Derive hash value of struct instances not only from the instance's values, but also its class

[janlelis]

Struct.new(:x).new.hash on TruffleRuby always creates the same hash, while on MRI/JRuby it creates a different hash for different struct classes.

@eregon: Actually Struct.new(:y).new.hash also has the same hash, the hash is only based on Struct values currently, which seems suboptimal.

[eregon]

Thanks for the report.

I think we should use something like val = Primitive.vm_hash_start(Truffle::Type.object_class(self).hash) in

truffleruby/src/main/ruby/truffleruby/core/struct.rb

Line 309 in 0dc999f

val = Primitive.vm_hash_start(CLASS_SALT)

and also in

truffleruby/src/main/ruby/truffleruby/core/struct.rb

Line 440 in 0dc999f

hash = Primitive.vm_hash_start CLASS_SALT

@bjfish Could you do that?

It seems a good idea to add a ruby/spec that Struct.new(:x).new(1).hash != Struct.new(:y).new(1).hash.

[eregon]

Fixed in d9235b8 by @bjfish, thanks for the report.