Scala compiler issue or JVM boxing subtlty? -


the following function part of code have interface particularly nasty (as in untyped) java api. intended safely perform casts context 'knows' type should be, want make sure won't have bad failure modes in unknown edge case @ runtime:

def safecast[a](o: any): option[a] =   try(o.asinstanceof[a]).tooption

now happens when it's used in repl session:

scala> val testdouble: double = 1.0  testdouble: double = 1.0  scala> safecast[int](testdouble)  res0: option[int] = some(1.0)

res0 claims have type option[int] value some(1.0) (i.e. - some[double]). class cast exception follows if try map on option.

this behavior happens polymorphic safecast. if tighten specific type:

def safeintcast(o: any): option[int] = try(o.asinstanceof[int]).tooption

then get:

scala> safeintcast(testdouble)  res1: option[int] = none

hence polymorphism somehow interacting boxing (i suspect??) or compiler issue (bug??). compiler version used 2.12.2

can provide explanation this?

please, see here , here further reference. explains lot scala asinstanceof.

hope helps!


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