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Accept __rvalue attribute on ref functions; which will force the result to be treated as __rvalue. (#20946)

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This is essential to implement `move`, `forward`, etc.
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Manu Evans 2025-03-10 21:06:29 +10:00
parent c6e387c448
commit 603225372b
5 changed files with 44 additions and 5 deletions
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15
changelog/dmd.rvalue.dd
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@ -23,5 +23,18 @@ This also applies to constructors and assignments, meaning move constructors and
move assignments are enabled. Moving instead of copying can be much more resource
efficient, as, say, a string can be moved rather than copied/deleted.
A moved object can still be destructed, so take that into account when moving
A moved object will still be destructed, so take that into account when moving
a field - set it to a benign value that can be destructed.
`__rvalue` may also be used as an attribute on a function which returns by ref
to declare that the result should be treated as an rvalue at the callsite:
```
ref T move(T)(return ref T source) __rvalue
{
return source;
}
S s;
S t = move(s); // call expression rewritten as: S t = __rvalue(move(s))
```
This is used as an internal tool to implement library primitives such as `move` and `forward`.