error_incompatible_fn_types.rs

fn parse_if<'a>(input: &mut Peekable<TokenIterator<'a>>) -> Result<Stmt, ParseError> {
    Ok(Stmt::Expr(Node::IntConst(3)))
}

fn parse_expr_stmt<'a>(input: &mut Peekable<TokenIterator<'a>>) -> Result<Stmt, ParseError> {
    Ok(Stmt::Expr(Node::IntConst(4)))
}

fn parse_stmt<'a>(input: &mut Peekable<TokenIterator<'a>>) -> Result<Stmt, ParseError> {
    let mut parser = match input.peek() {
        Some(_) => parse_if,
        _ => parse_expr_stmt
    };

    parser(input)
}