Commit 1e041b73 authored by Committed by Ben Gamari
Refactor treatment of wildcards
This patch began as a modest refactoring of HsType and friends, to clarify and tidy up exactly where quantification takes place in types. Although initially driven by making the implementation of wildcards more tidy (and fixing a number of bugs), I gradually got drawn into a pretty big process, which I've been doing on and off for quite a long time. There is one compiler performance regression as a result of all this, in perf/compiler/T3064. I still need to look into that. * The principal driving change is described in Note [HsType binders] in HsType. Well worth reading! * Those data type changes drive almost everything else. In particular we now statically know where (a) implicit quantification only (LHsSigType), e.g. in instance declaratios and SPECIALISE signatures (b) implicit quantification and wildcards (LHsSigWcType) can appear, e.g. in function type signatures * As part of this change, HsForAllTy is (a) simplified (no wildcards) and (b) split into HsForAllTy and HsQualTy. The two contructors appear when and only when the correponding user-level construct appears. Again see Note [HsType binders]. HsExplicitFlag disappears altogether. * Other simplifications - ExprWithTySig no longer needs an ExprWithTySigOut variant - TypeSig no longer needs a PostRn name [name] field for wildcards - PatSynSig records a LHsSigType rather than the decomposed pieces - The mysterious 'GenericSig' is now 'ClassOpSig' * Renamed LHsTyVarBndrs to LHsQTyVars * There are some uninteresting knock-on changes in Haddock, because of the HsSyn changes I also did a bunch of loosely-related changes: * We already had type synonyms CoercionN/CoercionR for nominal and representational coercions. I've added similar treatment for TcCoercionN/TcCoercionR mkWpCastN/mkWpCastN All just type synonyms but jolly useful. * I record-ised ForeignImport and ForeignExport * I improved the (poor) fix to Trac #10896, by making TcTyClsDecls.checkValidTyCl recover from errors, but adding a harmless, abstract TyCon to the envt if so. * I did some significant refactoring in RnEnv.lookupSubBndrOcc, for reasons that I have (embarrassingly) now totally forgotten. It had to do with something to do with import and export Updates haddock submodule.
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