Note [How tuples work]

 ~~~~~~~~~~~~~~~~~~~~~~

 * There are three families of tuple TyCons and corresponding

     data TupleSort = BoxedTuple | UnboxedTuple | ConstraintTuple

 * All three families are AlgTyCons, whose AlgTyConRhs is TupleTyCon

       stores them in the context field of types like HsQualTy.

 * In quite a lot of places things are restricted just to

   E.g. tupleTyCon has a Boxity argument

 * When looking up an OccName in the original-name cache

 GHC has severals types that represent various aspects of data format.

 These include:

    pipeline. This is a pair of a CmmCat and a Width.

  * 'Format.Format': The data format representation used by much of the backend.

 -}

 -- It looks very like the old MachRep, but it's now of purely local

 The rest of this note will document exactly how the first pass generates the map from labels to

 estimated source positions. The algorithms are different depending on whether tables-next-to-code

 (containing a `SourceNote`) that is near what we estimate to be the label of a return stack frame.

 With tables-next-to-code

 Please refer to the paper "Hoopl: A Modular, Reusable Library for Dataflow Analysis and Transformation"

 for a detailed explanation.

 (`CmmNode O C`, `O` means open, `C` closed). In other words, they are always at the end of a block.

 So, given a `CmmGraph`:

     beginning).

     found to it's payload as an `IpeSourceLocation`. (There are other `Tickish` constructors like

     `ProfNote` or `HpcTick`, these are ignored.)

 (SF4) The desugarer replaces a nested expression (static e) with a top-level

   binding for an application of the function 'makeStatic' (defined in module

    s = /\abc. makeStatic location e

    f x = ...(fromStaticPtr s)...

   - It is only called when applying an instance decl,

     in GHC.Tc.Solver.Dict.tryInstances

     used to solve the constraint.  In particular

       * LocalInstance identifies quantified constraints

       * BuiltinEqInstance identifies the strange built-in

     eg a wanted cannot rewrite a given)

   * CEqCan equalities: see Note [inert_eqs: the inert equalities]

 Note [inert_eqs: the inert equalities]

 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

 constructor wrappers].

 For further reading, see:

   * Note [Lone variables] in GHC.Core.Unfold

   * Note [exprIsConApp_maybe on data constructors with wrappers]

     in GHC.Core.SimpleOpt

 VarBndr is polymorphic in both var and visibility fields.

 Currently there are nine different uses of 'VarBndr':

   Binder of a forall-type; see ForAllTy in GHC.Core.TyCo.Rep

   Subset of ForAllTyBinder when we are sure the binder is a TyVar

   Specialised form of TyVarBinder, when ForAllTyFlag = Invisible s

   See GHC.Core.Type.splitForAllInvisTVBinders

   Specialised form of TyVarBinder, when ForAllTyFlag = Required

   See GHC.Core.Type.splitForAllReqTVBinders

   This one is barely used

   Binders of a TyCon; see TyCon in GHC.Core.TyCon

 -}

 data VarBndr var argf = Bndr var argf