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2.12 regression in BitSet/bitmask #10162

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scabug opened this issue Jan 24, 2017 · 4 comments
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2.12 regression in BitSet/bitmask #10162

scabug opened this issue Jan 24, 2017 · 4 comments
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@scabug
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scabug commented Jan 24, 2017

in 2.10/2.11 the following returns the input array, but in 2.12 the returned array is truncated to one element (the zero is dropped).

import scala.collection.immutable._ ; println(BitSet.fromBitMaskNoCopy(Array(-9223372036854775808L, 0L)).toBitMask.toList)

In ENSIME we were using the BitSet mask as a mechanism to encode/decode BigInts, but that now breaks.

It's no big deal, we weren't even using this functionality. I understand that this is potentially internal implementation detail.
@scabug
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scabug commented Jan 24, 2017

Imported From: https://issues.scala-lang.org/browse/SI-10162?orig=1
Reporter: Samuel Halliday (fommil)
Affected Versions: 2.12.1

@scabug
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scabug commented Jan 24, 2017

Samuel Halliday (fommil) said:
scala/scala#5127 looks like it caused this

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scabug commented Jan 24, 2017

Samuel Halliday (fommil) said:
for the gory details of how we were doing it: https://github.com/ensime/ensime-server/blob/63cf102bb4b50964a6e15591ba4d7da3e9fdf816/s-express/src/main/scala/org/ensime/sexp/formats/BigDecimalConvertor.scala#L49-L83

FYI this was very convenient because it aligned exactly with how emacs lisp stores larges numbers https://github.com/ensime/ensime-server/blob/63cf102bb4b50964a6e15591ba4d7da3e9fdf816/s-express/src/main/scala/org/ensime/sexp/formats/CollectionFormats.scala#L100-L155

but we didn't need it in the protocol... it was just for completeness.

@scabug
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scabug commented Jan 24, 2017

Samuel Halliday (fommil) said:
in fact, it may be the case that ensime doesn't need BigInt => BitSet => BigInt roundtripping. Only BitSet => BigInt => BitSet matters. I may just rewrite our tests and consider this a corner case.

@scabug scabug closed this as completed Jan 24, 2017
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