westonpace commented on code in PR #33912:
URL: https://github.com/apache/arrow/pull/33912#discussion_r1091309848
##########
cpp/src/arrow/result.h:
##########
@@ -371,7 +371,7 @@ class [[nodiscard]] Result : public
util::EqualityComparable<Result<T>> {
if (ok()) {
Review Comment:
> Proof that it works as intended: https://godbolt.org/z/5c17zjG89
I'm a little confused. In this example I get:
```
function &:
copy
copy
function && (with std::move):
move
move
```
If I change to `G&&` I get:
```
function &:
function && (with std::move):
```
It seems the version without the moves (and especially without the copies)
would be preferred.
Also, if your generator is stateful (e.g. a generator object that returns
the next id in a sequence) then it would make a big difference if you use & or
&&.
I agree, in this case, it seems rather unlikely that someone is going to be
passing in a stateful (or complex to copy, can't be inlined) generator.
Still, I don't think there is any penalty to the &&. And the standard [does
sometimes pass functions by forwarding
reference](https://en.cppreference.com/w/cpp/utility/functional/invoke).
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