The number of cases where a variable (including function parameters passed by value) is be passed by move should be extend to include at least assignments if that assignment statement is the last reference of the variable.
This enables non-copyable (r-value) ranges to be passed to common range-based Phobos algorithms. Such r-value ranges are typically created when a non-copyable C++/Rust-style containers is passed by move _into_ a specific range I propose to name `UniqueInputRange`. `UniqueInputRange`, itself non-copyable, can then with this change be passed to Phobos' higher-order algorithms, typically `map`, `filter`, `reduce` etc.
This idea has already be realized in Rust using [IntoIterator](https://doc.rust-lang.org/std/iter/trait.IntoIterator.html).
Specifically, range algorithm constructor should be able to take a non-copyable range as its source range parameter as in
```d
struct SomeRange
{
this(R range)
{
source = range; // TODO `range` should be passed by move to `source`
}
}
```
when `range` is not referenced after it being moved in the assignment. If the compiler is modified to automatically allow such assignments to perform move all the details described above can be implemented in phobos.
See also https://github.com/dlang/phobos/pull/4971.
Comment #1 by razvan.nitu1305 — 2021-10-19T07:17:38Z