1 files changed, 45 insertions, 7 deletions
diff --git a/lib/rubygems/resolver/conflict.rb b/lib/rubygems/resolver/conflict.rb
index 8830e8d1fb..902c286b6b 100644
--- a/lib/rubygems/resolver/conflict.rb
+++ b/lib/rubygems/resolver/conflict.rb
@@ -52,11 +52,40 @@ class Gem::Resolver::Conflict
 
   def explanation
     activated   = @activated.spec.full_name
-    requirement = @failed_dep.dependency.requirement
+    dependency  = @failed_dep.dependency
+    requirement = dependency.requirement
+    alternates  = dependency.matching_specs.map { |spec| spec.full_name }
 
-    "  Activated %s via:\n    %s\n  instead of (%s) via:\n    %s\n" % [
-      activated,   request_path(@activated).join(', '),
-      requirement, request_path(requester).join(', '),
+    unless alternates.empty? then
+      matching = <<-MATCHING.chomp
+
+  Gems matching %s:
+    %s
+      MATCHING
+
+      matching = matching % [
+        dependency,
+        alternates.join(', '),
+      ]
+    end
+
+    explanation = <<-EXPLANATION
+  Activated %s
+  which does not match conflicting dependency (%s)
+
+  Conflicting dependency chains:
+    %s
+
+  versus:
+    %s
+%s
+    EXPLANATION
+
+    explanation % [
+      activated, requirement,
+      request_path(@activated).reverse.join(", depends on\n    "),
+      request_path(@failed_dep).reverse.join(", depends on\n    "),
+      matching,
     ]
   end
 
@@ -95,10 +124,19 @@ class Gem::Resolver::Conflict
     path = []
 
     while current do
-      requirement = current.request.dependency.requirement
-      path << "#{current.spec.full_name} (#{requirement})"
+      case current
+      when Gem::Resolver::ActivationRequest then
+        path <<
+          "#{current.request.dependency}, #{current.spec.version} activated"
+
+        current = current.parent
+      when Gem::Resolver::DependencyRequest then
+        path << "#{current.dependency}"
 
-      current = current.parent
+        current = current.requester
+      else
+        raise Gem::Exception, "[BUG] unknown request class #{current.class}"
+      end
     end
 
     path = ['user request (gem command or Gemfile)'] if path.empty?