Function parse_index_or_slice_expression

crates/gitql-parser/src/parser.rs:2767–2956

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

}

pub(crate) fn parse_index_or_slice_expression(
    context: &mut ParserContext,
    env: &mut Environment,
    tokens: &[Token],
    position: &mut usize,
) -> Result<Box<dyn Expr>, Box<Diagnostic>> {
    let mut lhs = parse_prefix_unary_expression(context, env, tokens, position)?;

    'parse_expr: while *position < tokens.len() && tokens[*position].kind == TokenKind::LeftBracket
    {
        let operator = &tokens[*position];

        // Consume Left Bracket `[`
        *position += 1;

        let lhs_type = lhs.expr_type();

        // Slice with end only range [:end]
        if is_current_token(tokens, position, TokenKind::Colon) {
            // Consume Colon `:`
            *position += 1;

            // In case the user use default slice start and end, we can ignore the slice expression
            // and return array or any kind of expression value directly
            if is_current_token(tokens, position, TokenKind::RightBracket) {
                // Consume right bracket `]`
                *position += 1;
                return Ok(lhs);
            }

            let slice_end = parse_prefix_unary_expression(context, env, tokens, position)?;
            let end_type = slice_end.expr_type();

            // Check if LHS already support slice op
            if !lhs_type.can_perform_slice_op() {
                return Err(Diagnostic::error(&format!(
                    "Operator `[:]` can't be performed on type `{lhs_type}`"
                ))
                .with_location(calculate_safe_location(tokens, *position))
                .as_boxed());
            }

            // Check that LHS support slice op with this type
            let rhs_expected_types = lhs_type.can_perform_slice_op_with();
            if !rhs_expected_types.contains(&end_type) {
                return Err(Diagnostic::error(&format!(
                    "Operator `[:]` can't be performed with type of index `{}`",
                    end_type.literal()
                ))
                .with_location(calculate_safe_location(tokens, *position))
                .as_boxed());
            }

            // Consume Right Bracket `]`
            consume_token_or_error(
                tokens,
                position,
                TokenKind::RightBracket,