Open CaseyCarter opened 5 years ago
Working my way down meta.cpp, on line 67 (the last type alias (outer
) in Res tuple_cat(Tuples &&... tpls)
):
quote_i<std::size_t, make_index_sequence>
fails Invocable
(in a static_assert
). quote<std::index_sequence_for>
as a replacement works (not a good solution, but at least allows me down to the lambda tests).
There are issues in the interaction between the concept constraints in meta and the lambda implementation that need to be investigated. Concepts are applied when forming a template-id, even before instantiation, so e.g.:
Yet the implementation of lambdas relies on the ability to name "invalid" specializations which are later pattern-matched and substituted into valid specializations. GCC's concept implementation is lax enough that we've been getting by with some cheating in cmcstl2, but clang-concepts (and I suspect other implementations of C++20 concepts) refuses to compile the lambda test cases in meta.cpp.