java.util.HashMap.size has a double signature.

[nicolasstucki]

dotty> new java.util.HashMap[Int, Int]().size 
    ^
new java.util.HashMap[Int, Int]().size
<console>:8: error: cannot merge
  method size: ()Int  and
  variable size: Int;
they are both defined in class HashMap but have matching signatures
  ()Int and
  Int
when seen as members of java.util.HashMap[Int, Int]

[DarkDimius]

note that the field size should not be accessible as it has default access modifier.

[smarter]

Related: https://gitter.im/lampepfl/dotty?at=577ede1959cfbd4c5e437d70