https://issues.dlang.org/show_bug.cgi?id=23175
--- Comment #3 from Paul Backus <[email protected]> --- Some historical context: Prior to 2013-02-06, the spec defined `in` as a no-op attribute (likely a holdover from D1). On 2013-02-06, in commit 26d4aec9c [1], `in` was defined as equivalent to `const scope`. On 2018-01-25, in commit 71ad1b38d [2], the spec was changed to define `in` as equivalent to `const`. The commit message refers to issue 17928, which contains some relevant discussion. On 2018-06-14, in commit 93411bed2 [3], the spec was changed to define `in` as `const scope`, with a note that the current implementation treated it as equivalent to `const`. On 2020-08-16, in commit 52e211539 [4], the spec was changed to its current wording, which documents `-preview=in` and says that `in` parameters "behave as though" they are `const scope`. [1]: https://github.com/dlang/dlang.org/commit/26d4aec9c [2]: https://github.com/dlang/dlang.org/commit/71ad1b38d [3]: https://github.com/dlang/dlang.org/commit/93411bed2 [4]: https://github.com/dlang/dlang.org/commit/52e211539 --
