hashCode for NumericRange is computed by evaluating all values

[AvaPL]

Compiler version

3.3.0

Minimized code

val largeRangeHashCode = (Long.MinValue to Long.MaxValue).hashCode()

Output

java.lang.IllegalArgumentException: More than Int.MaxValue elements.
  at scala.collection.immutable.NumericRange$.check$1(NumericRange.scala:330)
  at scala.collection.immutable.NumericRange$.count(NumericRange.scala:361)
  at scala.collection.immutable.NumericRange.length$lzycompute(NumericRange.scala:75)
  at scala.collection.immutable.NumericRange.length(NumericRange.scala:75)
  at scala.util.hashing.MurmurHash3.indexedSeqHash(MurmurHash3.scala:239)
  at scala.util.hashing.MurmurHash3$.seqHash(MurmurHash3.scala:354)
  at scala.collection.immutable.NumericRange.hashCode$lzycompute(NumericRange.scala:246)
  at scala.collection.immutable.NumericRange.hashCode(NumericRange.scala:246)
  ... 32 elided

Expectation

The hash code of a numeric range should be calculated. It seems that NumericRange uses MurmurHash3.indexedSeqHash which evaluates all values in the range to compute the hash code.

Additionally, even when the range is small enough, the hash code computation is ineffective and may affect the code performance e.g. when a Set[NumericRange[Long]] is used.

[odersky]

This bug should be opened against scala/scala. We can't change the standard library on the dotty side.