Investigate/Verify diagnostic for `func<float>()` and 'func<int>()' for attributes

[smanna12]

Is it expected that we get an implicit conversion for func<float>() or was that a surprise (if a surprise, maybe open an issue for it)?

Also, is the inconsistency between the other attributes with func<int>() expected? I would assume we'd want all of these or none of these to behave the same way. If it's unexpected, maybe open another issue?

Originally posted by @AaronBallman in #3089 (comment)

[smanna12]

Not a issue based on note: f0112fc#r46386167