Implement with_hasher adaptors
#1007
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Two nits:
@jswrenn Feel free to proceed as you deem appropriate. |
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## master #1007 +/- ##
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+ Coverage 94.38% 94.67% +0.28%
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Files 48 50 +2
Lines 6665 7062 +397
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It would be a breaking change for Rust to change its default hasher, so we're fine to rely on |
| // A Hasher which forwards it's calls to RandomState to make sure different hashers | ||
| // are accepted in the various *_with_hasher methods. | ||
| #[derive(Default)] | ||
| struct TestHasher(RandomState); | ||
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| impl TestHasher { | ||
| fn new() -> Self { | ||
| TestHasher(RandomState::new()) | ||
| } | ||
| } | ||
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| impl BuildHasher for TestHasher { | ||
| type Hasher = <RandomState as BuildHasher>::Hasher; | ||
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| fn build_hasher(&self) -> Self::Hasher { | ||
| self.0.build_hasher() | ||
| } | ||
| } |
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Does this buy us much? If it behaves identically to RandomState, then what's the advantage of newtyping it? I'm not worried that we've defined our with_hasher methods to literally only accept RandomState.
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Because RandomState is the default for the type parameters, it's possible to implement the types only for S = RandomState. This is just the easiest way I thought of to catch that.
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Gotcha. We can test that more directly by doing:
let _: HashMap<_, _, TestHasher> = empty::<u8>().into_group_map_with_hasher(TestHasher::new());No need to then repeat the assertions on the output value.
New calls to the *_with_hasher methods are added to make sure they are callable with non-default hashers and provide the correct types.
Closes #998
Implementations for the following methods: