UserAgent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_13_3) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/66.0.3359.117 Safari/537.36

Steps to reproduce the problem:
1. I tried the attached javascript with devTools open, and with devTools closed (it gets an element, and then the data attribute from that element).
When using the step through debugger, the data attribute is not assigned to the variable. 
The same code works when used directly in the console.

2. Tried removing type="module" but then (another bug?) the dataset method breaks.
3. Tried in Chrome Canary - same error.

What is the expected behavior?
const greeting should be "Hello World", not ReferenceError when console is opened, and code is stepped through.

bizarrely, this is still printed to the console with the console.log statements, but I'm using this in a more complex piece of code, and it's causing problems when I debug.

What went wrong?
ReferenceError after assignment for otherwise working code.
Only happens when devTools is open / using step through debugger.

Did this work before? N/A 

Chrome version: 66.0.3359.117  Channel: n/a
OS Version: OS X 10.13.3
Flash Version: 

Apologies if this is an existing issue or me not doing something correctly. It really looks like a bug to me.
 

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