AbstractMethodError with vars implementing trait member #6387
Description
We recently had this problem with spray:
trait A {
def foo: Long
}
object Main {
def a(): A = new A {
var foo: Long = 1000L
val test = () => {
foo = 28
}
}
def main(args: Array[String]) {
println(a().foo)
}
}will throw
java.lang.AbstractMethodError: Main$$anon$1.foo()J
at Main$.main(Main.scala:14)
at Main.main(Main.scala)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:601)
Important things here:
- implementing foo with a var
- accessing the setter of foo in an inner anonymous class
- function a() having an explicit return-type
The same behavior can be observed in 2.8.2, 2.9.2, and 2.10.0-M7.
A workaround is not to implement A.foo directly with a var but use an auxiliary var and implement foo separately.