On Thursday, 1 October 2020 at 09:49:36 UTC, Mathias LANG wrote:
Author here. The most complete way to know would be to read the changelog: https://dlang.org/changelog/2.094.0.html#preview-in The TL;DR is that, in addition to `const scope`, `in` now automatically behaves as `ref` when "it makes sense" such as large value types or presence of destructors / postblit (more details in the changelog!) and will accept rvalues, unlike other ref parameters.
Why was this added when we already have `auto ref`? Yes, it makes the function a template, but if `in` can automatically choose whether the variable is ref or not, then auto ref could easily do the same.
