Symbol culling and dead code removal is already a thing in modern compilers and linkers, and rust can do it too: https://github.com/johnthagen/min-sized-rust
Part of the issue I have with the dependency bloat is how much effort we currently go through to download, distribute, compile, lint, typecheck, whatever 1000s of lines of code we don't want or need. I want software that allows me to build exactly as much as I need and never have to touch the things I don't want.
Why, in principle, wouldn't the same algorithms work before distribution?
For that matter, check out the `auditwheel` tool in the Python ecosystem.
For example, you have a function calling XML or PDF or JSON output functions depending on some output format parameter. That's three very different paths and includes, but if you don't know which values that parameter can take during runtime you will have to include all three paths, even if in reality only XML (for example) is ever used.
Or there may be higher level causes outside of any analysis, even if you managed a dynamic one. In a GUI, for example, it could be functionality only ever seen by a few with certain roles, but if there is only one app everything will have to be bundled. Similar scenarios are possible with all kinds of software, for example an analysis application that supports various input and output scenarios. It's a variation of the first example where the parameter is internal, but now it is external data not available for an analysis because it will be known only when the software is actually used.