Auto merge of #31028 - erickt:ast-json, r=michaelwoerister
Auto merge of #31028 - erickt:ast-json, r=michaelwoerister

The protocol for `serialize::{En,De}code` doesn't allow for two integers to be serialized next to each other.

Closes #31025.

cc @michaelwoerister

graydon/rust,aidancully/rust,aidancully/rust,GBGamer/rust,GBGamer/rust,GBGamer/rust,GBGamer/rust,graydon/rust,graydon/rust,GBGamer/rust,aidancully/rust,aidancully/rust,GBGamer/rust,GBGamer/rust,aidancully/rust,graydon/rust,aidancully/rust,GBGamer/rust,graydon/rust,graydon/rust