Hi Pawel,

Good analysis. The Map<String, @NotBlankTypeUse String> case was covered by a test but not with an additional constraint on the whole Map. I added a test case, which fails as reported.

In the case of another generic type, you have to provide an unwrapper anyway.

IMHO, the best way to fix this is to rely on the notion of indexable which is present in the code and covers Iterables, Maps and arrays. I prepared a patch along those lines. Will post the PR tomorrow.