[PATCH] D125609: [ADT] Adopt the new casting infrastructure for PointerUnion

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0x59616e added a comment.

I can only come up with this :

Define `CastInfoPointerUnionImpl` as below :

  template <typename... PTs> struct CastInfoPointerUnionImpl {
    using From = PointerUnion<PTs...>;
  
    template <typename To> static inline bool isPossible(From &F) {
     return  F.Val.getInt() == FirstIndexOfType<To, PTs...>::value;
    }
  
    template <typename To> static To doCast(From &F) {
      assert(isPossible<To>(F) && "cast to an incompatible type !");
      return PointerLikeTypeTraits<To>::getFromVoidPointer(F.Val.getPointer());
    }
  };

and declared it as a friend of PointerUnion.

And then `CastInfo`:

  template <typename To, typename... PTs>
  struct CastInfo<To, PointerUnion<PTs...>>
      : NullableValueCastFailed<To>,
        DefaultDoCastIfPossible<To, PointerUnion<PTs...>,
                                CastInfo<To, PointerUnion<PTs...>>> {
    using From = PointerUnion<PTs...>;
    using Impl = CastInfoPointerUnionImpl<PTs...>;
  
    static inline bool isPossible(From &f) {
      return Impl::template isPossible<To>(f);
    }
  
    static To doCast(From &f) {
      return Impl::template doCast<To>(f);
    }
  };

By doing this we can implement `PointerUnion::is` and `PointerUnion::get` in this way:

  /// Test if the Union currently holds the type matching T.
   template <typename T> bool is() const { return isa<T>(*this); }
  
   /// Returns the value of the specified pointer type.
   ///
   /// If the specified pointer type is incorrect, assert.
   template <typename T> T get() const {
     assert(isa<T>(*this) && "Invalid accessor called");
     return cast<T>(*this);
   }

Does this makes sense ?


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D125609/new/

https://reviews.llvm.org/D125609