public void makeFullyMutable() {
    if(this.ifFalse != null) {
      ValidationHelper.assertTrue(this.ifTrue != this.ifFalse, "VarMapHolder is in an illegal state");
      return;
    }

    this.ifFalse = this.ifTrue.getCopy();
  }
Makes sure that the returned values from getIfTrue() and getIfFalse()
are 2 different maps, and therefore can be mutated without affecting
the other map.
src/org/jetbrains/java/decompiler/modules/decompiler/sforms/VarMapHolder.java