Cannot launch Drupal 8 on Dev Desktop

I'm able to reproduce the issue @hatcat describes. Placing it in the Drupal core project queue, changing the priority to normal.

@hatcat's summary refers to the Drupal Ladder project, but the issue is not specific to Drupal Ladder.

After addressing other items on the Ladder that led me to this issue, I'll do some troubleshooting to see if the installation issue is specific to Dev Desktop.

Looks as if the issue is specific to Dev Desktop (using latest version: 7.14.14 on Mac). I am moving the issue back to the Ladder issue queue in case others have the same problem following the instructions there. I will also file a bug report on Acquia's Dev Desktop forum.

The issue referred to in the error on line 571 of settings.php is syntactically incorrect. This line of code is autogenerated by the Acquia Dev Desktop Control Panel to do what it claims is a D7 DB Config. In what I am seeing generated, there are 3 checks for $databases = NULL; without closing the logical statement. It appears to have been generated incorrectly. Not sure about the intention of what was supposed to be generated here.

As a workaround, I was able to just comment out the if check and Drupal installed just fine on the Dev Desktop.

New to Drupal and having this same issue - I tried to comment out the if check but got the same error. Perhaps I took out too much? Here's what I have:

///////////////////////////////////////////////////////////////////////
// Don't edit anything below this line! //
// This section is autogenerated by Acquia Dev Desktop Control Panel //
///////////////////////////////////////////////////////////////////////
//<@@ADCP_CONF@@>
$base_url = 'http://mydrupal8.localhost:8082';

//D6 DB config
$db_url = 'mysqli://drupaluser@127.0.0.1:33066/mydrupal8';

//D7 DB config
//if( !isset($databases = NULL;$databases = NULL;
//$databases = NULL;
//

That's what I've done but perhaps it was not in the correct file? I deleted the original system.php in the drupal8 downloaded file and replaced with a settings.php file that has the if check commented out. Didn't work.
I also tried editing the settings.php file in the new database I created on dev desktop. Still not working. I think I don't know enough to know what I'm doing wrong...? I guess my question at this point is about the process of commenting out the if check - what specific system.php file do I need to be changing? Any advice would be much appreciated!

It's very well possible that commenting out that if statement won't work for everyone. I'm not sure what the if check was supposed to do.

I ended up locating the appropriate settings.php file by modifying the exact file that was specified on the error page.

Could the problem be that a completely invalid line is being generated somehow? The if() lines listed in #4 above are not valid PHP.

Yes @DamienMcKenna. That is definitely not valid code. However, that is generated code. The root cause for the issue exists some place where that code is generated.

Accidentally put in an extra '\' before settings.php