If you have a `begin() const` member, you don't need a `begin()` member
unless you want it to do something different (e.g. have a different return
type). So in general, //view// types don't need `begin()` non-const members.
Also, static_assert some things about the types in "types.h", so that we
don't accidentally break those properties under refactoring.
Differential Revision: https://reviews.llvm.org/D111231
- Rename test files to follow conventions better
- Split constructor tests that were in a single file
- Add missing tests for take_view and transform_view's default constructors
- Add missing tests for transform_view's view/function constructor
- Fix include guards
- Mark some tests as being specific to libc++
Differential Revision: https://reviews.llvm.org/D108829
Arthur O'Dwyer