Update hash-map.dd #4246
Update hash-map.dd #4246
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This update is in reference to <dlang#4245>. The spec currently says that for classes to be used as keys in associative arrays, they *must* override toHash and opEquals. This is untrue because the default implementations use the address of the class instance for computing the hash and for comparisons.
fieldvoid
requested review from
andralex,
WalterBright,
maxhaton and
mdparker
as code owners
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spec/hash-map.dd
Outdated
| @@ -109,6 +108,8 @@ $(H2 $(LNAME2 using_classes_as_key, Using Classes as the KeyType)) | |||
| } | |||
| } | |||
| --- | |||
| The default implementations of $(D toHash) and $(D opEquals) for classes use $(D is) | |||
| semantics (the address of the class instance is used to compute the hash, and the address of the class instance is used for comparisons). | |||
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opEquals uses is semantics, toHash doesn't.
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The more accurate thing to say is that the default opEquals compares the addresses of the objects and that toHash hashes the address of the object (so both ignore the value of the object itself). opEquals does use is to do that, but AFAIK, the spec doesn't use the term "is semantics" anywhere, and is doesn't need to be explicitly mentioned to make the behavior clear.
Edited based on jmdavis' (https://github.com/jmdavis) input to more accurately reflect what takes place.
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I've edited it, thanks |
jmdavis
added
the
72h no objection -> merge
This update is in reference to #4245.
The spec currently says that for classes to be used as keys in associative arrays, they must override toHash and opEquals. This is untrue because the default implementations use the address of the class instance for computing the hash and for comparisons.