Quuxplusone added inline comments.
================
Comment at: llvm/include/llvm/IR/BasicBlock.h:324-325
+ template <typename PHINodeU, typename BBIteratorU,
+ typename = std::enable_if_t<
+ std::is_convertible<PHINodeU *, PHINodeT *>::value>>
phi_iterator_impl(const phi_iterator_impl<PHINodeU, BBIteratorU> &Arg)
----------------
dblaikie wrote:
> BRevzin wrote:
> > dblaikie wrote:
> > > What tripped over/required this SFINAE?
> > There's somewhere which compared a const iterator to a non-const iterator,
> > that ends up doing conversions in both directions under C++20 rules, one
> > direction of which is perfectly fine and the other was a hard error. Need
> > to make the non-const iterator not constructible from a const iterator.
> Is this true for all iterators? Or some quirk of how this one is written/used
> (that could be fixed/changed there instead)?
IMO there is a (much) bigger task hiding here, which is to audit every type in
the codebase whose name contains the string "Iterator" and compare them to the
C++20 Ranges `std::forward_iterator` concept. My impression is that the vast
majority of real-world "iterator types" are not iterators according to C++20
Ranges, and that this can have arbitrarily weird effects when you mix them with
the C++20 STL.
However, that is //massive// scope creep re this particular patch. I think the
larger question of "do all our iterators need X / are all our iterators written
wrong" should be scoped-outside-of this patch.
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D78938/new/
https://reviews.llvm.org/D78938
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