fails to compile with minimal-versions

[joseluis]

num-rational fails to compile with the minimal-versions indicated in the manifest because num-bigint version 0.4.0 is insufficient. It should be updated to version 0.4.2 since that's the first version that compiles.

Test:

cargo +nightly update -Z minimal-versions
cargo build

[cuviper]

The actual error:

error[E0308]: mismatched types
  --> /home/jistone/.cargo/registry/src/index.crates.io-6f17d22bba15001f/num-bigint-0.4.0/src/biguint/convert.rs:70:19
   |
70 |         .div_ceil(&big_digit::BITS.into())
   |          -------- ^^^^^^^^^^^^^^^^^^^^^^^ expected `u64`, found `&_`
   |          |
   |          arguments to this method are incorrect
   |
   = note:   expected type `u64`
           found reference `&_`

(and several more like that)

That's not a dependency problem, just that the older num-bigint has errors with newer toolchains since the stabilization of inherent div_ceil methods in Rust 1.73, when it intends to use Integer::div_ceil that takes a reference. (Fixed in rust-num/num-bigint#219.) It does work if you're using an older toolchain though, like the MSRV 1.60.0.

This is an example why -Z minimal-versions is not a great tool, IMO.
(-Z direct-minimal-versions is a little better, since it only affects those in your own control.)

[joseluis]

the older num-bigint has errors with newer toolchains (...)
It does work if you're using an older toolchain though

I see ... Although I'm not sure what the downside would be if requiring bigint 0.4.2 from num-rational 0.4.3, allowing them to be more in sync. MSRV would still be the same.

direct-minimal-versions is a little better, since it only affects those in your own control

I see them as complementary. minimal-versions goes deeper and does not forgive...