add perf side effect docs to Iterator::cloned()
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r? @yaahc (rust-highfive has picked a reviewer for you, use r? to override) |
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| /// // instead call `cloned` late: | ||
| /// let good: Vec<_> = a.iter().filter(|s| s.len() == 1).cloned().collect(); | ||
| /// assert_eq!(&[".".to_string()], &good[..]); | ||
| /// ``` |
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I think this part should be fairly uncontroversial (modulo readability nits), it simply adds an implementation hint.
| /// There is no guarantee whatsoever about the `clone` method actually | ||
| /// being called *or* optimized away. So code should not depend on | ||
| /// either. | ||
| /// |
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This one seems a little more troublesome to me. I don't think this adds anything new, it simply makes the "no guarantee in either direction" which was previously implicit in the absence of detailed specification explicit. But some libs team members interpret API contracts differently than I do, so I want some extra eyes on this. Wait, I'm not assigned reviewer, nevermind 😅
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At least making it explicit allows us to point the user to the docs when they bemoan their code breaking should we ever decide to improve perf on this.
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I don't mind making the lack of a guarantee explicit, I don't believe this restricts us in any way which is the main thing I worry about with docs changes
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@bors r+ rollup=always |
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📌 Commit 1fb43f6 has been approved by |
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Rollup of 6 pull requests Successful merges: - rust-lang#91608 (Fold aarch64 feature +fp into +neon) - rust-lang#92955 (add perf side effect docs to `Iterator::cloned()`) - rust-lang#94713 (Add u16::is_utf16_surrogate) - rust-lang#95212 (Replace `this.clone()` with `this.create_snapshot_for_diagnostic()`) - rust-lang#95219 (Modernize `alloc-no-oom-handling` test) - rust-lang#95222 (interpret/validity: improve clarity) Failed merges: r? `@ghost` `@rustbot` modify labels: rollup
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Now that #90209 has been closed, as the current state of affairs is neither here nor there, this at least adds a paragraph + example on what to expect performance-wise and how to deal with it to the .cloned() docs.
cc @the8472