42 lines
1.2 KiB
Plaintext
42 lines
1.2 KiB
Plaintext
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== Why is this an issue?
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When a type implements `Borrow<T>`, it should provide consistent behavior between the borrowed and owned values, especially regarding `Eq`, `Ord`, and `Hash`. However, `str` and `[u8]` have different Hash implementations, leading to inconsistent hash values for the same underlying data when accessed through different Borrow implementations. This violates the principle that `hash(x) == hash((x as Borrow<[u8]>).borrow()) == hash((x as Borrow<str>).borrow())` must hold, and can cause issues with hash-based collections and comparisons.
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=== Code examples
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==== Noncompliant code example
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[source,rust]
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----
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use std::borrow::Borrow;
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use std::hash::{Hash, Hasher};
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struct ExampleType {
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data: String,
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}
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impl Hash for ExampleType {
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fn hash<H: Hasher>(&self, state: &mut H) {
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self.data.hash(state); // Noncompliant: Inconsistent Hash
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}
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}
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impl Borrow<str> for ExampleType {
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fn borrow(&self) -> &str {
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&self.data
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}
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}
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impl Borrow<[u8]> for ExampleType {
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fn borrow(&self) -> &[u8] {
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self.data.as_bytes()
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}
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}
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----
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== Resources
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=== Documentation
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* Clippy Lints - https://rust-lang.github.io/rust-clippy/master/index.html#impl_hash_borrow_with_str_and_bytes
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