False warnings for obsolete features about cargo-outdated

[Frederick888]

@shssoichiro Haven't got time to actually look into it but it seems that Summary::features() does not include optional dependencies by default hence the false warnings.

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@oherrala Due to the fact that quickcheck has been yanked. Could you please file another issue?

[oherrala]

I have probably the same issue in our multicrate project. Simplified example:

Root Cargo.toml:

[workspace]
members = [ "dummylib", "dummybin" ]

dummylib/Cargo.toml:

[package]
name = "dummylib"

[dependencies]
quickcheck = { version = "*", optional = true }

dummybin/Cargo.toml:

[package]
name = "dummybin"

[dependencies]
dummylib = { path = "../dummylib" }

[dev-dependencies]
dummylib = { path = "../dummylib", features = ["quickcheck"] }

$ cargo outdated
warning: Feature quickcheck of package dummylib has been obsolete in version 0.1.0
warning: Feature quickcheck of package dummylib has been obsolete in version 0.1.0
error: no matching version `^0.4.2` found for package `quickcheck` (required by `dummylib`)
location searched: registry https://github.com/rust-lang/crates.io-index
versions found: 0.4.1, 0.4.0, 0.3.2, ...

"no matching version" error is in own issue: #101.