Function parse_case_expression

crates/gitql-parser/src/parser.rs:3552–3664

(
    context: &mut ParserContext,
    env: &mut Environment,
    tokens: &[Token],
    position: &mut usize,
)

}

fn parse_case_expression(
    context: &mut ParserContext,
    env: &mut Environment,
    tokens: &[Token],
    position: &mut usize,
) -> Result<Box<dyn Expr>, Box<Diagnostic>> {
    let mut conditions: Vec<Box<dyn Expr>> = vec![];
    let mut values: Vec<Box<dyn Expr>> = vec![];
    let mut default_value: Option<Box<dyn Expr>> = None;

    // Consume `case` keyword
    let case_location = tokens[*position].location;
    *position += 1;

    let mut has_else_branch = false;

    while *position < tokens.len() && tokens[*position].kind != TokenKind::End {
        // Else branch
        if tokens[*position].kind == TokenKind::Else {
            if has_else_branch {
                return Err(
                    Diagnostic::error("This `CASE` expression already has else branch")
                        .add_note("`CASE` expression can has only one `ELSE` branch")
                        .with_location(calculate_safe_location(tokens, *position))
                        .as_boxed(),
                );
            }

            // Consume `ELSE` keyword
            *position += 1;

            let default_value_expr = parse_expression(context, env, tokens, position)?;
            default_value = Some(default_value_expr);
            has_else_branch = true;
            continue;
        }

        // Consume `WHEN` keyword
        consume_token_or_error(
            tokens,
            position,
            TokenKind::When,
            "Expect `when` before case condition",
        )?;

        let condition = parse_expression(context, env, tokens, position)?;
        if !condition.expr_type().is_bool() {
            return Err(Diagnostic::error("Case condition must be a boolean type")
                .with_location(calculate_safe_location(tokens, *position))
                .as_boxed());
        }

        conditions.push(condition);

        // Consume `THEN` keyword
        consume_token_or_error(
            tokens,
            position,