The gem dependencies platform is different from Gem::Platform. A platform gem.deps.rb platform matches on the ruby engine, the ruby version and whether or not windows is allowed.

:ruby, :ruby_XY: Matches non-windows, non-jruby implementations where X and Y can be used to match releases in the 1.8, 1.9, 2.0 or 2.1 series.
:mri, :mri_XY: Matches non-windows C Ruby (Matz Ruby) or only the 1.8, 1.9, 2.0 or 2.1 series.
:mingw, :mingw_XY: Matches 32 bit C Ruby on MinGW or only the 1.8, 1.9, 2.0 or 2.1 series.
:x64_mingw, :x64_mingw_XY: Matches 64 bit C Ruby on MinGW or only the 1.8, 1.9, 2.0 or 2.1 series.
:mswin, :mswin_XY: Matches 32 bit C Ruby on Microsoft Windows or only the 1.8, 1.9, 2.0 or 2.1 series.
:mswin64, :mswin64_XY: Matches 64 bit C Ruby on Microsoft Windows or only the 1.8, 1.9, 2.0 or 2.1 series.
:jruby, :jruby_XY: Matches JRuby or JRuby in 1.8 or 1.9 mode.
:maglev: Matches Maglev
:rbx: Matches non-windows Rubinius

NOTE: There is inconsistency in what environment a platform matches. You may need to read the source to know the exact details.

Gem::RequestSet::GemDependencyAPI#platforms

Block form for restricting gems to a particular set of platforms. See platform.

Gem::Resolver::ActivationRequest#installed?

True if the requested gem has already been installed.

Gem::Resolver::Conflict#explanation

Explanation of the conflict used by exceptions to print useful messages

Gem::Resolver::DependencyRequest#match?

Does this dependency request match spec?

NOTE: match? only matches prerelease versions when dependency is a prerelease dependency.

Gem::Resolver::GitSpecification#install

Installing a git gem only involves building the extensions and generating the executables.

Gem::Resolver::InstalledSpecification#install

This is a null install as this specification is already installed. options are ignored.

Gem::Resolver::LockSpecification#install

This is a null install as a locked specification is considered installed. options are ignored.

Gem::Resolver::SpecSpecification#platform

The platform this gem works on.

Gem::Resolver::Specification#install

Installs this specification using the Gem::Installer options. The install method yields a Gem::Installer instance, which indicates the gem will be installed, or nil, which indicates the gem is already installed.

After installation spec is updated to point to the just-installed specification.

Gem::Resolver::Stats#iteration!

No documentation available

Gem::Resolver::VendorSpecification#install

This is a null install as this gem was unpacked into a directory. options are ignored.

WEBrick::HTTPAuth::BasicAuth#authenticate

Authenticates a req and returns a 401 Unauthorized using res if the authentication was not correct.

WEBrick::HTTPAuth::DigestAuth#authenticate

Authenticates a req and returns a 401 Unauthorized using res if the authentication was not correct.

WEBrick::HTTPServlet::ERBHandler#evaluate

Evaluates erb providing servlet_request and servlet_response as local variables.