Derive Copy for std::ops::Range and RangeFrom

[SimonSapin]

RangeTo and RangeFull already have it.

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[eddyb]

These don't have it because they're iterators.
The choice of removing Copy impls instead of adjusted for loop desugaring or linting was made to prevent this problematic case:

letmut iter = 0..n;for i in iter {if i > 2{break;}}
iter.collect()

Here iter is actually not mutated, but copied. for i in &mut iter is required to mutate the iterator.
We could switch to linting against using an iterator variable after it was copied by a for loop, but there was no decision towards that.

[SimonSapin]

Ok, so there was a reason.

“The choice […] was made” seems to contradict “no decision has been made yet.” If the decision against implementing Copy is made/confirmed, feel free to close this.

[alexcrichton]

Yeah we've decided in the past to not take this, so I'm going to close this for now.

[eddyb]

@SimonSapin original phrasing was a bit off. What I meant to say was that no decision has been made for switching to linting (which my personal preference).

[sanmai-NL]

I favor a lint, since this code pattern is now not possible:

let three_times = 0_u32..3_u32;for _ in three_times {
...}for _ in three_times {
...}