[xg15]

Yes, that's correct. In the GP example, c was const, so the type can be determined at compile time.

[simulate-me]

I was writing TypeScript, where const just means the variable is not reassigned. For instance this is valid:

    const c: C = Math.random() < 0.5 ? { type: 'a' } : { type: 'b' }.

[xg15]

Ah, I'm sorry. You're right of course!