Panic when marshaling embedded aliased primitive

[ericklaus-wf]

When marshaling a struct that has any field and also embeds an aliased primitive, go-json panics. Additionally, if the panic is resolved, the produced bytes are correct, but go-json ignores the aliased primitive when unmarshaling.

func TestEmbeddedPrimitiveAlias(t *testing.T) {
	type AliasedPrimitive int
	type Combiner struct {
		SomeField int
		AliasedPrimitive
	}
	originalCombiner := Combiner{AliasedPrimitive: 7}
	bytes, err := json.Marshal(originalCombiner)
	assertErr(t, err)
	newCombiner := Combiner{}
	err = json.Unmarshal(bytes, &newCombiner)
	assertErr(t, err)
	assertEq(t, "TestEmbeddedPrimitiveAlias", originalCombiner, newCombiner)
}

[ericklaus-wf]

I can fix the panic and get correct bytes by modifying lastAnonymousFieldCode to add a nil check on firstField.Next, but I've gotten lost trying to find the issue in the Unmarshal path.

[orisano]

Unmarshal path's issue is maybe here:

go-json/internal/runtime/struct_field.go

Line 16 in 22be3b9

if !(field.Type.Kind() == reflect.Ptr && field.Type.Elem().Kind() == reflect.Struct) && field.Type.Kind() != reflect.Struct {