json! unusable with no_std and feature alloc

[jendrikw]

When you use an array inside the json! macro, the expansion calls vec! unqualified. This is a problem in a no_std environment, because it requires the user to use alloc::vec. Which is weird and no expected from a macro.

Reproducer on rustexplorer: https://www.rustexplorer.com/b#LyoKW2RlcGVuZGVuY2llc10Kc2VyZGVfanNvbiA9IHsgdmVyc2lvbiA9ICIxLjAuMTIwIiwgZGVmYXVsdC1mZWF0dXJlcyA9IGZhbHNlLCBmZWF0dXJlcyA9IFsiYWxsb2MiXSB9CiovCgojIVtub19zdGRdCgpleHRlcm4gY3JhdGUgYWxsb2M7CgpmbiBtYWluKCkgewogICAgc2VyZGVfanNvbjo6anNvbiEoWyIiLCAiIl0pOwp9Cg==

Code:

/*
[dependencies]
serde_json = { version = "1.0.120", default-features = false, features = ["alloc"] }
*/

#![no_std]

extern crate alloc;

fn main() {
    serde_json::json!(["", ""]);
}

I think this issue has a simple solution by changing vec! to ::alloc::vec!, unless I'm missing something.

[jendrikw]

Wow that was quick. Thank you.