You tell the compiler what data type you're trying to use, and it finds a high-performance implementation for you over the internet.

That sounds incredibly safe.

Have you tried it? Or are you just imagining an extremely terrible implementation of the idea so you can write short quips about how bad it must be?

For basically every piece of software I work on this would have horrible security implications. Let me spell it out in black and white: every time someone does a deployment, by default it will download code from the internet and incorporate it into production code. All one would need do is subvert one external code provider and they'd have the ability to inject code into countless production systems at will. How much do you trust github or bitbucket? Would you give them the keys to your business, and your customer accounts?

Compile time never sounded so fun