After build some parts of code aren't minified

I have this Angular service:

class MyService extends BaseService  {
    constructor(
        private translationService: TranslationService, 
        private authService: AuthService) {
        super()
    }

    getActiveLang() {
        return this.translationService.getActiveLang()
    }

    getUserMail() {
        const user = this.authService.currentUser();
        return user  ? user .email : null
    }          
}

After build the code becomes:

class u extends w.PV {
    constructor(_, t) {
        super(),
        this.translationService = _,
        this.authService = t
    }
    getActiveLang() {
        return this.translationService.getActiveLang()
    }
    getUserMail() {
        const _ = this.authService.currentUser();
        return _ ? _.email : null
    }          
}

Why aren't the properties (translationService, authService) and methods (getActiveLang, getUserMail) of injected services minified?

I answer my self.

Instance properties can leak into basically anywhere, where the minifier is not guaranteed to have applied a consistent minification.

Eg

window.svc = new MyService();

and then some global script uses window.svc.translationService to be available. The private marker does not prevent this; it is a TypeScript only keyword that minifiers don't see.

Some optimizers are capable of this minification, like Closure Compiler using Advanced optimizations, but you have to follow its strict rules to make everything work that way. Angular does not integrate/support Closure Compiler though.