ES6 Inspection Differences in <script> vs .js

I'm seeing a syntax error when I use ES6 in a <script> tag that I'm not seeing in a separate .js file.  I set Settings > Languages & Frameworks > JavaScript > JavaScript language version to ECMAScript 6. Here are the two files:

foo.js


foo.html

(The yellow squiggle message is "Unreachable code".)

Is this a settings issue?  A bug?  Something else?