Compile only modules that are dependencies of the main module

[bugarela]

#725 (comment)

Depends on #129

[konnov]

Having #1008 merged, it is relatively easy to implement this feature. We could go even further and prune unused definitions. However, one thing that worries me is that we would miss definitions that otherwise could produce compile-time errors.

What is our concern here? Is it performance or something else?

[bugarela]

You're the one who brought this up: #725 (comment) 😄

But I believe it mainly affects performance.

This is related to what I mentioned here #1023 (comment). I might rewrite the flattener so it only copies actually used definitions.

one thing that worries me is that we would miss definitions that otherwise could produce compile-time errors.

But that's a good thing, right? Runtime errors should only occur when runtime reaches that branch, and compile-time errors should all be caught by static analysis (which runs before the flattener).

[bugarela]

Done by the new flattener