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len_zero with Range suggests code cannot compile #3807

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oxalica opened this issue Feb 24, 2019 · 2 comments · Fixed by #5656
Closed

len_zero with Range suggests code cannot compile #3807

oxalica opened this issue Feb 24, 2019 · 2 comments · Fixed by #5656
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C-bug Category: Clippy is not doing the correct thing I-suggestion-causes-error Issue: The suggestions provided by this Lint cause an ICE/error when applied L-suggestion Lint: Improving, adding or fixing lint suggestions

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@oxalica
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oxalica commented Feb 24, 2019

Code like (0..42).len() == 0 will trigger len_zero, but (0..42).is_empty() does not compile now.

Clippy version: 0.0.212 (2019-02-19)
Rustc version: 1.34.0-nightly (2019-02-22)

Playground link

  |
4 |     println!("{}", (0..42).is_empty());
  |                            ^^^^^^^^ multiple `is_empty` found
  |
  = note: candidate #1 is defined in an impl for the type `std::ops::Range<_>`
note: candidate #2 is defined in the trait `std::iter::ExactSizeIterator`
  = help: to disambiguate the method call, write `std::iter::ExactSizeIterator::is_empty(::std::ops::Range{start: 0, end: 42,})` instead
@flip1995 flip1995 added C-bug Category: Clippy is not doing the correct thing I-suggestion-causes-error Issue: The suggestions provided by this Lint cause an ICE/error when applied labels Feb 24, 2019
@ghost
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ghost commented Jul 5, 2019

This isn't a Clippy bug. See rust-lang/rust#48111.

@ghost
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ghost commented Jul 5, 2019

🤔 On the other hand, maybe it shouldn't be suggesting unstable methods...

@phansch phansch added the L-suggestion Lint: Improving, adding or fixing lint suggestions label Aug 24, 2019
@flip1995 flip1995 mentioned this issue Jan 15, 2020
Closed
traviscross added a commit to traviscross/async-h1 that referenced this issue Mar 25, 2020
@traviscross
Fix/ignore clippy warnings
b80e89f 
Clippy has some warnings for us.  For some of them, fixing the code
improves things.  For others, making clippy happy would make the code
worse (or in one case, even break compilation [1]).  Let's fix the
ones worth fixing, and for the others, let's tell clippy to ignore
them.

[1] rust-lang/rust-clippy#3807
@traviscross traviscross mentioned this issue Mar 25, 2020
Merged
@ebroto ebroto mentioned this issue May 27, 2020
Merged
bors added a commit that referenced this issue May 28, 2020
@bors
Auto merge of #5656 - ebroto:len_zero_ranges, r=matthiaskrgr
ebfbe2b 
len_zero: skip ranges if feature `range_is_empty` is not enabled

If the feature is not enabled, calling `is_empty()` on a range is ambiguous. Moreover, the two possible resolutions are unstable methods, one inherent to the range and the other being part of the `ExactSizeIterator` trait.

Since `len_zero` only checks for existing `is_empty()` inherent methods, we only take into account the `range_is_empty` feature.

Related: rust-lang/rust#48111 (comment)

changelog: len_zero: avoid linting ranges without #![feature(range_is_empty)]

Fixes: #3807
yvt added a commit to yvt/Stella2 that referenced this issue May 29, 2020
@yvt
refactor(tcw3): address clippy lints
fabbafa 
- `clone_on_copy`
- `type_complexity` (threshold adjusted)
- `collapsible_if`
- `option_map_unit_fn`
- `identity_conversion`
- `iter_nth_zero`
- `eval_order_dependence` (ignored)
- `new_without_default`

Unaddressed:
- `len_zero` - This is a bug in clippy:
  <rust-lang/rust-clippy#3807>
yvt added a commit to yvt/Stella2 that referenced this issue May 29, 2020
@yvt
refactor(pal): address clippy lints
1000fb9 
- `string_lit_as_bytes`
- `identity_op`
- `len_zero`
- `iter_nth_zero`
- `collapsible_if` (evaded)
- `let_and_return`
- `len_without_is_empty` (ignored)
- `or_fun_call`
- `redundant_clone`
- `option_as_ref_deref`

Unaddressed:
- `len_zero` - This is a bug in clippy:
  <rust-lang/rust-clippy#3807>
yvt added a commit to yvt/Stella2 that referenced this issue May 29, 2020
@yvt
feat(tcw3): address clippy lints
179598e 
- `clone_on_copy`
- `type_complexity` (threshold adjusted)
- `collapsible_if`
- `option_map_unit_fn`
- `identity_conversion`
- `iter_nth_zero`
- `eval_order_dependence` (ignored)
- `new_without_default` (adds `impl Default` for a public type)

Unaddressed:
- `len_zero` - This is a bug in clippy:
  <rust-lang/rust-clippy#3807>
yvt added a commit to yvt/Stella2 that referenced this issue May 29, 2020
@yvt
refactor(pal): address clippy lints
5f33906 
- `string_lit_as_bytes`
- `identity_op`
- `len_zero`
- `iter_nth_zero`
- `collapsible_if` (evaded)
- `let_and_return`
- `len_without_is_empty` (ignored)
- `or_fun_call`
- `redundant_clone`
- `option_as_ref_deref`

Unaddressed:
- `len_zero` - This is a bug in clippy:
  <rust-lang/rust-clippy#3807>
@bors bors closed this as completed in 873c9fc May 31, 2020
@scottmcm scottmcm mentioned this issue Aug 4, 2020
Merged
scottmcm added a commit to scottmcm/rust that referenced this issue Aug 24, 2020
@scottmcm
Stabilize Range[Inclusive]::is_empty
c20ad72 
I would like to propose these two simple methods for stabilization:
- Knowing that a range is exhaused isn't otherwise trivial
- Clippy would like to suggest them, but had to do extra work to disable that path <rust-lang/rust-clippy#3807> because they're unstable
- These work on `PartialOrd`, consistently with now-stable `contains`, and are thus more general than iterator-based approaches that need `Step`
- They've been unchanged for some time, and have picked up uses in the compiler
- Stabilizing them doesn't block any future iterator-based is_empty plans, as the inherent ones are preferred in name resolution
bors added a commit to rust-lang-ci/rust that referenced this issue Aug 25, 2020
@bors
Auto merge of rust-lang#75132 - scottmcm:stabilize-range-is-empty, r=…
c30341d 
…dtolnay

Stabilize Range[Inclusive]::is_empty

I would like to propose these two simple methods for stabilization:
- Knowing that a range is exhausted isn't otherwise trivial
- Clippy would like to suggest them, but had to do extra work to disable that path <rust-lang/rust-clippy#3807> because they're unstable
- These work on `PartialOrd`, consistently with the stable `contains` method, and are thus more general than iterator-based approaches that need `Step`
- They've been unchanged for some time, and have picked up uses in the compiler
- Stabilizing them doesn't block any future iterator-based `is_empty` plans, as these inherent ones are preferred in name resolution

https://doc.rust-lang.org/nightly/std/ops/struct.Range.html#method.is_empty
https://doc.rust-lang.org/nightly/std/ops/struct.RangeInclusive.html#method.is_empty

Closes rust-lang#48111
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C-bug Category: Clippy is not doing the correct thing I-suggestion-causes-error Issue: The suggestions provided by this Lint cause an ICE/error when applied L-suggestion Lint: Improving, adding or fixing lint suggestions
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len_zero: skip ranges if feature range_is_empty is not enabled ebroto/rust-clippy
3 participants
@phansch @flip1995 @oxalica