Remove now unecessary MSVC trailing objects workaround

[hughbe]

Unfortunately, MSVC is still buggy, and reports that the functions

size_t numTrailingObjects(typename TrailingObjectsIdentifier::template OverloadToken<Identifier>) const;

and

size_t numTrailingObjects(typename TrailingObjectsIdentifier::template OverloadToken<SourceLoc>) const;

have identical function parameters, which is obviously incorrect. But apparently this is because we're using TrailingObjects incorrectly here:

https://reviews.llvm.org/D29880

I just noticed that the test case I wrote is passing a bogus first-argument to the template -- and so is your modified version in the comment above. So any errors resulting from that are probably not useful to examine. The testcase should've look like this instead:

I'm assuming the error coming from swift is actually from something else?

[hughbe]

@swift-ci please smoke test

[hughbe]

@swift-ci please smoke test

[hughbe]

@swift-ci please smoke test

[jrose-apple]

I'm sorry, I don't understand this change, and looking back at the comment on the LLVM review I don't understand it there either. I see that TrailingObjectsBase isn't actually a templated type, and so it doesn't matter how we get there through TrailingObjects, but isn't it still more correct to use the type we're actually inheriting from? And if it doesn't matter at all, we should still be consistent, possibly standardizing on TrailingObjectsBase instead of TrailingObjects-with-only-one-trailing-type.

[hughbe]

No problem, I was confused too. Basically, the code should be the following in Expr.h:

  // ...

  using TrailingObjects = llvm::TrailingObjects<Derived, Identifier, SourceLoc>;
  friend TrailingObjects;

  // ...

  size_t numTrailingObjects(
      typename TrailingObjects::template OverloadToken<Identifier>) const {
    return asDerived().getNumArguments();
  }

  size_t numTrailingObjects(
      typename TrailingObjects::template OverloadToken<SourceLoc>) const {
    return asDerived().hasArgumentLabelLocs() ? asDerived().getNumArguments()
                                              : 0;
  }

  // ...

but for some reason, MSVC gets horribly confused, and thinks these are the same functions:

swift\include\swift/AST/Expr.h(681): error C2535: 'size_t swift::TrailingCallArguments::numTrailingObjects(TrailingObjects<BaseTy,TrailingTys...>::TrailingObjectsImpl<llvm::trailing_objects_internal::AlignmentCalcHelper<TrailingTys...>::Alignment,BaseTy,llvm::TrailingObjects<BaseTy,TrailingTys...>,BaseTy,TrailingTys...>::OverloadToken) const': member function already defined or declared (compiling source file swift\lib\AST\ASTNode.cpp)

swift\include\swift/AST/Expr.h(675): note: see declaration of 'swift::TrailingCallArguments::numTrailingObjects' (compiling source file swift\lib\AST\ASTNode.cpp)

swift\include\swift/AST/Expr.h(745): note: see reference to class template instantiation 'swift::TrailingCallArguments' being compiled (compiling source file swift\lib\AST\ASTNode.cpp)

The fix (/workaround/hack) is like the following here:

template <typename Derived>
class Class5Tmpl : private llvm::TrailingObjects<Derived, float, int> {
  using TrailingObjects = typename llvm::TrailingObjects<Derived, float>;
  friend TrailingObjects;

  size_t numTrailingObjects(
      typename TrailingObjects::template OverloadToken<float>) const {
    return 1;
  }

  size_t numTrailingObjects(
      typename TrailingObjects::template OverloadToken<int>) const {
    return 2;
  }
}

class Class5 : public Class5Tmpl<Class5> {};

However, then we get errors in the following code in Expr.h:

  // ...

  /// Determine the total size to allocate.
  static size_t totalSizeToAlloc(ArrayRef<Identifier> argLabels,
                                 ArrayRef<SourceLoc> argLabelLocs,
                                 bool hasTrailingClosure) {
    return TrailingObjects::template totalSizeToAlloc<Identifier, SourceLoc>(
        argLabels.size(), argLabelLocs.size());
  }

  // ...

> swift\include\swift/AST/Expr.h(707): error C2672: 'llvm::TrailingObjects<Derived,swift::Identifier>::totalSizeToAlloc': no matching overloaded function found
>           with
>           [
>               Derived=swift::CallExpr
>           ] (compiling source file swift\lib\AST\Expr.cpp)
>   swift\include\swift/AST/Expr.h(705): note: while compiling class template member function 'size_t swift::TrailingCallArguments<swift::CallExpr>::totalSizeToAlloc(llvm::ArrayRef<swift::Identifier>,llvm::ArrayRef<swift::SourceLoc>,bool)' (compiling source file swift\lib\AST\Expr.cpp)
>   swift\lib\AST\Expr.cpp(1734): note: see reference to function template instantiation 'size_t swift::TrailingCallArguments<swift::CallExpr>::totalSizeToAlloc(llvm::ArrayRef<swift::Identifier>,llvm::ArrayRef<swift::SourceLoc>,bool)' being compiled
>   swift\include\swift/AST/Expr.h(3753): note: see reference to class template instantiation 'swift::TrailingCallArguments<swift::CallExpr>' being compiled (compiling source file swift\lib\AST\Expr.cpp)
> swift\include\swift/AST/Expr.h(707): error C2780: 'std::enable_if<std::is_same<llvm::TrailingObjects<Derived,swift::Identifier>::Foo<swift::Identifier>,llvm::TrailingObjects<Derived,swift::Identifier>::Foo<Tys...>>::value,std::size_t>::type llvm::TrailingObjects<Derived,swift::Identifier>::totalSizeToAlloc(std::Ty2)': expects 1 arguments - 2 provided
>           with
>           [
>               Derived=swift::CallExpr,
>               Ty2=std::size_t
>           ] (compiling source file swift\lib\AST\Expr.cpp)
>   llvm\include\llvm/Support/TrailingObjects.h(350): note: see declaration of 'llvm::TrailingObjects<Derived,swift::Identifier>::totalSizeToAlloc'
>           with
>           [
>               Derived=swift::CallExpr
>           ] (compiling source file swift\lib\AST\Expr.cpp)

[jrose-apple]

All right, I'll trust you on this. Maybe leave a comment behind to note why we're doing something so strange. :-)

[hughbe]

@swift-ci please smoke test and merge

[hughbe]

@swift-ci please smoke test and merge