wiki:TypeFunctionsIface

Version 5 (modified by chak, 8 years ago) (diff)

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Type Functions: Interface

Representation of family instances

The IfaceSyn.IfaceData variant of IfaceDecl contains a new ifFamInst :: Maybe IfaceFamInst field that is distinguishes ordinary data/newtype declarations from family instances. In the latter case, a IfaceFamInst value gives the instances head of the family instance. Moreover, all family instance heads of a module are collected in the new mi_fam_insts :: [(IfaceFamInst, IfaceDecl)] field of HscTypes.ModIface. We don't include the IfaceDecl component into IfaceFamInst, as we otherwise would get a cyclic dependency - the IfaceDecl must include IfaceFamInst, so that we can generate the correct wrapper signature for family data constructors during type checking the interface declarations.

The serialised interface description does not explicitly contain the value of mi_fam_insts. Instead, the get method of Binary ModIface (in BinIface) constructs the value on the fly.