Throw on clear(fn) if fn’s cache can't be cleared

[fregante]

Breaking change, to be released after #58 (which is a patch for the current version)

What's the point of calling clear(fn) if it does nothing? This just causes silent errors.

Regarding throwing errors:

• I can drop the explicit Can't clear a function that was not memoized! error since now it throws anyway, OR
• I can add an unclearable cache error

[sindresorhus]

When would cacheStore.get(fn).clear(); throw?

[fregante]

It throws if fn is missing: cacheStore.get(fn) is undefined because it’s undefined.clear

It throws if fn’s Map doesn’t have clear: cacheStore.get(fn).clear is not a function

[sindresorhus]

I can add an unclearable cache error

👍

[sindresorhus]

Is it really worth doing another breaking release just for this? I suggest releasing what's in master as a minor release and then merging this, but not release it until we need to do another release.

[fregante]

You could also keep this PR open until there’s another reason to release a breaking version.

[sindresorhus]

Yeah, we can do that.

[fregante]

I can add an unclearable cache error

I pushed a change based on the latest version and added a test. This is now ready to be merged