type_name doesn't get correct type_name with const generics.

[crlf0710]

Example code:
https://play.rust-lang.org/?version=nightly&mode=debug&edition=2018&gist=2dd38f47a052e3545fad6cd1249d6a6a

dbg!(std::any::type_name::<Test<isize, {3}>>());
=>
[src/main.rs:11] std::any::type_name::<Test<isize, { 3 }>>() = "playground::Test<isize, >"