Bug#1120463: apt: Unable to satisfy dep when a amd64 Depends on a versioned virtual i386 package

[Tianyu Chen <sweetyfish@deepin.org>]

Package: apt
Version: 3.1.11
Severity: normal
X-Debbugs-Cc: sweetyfish@deepin.org

Hi,

I've come up with this problem:

	Package: dep
	Version: 1.0.0
	Architecture: amd64
	Maintainer: test <test@example.com>
	Provides: dep-virt (= 2.0.0)

	Package: app
	Version: 1.0.0
	Architecture: i386
	Maintainer: test <test@example.com>
	Depends: dep-virt:amd64 (>= 2.0.0)

With these two packages:

	$ apt install ./app_1.0.0_i386.deb ./dep_1.0.0_amd64.deb # Success
	$ apt install ./dep_1.0.0_amd64.deb ./app_1.0.0_i386.deb # Fail

In the latter, apt shows:

	Unsatisfied dependencies:
	 app:i386 : Depends: dep-virt:amd64 (>= 2.0.0)
	Error: Unable to satisfy dependencies. Reached two conflicting decisions:
	   1. app:i386=1.0.0 is selected for install
	   2. app:i386 Depends dep-virt:amd64 (>= 2.0.0)
	      but none of the choices are installable:
	      [no choices]

I've also run apt with -o Debug::APT::Solver=3, and I've found in the
former, there's a line:

	Adding work to  item app:i386 -> dep:amd64=1.0.0

But this line does not exist in the latter.

Best regards,
Tianyu Chen @ deepin