Function parse_trailer_expr 

fn parse_trailer_expr(
    cx: &mut ParseCtxt<'_>,
    allow_struct: bool,
) -> ParseResult<Expr>

⟨trailer_expr⟩ :=  ⟨trailer_expr⟩ . ⟨ident⟩
                |  ⟨trailer_expr⟩ ( ⟨expr⟩,* )
                |  ⟨atom⟩