putAt and @CompileStatic

[Per Nyfelt]

Hi,
I was recently experimenting with @CompileStatic for performance improvements 
and noticed that when using the short notation of putAt to assign a null value 
I get the following error
[Static type checking] - Cannot call <T> 
org.codehaus.groovy.runtime.DefaultGroovyMethods#putAt(java.util.List<T>, int, 
T) with arguments [java.util.List<java.lang.String>, int, java.lang.Object]

Here is an example:

import groovy.transform.CompileStatic
import org.junit.jupiter.api.Test

@CompileStatic
class PutAtTest {

  @Test
  void testList() {
    // These all work
    def list = ['a', 'b', 'c']
    list[0] = 'aa'
    assert list[0] == 'aa'

    list.set(2, null)
    assert list[2] == null

    list.putAt(0, null)
    assert list[0] == null

    // This Fails
    list[1] = null
    assert list[1] == null : "Short notation not working when assigning null"
  }

  @Test
  void testMap() {
    // These all work
    def map = [a: 'foo', b: 'bar', c: 'baz']
    map['a'] = 'aa'
    assert map['a'] == 'aa'

    map.put('c', null)
    assert map['c'] == null

    map.putAt('a', null)
    assert map['a'] == null

    // This Fails
    map['b'] = null
    assert map['b'] == null  : "Short notation not working when assigning null"
  }
}

Is this expected behavior or a bug? Does anyone know of workaround?

Regards,
Per