Language.Haskell.Syntax.Extension

A placeholder type for TTG extension points that are not currently used to represent any particular value.

This should not be confused with DataConCantHappen, which are found in unused extension constructors and therefore should never be inhabited. In contrast, NoExtField is used in extension points (e.g., as the field of some constructor), so it must have an inhabitant to construct AST passes that manipulate fields with that extension point as their type.

Used when constructing a term with an unused extension point.

Eliminate a DataConCantHappen. See Note [Constructor cannot occur].

GHC's L prefixed variants wrap their vanilla variant in this type family, to add SrcLoc info via Located. Other passes than GhcPass not interested in location information can define this as type instance XRec NoLocated a = a. See Note [XRec and SrcSpans in the AST]

We can strip off the XRec to access the underlying data. See Note [XRec and SrcSpans in the AST]

We can map over the underlying type contained in an XRec while preserving the annotation as is.

The trivial wrapper that carries no additional information See Note [XRec and SrcSpans in the AST]

Maps the "normal" id type for a given pass

Like IdP, except it keeps track of the user-written module qualification, if any.

See Note [IdOcc].