Attribute bound does not work with stringify!

[entropylost]

Describe the bug

Using macros, including stringify! as arguments to the bound= errors.

To Reproduce

Compile

#[derivative(PartialEq(bound=stringify!()))]
struct Foo();

Errors

error: invalid attribute: expected literal

Version (please complete the following information):

rustup --version
rustup 1.24.3 (ce5817a94 2021-05-31)
cargo --version
cargo 1.56.0-nightly (cc17afbb0 2021-08-02)
rustc --version
rustc 1.56.0-nightly (ae90dcf02 2021-08-09)

• Version of derivative: 2.2.0