Note known false positives in unnecessary_fold lint #3303
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Methods like `Iterator::any` borrow the iterator mutably, which is not allowed within a pattern guard and will fail to compile. This commit prevents clippy from suggesting this type of change. Closes rust-lang#3069
clippy_lints/src/methods/mod.rs
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| // `Iterator::any` cannot be used within a pattern guard | ||
| // See https://github.com/rust-lang-nursery/rust-clippy/issues/3069 | ||
| if_chain! { | ||
| if let Some(fold_parent) = cx.tcx.hir.find(cx.tcx.hir.get_parent_node(expr.id)); |
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This probably doesn't work if the pattern guard is even a slight variation of the test (so e.g. ((0..3).fold(false, |acc, x| acc || x > 2), 42).0. I don't see a good way to fix this issue. It seems like an unfortunate restriction of the language that will get fixed at some point. I think users should rather disable the lint than us trying to hide the false positive.
It also seems like there's ongoing work in the compiler towards fixing this: https://play.rust-lang.org/?gist=1ec006ebd816427e4acbf21f2156d6e2&version=nightly&mode=debug&edition=2015
We could list this as a known issue in the lint description.
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I see; that is indeed an issue. If there is an upcoming compiler feature to fix this, then I agree, I would rather wait for that, and update the documentation instead.
shssoichiro
changed the title
Methods like
Iterator::anyborrow the iterator mutably,which is not allowed within a pattern guard and will fail to compile.
See #3069