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  • Simon Peyton Jones's avatar
    Fix scoping of TyCon binders in TcTyClsDecls · 913287a0
    Simon Peyton Jones authored and Marge Bot's avatar Marge Bot committed
    This patch fixes #17566 by refactoring the way we decide the final
    identity of the tyvars in the TyCons of a possibly-recursive nest
    of type and class decls, possibly with associated types.
    
    It's all laid out in
      Note [Swizzling the tyvars before generaliseTcTyCon]
    
    Main changes:
    
    * We have to generalise each decl (with its associated types)
      all at once: TcTyClsDecls.generaliseTyClDecl
    
    * The main new work is done in TcTyClsDecls.swizzleTcTyConBndrs
    
    * The mysterious TcHsSyn.zonkRecTyVarBndrs dies altogether
    
    Other smaller things:
    
    * A little refactoring, moving bindTyClTyVars from tcTyClDecl1
      to tcDataDefn, tcSynRhs, etc.  Clearer, reduces the number of
      parameters
    
    * Reduce the amount of swizzling required.
      Specifically, bindExplicitTKBndrs_Q_Tv doesn't need
        to clone a new Name for the TyVarTv, and not
        cloning means that in the vasly common case,
        swizzleTyConBndrs is a no-op
    
      In detail:
        Rename newTyVarTyVar --> cloneTyVarTyVar
        Add newTyVarTyTyVar that doesn't clone
        Use the non-cloning newTyVarTyVar in
           bindExplicitTKBndrs_Q_Tv
           Rename newFlexiKindedTyVarTyVar
               --> cloneFlexiKindedTyVarTyVar
    
    * Define new utility function and use it
         HsDecls.familyDeclName ::
            FamilyDecl (GhcPass p) -> IdP (GhcPass p)
    
    Updates haddock submodule.
    913287a0