The main downside I see to branching on the next token within the parse_statement function itself is that doing so would split logic between the parse_* functions called by parse_statement (parse_if_statement, parse_while_statement, etc) and the parse_statement function itself.

For example, suppose parse_statement was modified to only calling `parse_if_statement` if the next token was an `if`, thus avoiding the try-except pattern. Then, while parse_statement would be responsible for checking if the next token is `if`, parse_if_statement would be responsible for parsing the `(` token, the expression that follows, the closing `)`, and so on. I figured it was easier to keep the entire identity of an if-statement within the parse_if_statement function itself rather than splitting it between the parse_statement and parse_if_statement functions.