Before You File a Proposal Please Confirm You Have Done The Following...

• I havesearched for related issues and found none that match my proposal.
• I have searched thecurrent rule list and found no rules that match my proposal.
• I haveread the FAQ and my problem is not listed.

My proposal is suitable for this project

• My proposal specifically checks TypeScript syntax, or it proposes a check that requires type information to be accurate.
• My proposal is not a "formatting rule"; meaning it does not just enforce how code is formatted (whitespace, brace placement, etc).
• I believe my proposal would be useful to the broader TypeScript community (meaning it is not a niche proposal).

Description

I would love a rule that forces users to useprivate class members over using theprivate keyword.

Private class members have been added in ES 2022 and are supported in most major browsers as well as Node 14 and up. Time for libraries to migrate.

Fail Cases

classFoo{// Errorprivatebar=0;// Errorconstructor(privatebaz:number){}// ErrorprivatetoString():string{return'';}}

Pass Cases

classFoo{   #bar=0;    #baz:number;constructor(baz:number){this.#baz=baz;}// Error  #toString():string{return'';}}

Additional Info

This might be auto-fixable, that would be sweet! But it might make it very difficult.