Auto merge of #29948 - devonhollowood:fromstr-parse, r=steveklabnik
Auto merge of #29948 - devonhollowood:fromstr-parse, r=steveklabnik

Implement #29919

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