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Remove needless TypeBinding hashCode() implementations #3412 #3477

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Remove needless TypeBinding hashCode() implementations #3412 #3477

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jukzi
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@jukzi jukzi commented Dec 18, 2024

Without overriding equals() any custom hashCode() implementation is likely to introduce hash collisions.

#3412

@jukzi jukzi force-pushed the TypeBindingWrapper_hashCodes branch from 4ada025 to d73c10b Compare December 18, 2024 12:20
jukzi added 3 commits December 18, 2024 14:23
@jukzi
remove ArrayBinding.hashCode() eclipse-jdt#3412
b9204f2 
Since ArrayBinding does not override equals() any custom hashCode()
implementation is likely to introduce hash collisions. Especially for
same "leafComponentType" but different "dimensions"

eclipse-jdt#3412
@jukzi
remove LocalTypeBinding.hashCode() eclipse-jdt#3412
8094bfe 
Since LocalTypeBinding does not override equals() any custom hashCode()
implementation is likely to introduce hash collisions. Especially for
same "enclosingType" but different "enclosingCase"

eclipse-jdt#3412
@jukzi
remove WildcardBinding.hashCode() eclipse-jdt#3412
79091ce 
Since WildcardBinding does not override equals() any custom hashCode()
implementation is likely to introduce hash collisions. Especially for
same "genericType" but different "bound"

eclipse-jdt#3412
@jukzi jukzi force-pushed the TypeBindingWrapper_hashCodes branch from d73c10b to 79091ce Compare December 18, 2024 13:23
@jukzi jukzi marked this pull request as ready for review December 18, 2024 13:23
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jukzi commented Jan 20, 2025

@srikanth-sankaran can you review, please?

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Right now I am unable to access https://bugs.eclipse.org/bugs/show_bug.cgi?id=430425 which is referenced from org.eclipse.jdt.internal.compiler.lookup.ArrayBinding.swapUnresolved(UnresolvedReferenceBinding, ReferenceBinding, LookupEnvironment)

I will state that I am nervous about this change - Do we have data to show hash code collisions are a real BURNING issue ?

I wrote much of TypeSystem and AnnotatableTypeSystem but that was ages ago and my recall is quite rusty. It would take a lot more time to study it detail to conclude whether this patch is safe to move forward with and I am afraid scheduling that time is going to be challenging against other commitments :-(

I am inclined to say let us leave this as is - unless it is a burning issue somewhere. Sorry that cannot be the answer you are looking for having invested your time.

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jukzi commented Jan 21, 2025

I can't access bugzilla either, but you submitted a test org.eclipse.jdt.core.tests.builder.IncrementalTests18.test430425() with it which still holds.
It's pretty clear that none of the callers of the constructor org.eclipse.jdt.internal.compiler.lookup.ArrayBinding.ArrayBinding(TypeBinding, int, LookupEnvironment) does use any hashing. Both AnnotatableTypeSystem.getArrayType() linearly iterate through the list of existing derivedTypes.

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jukzi commented Jan 21, 2025

Right now I am unable to access https://bugs.eclipse.org/bugs/show_bug.cgi?id=430425

it's available now (https://gitlab.eclipse.org/eclipsefdn/helpdesk/-/issues/5555#note_2956610)

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jukzi commented Jan 29, 2025

I am inclined to say let us leave this as is - unless it is a burning issue somewhere.

OK, i close this PR and issue and would reopen if i stumble across a non-synthetic reproducer.

@jukzi jukzi closed this Jan 29, 2025
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