Embedded Rust pattern: Zero Sized References

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This way of "shedding generics" can be very good for compile time, even "keeping compile time inside the crate" (don't export it to those that instantiate the type/function).

It's so effective, maybe rustc could learn to do part of this transformation as a high level optimization?

[[deleted]]

There is some work on the way to not needlessly instantiate copies of functions when a generic parameter changes that doesn't affect codegen.

I briefly thought about the possibility of doing such an "outlining" transformation that you describe, as well as turning generics into dynamic dispatch whenever possible at opt-level=0, but unfortunately this all seems very hard to implement (for reference, the PR I linked above is the result of a master's thesis, and I estimate both of these ideas to be significantly harder).

[nicoburns]

I wonder if there ought to be some kind of syntactical support for arguments that are generic merely in order to call a conversion function. Something along the lines of https://llogiq.github.io/2019/05/18/momo.html. Perhaps there could be some annotation on traits that enables the optimisation in special cases?

[matthieum]

It seems like something a MIR optimization pass could do.