On Friday, 6 May 2022 at 09:24:06 UTC, vit wrote:
It look like examples at page
https://dlang.org/spec/function.html#ref-return-scope-parameters are no longer relevant.
They were recently updated to match the implementation in 2.100.
What difference are between `return scope`, `scope return` and
`return`?
`return scope` means pointer members (such `this.ptr`, `C.ptr`)
may not escape the function, unless they are returned. If you
call `test()` on a `scope` variable, the return value will be a
scope pointer.
`scope return` on a struct member is `scope` + `return ref`,
meaning pointer members may not escape the function (the `scope`
part), but you can return a reference to the struct member itself
(``, the `return ref` part). If you call `test()` on a
local variable (`scope` or not), the return value will be a scope
pointer.
Just `return` allows you to return a reference to the struct
member itself (``), and also to escape pointer members
(`this.ptr`) since there is no `scope`. However, that means you
can't call `test` on `scope` variables.
```
int* test() scope return{
return // Error: returning `` escapes a
reference to parameter `this`
}
}
```
I think you're using an older DMD version, the error should be
gone in 2.100
Why void* ptr in struct change effect of scope return ?
`scope` is ignored when the struct has no pointers, and before
2.100, the meaning of `return` + `scope` on `ref` parameters was
very inconsistent.
