Simple enum objects cannot be inlined.

[blickly]

This issue was imported from Closure Compiler's previous home at http://closure-compiler.googlecode.com

The link to the original issue is:
https://blickly.github.io/closure-compiler-issues/#1310

[concavelenz]

So this is the issue. Because it is in an anonymous closure the function is hoisted to the top of the scope. Now, the variable is referenced before its declaration (in the AST). Changing the code to:

/** @constructor */
var Interpreter = function () {
    this.v = OP.k;
}

Allows the value to be inlined. I'm not sure what else is going on.