Rollup merge of #26073 - chuckSMASH:trpl-5-4-comments, r=steveklabnik
Rollup merge of #26073 - chuckSMASH:trpl-5-4-comments, r=steveklabnik

For a user following the path of reading Chapter 5: Syntax & Symantics
prior to Chapter 4: Learn Rust, this will be the first time they have
encountered executable tests inside documentation comments.

The test will fail because the `add_one` function is not defined in
the context of the doctest. This might not be the optimal place to
introduce and explain the `/// #` notation but I think it is important
that this snippet pass as a test when `rustdoc --test` is run against
it.

mvdnes/rust,jroesch/rust,graydon/rust,omasanori/rust,nwin/rust,aneeshusa/rust,zachwick/rust,l0kod/rust,mvdnes/rust,vhbit/rust,l0kod/rust,zubron/rust,GBGamer/rust,graydon/rust,pelmers/rust,jroesch/rust,KokaKiwi/rust,zubron/rust,aepsil0n/rust,KokaKiwi/rust,jroesch/rust,jroesch/rust,mihneadb/rust,omasanori/rust,jroesch/rust,pelmers/rust,GBGamer/rust,graydon/rust,vhbit/rust,robertg/rust,omasanori/rust,jroesch/rust,graydon/rust,pshc/rust,KokaKiwi/rust,vhbit/rust,reem/rust,jroesch/rust,dwillmer/rust,l0kod/rust,vhbit/rust,aepsil0n/rust,jashank/rust,robertg/rust,reem/rust,pshc/rust,aidancully/rust,GBGamer/rust,l0kod/rust,omasanori/rust,dwillmer/rust,nwin/rust,GBGamer/rust,dwillmer/rust,aidancully/rust,pelmers/rust,reem/rust,GBGamer/rust,l0kod/rust,vhbit/rust,reem/rust,pelmers/rust,zachwick/rust,jashank/rust,nwin/rust,aepsil0n/rust,dwillmer/rust,nwin/rust,graydon/rust,GBGamer/rust,vhbit/rust,zachwick/rust,jashank/rust,vhbit/rust,aidancully/rust,nwin/rust,aepsil0n/rust,jashank/rust,mihneadb/rust,robertg/rust,pshc/rust,aneeshusa/rust,pshc/rust,mvdnes/rust,mihneadb/rust,zubron/rust,l0kod/rust,pshc/rust,zachwick/rust,nwin/rust,jashank/rust,pelmers/rust,KokaKiwi/rust,mvdnes/rust,mihneadb/rust,mvdnes/rust,aepsil0n/rust,pshc/rust,omasanori/rust,aepsil0n/rust,jashank/rust,aneeshusa/rust,aidancully/rust,pelmers/rust,robertg/rust,dwillmer/rust,zubron/rust,mihneadb/rust,aidancully/rust,l0kod/rust,dwillmer/rust,dwillmer/rust,zubron/rust,aidancully/rust,robertg/rust,graydon/rust,GBGamer/rust,nwin/rust,robertg/rust,l0kod/rust,dwillmer/rust,aneeshusa/rust,jashank/rust,aneeshusa/rust,mvdnes/rust,pshc/rust,zubron/rust,jroesch/rust,reem/rust,vhbit/rust,pshc/rust,KokaKiwi/rust,zachwick/rust,omasanori/rust,mihneadb/rust,KokaKiwi/rust,jashank/rust,zubron/rust,zachwick/rust,zubron/rust,GBGamer/rust,aneeshusa/rust,reem/rust,nwin/rust