Steps to reproduce:

- Create a Class diagram
- Put Interface element on the diagram and name it 'MyInterface'
- Insert 'void op()' operation into Interface element
- Put Class element on the diagram and name it 'MyClass'
- Draw 'Implementation' link from Class element to Interface element
- Go to source of 'MyClass' class element
- Insert 'System.out.println("Hello World!");' line into 'void op()' 
  operation
  ----------------------------------------------------------
  public class MyClass implements MyInterface{
    public MyClass() {
    }

    public void op() {
        System.out.println("Hello World!");
    }
  }
  ----------------------------------------------------------
- Go to the diagram
- Select 'MyInterface' interface element
- Change 'op' operation type from 'void' to 'int' for Interface element
- Go to the source of 'MyClass' class element
  'op' operation body was removed

  ----------------------------------------------------------
  public class MyClass implements MyInterface{
    public MyClass() {
    }

    public int op() {
        return 0;
    }
  }
  ----------------------------------------------------------