babel: retainLines doesn't work with class-properties-transform

Given this input:

 class SourceMapTest {
   /* some comment */
   foo() {
     debugger;
   }
   bar() {
     alert(1);
   }
 }

“retainLines” produces correct output:

SourceMapTest.prototype.
foo=function(){'use strict';
debugger;
};SourceMapTest.prototype.
bar=function(){'use strict';
alert(1);
};function SourceMapTest(){'use strict';}

However, with “class-properties-transform”, “retainLines” no longer works correctly:

class SourceMapTest {
 /* some comment */
 foo() {
   debugger;
 }
 bar = function() {
    alert(1);
  };
}

function SourceMapTest(){'use strict';this.





bar=function(){
alert(1);
};}SourceMapTest.prototype.foo=function(){'use strict';debugger;};

Notice that foo is not at the correct line.