Static compilation confused by factory methods, map initializers and generics

@groovy.transform.CompileStatic
class TestFails<T extends Comparable> {
    List<T> x
    static <M extends Comparable> TestFails<M> select(List<M> x) { 
        new TestFails<M>(x: x) 
    }
}

@groovy.transform.CompileStatic
class TestWorks<T extends Comparable> {
    List<T> x
    static <M extends Comparable> TestWorks<M> select(List<M> x) {
        new TestWorks<M>()
    }
}