patch applied (ghc): Make record selectors into ordinary functions

[Simon Peyton Jones]

Fri Jan  2 06:28:51 PST 2009  simonpj at microsoft.com
  * Make record selectors into ordinary functions
  
  This biggish patch addresses Trac #2670.  The main effect is to make
  record selectors into ordinary functions, whose unfoldings appear in
  interface files, in contrast to their previous existence as magic
  "implicit Ids".  This means that the usual machinery of optimisation,
  analysis, and inlining applies to them, which was failing before when
  the selector was somewhat complicated.  (Which it can be when
  strictness annotations, unboxing annotations, and GADTs are involved.)
  
  The change involves the following points
  
  * Changes in Var.lhs to the representation of Var.  Now a LocalId can
    have an IdDetails as well as a GlobalId.  In particular, the
    information that an Id is a record selector is kept in the
    IdDetails.  While compiling the current module, the record selector
    *must* be a LocalId, so that it participates properly in compilation
    (free variables etc).
  
    This led me to change the (hidden) representation of Var, so that there
    is now only one constructor for Id, not two.
  
  * The IdDetails is persisted into interface files, so that an
    importing module can see which Ids are records selectors.
  
  * In TcTyClDecls, we generate the record-selector bindings in renamed,
    but not typechecked form.  In this way, we can get the typechecker
    to add all the types and so on, which is jolly helpful especially
    when GADTs or type families are involved.  Just like derived
    instance declarations.
  
    This is the big new chunk of 180 lines of code (much of which is
    commentary).  A call to the same function, mkAuxBinds, is needed in
    TcInstDcls for associated types.
  
  * The typechecker therefore has to pin the correct IdDetails on to 
    the record selector, when it typechecks it.  There was a neat way
    to do this, by adding a new sort of signature to HsBinds.Sig, namely
    IdSig.  This contains an Id (with the correct Name, Type, and IdDetails);
    the type checker uses it as the binder for the final binding.  This
    worked out rather easily.
  
  * Record selectors are no longer "implicit ids", which entails changes to
       IfaceSyn.ifaceDeclSubBndrs
       HscTypes.implicitTyThings
       TidyPgm.getImplicitBinds
    (These three functions must agree.)
  
  * MkId.mkRecordSelectorId is deleted entirely, some 300+ lines (incl
    comments) of very error prone code.  Happy days.
  
  * A TyCon no longer contains the list of record selectors: 
    algTcSelIds is gone
  
  The renamer is unaffected, including the way that import and export of
  record selectors is handled.
  
  Other small things
  
  * IfaceSyn.ifaceDeclSubBndrs had a fragile test for whether a data
    constructor had a wrapper.  I've replaced that with an explicit flag
    in the interface file. More robust I hope.
  
  * I renamed isIdVar to isId, which touched a few otherwise-unrelated files.
  
  

    M ./compiler/basicTypes/DataCon.lhs -4 +5
    M ./compiler/basicTypes/Id.lhs -72 +45
    M ./compiler/basicTypes/IdInfo.lhs -32 +28
    M ./compiler/basicTypes/IdInfo.lhs-boot -4 +3
    M ./compiler/basicTypes/MkId.lhs -401 +85
    M ./compiler/basicTypes/Var.lhs -113 +93
    M ./compiler/coreSyn/CoreSyn.lhs -6 +6
    M ./compiler/coreSyn/CoreUnfold.lhs -2 +2
    M ./compiler/coreSyn/CoreUtils.lhs -5 +5
    M ./compiler/coreSyn/MkExternalCore.lhs -1 +1
    M ./compiler/coreSyn/PprCore.lhs -5 +7
    M ./compiler/ghci/Debugger.hs -3 +2
    M ./compiler/hsSyn/HsBinds.lhs -4 +20
    M ./compiler/iface/BinIface.hs -17 +28
    M ./compiler/iface/BuildTyCl.lhs -21 +20
    M ./compiler/iface/IfaceSyn.lhs -25 +38
    M ./compiler/iface/LoadIface.lhs -22 +1
    M ./compiler/iface/MkIface.lhs -3 +12
    M ./compiler/iface/TcIface.lhs -42 +98
    M ./compiler/main/HscTypes.lhs -7 +6
    M ./compiler/main/InteractiveEval.hs -5 +3
    M ./compiler/main/TidyPgm.lhs -28 +20
    M ./compiler/prelude/TysWiredIn.lhs -1
    M ./compiler/rename/RnBinds.lhs +2
    M ./compiler/simplCore/CSE.lhs -1 +1
    M ./compiler/simplCore/FloatIn.lhs -1 +1
    M ./compiler/simplCore/SetLevels.lhs -9 +9
    M ./compiler/simplCore/SimplCore.lhs -1 +1
    M ./compiler/stgSyn/CoreToStg.lhs -1 +1
    M ./compiler/stranal/DmdAnal.lhs -2 +2
    M ./compiler/stranal/WorkWrap.lhs -1 +1
    M ./compiler/stranal/WwLib.lhs -4 +4
    M ./compiler/typecheck/TcBinds.lhs -6 +9
    M ./compiler/typecheck/TcEnv.lhs -5 +2
    M ./compiler/typecheck/TcInstDcls.lhs -9 +8
    M ./compiler/typecheck/TcRnDriver.lhs -28 +35
    M ./compiler/typecheck/TcSplice.lhs -1 +1
    M ./compiler/typecheck/TcTyClsDecls.lhs -19 +190
    M ./compiler/types/TyCon.lhs -12 +2
    M ./compiler/vectorise/VectUtils.hs -2 +2

View patch online:
http://darcs.haskell.org/ghc/_darcs/patches/20090102142851-1287e-90ec4f4e1abfe587df342834bf0599bec2c35c2e.gz