https://issues.dlang.org/show_bug.cgi?id=23175

--- Comment #11 from Steven Schveighoffer <schveiguy@gmail.com> ---
(In reply to Mathias LANG from comment #9)
> You should have led with this. That's what `-transition` is for. It lists all instances of `in` usage so you can inspect them.

Thanks, I didn't know about this switch. However, it just lists all the places where `in` is a parameter, even ones where it is effectively const, i.e.:

`void foo(in int x){}`

It doesn't warn about the problems here.

I also get 100 listings of `in` on parameters in `object.d`, probably all of which are fine. This isn't helpful. The compiler can do better, it knows when it might try this optimization, I don't.

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https://issues.dlang.org/show_bug.cgi?id=23175

--- Comment #12 from Paul Backus <snarwin+bugzilla@gmail.com> ---
The most straightforward fix would be to have the compiler emit a warning any time an `in` parameter escapes from a function in @system or @trusted code (i.e., the same thing it currently emits an error for in @safe code).

If we don't want to make the warning part of `-preview=in` itself, having it enabled by `-transition=in` could also work (though I suspect the vast majority of users will never discover it there).

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https://issues.dlang.org/show_bug.cgi?id=23175

--- Comment #13 from Mathias LANG <pro.mathias.lang@gmail.com> ---
> Thanks, I didn't know about this switch. However, it just lists all the places where `in` is a parameter, even ones where it is effectively const, i.e.:

The `-transition` switch was put in place because `in` also means `ref`, which one may find "breaks code" (hint: it doesn't). The compiler *will* tell you when you're doing something wrong, though: With DIP1000 and @safe. As the spec says it will.

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https://issues.dlang.org/show_bug.cgi?id=23175

Iain Buclaw <ibuclaw@gdcproject.org> changed:

           What    |Removed                     |Added
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           Priority|P1                          |P4

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