cargo update hangs in cargo::core::resolver::activate_deps_loop

[codewiz]

I hit this while running "cargo update" on the master branch of https://github.com/paritytech/parity .

Trace: cargo-update.txt
Produced with RUST_LOG=cargo::core::resolver=trace cargo generate-lockfile

Cargo.lock.txt
Cargo.toml.txt

[codewiz]

Affects both cargo 1.18 and cargo nightly 0.20.0-nightly (9fcdbb4 2017-05-22)

[bennofs]

Looks like the problem is that multihash depends on ring ~0.7.1 which has been yanked --> the solver never finds a solution for ring and backtracks through the entire search space.

[bennofs]

The activation/backtracking chain seems to go something like this:

... -> isatty -> bitflags -> rpassword -> semver -> pretty_assertions -> difference -> matches -> quine-mc_cluskey -> miow -> multihash -> ring (fail)

and for each of the packages in the chain, cargo tries a few possibilities (and the chain is probably longer)

[alexcrichton]

Thanks for the investigation @bennofs! In that case I'm going to close this in favor of #4066 as I think it's a dupe of that issue.