build failure (linking) when upgrading from `windows` `0.59` to `0.60`

[rursprung]

Summary

i originally reported this here: twistedfall/opencv-rust#660
however, i think this is related to the switch from windows-targets to windows-link.

see the linked issue for all the details (incl. full cargo build -vv output) . but in short:
the test repository has a Cargo.lock with windows 0.59 in it and builds fine.
when i run cargo update (which primarily updates opencv-rust which in turn pulls in the windows update to 0.61) it fails with linking errors.

i now cloned opencv-rust and used [patch.crates-io] with a path override for it to link that into the test project. then i modified only the windows dependency there: if i set it to 0.59 everything compiles fine. if i set it to 0.60 it starts failing.

Crate manifest

see link to test repo above

Crate code

see link to test repo above

[kennykerr]

Do you have a minimal repro you can share?

[rursprung]

the smallest repro i could make was the linked repo (i'm not familiar with the windows crate at all, it's just a transitive dependency for me), sorry 🙁.
if i interpret the linker errors correctly then it fails to link the OpenCV library (written in C++) to the Windows API - opencv-rust is just a rust wrapper around OpenCV (which, in my case, is built by vcpkg as a static library using cargo-vcpkg and resolved by the vcpkg crate). so this might require a minimal repro to still include the language Rust->C++ boundary?

the only use windows i can find anywhere in opencv-rust is this one here, so i don't think that this is causing it?
https://github.com/twistedfall/opencv-rust/blob/edc443106d905f444b3114d59fd32b05628d7f29/src/manual/core/directx.rs#L35-L38

maybe the most important point from the other issue:

based on the diff (i removed the [opencv 0.94.*] at the beginning of the lines for this diff) i think the problem is that -L 'native=....cargo\registry\src\index.crates.io-1949cf8c6b5b557f\windows_x86_64_msvc-0.53.0\lib' went missing in the last two calls.

i'm not familiar with your switch from windows-targets to windows-link, but i'm surprised that windows_x86_64_msvc et al were removed as dependencies as part of the 0.59 -> 0.60 update of windows - is this correct?

[ChrisDenton]

So from your description it sounds like the OpenCV wrapper was implicitly depending on the windows-targets crate for C++ code rather than just Rust? Usually, when linking C++, crates would add the import libraries the C++ code requires. If it instead wants to depend on windows-targets crate then it should ideally add it as an explicit dependency. Relying on implementation details of windows is going to be more fragile.

[rursprung]

i added an explicit dependency from opencv-rust to windows-targets, but that had no effect (it still fails with windows 0.60 and 0.61). so it doesn't seem to be that.
i'm still not sure what - if anything - opencv-rust should be doing different? i'd have expected the win32 methods to be part of kernel32.lib, which is however present in the link.exe call which failed. i hope @twistedfall will be able to spot the problem

[kennykerr]

I don't see a problem with windows-rs but feel to keep the discussion going.