fn add_src(&mut self, txt: impl AsRef<str>) -> usize {
        self.source.push_str(txt.as_ref());
        self.source.push(' ');
        self.source.len()
    }
/// Return end index of source slice.
Return end index of source slice.
Return end index of source slice .
fn add_src(&mut self, txt: impl AsRef<str>) -> usize {
        self.source.push_str(txt.as_ref());
        self.source.push(' ');
        self.source.len()
    }
fn add_src ( & mut self , txt : impl AsRef < str > ) -> usize { self . source . push_str ( txt . as_ref ( ) ) ; self . source . push ( ' ' ) ; self . source . len ( ) }
Return end index of source slice.
Return end index of source slice .
&mut self
txt
impl AsRef<str>
&mut self
txt
impl AsRef<str>