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Simon Peyton Jones authored
The situation was pretty dire. The way in which data constructors were handled, notably the mapping between their *source* argument types and their *representation* argument types (after seq'ing and unpacking) was scattered in three different places, and hard to keep in sync. Now it is all in one place: * The dcRep field of a DataCon gives its representation, specified by a DataConRep * As well as having the wrapper, the DataConRep has a "boxer" of type DataConBoxer (defined in MkId for loopy reasons). The boxer used at a pattern match to reconstruct the source-level arguments from the rep-level bindings in the pattern match. * The unboxing in the wrapper and the boxing in the boxer are dual, and are now constructed together, by MkId.mkDataConRep. This is the key function of this change. * All the computeBoxingStrategy code in TcTyClsDcls disappears. Much nicer. There is a little bit of refactoring left to do; the strange deepSplitProductType functions are now called only in WwLib, so I moved them there, and I think they could be tidied up further.
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