Rollup merge of #24864 - astraw:patch-1, r=steveklabnik
Rollup merge of #24864 - astraw:patch-1, r=steveklabnik

If you have 0 references (`&T`) to a resource, presumably, you could have a mutable reference (`&mut T`). So this only start to make sense at having 1 reference to a resource.

zachwick/rust,GBGamer/rust,robertg/rust,reem/rust,vhbit/rust,cllns/rust,KokaKiwi/rust,vhbit/rust,aepsil0n/rust,philyoon/rust,zachwick/rust,sae-bom/rust,robertg/rust,mdinger/rust,XMPPwocky/rust,ejjeong/rust,kwantam/rust,andars/rust,seanrivera/rust,aidancully/rust,mvdnes/rust,aidancully/rust,XMPPwocky/rust,TheNeikos/rust,victorvde/rust,mdinger/rust,kwantam/rust,gifnksm/rust,graydon/rust,rohitjoshi/rust,krzysz00/rust,XMPPwocky/rust,l0kod/rust,vhbit/rust,XMPPwocky/rust,jashank/rust,pshc/rust,cllns/rust,KokaKiwi/rust,aepsil0n/rust,aidancully/rust,sae-bom/rust,l0kod/rust,GBGamer/rust,sae-bom/rust,aidancully/rust,XMPPwocky/rust,vhbit/rust,mihneadb/rust,TheNeikos/rust,l0kod/rust,kwantam/rust,aepsil0n/rust,reem/rust,zubron/rust,aepsil0n/rust,aidancully/rust,rohitjoshi/rust,mihneadb/rust,pelmers/rust,victorvde/rust,seanrivera/rust,victorvde/rust,pshc/rust,mihneadb/rust,philyoon/rust,ejjeong/rust,ejjeong/rust,jroesch/rust,graydon/rust,l0kod/rust,andars/rust,rohitjoshi/rust,nwin/rust,seanrivera/rust,pelmers/rust,zubron/rust,zachwick/rust,XMPPwocky/rust,aneeshusa/rust,pshc/rust,aneeshusa/rust,dwillmer/rust,GBGamer/rust,ejjeong/rust,kwantam/rust,zubron/rust,pshc/rust,TheNeikos/rust,seanrivera/rust,jroesch/rust,omasanori/rust,andars/rust,mdinger/rust,cllns/rust,GBGamer/rust,rohitjoshi/rust,dwillmer/rust,TheNeikos/rust,aneeshusa/rust,zubron/rust,zachwick/rust,pshc/rust,philyoon/rust,pelmers/rust,philyoon/rust,l0kod/rust,dwillmer/rust,krzysz00/rust,gifnksm/rust,mvdnes/rust,sae-bom/rust,krzysz00/rust,carols10cents/rust,mdinger/rust,mdinger/rust,pelmers/rust,graydon/rust,nwin/rust,krzysz00/rust,zubron/rust,gifnksm/rust,nwin/rust,philyoon/rust,cllns/rust,aneeshusa/rust,robertg/rust,vhbit/rust,nwin/rust,zachwick/rust,krzysz00/rust,zachwick/rust,robertg/rust,jashank/rust,sae-bom/rust,jashank/rust,jroesch/rust,krzysz00/rust,robertg/rust,zubron/rust,pelmers/rust,ejjeong/rust,kwantam/rust,aidancully/rust,jroesch/rust,philyoon/rust,andars/rust,nwin/rust,KokaKiwi/rust,seanrivera/rust,reem/rust,l0kod/rust,mihneadb/rust,graydon/rust,KokaKiwi/rust,dwillmer/rust,kwantam/rust,aneeshusa/rust,nwin/rust,jashank/rust,sae-bom/rust,andars/rust,l0kod/rust,gifnksm/rust,mvdnes/rust,carols10cents/rust,pshc/rust,graydon/rust,rohitjoshi/rust,zubron/rust,vhbit/rust,pelmers/rust,TheNeikos/rust,mvdnes/rust,jashank/rust,jashank/rust,pshc/rust,victorvde/rust,rohitjoshi/rust,mvdnes/rust,andars/rust,robertg/rust,mihneadb/rust,vhbit/rust,graydon/rust,cllns/rust,jashank/rust,omasanori/rust,pshc/rust,GBGamer/rust,seanrivera/rust,nwin/rust,jroesch/rust,omasanori/rust,TheNeikos/rust,mdinger/rust,reem/rust,reem/rust,carols10cents/rust,GBGamer/rust,victorvde/rust,mihneadb/rust,dwillmer/rust,reem/rust,omasanori/rust,ejjeong/rust,omasanori/rust,jroesch/rust,jashank/rust,carols10cents/rust,KokaKiwi/rust,GBGamer/rust,aneeshusa/rust,jroesch/rust,dwillmer/rust,dwillmer/rust,dwillmer/rust,aepsil0n/rust,aepsil0n/rust,nwin/rust,GBGamer/rust,victorvde/rust,carols10cents/rust,cllns/rust,l0kod/rust,omasanori/rust,mvdnes/rust,gifnksm/rust,gifnksm/rust,jroesch/rust,KokaKiwi/rust,vhbit/rust,zubron/rust,carols10cents/rust