLine doc => doc -> doc -> doc
<+> (HsExpr GhcTc, AppCtxt) -> SDoc
forall a. Outputable a => a -> SDoc
ppr (HsExpr GhcTc, AppCtxt)
fun)
         ThLevel
2 ([SDoc] -> SDoc
forall doc. IsDoc doc => [doc] -> doc
vcat [ [HsExprArg 'TcpInst] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [HsExprArg 'TcpInst]
args, String -> SDoc
forall doc. IsLine doc => String -> doc
text String
"va_ty:" SDoc -> SDoc -> SDoc
forall doc. IsLine doc => doc -> doc -> doc
<+> TcSigmaType -> SDoc
forall a. Outputable a => a -> SDoc
ppr TcSigmaType
ty ])

pprHsExprArgTc :: HsExprArg 'TcpInst -> SDoc
pprHsExprArgTc :: HsExprArg 'TcpInst -> SDoc
pprHsExprArgTc (EValArg { eva_arg :: forall (p :: TcPass). HsExprArg p -> EValArg p
eva_arg = EValArg 'TcpInst
tm, eva_arg_ty :: forall (p :: TcPass). HsExprArg p -> XEVAType p
eva_arg_ty = XEVAType 'TcpInst
ty })
  = String -> SDoc
forall doc. IsLine doc => String -> doc
text String
"EValArg" SDoc -> SDoc -> SDoc
forall doc. IsLine doc => doc -> doc -> doc
<+> SDoc -> ThLevel -> SDoc -> SDoc
hang (EValArg 'TcpInst -> SDoc
forall a. Outputable a => a -> SDoc
ppr EValArg 'TcpInst
tm) ThLevel
2 (SDoc
dcolon SDoc -> SDoc -> SDoc
forall doc. IsLine doc => doc -> doc -> doc
<+> Scaled TcSigmaType -> SDoc
forall a. Outputable a => a -> SDoc
ppr Scaled TcSigmaType
XEVAType 'TcpInst
ty)
pprHsExprArgTc HsExprArg 'TcpInst
arg = HsExprArg 'TcpInst -> SDoc
forall a. Outputable a => a -> SDoc
ppr HsExprArg 'TcpInst
arg

{- Note [Desugar OpApp in the typechecker]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Operator sections are desugared in the renamer; see GHC.Rename.Expr
Note [Handling overloaded and rebindable constructs].
But for reasons explained there, we rename OpApp to OpApp.  Then,
here in the typechecker, we desugar it to a use of ExpandedThingRn.
That makes it possible to typecheck something like
     e1 `f` e2
where
   f :: forall a. t1 -> forall b. t2 -> t3

Note [Looking through ExpandedThingRn]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
When creating an application chain in splitHsApps, we must deal with
     ExpandedThingRn f1 (f `HsApp` e1) `HsApp` e2 `HsApp` e3

as a single application chain `f e1 e2 e3`.  Otherwise stuff like overloaded
labels (#19154) won't work.

It's easy to achieve this: `splitHsApps` unwraps `ExpandedThingRn`.

In order to be able to more accurately reconstruct the original `SrcSpan`s
from the renamer in `rebuildHsApps`, we also have to track the `SrcSpan`
of the current application in `VAExpansion` when unwrapping `ExpandedThingRn`
in `splitHsApps`, just as we track it in a non-expanded expression.

Previously, `rebuildHsApps` substituted the location of the original
expression as given by `splitHsApps` for this. As a result, the application
head in expanded expressions, e.g. the call to `fromListN`, would either
have `noSrcSpan` set as its location post-typecheck, or get the location
of the original expression, depending on whether the `XExpr` given to
`splitHsApps` is in the outermost layer. The span it got in the renamer
would always be discarded, causing #23120.

Note [Looking through Template Haskell splices in splitHsApps]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
When typechecking an application, we must look through untyped TH splices in
order to typecheck examples like the one in #21077:

  data Foo = MkFoo () (forall a. a -> a)

  foo :: Foo
  foo = $([| MkFoo () |]) $ \x -> x

In principle, this is straightforward to accomplish. By the time we typecheck
`foo`, the renamer will have already run the splice, so all we have to do is
look at the expanded version of the splice in `splitHsApps`. See the
`HsUntypedSplice` case in `splitHsApps` for how this is accomplished.

There is one slight complication in that untyped TH splices also include
modFinalizers (see Note [Delaying modFinalizers in untyped splices] in
GHC.Rename.Splice), which must be run during typechecking. splitHsApps is a
convenient place to run the modFinalizers, so we do so there. This is the only
reason that `splitHsApps` uses the TcM monad.

`HsUntypedSplice` covers both ordinary TH splices, such as the example above,
as well as quasiquotes (see Note [Quasi-quote overview] in
Language.Haskell.Syntax.Expr). The `splitHsApps` case for `HsUntypedSplice`
handles both of these. This is easy to accomplish, since all the real work in
handling splices and quasiquotes has already been performed by the renamer by
the time we get to `splitHsApps`.

Wrinkle (UTS1):
  `tcExpr` has a separate case for `HsUntypedSplice`s that do /not/ occur at the
  head of an application. This is important to handle programs like this one:

    foo :: (forall a. a -> a) -> b -> b
    foo = $([| \g x -> g x |])

  Here, it is vital that we push the expected type inwards so that `g` gets the
  type `forall a. a -> a`, and the `tcExpr` case for `HsUntypedSplice` performs
  this pushing. Without it, we would instead infer `g` to have type `b -> b`,
  which isn't sufficiently general. Unfortunately, this does mean that there are
  two different places in the code where an `HsUntypedSplice`'s modFinalizers can
  be ran, depending on whether the splice appears at the head of an application
  or not.
-}

{- *********************************************************************
*                                                                      *
                 tcInferAppHead
*                                                                      *
********************************************************************* -}

tcInferAppHead :: (HsExpr GhcRn, AppCtxt)
               -> TcM (HsExpr GhcTc, TcSigmaType)
-- Infer type of the head of an application
--   i.e. the 'f' in (f e1 ... en)
-- See Note [Application chains and heads] in GHC.Tc.Gen.App
-- We get back a /SigmaType/ because we have special cases for
--   * A bare identifier (just look it up)
--     This case also covers a record selector HsRecSel
--   * An expression with a type signature (e :: ty)
-- See Note [Application chains and heads] in GHC.Tc.Gen.App
--
-- Note that [] and (,,) are both HsVar:
--   see Note [Empty lists] and [ExplicitTuple] in GHC.Hs.Expr
--
-- NB: 'e' cannot be HsApp, HsTyApp, HsPrag, HsPar, because those
--     cases are dealt with by splitHsApps.
--
-- See Note [tcApp: typechecking applications] in GHC.Tc.Gen.App
tcInferAppHead :: (HsExpr (GhcPass 'Renamed), AppCtxt)
-> TcM (HsExpr GhcTc, TcSigmaType)
tcInferAppHead (HsExpr (GhcPass 'Renamed)
fun,AppCtxt
ctxt)
  = AppCtxt
-> TcM (HsExpr GhcTc, TcSigmaType)
-> TcM (HsExpr GhcTc, TcSigmaType)
forall a. AppCtxt -> TcM a -> TcM a
addHeadCtxt AppCtxt
ctxt (TcM (HsExpr GhcTc, TcSigmaType)
 -> TcM (HsExpr GhcTc, TcSigmaType))
-> TcM (HsExpr GhcTc, TcSigmaType)
-> TcM (HsExpr GhcTc, TcSigmaType)
forall a b. (a -> b) -> a -> b
$
    do { mb_tc_fun <- HsExpr (GhcPass 'Renamed)
-> TcM (Maybe (HsExpr GhcTc, TcSigmaType))
tcInferAppHead_maybe HsExpr (GhcPass 'Renamed)
fun
       ; case mb_tc_fun of
            Just (HsExpr GhcTc
fun', TcSigmaType
fun_sigma) -> (HsExpr GhcTc, TcSigmaType) -> TcM (HsExpr GhcTc, TcSigmaType)
forall a. a -> IOEnv (Env TcGblEnv TcLclEnv) a
forall (m :: * -> *) a. Monad m => a -> m a
return (HsExpr GhcTc
fun', TcSigmaType
fun_sigma)
            Maybe (HsExpr GhcTc, TcSigmaType)
Nothing -> (ExpRhoType -> TcM (HsExpr GhcTc))
-> TcM (HsExpr GhcTc, TcSigmaType)
forall a. (ExpRhoType -> TcM a) -> TcM (a, TcSigmaType)
tcInfer (HsExpr (GhcPass 'Renamed) -> ExpRhoType -> TcM (HsExpr GhcTc)
tcExpr HsExpr (GhcPass 'Renamed)
fun) }

tcInferAppHead_maybe :: HsExpr GhcRn
                     -> TcM (Maybe (HsExpr GhcTc, TcSigmaType))
-- See Note [Application chains and heads] in GHC.Tc.Gen.App
-- Returns Nothing for a complicated head
tcInferAppHead_maybe :: HsExpr (GhcPass 'Renamed)
-> TcM (Maybe (HsExpr GhcTc, TcSigmaType))
tcInferAppHead_maybe HsExpr (GhcPass 'Renamed)
fun
  = case HsExpr (GhcPass 'Renamed)
fun of
      HsVar XVar (GhcPass 'Renamed)
_ (L SrcSpanAnnN
_ Name
nm)          -> (HsExpr GhcTc, TcSigmaType) -> Maybe (HsExpr GhcTc, TcSigmaType)
forall a. a -> Maybe a
Just ((HsExpr GhcTc, TcSigmaType) -> Maybe (HsExpr GhcTc, TcSigmaType))
-> TcM (HsExpr GhcTc, TcSigmaType)
-> TcM (Maybe (HsExpr GhcTc, TcSigmaType))
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
<$> Name -> TcM (HsExpr GhcTc, TcSigmaType)
tcInferId Name
nm
      HsRecSel XRecSel (GhcPass 'Renamed)
_ FieldOcc (GhcPass 'Renamed)
f              -> (HsExpr GhcTc, TcSigmaType) -> Maybe (HsExpr GhcTc, TcSigmaType)
forall a. a -> Maybe a
Just ((HsExpr GhcTc, TcSigmaType) -> Maybe (HsExpr GhcTc, TcSigmaType))
-> TcM (HsExpr GhcTc, TcSigmaType)
-> TcM (Maybe (HsExpr GhcTc, TcSigmaType))
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
<$> FieldOcc (GhcPass 'Renamed) -> TcM (HsExpr GhcTc, TcSigmaType)
tcInferRecSelId FieldOcc (GhcPass 'Renamed)
f
      ExprWithTySig XExprWithTySig (GhcPass 'Renamed)
_ LHsExpr (GhcPass 'Renamed)
e LHsSigWcType (NoGhcTc (GhcPass 'Renamed))
hs_ty   -> (HsExpr GhcTc, TcSigmaType) -> Maybe (HsExpr GhcTc, TcSigmaType)
forall a. a -> Maybe a
Just ((HsExpr GhcTc, TcSigmaType) -> Maybe (HsExpr GhcTc, TcSigmaType))
-> TcM (HsExpr GhcTc, TcSigmaType)
-> TcM (Maybe (HsExpr GhcTc, TcSigmaType))
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
<$> LHsExpr (GhcPass 'Renamed)
-> LHsSigWcType (NoGhcTc (GhcPass 'Renamed))
-> TcM (HsExpr GhcTc, TcSigmaType)
tcExprWithSig LHsExpr (GhcPass 'Renamed)
e LHsSigWcType (NoGhcTc (GhcPass 'Renamed))
hs_ty
      HsOverLit XOverLitE (GhcPass 'Renamed)
_ HsOverLit (GhcPass 'Renamed)
lit           -> (HsExpr GhcTc, TcSigmaType) -> Maybe (HsExpr GhcTc, TcSigmaType)
forall a. a -> Maybe a
Just ((HsExpr GhcTc, TcSigmaType) -> Maybe (HsExpr GhcTc, TcSigmaType))
-> TcM (HsExpr GhcTc, TcSigmaType)
-> TcM (Maybe (HsExpr GhcTc, TcSigmaType))
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
<$> HsOverLit (GhcPass 'Renamed) -> TcM (HsExpr GhcTc, TcSigmaType)
tcInferOverLit HsOverLit (GhcPass 'Renamed)
lit
      HsExpr (GhcPass 'Renamed)
_                         -> Maybe (HsExpr GhcTc, TcSigmaType)
-> TcM (Maybe (HsExpr GhcTc, TcSigmaType))
forall a. a -> IOEnv (Env TcGblEnv TcLclEnv) a
forall (m :: * -> *) a. Monad m => a -> m a
return Maybe (HsExpr GhcTc, TcSigmaType)
forall a. Maybe a
Nothing

addHeadCtxt :: AppCtxt -> TcM a -> TcM a
addHeadCtxt :: forall a. AppCtxt -> TcM a -> TcM a
addHeadCtxt (VAExpansion (OrigStmt (L SrcSpanAnnA
loc StmtLR
  (GhcPass 'Renamed)
  (GhcPass 'Renamed)
  (GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Renamed)))
stmt)) SrcSpan
_ SrcSpan
_) TcM a
thing_inside =
  do SrcSpanAnnA -> TcM a -> TcM a
forall ann a. EpAnn ann -> TcRn a -> TcRn a
setSrcSpanA SrcSpanAnnA
loc (TcM a -> TcM a) -> TcM a -> TcM a
forall a b. (a -> b) -> a -> b
$
       ExprStmt (GhcPass 'Renamed) -> TcM a -> TcM a
forall a. ExprStmt (GhcPass 'Renamed) -> TcRn a -> TcRn a
addStmtCtxt ExprStmt (GhcPass 'Renamed)
StmtLR
  (GhcPass 'Renamed)
  (GhcPass 'Renamed)
  (GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Renamed)))
stmt
         TcM a
thing_inside
addHeadCtxt AppCtxt
fun_ctxt TcM a
thing_inside
  | Bool -> Bool
not (SrcSpan -> Bool
isGoodSrcSpan SrcSpan
fun_loc)   -- noSrcSpan => no arguments
  = TcM a
thing_inside                  -- => context is already set
  | Bool
otherwise
  = SrcSpan -> TcM a -> TcM a
forall a. SrcSpan -> TcRn a -> TcRn a
setSrcSpan SrcSpan
fun_loc (TcM a -> TcM a) -> TcM a -> TcM a
forall a b. (a -> b) -> a -> b
$
    do case AppCtxt
fun_ctxt of
         VAExpansion (OrigExpr HsExpr (GhcPass 'Renamed)
orig) SrcSpan
_ SrcSpan
_ -> HsExpr (GhcPass 'Renamed) -> TcM a -> TcM a
forall a. HsExpr (GhcPass 'Renamed) -> TcRn a -> TcRn a
addExprCtxt HsExpr (GhcPass 'Renamed)
orig TcM a
thing_inside
         AppCtxt
_                               -> TcM a
thing_inside
  where
    fun_loc :: SrcSpan
fun_loc = AppCtxt -> SrcSpan
appCtxtLoc AppCtxt
fun_ctxt


{- *********************************************************************
*                                                                      *
                 Record selectors
*                                                                      *
********************************************************************* -}

tcInferRecSelId :: FieldOcc GhcRn
                -> TcM (HsExpr GhcTc, TcSigmaType)
tcInferRecSelId :: FieldOcc (GhcPass 'Renamed) -> TcM (HsExpr GhcTc, TcSigmaType)
tcInferRecSelId (FieldOcc XCFieldOcc (GhcPass 'Renamed)
sel_name XRec (GhcPass 'Renamed) RdrName
lbl)
   = do { sel_id <- TcM Var
tc_rec_sel_id
        ; let expr = XRecSel GhcTc -> FieldOcc GhcTc -> HsExpr GhcTc
forall p. XRecSel p -> FieldOcc p -> HsExpr p
HsRecSel XRecSel GhcTc
NoExtField
noExtField (XCFieldOcc GhcTc -> XRec GhcTc RdrName -> FieldOcc GhcTc
forall pass. XCFieldOcc pass -> XRec pass RdrName -> FieldOcc pass
FieldOcc XCFieldOcc GhcTc
Var
sel_id XRec (GhcPass 'Renamed) RdrName
XRec GhcTc RdrName
lbl)
        ; return (expr, idType sel_id)
        }
     where
       occ :: OccName
       occ :: OccName
occ = RdrName -> OccName
rdrNameOcc (GenLocated SrcSpanAnnN RdrName -> RdrName
forall l e. GenLocated l e -> e
unLoc XRec (GhcPass 'Renamed) RdrName
GenLocated SrcSpanAnnN RdrName
lbl)

       tc_rec_sel_id :: TcM TcId
       -- Like tc_infer_id, but returns an Id not a HsExpr,
       -- so we can wrap it back up into a HsRecSel
       tc_rec_sel_id :: TcM Var
tc_rec_sel_id
         = do { thing <- Name -> TcM TcTyThing
tcLookup XCFieldOcc (GhcPass 'Renamed)
Name
sel_name
              ; case thing of
                    ATcId { tct_id :: TcTyThing -> Var
tct_id = Var
id }
                      -> do { OccName -> Var -> TcM ()
check_naughty OccName
occ Var
id  -- See Note [Local record selectors]
                            ; Var -> TcM ()
check_local_id Var
id
                            ; Var -> TcM Var
forall a. a -> IOEnv (Env TcGblEnv TcLclEnv) a
forall (m :: * -> *) a. Monad m => a -> m a
return Var
id }

                    AGlobal (AnId Var
id)
                      -> do { OccName -> Var -> TcM ()
check_naughty OccName
occ Var
id
                            ; Var -> TcM Var
forall a. a -> IOEnv (Env TcGblEnv TcLclEnv) a
forall (m :: * -> *) a. Monad m => a -> m a
return Var
id }
                           -- A global cannot possibly be ill-staged
                           -- nor does it need the 'lifting' treatment
                           -- hence no checkTh stuff here

                    TcTyThing
_ -> TcRnMessage -> TcM Var
forall a. TcRnMessage -> TcM a
failWithTc (TcRnMessage -> TcM Var) -> TcRnMessage -> TcM Var
forall a b. (a -> b) -> a -> b
$ TcTyThing -> TcRnMessage
TcRnExpectedValueId TcTyThing
thing }

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

-- A type signature on the argument of an ambiguous record selector or
-- the record expression in an update must be "obvious", i.e. the
-- outermost constructor ignoring parentheses.
obviousSig :: HsExpr GhcRn -> Maybe (LHsSigWcType GhcRn)
obviousSig :: HsExpr (GhcPass 'Renamed)
-> Maybe (LHsSigWcType (GhcPass 'Renamed))
obviousSig (ExprWithTySig XExprWithTySig (GhcPass 'Renamed)
_ LHsExpr (GhcPass 'Renamed)
_ LHsSigWcType (NoGhcTc (GhcPass 'Renamed))
ty) = HsWildCardBndrs
  (GhcPass 'Renamed)
  (GenLocated SrcSpanAnnA (HsSigType (GhcPass 'Renamed)))
-> Maybe
     (HsWildCardBndrs
        (GhcPass 'Renamed)
        (GenLocated SrcSpanAnnA (HsSigType (GhcPass 'Renamed))))
forall a. a -> Maybe a
Just LHsSigWcType (NoGhcTc (GhcPass 'Renamed))
HsWildCardBndrs
  (GhcPass 'Renamed)
  (GenLocated SrcSpanAnnA (HsSigType (GhcPass 'Renamed)))
ty
obviousSig (HsPar XPar (GhcPass 'Renamed)
_ LHsExpr (GhcPass 'Renamed)
p)            = HsExpr (GhcPass 'Renamed)
-> Maybe (LHsSigWcType (GhcPass 'Renamed))
obviousSig (GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Renamed))
-> HsExpr (GhcPass 'Renamed)
forall l e. GenLocated l e -> e
unLoc LHsExpr (GhcPass 'Renamed)
GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Renamed))
p)
obviousSig (HsPragE XPragE (GhcPass 'Renamed)
_ HsPragE (GhcPass 'Renamed)
_ LHsExpr (GhcPass 'Renamed)
p)        = HsExpr (GhcPass 'Renamed)
-> Maybe (LHsSigWcType (GhcPass 'Renamed))
obviousSig (GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Renamed))
-> HsExpr (GhcPass 'Renamed)
forall l e. GenLocated l e -> e
unLoc LHsExpr (GhcPass 'Renamed)
GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Renamed))
p)
obviousSig HsExpr (GhcPass 'Renamed)
_                      = Maybe (LHsSigWcType (GhcPass 'Renamed))
Maybe
  (HsWildCardBndrs
     (GhcPass 'Renamed)
     (GenLocated SrcSpanAnnA (HsSigType (GhcPass 'Renamed))))
forall a. Maybe a
Nothing

-- Extract the outermost TyCon of a type, if there is one; for
-- data families this is the representation tycon (because that's
-- where the fields live).
tyConOf :: FamInstEnvs -> TcSigmaType -> Maybe TyCon
tyConOf :: FamInstEnvs -> TcSigmaType -> Maybe TyCon
tyConOf FamInstEnvs
fam_inst_envs TcSigmaType
ty0
  = case HasCallStack => TcSigmaType -> Maybe (TyCon, [TcSigmaType])
TcSigmaType -> Maybe (TyCon, [TcSigmaType])
tcSplitTyConApp_maybe TcSigmaType
ty of
      Just (TyCon
tc, [TcSigmaType]
tys) -> TyCon -> Maybe TyCon
forall a. a -> Maybe a
Just ((TyCon, [TcSigmaType], Coercion) -> TyCon
forall a b c. (a, b, c) -> a
fstOf3 (FamInstEnvs
-> TyCon -> [TcSigmaType] -> (TyCon, [TcSigmaType], Coercion)
tcLookupDataFamInst FamInstEnvs
fam_inst_envs TyCon
tc [TcSigmaType]
tys))
      Maybe (TyCon, [TcSigmaType])
Nothing        -> Maybe TyCon
forall a. Maybe a
Nothing
  where
    ([Var]
_, [TcSigmaType]
_, TcSigmaType
ty) = TcSigmaType -> ([Var], [TcSigmaType], TcSigmaType)
tcSplitSigmaTy TcSigmaType
ty0

-- Variant of tyConOf that works for ExpTypes
tyConOfET :: FamInstEnvs -> ExpRhoType -> Maybe TyCon
tyConOfET :: FamInstEnvs -> ExpRhoType -> Maybe TyCon
tyConOfET FamInstEnvs
fam_inst_envs ExpRhoType
ty0 = FamInstEnvs -> TcSigmaType -> Maybe TyCon
tyConOf FamInstEnvs
fam_inst_envs (TcSigmaType -> Maybe TyCon) -> Maybe TcSigmaType -> Maybe TyCon
forall (m :: * -> *) a b. Monad m => (a -> m b) -> m a -> m b
=<< ExpRhoType -> Maybe TcSigmaType
checkingExpType_maybe ExpRhoType
ty0

fieldNotInType :: RecSelParent -> RdrName -> TcRnMessage
fieldNotInType :: RecSelParent -> RdrName -> TcRnMessage
fieldNotInType RecSelParent
p RdrName
rdr
  = RdrName -> NotInScopeError -> TcRnMessage
mkTcRnNotInScope RdrName
rdr (NotInScopeError -> TcRnMessage) -> NotInScopeError -> TcRnMessage
forall a b. (a -> b) -> a -> b
$
    SDoc -> NotInScopeError
UnknownSubordinate (String -> SDoc
forall doc. IsLine doc => String -> doc
text String
"field of type" SDoc -> SDoc -> SDoc
forall doc. IsLine doc => doc -> doc -> doc
<+> SDoc -> SDoc
quotes (RecSelParent -> SDoc
forall a. Outputable a => a -> SDoc
ppr RecSelParent
p))


{- *********************************************************************
*                                                                      *
                Expressions with a type signature
                        expr :: type
*                                                                      *
********************************************************************* -}

tcExprWithSig :: LHsExpr GhcRn -> LHsSigWcType (NoGhcTc GhcRn)
              -> TcM (HsExpr GhcTc, TcSigmaType)
tcExprWithSig :: LHsExpr (GhcPass 'Renamed)
-> LHsSigWcType (NoGhcTc (GhcPass 'Renamed))
-> TcM (HsExpr GhcTc, TcSigmaType)
tcExprWithSig LHsExpr (GhcPass 'Renamed)
expr LHsSigWcType (NoGhcTc (GhcPass 'Renamed))
hs_ty
  = do { sig_info <- TcM TcIdSig -> TcM TcIdSig
forall r. TcM r -> TcM r
checkNoErrs (TcM TcIdSig -> TcM TcIdSig) -> TcM TcIdSig -> TcM TcIdSig
forall a b. (a -> b) -> a -> b
$  -- Avoid error cascade
                     SrcSpan
-> LHsSigWcType (GhcPass 'Renamed) -> Maybe Name -> TcM TcIdSig
tcUserTypeSig SrcSpan
loc LHsSigWcType (NoGhcTc (GhcPass 'Renamed))
LHsSigWcType (GhcPass 'Renamed)
hs_ty Maybe Name
forall a. Maybe a
Nothing
       ; (expr', poly_ty) <- tcExprSig expr sig_info
       ; return (ExprWithTySig noExtField expr' hs_ty, poly_ty) }
  where
    loc :: SrcSpan
loc = GenLocated SrcSpanAnnA (HsSigType (GhcPass 'Renamed)) -> SrcSpan
forall a e. HasLoc a => GenLocated a e -> SrcSpan
getLocA (LHsSigWcType (GhcPass 'Renamed) -> LHsSigType (GhcPass 'Renamed)
forall pass. LHsSigWcType pass -> LHsSigType pass
dropWildCards LHsSigWcType (NoGhcTc (GhcPass 'Renamed))
LHsSigWcType (GhcPass 'Renamed)
hs_ty)

tcExprSig :: LHsExpr GhcRn -> TcIdSig -> TcM (LHsExpr GhcTc, TcSigmaType)
tcExprSig :: LHsExpr (GhcPass 'Renamed)
-> TcIdSig -> TcM (LHsExpr GhcTc, TcSigmaType)
tcExprSig LHsExpr (GhcPass 'Renamed)
expr (TcCompleteSig TcCompleteSig
sig)
   = do { expr' <- LHsExpr (GhcPass 'Renamed) -> TcCompleteSig -> TcM (LHsExpr GhcTc)
tcPolyLExprSig LHsExpr (GhcPass 'Renamed)
expr TcCompleteSig
sig
        ; return (expr', idType (sig_bndr sig)) }

tcExprSig LHsExpr (GhcPass 'Renamed)
expr sig :: TcIdSig
sig@(TcPartialSig (PSig { psig_name :: TcPartialSig -> Name
psig_name = Name
name, psig_loc :: TcPartialSig -> SrcSpan
psig_loc = SrcSpan
loc }))
  = SrcSpan
-> TcM (LHsExpr GhcTc, TcSigmaType)
-> TcM (LHsExpr GhcTc, TcSigmaType)
forall a. SrcSpan -> TcRn a -> TcRn a
setSrcSpan SrcSpan
loc (TcM (LHsExpr GhcTc, TcSigmaType)
 -> TcM (LHsExpr GhcTc, TcSigmaType))
-> TcM (LHsExpr GhcTc, TcSigmaType)
-> TcM (LHsExpr GhcTc, TcSigmaType)
forall a b. (a -> b) -> a -> b
$   -- Sets the location for the implication constraint
    do { (tclvl, wanted, (expr', sig_inst))
             <- TcM (GenLocated SrcSpanAnnA (HsExpr GhcTc), TcIdSigInst)
-> TcM
     (TcLevel, WantedConstraints,
      (GenLocated SrcSpanAnnA (HsExpr GhcTc), TcIdSigInst))
forall a. TcM a -> TcM (TcLevel, WantedConstraints, a)
pushLevelAndCaptureConstraints  (TcM (GenLocated SrcSpanAnnA (HsExpr GhcTc), TcIdSigInst)
 -> TcM
      (TcLevel, WantedConstraints,
       (GenLocated SrcSpanAnnA (HsExpr GhcTc), TcIdSigInst)))
-> TcM (GenLocated SrcSpanAnnA (HsExpr GhcTc), TcIdSigInst)
-> TcM
     (TcLevel, WantedConstraints,
      (GenLocated SrcSpanAnnA (HsExpr GhcTc), TcIdSigInst))
forall a b. (a -> b) -> a -> b
$
                do { sig_inst <- TcIdSig -> TcM TcIdSigInst
tcInstSig TcIdSig
sig
                   ; expr' <- tcExtendNameTyVarEnv (mapSnd binderVar $ sig_inst_skols sig_inst) $
                              tcExtendNameTyVarEnv (sig_inst_wcs   sig_inst) $
                              tcCheckPolyExprNC expr (sig_inst_tau sig_inst)
                   ; return (expr', sig_inst) }
       -- See Note [Partial expression signatures]
       ; let tau = TcIdSigInst -> TcSigmaType
sig_inst_tau TcIdSigInst
sig_inst
             infer_mode | [TcSigmaType] -> Bool
forall a. [a] -> Bool
forall (t :: * -> *) a. Foldable t => t a -> Bool
null (TcIdSigInst -> [TcSigmaType]
sig_inst_theta TcIdSigInst
sig_inst)
                        , Maybe TcSigmaType -> Bool
forall a. Maybe a -> Bool
isNothing (TcIdSigInst -> Maybe TcSigmaType
sig_inst_wcx TcIdSigInst
sig_inst)
                        = InferMode
ApplyMR
                        | Bool
otherwise
                        = InferMode
NoRestrictions
       ; ((qtvs, givens, ev_binds, _), residual)
           <- captureConstraints $ simplifyInfer tclvl infer_mode [sig_inst] [(name, tau)] wanted
       ; emitConstraints residual

       ; tau <- liftZonkM $ zonkTcType tau
       ; let inferred_theta = (Var -> TcSigmaType) -> [Var] -> [TcSigmaType]
forall a b. (a -> b) -> [a] -> [b]
map Var -> TcSigmaType
evVarPred [Var]
givens
             tau_tvs        = TcSigmaType -> TyCoVarSet
tyCoVarsOfType TcSigmaType
tau
       ; (binders, my_theta) <- chooseInferredQuantifiers residual inferred_theta
                                   tau_tvs qtvs (Just sig_inst)
       ; let inferred_sigma = [Var] -> [TcSigmaType] -> TcSigmaType -> TcSigmaType
HasDebugCallStack =>
[Var] -> [TcSigmaType] -> TcSigmaType -> TcSigmaType
mkInfSigmaTy [Var]
qtvs [TcSigmaType]
inferred_theta TcSigmaType
tau
             my_sigma       = [InvisTVBinder] -> TcSigmaType -> TcSigmaType
mkInvisForAllTys [InvisTVBinder]
binders ([TcSigmaType] -> TcSigmaType -> TcSigmaType
HasDebugCallStack => [TcSigmaType] -> TcSigmaType -> TcSigmaType
mkPhiTy  [TcSigmaType]
my_theta TcSigmaType
tau)
       ; wrap <- if inferred_sigma `eqType` my_sigma -- NB: eqType ignores vis.
                 then return idHsWrapper  -- Fast path; also avoids complaint when we infer
                                          -- an ambiguous type and have AllowAmbiguousType
                                          -- e..g infer  x :: forall a. F a -> Int
                 else tcSubTypeSigma ExprSigOrigin (ExprSigCtxt NoRRC) inferred_sigma my_sigma

       ; traceTc "tcExpSig" (ppr qtvs $$ ppr givens $$ ppr inferred_sigma $$ ppr my_sigma)
       ; let poly_wrap = HsWrapper
wrap
                         HsWrapper -> HsWrapper -> HsWrapper
<.> [Var] -> HsWrapper
mkWpTyLams [Var]
qtvs
                         HsWrapper -> HsWrapper -> HsWrapper
<.> [Var] -> HsWrapper
mkWpEvLams [Var]
givens
                         HsWrapper -> HsWrapper -> HsWrapper
<.> TcEvBinds -> HsWrapper
mkWpLet  TcEvBinds
ev_binds
       ; return (mkLHsWrap poly_wrap expr', my_sigma) }


{- Note [Partial expression signatures]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Partial type signatures on expressions are easy to get wrong.  But
here is a guiding principle
    e :: ty
should behave like
    let x :: ty
        x = e
    in x

So for partial signatures we apply the MR if no context is given.  So
   e :: IO _          apply the MR
   e :: _ => IO _     do not apply the MR
just like in GHC.Tc.Gen.Bind.decideGeneralisationPlan

This makes a difference (#11670):
   peek :: Ptr a -> IO CLong
   peek ptr = peekElemOff undefined 0 :: _
from (peekElemOff undefined 0) we get
          type: IO w
   constraints: Storable w

We must NOT try to generalise over 'w' because the signature specifies
no constraints so we'll complain about not being able to solve
Storable w.  Instead, don't generalise; then _ gets instantiated to
CLong, as it should.
-}


{- *********************************************************************
*                                                                      *
                 Overloaded literals
*                                                                      *
********************************************************************* -}

tcInferOverLit :: HsOverLit GhcRn -> TcM (HsExpr GhcTc, TcSigmaType)
tcInferOverLit :: HsOverLit (GhcPass 'Renamed) -> TcM (HsExpr GhcTc, TcSigmaType)
tcInferOverLit lit :: HsOverLit (GhcPass 'Renamed)
lit@(OverLit { ol_val :: forall p. HsOverLit p -> OverLitVal
ol_val = OverLitVal
val
                            , ol_ext :: forall p. HsOverLit p -> XOverLit p
ol_ext = OverLitRn { ol_rebindable :: OverLitRn -> Bool
ol_rebindable = Bool
rebindable
                                                 , ol_from_fun :: OverLitRn -> LIdP (GhcPass 'Renamed)
ol_from_fun = L SrcSpanAnnN
loc Name
from_name } })
  = -- Desugar "3" to (fromInteger (3 :: Integer))
    --   where fromInteger is gotten by looking up from_name, and
    --   the (3 :: Integer) is returned by mkOverLit
    -- Ditto the string literal "foo" to (fromString ("foo" :: String))
    do { hs_lit <- OverLitVal -> TcM (HsLit GhcTc)
forall (p :: Pass). OverLitVal -> TcM (HsLit (GhcPass p))
mkOverLit OverLitVal
val
       ; from_id <- tcLookupId from_name
       ; (wrap1, from_ty) <- topInstantiate (LiteralOrigin lit) (idType from_id)
       ; let
           thing    = Name -> TypedThing
NameThing Name
from_name
           mb_thing = TypedThing -> Maybe TypedThing
forall a. a -> Maybe a
Just TypedThing
thing
           herald   = TypedThing -> HsExpr GhcTc -> ExpectedFunTyOrigin
forall (p :: Pass).
Outputable (HsExpr (GhcPass p)) =>
TypedThing -> HsExpr (GhcPass p) -> ExpectedFunTyOrigin
ExpectedFunTyArg TypedThing
thing (XLitE GhcTc -> HsLit GhcTc -> HsExpr GhcTc
forall p. XLitE p -> HsLit p -> HsExpr p
HsLit XLitE GhcTc
NoExtField
noExtField HsLit GhcTc
hs_lit)
       ; (wrap2, sarg_ty, res_ty) <- matchActualFunTy herald mb_thing (1, from_ty) from_ty

       ; co <- unifyType mb_thing (hsLitType hs_lit) (scaledThing sarg_ty)
       -- See Note [Source locations for implicit function calls] in GHC.Iface.Ext.Ast
       ; let lit_expr = SrcSpanAnnA
-> HsExpr GhcTc -> GenLocated SrcSpanAnnA (HsExpr GhcTc)
forall l e. l -> e -> GenLocated l e
L (SrcSpanAnnN -> SrcSpanAnnA
forall a b. (HasLoc a, HasAnnotation b) => a -> b
l2l SrcSpanAnnN
loc) (HsExpr GhcTc -> GenLocated SrcSpanAnnA (HsExpr GhcTc))
-> HsExpr GhcTc -> GenLocated SrcSpanAnnA (HsExpr GhcTc)
forall a b. (a -> b) -> a -> b
$ Coercion -> HsExpr GhcTc -> HsExpr GhcTc
mkHsWrapCo Coercion
co (HsExpr GhcTc -> HsExpr GhcTc) -> HsExpr GhcTc -> HsExpr GhcTc
forall a b. (a -> b) -> a -> b
$
                        XLitE GhcTc -> HsLit GhcTc -> HsExpr GhcTc
forall p. XLitE p -> HsLit p -> HsExpr p
HsLit XLitE GhcTc
NoExtField
noExtField HsLit GhcTc
hs_lit
             from_expr = HsWrapper -> HsExpr GhcTc -> HsExpr GhcTc
mkHsWrap (HsWrapper
wrap2 HsWrapper -> HsWrapper -> HsWrapper
<.> HsWrapper
wrap1) (HsExpr GhcTc -> HsExpr GhcTc) -> HsExpr GhcTc -> HsExpr GhcTc
forall a b. (a -> b) -> a -> b
$
                         XVar GhcTc -> LIdP GhcTc -> HsExpr GhcTc
forall p. XVar p -> LIdP p -> HsExpr p
HsVar XVar GhcTc
NoExtField
noExtField (SrcSpanAnnN -> Var -> GenLocated SrcSpanAnnN Var
forall l e. l -> e -> GenLocated l e
L SrcSpanAnnN
loc Var
from_id)
             witness = XApp GhcTc -> LHsExpr GhcTc -> LHsExpr GhcTc -> HsExpr GhcTc
forall p. XApp p -> LHsExpr p -> LHsExpr p -> HsExpr p
HsApp XApp GhcTc
NoExtField
noExtField (SrcSpanAnnA
-> HsExpr GhcTc -> GenLocated SrcSpanAnnA (HsExpr GhcTc)
forall l e. l -> e -> GenLocated l e
L (SrcSpanAnnN -> SrcSpanAnnA
forall a b. (HasLoc a, HasAnnotation b) => a -> b
l2l SrcSpanAnnN
loc) HsExpr GhcTc
from_expr) LHsExpr GhcTc
GenLocated SrcSpanAnnA (HsExpr GhcTc)
lit_expr
             lit' = HsOverLit (GhcPass 'Renamed)
lit { ol_ext = OverLitTc { ol_rebindable = rebindable
                                             , ol_witness = witness
                                             , ol_type = res_ty } }
       ; return (HsOverLit noExtField lit', res_ty) }

{- *********************************************************************
*                                                                      *
                 tcInferId, tcCheckId
*                                                                      *
********************************************************************* -}

tcCheckId :: Name -> ExpRhoType -> TcM (HsExpr GhcTc)
tcCheckId :: Name -> ExpRhoType -> TcM (HsExpr GhcTc)
tcCheckId Name
name ExpRhoType
res_ty
  = do { (expr, actual_res_ty) <- Name -> TcM (HsExpr GhcTc, TcSigmaType)
tcInferId Name
name
       ; traceTc "tcCheckId" (vcat [ppr name, ppr actual_res_ty, ppr res_ty])
       ; addFunResCtxt rn_fun [] actual_res_ty res_ty $
         tcWrapResultO (OccurrenceOf name) rn_fun expr actual_res_ty res_ty }
  where
    rn_fun :: HsExpr (GhcPass 'Renamed)
rn_fun = XVar (GhcPass 'Renamed)
-> LIdP (GhcPass 'Renamed) -> HsExpr (GhcPass 'Renamed)
forall p. XVar p -> LIdP p -> HsExpr p
HsVar XVar (GhcPass 'Renamed)
NoExtField
noExtField (Name -> GenLocated SrcSpanAnnN Name
forall e a. HasAnnotation e => a -> GenLocated e a
noLocA Name
name)

------------------------
tcInferId :: Name -> TcM (HsExpr GhcTc, TcSigmaType)
-- Look up an occurrence of an Id
-- Do not instantiate its type
tcInferId :: Name -> TcM (HsExpr GhcTc, TcSigmaType)
tcInferId Name
id_name
  | Name
id_name Name -> Unique -> Bool
forall a. Uniquable a => a -> Unique -> Bool
`hasKey` Unique
assertIdKey
  = do { dflags <- IOEnv (Env TcGblEnv TcLclEnv) DynFlags
forall (m :: * -> *). HasDynFlags m => m DynFlags
getDynFlags
       ; if gopt Opt_IgnoreAsserts dflags
         then tc_infer_id id_name
         else tc_infer_assert id_name }

  | Bool
otherwise
  = do { (expr, ty) <- Name -> TcM (HsExpr GhcTc, TcSigmaType)
tc_infer_id Name
id_name
       ; traceTc "tcInferId" (ppr id_name <+> dcolon <+> ppr ty)
       ; return (expr, ty) }

tc_infer_assert :: Name -> TcM (HsExpr GhcTc, TcSigmaType)
-- Deal with an occurrence of 'assert'
-- See Note [Adding the implicit parameter to 'assert']
tc_infer_assert :: Name -> TcM (HsExpr GhcTc, TcSigmaType)
tc_infer_assert Name
assert_name
  = do { assert_error_id <- Name -> TcM Var
tcLookupId Name
assertErrorName
       ; (wrap, id_rho) <- topInstantiate (OccurrenceOf assert_name)
                                          (idType assert_error_id)
       ; return (mkHsWrap wrap (HsVar noExtField (noLocA assert_error_id)), id_rho)
       }

tc_infer_id :: Name -> TcM (HsExpr GhcTc, TcSigmaType)
tc_infer_id :: Name -> TcM (HsExpr GhcTc, TcSigmaType)
tc_infer_id Name
id_name
 = do { thing <- Name -> TcM TcTyThing
tcLookup Name
id_name
      ; case thing of
             ATcId { tct_id :: TcTyThing -> Var
tct_id = Var
id }
               -> do { Var -> TcM ()
check_local_id Var
id
                     ; Var -> TcM (HsExpr GhcTc, TcSigmaType)
forall {p} {e} {m :: * -> *}.
(XVar p ~ NoExtField, IdP p ~ Var, XRec p Var ~ GenLocated e Var,
 Monad m, HasAnnotation e) =>
Var -> m (HsExpr p, TcSigmaType)
return_id Var
id }

             AGlobal (AnId Var
id) -> Var -> TcM (HsExpr GhcTc, TcSigmaType)
forall {p} {e} {m :: * -> *}.
(XVar p ~ NoExtField, IdP p ~ Var, XRec p Var ~ GenLocated e Var,
 Monad m, HasAnnotation e) =>
Var -> m (HsExpr p, TcSigmaType)
return_id Var
id
               -- A global cannot possibly be ill-staged
               -- nor does it need the 'lifting' treatment
               -- Hence no checkTh stuff here

             AGlobal (AConLike (RealDataCon DataCon
con)) -> DataCon -> TcM (HsExpr GhcTc, TcSigmaType)
tcInferDataCon DataCon
con
             AGlobal (AConLike (PatSynCon PatSyn
ps)) -> Name -> PatSyn -> TcM (HsExpr GhcTc, TcSigmaType)
tcInferPatSyn Name
id_name PatSyn
ps
             (TcTyThing -> Maybe TyCon
tcTyThingTyCon_maybe -> Just TyCon
tc) -> TyCon -> TcM (HsExpr GhcTc, TcSigmaType)
fail_tycon TyCon
tc -- TyCon or TcTyCon
             ATyVar Name
name Var
_ -> Name -> TcM (HsExpr GhcTc, TcSigmaType)
fail_tyvar Name
name

             TcTyThing
_ -> TcRnMessage -> TcM (HsExpr GhcTc, TcSigmaType)
forall a. TcRnMessage -> TcM a
failWithTc (TcRnMessage -> TcM (HsExpr GhcTc, TcSigmaType))
-> TcRnMessage -> TcM (HsExpr GhcTc, TcSigmaType)
forall a b. (a -> b) -> a -> b
$ TcTyThing -> TcRnMessage
TcRnExpectedValueId TcTyThing
thing }
  where
    fail_tycon :: TyCon -> TcM (HsExpr GhcTc, TcSigmaType)
fail_tycon TyCon
tc = do
      gre <- TcRn GlobalRdrEnv
getGlobalRdrEnv
      let nm = TyCon -> Name
tyConName TyCon
tc
          pprov = case GlobalRdrEnv -> Name -> Maybe (GlobalRdrEltX GREInfo)
forall info.
Outputable info =>
GlobalRdrEnvX info -> Name -> Maybe (GlobalRdrEltX info)
lookupGRE_Name GlobalRdrEnv
gre Name
nm of
                      Just GlobalRdrEltX GREInfo
gre -> ThLevel -> SDoc -> SDoc
nest ThLevel
2 (GlobalRdrEltX GREInfo -> SDoc
forall info. GlobalRdrEltX info -> SDoc
pprNameProvenance GlobalRdrEltX GREInfo
gre)
                      Maybe (GlobalRdrEltX GREInfo)
Nothing  -> SDoc
forall doc. IsOutput doc => doc
empty
          err | TyCon -> Bool
isClassTyCon TyCon
tc = TermLevelUseErr
ClassTE
              | Bool
otherwise       = TermLevelUseErr
TyConTE
      fail_with_msg dataName nm pprov err

    fail_tyvar :: Name -> TcM (HsExpr GhcTc, TcSigmaType)
fail_tyvar Name
nm =
      let pprov :: SDoc
pprov = ThLevel -> SDoc -> SDoc
nest ThLevel
2 (String -> SDoc
forall doc. IsLine doc => String -> doc
text String
"bound at" SDoc -> SDoc -> SDoc
forall doc. IsLine doc => doc -> doc -> doc
<+> SrcLoc -> SDoc
forall a. Outputable a => a -> SDoc
ppr (Name -> SrcLoc
forall a. NamedThing a => a -> SrcLoc
getSrcLoc Name
nm))
      in NameSpace
-> Name
-> SDoc
-> TermLevelUseErr
-> TcM (HsExpr GhcTc, TcSigmaType)
fail_with_msg NameSpace
varName Name
nm SDoc
pprov TermLevelUseErr
TyVarTE

    fail_with_msg :: NameSpace
-> Name
-> SDoc
-> TermLevelUseErr
-> TcM (HsExpr GhcTc, TcSigmaType)
fail_with_msg NameSpace
whatName Name
nm SDoc
pprov TermLevelUseErr
err = do
      (import_errs, hints) <- NameSpace
-> IOEnv (Env TcGblEnv TcLclEnv) ([ImportError], [GhcHint])
get_suggestions NameSpace
whatName
      unit_state <- hsc_units <$> getTopEnv
      let
        -- TODO: unfortunate to have to convert to SDoc here.
        -- This should go away once we refactor ErrInfo.
        hint_msg = [SDoc] -> SDoc
forall doc. IsDoc doc => [doc] -> doc
vcat ([SDoc] -> SDoc) -> [SDoc] -> SDoc
forall a b. (a -> b) -> a -> b
$ (GhcHint -> SDoc) -> [GhcHint] -> [SDoc]
forall a b. (a -> b) -> [a] -> [b]
map GhcHint -> SDoc
forall a. Outputable a => a -> SDoc
ppr [GhcHint]
hints
        import_err_msg = [SDoc] -> SDoc
forall doc. IsDoc doc => [doc] -> doc
vcat ([SDoc] -> SDoc) -> [SDoc] -> SDoc
forall a b. (a -> b) -> a -> b
$ (ImportError -> SDoc) -> [ImportError] -> [SDoc]
forall a b. (a -> b) -> [a] -> [b]
map ImportError -> SDoc
forall a. Outputable a => a -> SDoc
ppr [ImportError]
import_errs
        info = ErrInfo { errInfoContext :: SDoc
errInfoContext = SDoc
pprov, errInfoSupplementary :: SDoc
errInfoSupplementary = SDoc
import_err_msg SDoc -> SDoc -> SDoc
forall doc. IsDoc doc => doc -> doc -> doc
$$ SDoc
hint_msg }
      failWithTc $ TcRnMessageWithInfo unit_state (
              mkDetailedMessage info (TcRnIllegalTermLevelUse nm err))

    get_suggestions :: NameSpace
-> IOEnv (Env TcGblEnv TcLclEnv) ([ImportError], [GhcHint])
get_suggestions NameSpace
ns = do
      required_type_arguments <- Extension -> TcRnIf TcGblEnv TcLclEnv Bool
forall gbl lcl. Extension -> TcRnIf gbl lcl Bool
xoptM Extension
LangExt.RequiredTypeArguments
      if required_type_arguments && isVarNameSpace ns
      then return ([], [])  -- See Note [Suppress hints with RequiredTypeArguments]
      else do
        let occ = NameSpace -> FastString -> OccName
mkOccNameFS NameSpace
ns (OccName -> FastString
occNameFS (Name -> OccName
forall name. HasOccName name => name -> OccName
occName Name
id_name))
        lcl_env <- getLocalRdrEnv
        unknownNameSuggestions lcl_env WL_Anything (mkRdrUnqual occ)

    return_id :: Var -> m (HsExpr p, TcSigmaType)
return_id Var
id = (HsExpr p, TcSigmaType) -> m (HsExpr p, TcSigmaType)
forall a. a -> m a
forall (m :: * -> *) a. Monad m => a -> m a
return (XVar p -> LIdP p -> HsExpr p
forall p. XVar p -> LIdP p -> HsExpr p
HsVar XVar p
NoExtField
noExtField (Var -> GenLocated e Var
forall e a. HasAnnotation e => a -> GenLocated e a
noLocA Var
id), Var -> TcSigmaType
idType Var
id)

{- Note [Suppress hints with RequiredTypeArguments]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
When a type variable is used at the term level, GHC assumes the user might
have made a typo and suggests a term variable with a similar name.

For example, if the user writes
  f (Proxy :: Proxy nap) (Proxy :: Proxy gap) = nap (+1) [1,2,3]
then GHC will helpfully suggest `map` instead of `nap`
  • Illegal term-level use of the type variable ‘nap’
  • Perhaps use ‘map’ (imported from Prelude)

Importantly, GHC does /not/ suggest `gap`, which is in scope.
Question: How does GHC know not to suggest `gap`?  After all, the edit distance
          between `map`, `nap`, and `gap` is equally short.
Answer: GHC takes the namespace into consideration. `gap` is a `tvName`, and GHC
        would only suggest a `varName` at the term level.

In other words, the current hint infrastructure assumes that the namespace of an
entity is a reliable indicator of its level
   term-level name <=> term-level entity
   type-level name <=> type-level entity

With RequiredTypeArguments, this assumption does not hold. Consider
  bad :: forall a b -> ...
  bad nap gap = nap

This use of `nap` on the RHS is illegal because `nap` stands for a type
variable. It cannot be returned as the result of a function. At the same time,
it is bound as a `varName`, i.e. in the term-level namespace.

Unless we suppress hints, GHC gets awfully confused
    • Illegal term-level use of the variable ‘nap’
    • Perhaps use one of these:
        ‘nap’ (line 2), ‘gap’ (line 2), ‘map’ (imported from Prelude)

GHC shouldn't suggest `gap`, which is also a type variable; using it would
result in the same error. And it especially shouldn't suggest using `nap`
instead of `nap`, which is absurd.

The proper solution is to overhaul the hint system to consider what a name
stands for instead of looking at its namespace alone. This is tracked in #24231.
As a temporary measure, we avoid those potentially misleading hints by
suppressing them entirely if RequiredTypeArguments is in effect.
-}

check_local_id :: Id -> TcM ()
check_local_id :: Var -> TcM ()
check_local_id Var
id
  = do { Var -> TcM ()
checkThLocalId Var
id
       ; UsageEnv -> TcM ()
tcEmitBindingUsage (UsageEnv -> TcM ()) -> UsageEnv -> TcM ()
forall a b. (a -> b) -> a -> b
$ Var -> UsageEnv
singleUsageUE Var
id }

check_naughty :: OccName -> TcId -> TcM ()
check_naughty :: OccName -> Var -> TcM ()
check_naughty OccName
lbl Var
id
  | Var -> Bool
isNaughtyRecordSelector Var
id = TcRnMessage -> TcM ()
forall a. TcRnMessage -> TcM a
failWithTc (OccName -> TcRnMessage
TcRnRecSelectorEscapedTyVar OccName
lbl)
  | Bool
otherwise                  = () -> TcM ()
forall a. a -> IOEnv (Env TcGblEnv TcLclEnv) a
forall (m :: * -> *) a. Monad m => a -> m a
return ()

tcInferDataCon :: DataCon -> TcM (HsExpr GhcTc, TcSigmaType)
-- See Note [Typechecking data constructors]
tcInferDataCon :: DataCon -> TcM (HsExpr GhcTc, TcSigmaType)
tcInferDataCon DataCon
con
  = do { let tvbs :: [InvisTVBinder]
tvbs  = DataCon -> [InvisTVBinder]
dataConUserTyVarBinders DataCon
con
             tvs :: [Var]
tvs   = [InvisTVBinder] -> [Var]
forall tv argf. [VarBndr tv argf] -> [tv]
binderVars [InvisTVBinder]
tvbs
             theta :: [TcSigmaType]
theta = DataCon -> [TcSigmaType]
dataConOtherTheta DataCon
con
             args :: [Scaled TcSigmaType]
args  = DataCon -> [Scaled TcSigmaType]
dataConOrigArgTys DataCon
con
             res :: TcSigmaType
res   = DataCon -> TcSigmaType
dataConOrigResTy DataCon
con
             stupid_theta :: [TcSigmaType]
stupid_theta = DataCon -> [TcSigmaType]
dataConStupidTheta DataCon
con

       ; scaled_arg_tys <- (Scaled TcSigmaType
 -> IOEnv (Env TcGblEnv TcLclEnv) (Scaled TcSigmaType))
-> [Scaled TcSigmaType]
-> IOEnv (Env TcGblEnv TcLclEnv) [Scaled TcSigmaType]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
forall (m :: * -> *) a b. Monad m => (a -> m b) -> [a] -> m [b]
mapM Scaled TcSigmaType
-> IOEnv (Env TcGblEnv TcLclEnv) (Scaled TcSigmaType)
linear_to_poly [Scaled TcSigmaType]
args

       ; let full_theta  = [TcSigmaType]
stupid_theta [TcSigmaType] -> [TcSigmaType] -> [TcSigmaType]
forall a. [a] -> [a] -> [a]
++ [TcSigmaType]
theta
             all_arg_tys = (TcSigmaType -> Scaled TcSigmaType)
-> [TcSigmaType] -> [Scaled TcSigmaType]
forall a b. (a -> b) -> [a] -> [b]
map TcSigmaType -> Scaled TcSigmaType
forall a. a -> Scaled a
unrestricted [TcSigmaType]
full_theta [Scaled TcSigmaType]
-> [Scaled TcSigmaType] -> [Scaled TcSigmaType]
forall a. [a] -> [a] -> [a]
++ [Scaled TcSigmaType]
scaled_arg_tys
                -- We are building the type of the data con wrapper, so the
                -- type must precisely match the construction in
                -- GHC.Core.DataCon.dataConWrapperType.
                -- See Note [Instantiating stupid theta]
                -- in GHC.Core.DataCon.

       ; return ( XExpr (ConLikeTc (RealDataCon con) tvs all_arg_tys)
                , mkInvisForAllTys tvbs $ mkPhiTy full_theta $
                  mkScaledFunTys scaled_arg_tys res ) }
  where
    linear_to_poly :: Scaled Type -> TcM (Scaled Type)
    -- linear_to_poly implements point (3,4)
    -- of Note [Typechecking data constructors]
    linear_to_poly :: Scaled TcSigmaType
-> IOEnv (Env TcGblEnv TcLclEnv) (Scaled TcSigmaType)
linear_to_poly (Scaled TcSigmaType
OneTy TcSigmaType
ty) = do { mul_var <- TcSigmaType -> TcM TcSigmaType
newFlexiTyVarTy TcSigmaType
multiplicityTy
                                          ; return (Scaled mul_var ty) }
    linear_to_poly Scaled TcSigmaType
scaled_ty         = Scaled TcSigmaType
-> IOEnv (Env TcGblEnv TcLclEnv) (Scaled TcSigmaType)
forall a. a -> IOEnv (Env TcGblEnv TcLclEnv) a
forall (m :: * -> *) a. Monad m => a -> m a
return Scaled TcSigmaType
scaled_ty

tcInferPatSyn :: Name -> PatSyn -> TcM (HsExpr GhcTc, TcSigmaType)
tcInferPatSyn :: Name -> PatSyn -> TcM (HsExpr GhcTc, TcSigmaType)
tcInferPatSyn Name
id_name PatSyn
ps
  = case PatSyn -> Maybe (HsExpr GhcTc, TcSigmaType)
patSynBuilderOcc PatSyn
ps of
       Just (HsExpr GhcTc
expr,TcSigmaType
ty) -> (HsExpr GhcTc, TcSigmaType) -> TcM (HsExpr GhcTc, TcSigmaType)
forall a. a -> IOEnv (Env TcGblEnv TcLclEnv) a
forall (m :: * -> *) a. Monad m => a -> m a
return (HsExpr GhcTc
expr,TcSigmaType
ty)
       Maybe (HsExpr GhcTc, TcSigmaType)
Nothing        -> TcRnMessage -> TcM (HsExpr GhcTc, TcSigmaType)
forall a. TcRnMessage -> TcM a
failWithTc (Name -> TcRnMessage
nonBidirectionalErr Name
id_name)

nonBidirectionalErr :: Name -> TcRnMessage
nonBidirectionalErr :: Name -> TcRnMessage
nonBidirectionalErr = Name -> TcRnMessage
TcRnPatSynNotBidirectional

{- Note [Adding the implicit parameter to 'assert']
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The typechecker transforms (assert e1 e2) to (assertError e1 e2).
This isn't really the Right Thing because there's no way to "undo"
if you want to see the original source code in the typechecker
output.  We'll have fix this in due course, when we care more about
being able to reconstruct the exact original program.

Note [Typechecking data constructors]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
As per Note [Polymorphisation of linear fields] in
GHC.Core.Multiplicity, linear fields of data constructors get a
polymorphic multiplicity when the data constructor is used as a term:

    Just :: forall {p} a. a %p -> Maybe a

So at an occurrence of a data constructor we do the following:

1. Typechecking, in tcInferDataCon.

  a. Get the original type of the constructor, say
     K :: forall (r :: RuntimeRep) (a :: TYPE r). a %1 -> T r a
     Note the %1: it is linear

  b. We are going to return a ConLikeTc, thus:
     XExpr (ConLikeTc K [r,a] [Scaled p a])
      :: forall (r :: RuntimeRep) (a :: TYPE r). a %p -> T r a
   where 'p' is a fresh multiplicity unification variable.

   To get the returned ConLikeTc, we allocate a fresh multiplicity
   variable for each linear argument, and store the type, scaled by
   the fresh multiplicity variable in the ConLikeTc; along with
   the type of the ConLikeTc. This is done by linear_to_poly.

   If the argument is not linear (perhaps explicitly declared as
   non-linear by the user), don't bother with this.

2. Desugaring, in dsConLike.

  a. The (ConLikeTc K [r,a] [Scaled p a]) is desugared to
     (/\r (a :: TYPE r). \(x %p :: a). K @r @a x)
   which has the desired type given in the previous bullet.

   The 'p' is the multiplicity unification variable, which
   will by now have been unified to something, or defaulted in
   `GHC.Tc.Zonk.Type.commitFlexi`. So it won't just be an
   (unbound) variable.

   So a saturated application (K e), where e::Int will desugar to
     (/\r (a :: TYPE r). ..etc..)
        @LiftedRep @Int e
   and all those lambdas will beta-reduce away in the simple optimiser
   (see Wrinkle [Representation-polymorphic lambdas] below).

   But for an /unsaturated/ application, such as `map (K @LiftedRep @Int) xs`,
   beta reduction will leave (\x %Many :: Int. K x), which is the type `map`
   expects whereas if we had just plain K, with its linear type, we'd
   get a type mismatch. That's why we do this funky desugaring.

Wrinkles

  [ConLikeTc arguments]

    Note that the [TcType] argument to ConLikeTc is strictly redundant; those are
    the type variables from the dataConUserTyVarBinders of the data constructor.
    Similarly in the [Scaled TcType] field of ConLikeTc, the types come directly
    from the data constructor.  The only bit that /isn't/ redundant is the
    fresh multiplicity variables!

    So an alternative would be to define ConLikeTc like this:
        | ConLikeTc [TcType]    -- Just the multiplicity variables
    But then the desugarer would need to repeat some of the work done here.
    So for now at least ConLikeTc records this strictly-redundant info.

  [Representation-polymorphic lambdas]

    The lambda expression we produce in (4) can have representation-polymorphic
    arguments, as indeed in (/\r (a :: TYPE r). \(x %p :: a). K @r @a x),
    we have a lambda-bound variable x :: (a :: TYPE r).
    This goes against the representation polymorphism invariants given in
    Note [Representation polymorphism invariants] in GHC.Core. The trick is that
    this this lambda will always be instantiated in a way that upholds the invariants.
    This is achieved as follows:

      A. Any arguments to such lambda abstractions are guaranteed to have
         a fixed runtime representation. This is enforced in 'tcApp' by
         'matchActualFunTy'.

      B. If there are fewer arguments than there are bound term variables,
         we will ensure that the appropriate type arguments are instantiated
         concretely, such as 'r' in

         ( /\r (a :: TYPE r). \ (x %p :: a). K @r @a x) @IntRep @Int#
           :: Int# -> T IntRep Int#

         See Note [Representation-polymorphic Ids with no binding] in GHC.Tc.Gen.Head.

      C. In the output of the desugarer in (4) above, we have a representation
         polymorphic lambda, which Lint would normally reject. So for that one
         pass, we switch off Lint's representation-polymorphism checks; see
         the `lf_check_fixed_rep` flag in `LintFlags`.
-}

{-
************************************************************************
*                                                                      *
                 Template Haskell checks
*                                                                      *
************************************************************************
-}

checkThLocalId :: Id -> TcM ()
-- The renamer has already done checkWellStaged,
--   in RnSplice.checkThLocalName, so don't repeat that here.
-- Here we just add constraints for cross-stage lifting
checkThLocalId :: Var -> TcM ()
checkThLocalId Var
id
  = do  { mb_local_use <- Name -> TcRn (Maybe (TopLevelFlag, ThLevel, ThStage))
getStageAndBindLevel (Var -> Name
idName Var
id)
        ; case mb_local_use of
             Just (TopLevelFlag
top_lvl, ThLevel
bind_lvl, ThStage
use_stage)
                | ThStage -> ThLevel
thLevel ThStage
use_stage ThLevel -> ThLevel -> Bool
forall a. Ord a => a -> a -> Bool
> ThLevel
bind_lvl
                -> TopLevelFlag -> Var -> ThStage -> TcM ()
checkCrossStageLifting TopLevelFlag
top_lvl Var
id ThStage
use_stage
             Maybe (TopLevelFlag, ThLevel, ThStage)
_  -> () -> TcM ()
forall a. a -> IOEnv (Env TcGblEnv TcLclEnv) a
forall (m :: * -> *) a. Monad m => a -> m a
return ()   -- Not a locally-bound thing, or
                               -- no cross-stage link
    }

--------------------------------------
checkCrossStageLifting :: TopLevelFlag -> Id -> ThStage -> TcM ()
-- If we are inside typed brackets, and (use_lvl > bind_lvl)
-- we must check whether there's a cross-stage lift to do
-- Examples   \x -> [|| x ||]
--            [|| map ||]
--
-- This is similar to checkCrossStageLifting in GHC.Rename.Splice, but
-- this code is applied to *typed* brackets.

checkCrossStageLifting :: TopLevelFlag -> Var -> ThStage -> TcM ()
checkCrossStageLifting TopLevelFlag
top_lvl Var
id (Brack ThStage
_ (TcPending TcRef [PendingTcSplice]
ps_var TcRef WantedConstraints
lie_var QuoteWrapper
q))
  | TopLevelFlag -> Bool
isTopLevel TopLevelFlag
top_lvl
  = Bool -> TcM () -> TcM ()
forall (f :: * -> *). Applicative f => Bool -> f () -> f ()
when (Name -> Bool
isExternalName Name
id_name) (Name -> TcM ()
keepAlive Name
id_name)
    -- See Note [Keeping things alive for Template Haskell] in GHC.Rename.Splice

  | Bool
otherwise
  =     -- Nested identifiers, such as 'x' in
        -- E.g. \x -> [|| h x ||]
        -- We must behave as if the reference to x was
        --      h $(lift x)
        -- We use 'x' itself as the splice proxy, used by
        -- the desugarer to stitch it all back together.
        -- If 'x' occurs many times we may get many identical
        -- bindings of the same splice proxy, but that doesn't
        -- matter, although it's a mite untidy.
    do  { let id_ty :: TcSigmaType
id_ty = Var -> TcSigmaType
idType Var
id
        ; Bool -> TcRnMessage -> TcM ()
checkTc (TcSigmaType -> Bool
isTauTy TcSigmaType
id_ty) (TcRnMessage -> TcM ()) -> TcRnMessage -> TcM ()
forall a b. (a -> b) -> a -> b
$
          THError -> TcRnMessage
TcRnTHError (THError -> TcRnMessage) -> THError -> TcRnMessage
forall a b. (a -> b) -> a -> b
$ TypedTHError -> THError
TypedTHError (TypedTHError -> THError) -> TypedTHError -> THError
forall a b. (a -> b) -> a -> b
$ Var -> TypedTHError
SplicePolymorphicLocalVar Var
id
               -- If x is polymorphic, its occurrence sites might
               -- have different instantiations, so we can't use plain
               -- 'x' as the splice proxy name.  I don't know how to
               -- solve this, and it's probably unimportant, so I'm
               -- just going to flag an error for now

        ; lift <- if TcSigmaType -> Bool
isStringTy TcSigmaType
id_ty then
                     do { sid <- Name -> TcM Var
tcLookupId Name
GHC.Builtin.Names.TH.liftStringName
                                     -- See Note [Lifting strings]
                        ; return (HsVar noExtField (noLocA sid)) }
                  else
                     TcRef WantedConstraints -> TcM (HsExpr GhcTc) -> TcM (HsExpr GhcTc)
forall a. TcRef WantedConstraints -> TcM a -> TcM a
setConstraintVar TcRef WantedConstraints
lie_var   (TcM (HsExpr GhcTc) -> TcM (HsExpr GhcTc))
-> TcM (HsExpr GhcTc) -> TcM (HsExpr GhcTc)
forall a b. (a -> b) -> a -> b
$
                          -- Put the 'lift' constraint into the right LIE
                     CtOrigin -> Name -> [TcSigmaType] -> TcM (HsExpr GhcTc)
newMethodFromName (Name -> CtOrigin
OccurrenceOf Name
id_name)
                                       Name
GHC.Builtin.Names.TH.liftName
                                       [HasDebugCallStack => TcSigmaType -> TcSigmaType
TcSigmaType -> TcSigmaType
getRuntimeRep TcSigmaType
id_ty, TcSigmaType
id_ty]

                   -- Warning for implicit lift (#17804)
        ; addDetailedDiagnostic (TcRnImplicitLift $ idName id)

                   -- Update the pending splices
        ; ps <- readMutVar ps_var
        ; let pending_splice = Name -> LHsExpr GhcTc -> PendingTcSplice
PendingTcSplice Name
id_name
                                 (LHsExpr GhcTc -> LHsExpr GhcTc -> LHsExpr GhcTc
forall (id :: Pass).
IsPass id =>
LHsExpr (GhcPass id)
-> LHsExpr (GhcPass id) -> LHsExpr (GhcPass id)
nlHsApp (HsWrapper -> LHsExpr GhcTc -> LHsExpr GhcTc
mkLHsWrap (QuoteWrapper -> HsWrapper
applyQuoteWrapper QuoteWrapper
q) (HsExpr GhcTc -> GenLocated SrcSpanAnnA (HsExpr GhcTc)
forall e a. HasAnnotation e => a -> GenLocated e a
noLocA HsExpr GhcTc
lift))
                                          (IdP GhcTc -> LHsExpr GhcTc
forall (p :: Pass) a.
IsSrcSpanAnn p a =>
IdP (GhcPass p) -> LHsExpr (GhcPass p)
nlHsVar IdP GhcTc
Var
id))
        ; writeMutVar ps_var (pending_splice : ps)

        ; return () }
  where
    id_name :: Name
id_name = Var -> Name
idName Var
id

checkCrossStageLifting TopLevelFlag
_ Var
_ ThStage
_ = () -> TcM ()
forall a. a -> IOEnv (Env TcGblEnv TcLclEnv) a
forall (m :: * -> *) a. Monad m => a -> m a
return ()

{-
Note [Lifting strings]
~~~~~~~~~~~~~~~~~~~~~~
If we see $(... [| s |] ...) where s::String, we don't want to
generate a mass of Cons (CharL 'x') (Cons (CharL 'y') ...)) etc.
So this conditional short-circuits the lifting mechanism to generate
(liftString "xy") in that case.  I didn't want to use overlapping instances
for the Lift class in TH.Syntax, because that can lead to overlapping-instance
errors in a polymorphic situation.

If this check fails (which isn't impossible) we get another chance; see
Note [Converting strings] in Convert.hs

Note [Local record selectors]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Record selectors for TyCons in this module are ordinary local bindings,
which show up as ATcIds rather than AGlobals.  So we need to check for
naughtiness in both branches.  c.f. GHC.Tc.TyCl.Utils.mkRecSelBinds.
-}


{- *********************************************************************
*                                                                      *
         Error reporting for function result mis-matches
*                                                                      *
********************************************************************* -}

addFunResCtxt :: HsExpr GhcRn -> [HsExprArg 'TcpRn]
              -> TcType -> ExpRhoType
              -> TcM a -> TcM a
-- When we have a mis-match in the return type of a function
-- try to give a helpful message about too many/few arguments
-- But not in generated code, where we don't want
-- to mention internal (rebindable syntax) function names
addFunResCtxt :: forall a.
HsExpr (GhcPass 'Renamed)
-> [HsExprArg 'TcpRn]
-> TcSigmaType
-> ExpRhoType
-> TcM a
-> TcM a
addFunResCtxt HsExpr (GhcPass 'Renamed)
fun [HsExprArg 'TcpRn]
args TcSigmaType
fun_res_ty ExpRhoType
env_ty TcM a
thing_inside
  = do { env_tv  <- TcSigmaType -> TcM TcSigmaType
newFlexiTyVarTy TcSigmaType
liftedTypeKind
       ; dumping <- doptM Opt_D_dump_tc_trace
       ; addLandmarkErrCtxtM (\TidyEnv
env -> (TidyEnv
env, ) (SDoc -> (TidyEnv, SDoc)) -> ZonkM SDoc -> ZonkM (TidyEnv, SDoc)
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
<$> Bool -> TcSigmaType -> ZonkM SDoc
mk_msg Bool
dumping TcSigmaType
env_tv) thing_inside }
      -- NB: use a landmark error context, so that an empty context
      -- doesn't suppress some more useful context
  where
    mk_msg :: Bool -> TcSigmaType -> ZonkM SDoc
mk_msg Bool
dumping TcSigmaType
env_tv
      = do { mb_env_ty <- ExpRhoType -> ZonkM (Maybe TcSigmaType)
forall (m :: * -> *).
MonadIO m =>
ExpRhoType -> m (Maybe TcSigmaType)
readExpType_maybe ExpRhoType
env_ty
                     -- by the time the message is rendered, the ExpType
                     -- will be filled in (except if we're debugging)
           ; fun_res' <- zonkTcType fun_res_ty
           ; env'     <- case mb_env_ty of
                           Just TcSigmaType
env_ty -> TcSigmaType -> ZonkM TcSigmaType
zonkTcType TcSigmaType
env_ty
                           Maybe TcSigmaType
Nothing     -> do { Bool -> ZonkM ()
forall (m :: * -> *). (HasCallStack, Applicative m) => Bool -> m ()
massert Bool
dumping; TcSigmaType -> ZonkM TcSigmaType
forall a. a -> ZonkM a
forall (m :: * -> *) a. Monad m => a -> m a
return TcSigmaType
env_tv }
           ; let -- See Note [Splitting nested sigma types in mismatched
                 --           function types]
                 (_, _, fun_tau) = tcSplitNestedSigmaTys fun_res'
                 (_, _, env_tau) = tcSplitNestedSigmaTys env'
                     -- env_ty is an ExpRhoTy, but with simple subsumption it
                     -- is not deeply skolemised, so still use tcSplitNestedSigmaTys
                 (args_fun, res_fun) = tcSplitFunTys fun_tau
                 (args_env, res_env) = tcSplitFunTys env_tau
                 n_fun = [Scaled TcSigmaType] -> ThLevel
forall a. [a] -> ThLevel
forall (t :: * -> *) a. Foldable t => t a -> ThLevel
length [Scaled TcSigmaType]
args_fun
                 n_env = [Scaled TcSigmaType] -> ThLevel
forall a. [a] -> ThLevel
forall (t :: * -> *) a. Foldable t => t a -> ThLevel
length [Scaled TcSigmaType]
args_env
                 info  | -- Check for too few args
                         --  fun_tau = a -> b, res_tau = Int
                         ThLevel
n_fun ThLevel -> ThLevel -> Bool
forall a. Ord a => a -> a -> Bool
> ThLevel
n_env
                       , TcSigmaType -> Bool
not_fun TcSigmaType
res_env
                       = String -> SDoc
forall doc. IsLine doc => String -> doc
text String
"Probable cause:" SDoc -> SDoc -> SDoc
forall doc. IsLine doc => doc -> doc -> doc
<+> SDoc -> SDoc
quotes (HsExpr (GhcPass 'Renamed) -> SDoc
forall a. Outputable a => a -> SDoc
ppr HsExpr (GhcPass 'Renamed)
fun)
                         SDoc -> SDoc -> SDoc
forall doc. IsLine doc => doc -> doc -> doc
<+> String -> SDoc
forall doc. IsLine doc => String -> doc
text String
"is applied to too few arguments"

                       | -- Check for too many args
                         -- fun_tau = a -> Int,   res_tau = a -> b -> c -> d
                         -- The final guard suppresses the message when there
                         -- aren't enough args to drop; eg. the call is (f e1)
                         ThLevel
n_fun ThLevel -> ThLevel -> Bool
forall a. Ord a => a -> a -> Bool
< ThLevel
n_env
                       , TcSigmaType -> Bool
not_fun TcSigmaType
res_fun
                       , (ThLevel
n_fun ThLevel -> ThLevel -> ThLevel
forall a. Num a => a -> a -> a
+ (HsExprArg 'TcpRn -> Bool) -> [HsExprArg 'TcpRn] -> ThLevel
forall a. (a -> Bool) -> [a] -> ThLevel
count HsExprArg 'TcpRn -> Bool
forall (id :: TcPass). HsExprArg id -> Bool
isValArg [HsExprArg 'TcpRn]
args) ThLevel -> ThLevel -> Bool
forall a. Ord a => a -> a -> Bool
>= ThLevel
n_env
                          -- Never suggest that a naked variable is
                                           -- applied to too many args!
                       = String -> SDoc
forall doc. IsLine doc => String -> doc
text String
"Possible cause:" SDoc -> SDoc -> SDoc
forall doc. IsLine doc => doc -> doc -> doc
<+> SDoc -> SDoc
quotes (HsExpr (GhcPass 'Renamed) -> SDoc
forall a. Outputable a => a -> SDoc
ppr HsExpr (GhcPass 'Renamed)
fun)
                         SDoc -> SDoc -> SDoc
forall doc. IsLine doc => doc -> doc -> doc
<+> String -> SDoc
forall doc. IsLine doc => String -> doc
text String
"is applied to too many arguments"

                       | Bool
otherwise
                       = SDoc
forall doc. IsOutput doc => doc
Outputable.empty

           ; return info }

    not_fun :: TcSigmaType -> Bool
not_fun TcSigmaType
ty   -- ty is definitely not an arrow type,
                 -- and cannot conceivably become one
      = case HasCallStack => TcSigmaType -> Maybe (TyCon, [TcSigmaType])
TcSigmaType -> Maybe (TyCon, [TcSigmaType])
tcSplitTyConApp_maybe TcSigmaType
ty of
          Just (TyCon
tc, [TcSigmaType]
_) -> TyCon -> Bool
isAlgTyCon TyCon
tc
          Maybe (TyCon, [TcSigmaType])
Nothing      -> Bool
False

{-
Note [Splitting nested sigma types in mismatched function types]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
When one applies a function to too few arguments, GHC tries to determine this
fact if possible so that it may give a helpful error message. It accomplishes
this by checking if the type of the applied function has more argument types
than supplied arguments.

Previously, GHC computed the number of argument types through tcSplitSigmaTy.
This is incorrect in the face of nested foralls, however!
This caused Ticket #13311, for instance:

  f :: forall a. (Monoid a) => Int -> forall b. (Monoid b) => Maybe a -> Maybe b

If one uses `f` like so:

  do { f; putChar 'a' }

Then tcSplitSigmaTy will decompose the type of `f` into:

  Tyvars: [a]
  Context: (Monoid a)
  Argument types: []
  Return type: Int -> forall b. Monoid b => Maybe a -> Maybe b

That is, it will conclude that there are *no* argument types, and since `f`
was given no arguments, it won't print a helpful error message. On the other
hand, tcSplitNestedSigmaTys correctly decomposes `f`'s type down to:

  Tyvars: [a, b]
  Context: (Monoid a, Monoid b)
  Argument types: [Int, Maybe a]
  Return type: Maybe b

So now GHC recognizes that `f` has one more argument type than it was actually
provided.

Notice that tcSplitNestedSigmaTys looks through function arrows too, regardless
of simple/deep subsumption.  Here we are concerned only whether there is a
mis-match in the number of value arguments.
-}


{- *********************************************************************
*                                                                      *
             Misc utility functions
*                                                                      *
********************************************************************* -}

addStmtCtxt :: ExprStmt GhcRn -> TcRn a -> TcRn a
addStmtCtxt :: forall a. ExprStmt (GhcPass 'Renamed) -> TcRn a -> TcRn a
addStmtCtxt ExprStmt (GhcPass 'Renamed)
stmt TcRn a
thing_inside
  = do let err_doc :: SDoc
err_doc = HsStmtContextRn -> ExprStmt (GhcPass 'Renamed) -> SDoc
pprStmtInCtxt (HsDoFlavour -> HsStmtContext (GenLocated SrcSpanAnnN Name)
forall fn. HsDoFlavour -> HsStmtContext fn
HsDoStmt (Maybe ModuleName -> HsDoFlavour
DoExpr Maybe ModuleName
forall a. Maybe a
Nothing)) ExprStmt (GhcPass 'Renamed)
stmt
       SDoc -> TcRn a -> TcRn a
forall a. SDoc -> TcM a -> TcM a
addErrCtxt SDoc
err_doc TcRn a
thing_inside
  where
    pprStmtInCtxt :: HsStmtContextRn -> StmtLR GhcRn GhcRn (LHsExpr GhcRn) -> SDoc
    pprStmtInCtxt :: HsStmtContextRn -> ExprStmt (GhcPass 'Renamed) -> SDoc
pprStmtInCtxt HsStmtContextRn
ctxt ExprStmt (GhcPass 'Renamed)
stmt
      = [SDoc] -> SDoc
forall doc. IsDoc doc => [doc] -> doc
vcat [ SDoc -> ThLevel -> SDoc -> SDoc
hang (String -> SDoc
forall doc. IsLine doc => String -> doc
text String
"In a stmt of"
                     SDoc -> SDoc -> SDoc
forall doc. IsLine doc => doc -> doc -> doc
<+> HsStmtContext (GenLocated SrcSpanAnnN Name) -> SDoc
forall fn. Outputable fn => HsStmtContext fn -> SDoc
pprAStmtContext HsStmtContextRn
HsStmtContext (GenLocated SrcSpanAnnN Name)
ctxt SDoc -> SDoc -> SDoc
forall doc. IsLine doc => doc -> doc -> doc
<> SDoc
forall doc. IsLine doc => doc
colon) ThLevel
2 (StmtLR
  (GhcPass 'Renamed)
  (GhcPass 'Renamed)
  (GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Renamed)))
-> SDoc
forall (idL :: Pass) (idR :: Pass) body.
(OutputableBndrId idL, OutputableBndrId idR,
 Anno (StmtLR (GhcPass idL) (GhcPass idR) body) ~ SrcSpanAnnA,
 Outputable body) =>
StmtLR (GhcPass idL) (GhcPass idR) body -> SDoc
pprStmt ExprStmt (GhcPass 'Renamed)
StmtLR
  (GhcPass 'Renamed)
  (GhcPass 'Renamed)
  (GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Renamed)))
stmt)
             ]

addExprCtxt :: HsExpr GhcRn -> TcRn a -> TcRn a
addExprCtxt :: forall a. HsExpr (GhcPass 'Renamed) -> TcRn a -> TcRn a
addExprCtxt HsExpr (GhcPass 'Renamed)
e TcRn a
thing_inside
  = case HsExpr (GhcPass 'Renamed)
e of
      HsUnboundVar {} -> TcRn a
thing_inside
      HsExpr (GhcPass 'Renamed)
_ -> SDoc -> TcRn a -> TcRn a
forall a. SDoc -> TcM a -> TcM a
addErrCtxt (HsExpr (GhcPass 'Renamed) -> SDoc
exprCtxt HsExpr (GhcPass 'Renamed)
e) TcRn a
thing_inside
   -- The HsUnboundVar special case addresses situations like
   --    f x = _
   -- when we don't want to say "In the expression: _",
   -- because it is mentioned in the error message itself

exprCtxt :: HsExpr GhcRn -> SDoc
exprCtxt :: HsExpr (GhcPass 'Renamed) -> SDoc
exprCtxt HsExpr (GhcPass 'Renamed)
expr = SDoc -> ThLevel -> SDoc -> SDoc
hang (String -> SDoc
forall doc. IsLine doc => String -> doc
text String
"In the expression:") ThLevel
2 (HsExpr (GhcPass 'Renamed) -> SDoc
forall a. Outputable a => a -> SDoc
ppr (HsExpr (GhcPass 'Renamed) -> HsExpr (GhcPass 'Renamed)
forall (p :: Pass). HsExpr (GhcPass p) -> HsExpr (GhcPass p)
stripParensHsExpr HsExpr (GhcPass 'Renamed)
expr))