min_const_generics prevents references to concrete Self param

[lcnr]

👋 I'm trying to understand the limitations of min_const_generics. Is it expected that https://play.rust-lang.org/?version=nightly&mode=debug&edition=2018&gist=59cca2f3891e9fa921afdcbcda9f2588 compiles ok without min_const_generics, but fails with it?

Originally posted by @alex in #74878 (comment)

[lcnr]

We should not break stable code and change the generic parameters must not be used inside of non trivial constant values check to only run for const parameters.

So this is a bug of the current min_const_generics implementation.

[alex]

Thank @lcnr! Sorry about the noise on the tracking bug!

[alex]

FWIW, I was able to work around this in my own code by replacing mem::size_of::<Self>() with mem::size_of::<what self is>(): https://github.com/alex/rust-asn1/compare/ee5e5b48b5c765b8d460dc1b44b7716c59325706..bc7be1da41d86e99b602c8df66c320f8edc01f63

[varkor]

Self might be special enough that we can make this work in general, rather than limiting the scope of the generic parameters must not be used… error, because the parameter is effectively fixed. At the very least, we should have a better error message, because Self is not thought of as a generic parameter to users.

[lcnr]

We should be able to fix this, so I am not too worried about this yet

Will try to do so next week.