Auto merge of #38947 - nrc:custom-derive-span, r=jseyfried
Auto merge of #38947 - nrc:custom-derive-span, r=jseyfried

Give custom derive spans an expansion ID

r? @jseyfried

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