ghc-7.0.1: The GHC API




GHC uses several kinds of name internally:

  • OccName.OccName: see OccName
  • RdrName.RdrName: see RdrName
  • Name: see Name
  • Id.Id: see Id
  • Var is a synonym for the Id.Id type but it may additionally potentially contain type variables, which have a Kind rather than a Type and only contain some extra details during typechecking. These Var names may either be global or local, see Var

Global Ids and Vars are those that are imported or correspond to a data constructor, primitive operation, or record selectors. Local Ids and Vars are those bound within an expression (e.g. by a lambda) or at the top level of the module being compiled.


The main data type and synonyms

data Var Source

Essentially a typed Name, that may also contain some additional information about the Var and it's use sites.

type Id = VarSource

type EvId = IdSource

Taking Vars apart

Modifying Vars

Constructing, taking apart, modifying Ids

mkExportedLocalVar :: IdDetails -> Name -> Type -> IdInfo -> IdSource

Exported Vars will not be removed as dead code

globaliseId :: Id -> IdSource

If it's a local, make it global

setIdExported :: Id -> IdSource

Exports the given local Id. Can also be called on global Ids, such as data constructors and class operations, which are born as global Ids and automatically exported

setIdNotExported :: Id -> IdSource

We can only do this to LocalIds


isLocalVar :: Var -> BoolSource

isLocalVar returns True for type variables as well as local Ids These are the variables that we need to pay attention to when finding free variables, or doing dependency analysis.

isExportedId :: Var -> BoolSource

isExportedIdVar means "don't throw this away"

mustHaveLocalBinding :: Var -> BoolSource

mustHaveLocalBinding returns True of Ids and TyVars that must have a binding in this module. The converse is not quite right: there are some global Ids that must have bindings, such as record selectors. But that doesn't matter, because it's only used for assertions

Constructing TyVars

mkWildCoVar :: Kind -> TyVarSource

Create a type variable that is never referred to, so its unique doesn't matter

Taking TyVars apart

Modifying TyVars

Constructing CoVars

Taking CoVars apart

Modifying CoVars