parseBlock

fn parseBlock(p: *Parse) !?Node.Index {
    const lbrace = p.eatToken(.l_brace) orelse return null;
    const scratch_top = p.scratch.items.len;
    defer p.scratch.shrinkRetainingCapacity(scratch_top);
    while (true) {
        if (p.tokenTag(p.tok_i) == .r_brace) break;
        const statement = try p.expectStatementRecoverable() orelse break;
        try p.scratch.append(p.gpa, statement);
    }
    _ = try p.expectToken(.r_brace);
    const statements = p.scratch.items[scratch_top..];
    const semicolon = statements.len != 0 and (p.tokenTag(p.tok_i - 2)) == .semicolon;
    if (statements.len <= 2) {
        return try p.addNode(.{
            .tag = if (semicolon) .block_two_semicolon else .block_two,
            .main_token = lbrace,
            .data = .{ .opt_node_and_opt_node = .{
                if (statements.len >= 1) statements[0].toOptional() else .none,
                if (statements.len >= 2) statements[1].toOptional() else .none,
            } },
        });
    } else {
        return try p.addNode(.{
            .tag = if (semicolon) .block_semicolon else .block,
            .main_token = lbrace,
            .data = .{ .extra_range = try p.listToSpan(statements) },
        });
    }
}