matcher for nil interface value

[tyro-jason]

Existing matchers can do nil assertions on interface values because they match on T or *T but not a T that can be an interface(ie ptr)

type Blah interface{
   DoSomething()
}

func TestShouldHaveANilBlah(t *testing.T){
var myBlah Blah

then.AssertThat(t, myBlah, is.NilPtr[Blah])

}

wont compile - as the signature for NilPtr is assuming a struct T and returns a [*T] matcher...

[corbym]

myBlah isn't being declared as a pointer in your example, its a value. is.NilPtr only works on pointers declared with *.

The test should be:

func TestShouldHaveANilBlah(t *testing.T) {
	var myBlah *Blah

	then.AssertThat(t, myBlah, is.NilPtr[Blah]())

}

I am not sure what the correct generic version of what you are looking for should look like.. knowing Blah is an interface not a real type is a hard problem. Knowing whether something can be nil given only a type isn't, as far as I know, possible with Go.

If you have an idea how to do what you say with types, please feel free to raise a PR and I will take a look.