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Range<u64> implements ExactSizeIterator #22047

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bluss opened this Issue Feb 7, 2015 · 2 comments

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bluss commented Feb 7, 2015

What does (0..std::u64::MAX).size_hint() return on a 32-bit build? Range<u64> and Range<i64> cannot fulfill the requirements of the ExactSizeIterator trait, and the implementations must be removed.

@sfackler sfackler added the A-libs label Feb 7, 2015

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bluss commented Feb 7, 2015

I checked the code and it turns out the impl is conditional -- only on 64-bit platforms. So that's correct and for me it turned into a different question of whether that kind of platform dependence is good. I've started a discussion about that here.

@bluss bluss closed this Feb 7, 2015

@bluss bluss reopened this Feb 13, 2015

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bluss commented Feb 13, 2015

Reopened, got some voices backing that this is a bug.

Soft solution would be to warn on using that particular impl of ExactSizeIterator for Range and i64, but I don't know if we can even do that.

Otherwise we can just remove the impls.

bluss pushed a commit to bluss/rust that referenced this issue Feb 13, 2015

Ulrik Sverdrup
Remove ExactSizeIterator from 64-bit ranges. 
Fixes rust-lang#22047

Range<u64> and Range<i64> may be longer than usize::MAX on 32-bit
platforms, and thus they cannot fulfill the protocol for
ExactSizeIterator. We don't want a nonobvious platform dependency in
basic iterator traits, so the trait impl is removed.

The logic of this change assumes that usize is at least 32-bit.

This is technically a breaking change; note that Range<usize> and
Range<isize> are always ExactSizeIterators.

[breaking-change]
b19fda0

@bluss bluss referenced this issue Feb 13, 2015

Merged

Remove ExactSizeIterator from 64-bit ranges. #22299

steveklabnik added a commit to steveklabnik/rust that referenced this issue Feb 14, 2015

@steveklabnik
Rollup merge of rust-lang#22299 - bluss:range-64-is-not-exact-size, r… 
…=alexcrichton

Fixes rust-lang#22047

Range<u64> and Range<i64> may be longer than usize::MAX on 32-bit
platforms, and thus they cannot fulfill the protocol for
ExactSizeIterator. We don't want a nonobvious platform dependency in
basic iterator traits, so the trait impl is removed.

The logic of this change assumes that usize is at least 32-bit.

This is technically a breaking change; note that Range<usize> and
Range<isize> are always ExactSizeIterators.

[breaking-change]
fb655d0

steveklabnik added a commit to steveklabnik/rust that referenced this issue Feb 15, 2015

@steveklabnik
Rollup merge of rust-lang#22299 - bluss:range-64-is-not-exact-size, r… 
…=alexcrichton

Fixes rust-lang#22047

`Range<u64>` and `Range<i64>` may be longer than usize::MAX on 32-bit
platforms, and thus they cannot fulfill the protocol for
ExactSizeIterator. We don't want a nonobvious platform dependency in
basic iterator traits, so the trait impl is removed.

The logic of this change assumes that usize is at least 32-bit.

This is technically a breaking change; note that `Range<usize>` and
`Range<isize>` are always ExactSizeIterators.

[breaking-change]
f89168e

Manishearth added a commit to Manishearth/rust that referenced this issue Feb 15, 2015

@Manishearth
Rollup merge of rust-lang#22299 - bluss:range-64-is-not-exact-size, r… 
…=alexcrichton

 Fixes rust-lang#22047

`Range<u64>` and `Range<i64>` may be longer than usize::MAX on 32-bit
platforms, and thus they cannot fulfill the protocol for
ExactSizeIterator. We don't want a nonobvious platform dependency in
basic iterator traits, so the trait impl is removed.

The logic of this change assumes that usize is at least 32-bit.

This is technically a breaking change; note that `Range<usize>` and
`Range<isize>` are always ExactSizeIterators.

[breaking-change]
ffe0144

Manishearth added a commit to Manishearth/rust that referenced this issue Feb 15, 2015

@Manishearth
Rollup merge of rust-lang#22299 - bluss:range-64-is-not-exact-size, r… 
…=alexcrichton

 Fixes rust-lang#22047

`Range<u64>` and `Range<i64>` may be longer than usize::MAX on 32-bit
platforms, and thus they cannot fulfill the protocol for
ExactSizeIterator. We don't want a nonobvious platform dependency in
basic iterator traits, so the trait impl is removed.

The logic of this change assumes that usize is at least 32-bit.

This is technically a breaking change; note that `Range<usize>` and
`Range<isize>` are always ExactSizeIterators.

[breaking-change]
1b86ebe

@bors bors closed this in #22299 Feb 16, 2015

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