Optimize push_state_for_requirements by removing N^2 lookup

lib/molinillo/resolution.rb

@@ -155,6 +155,7 @@ def initialize(specification_provider, resolver_ui, requested, base)
         @original_requested = requested
         @base = base
         @states = []
+        @states_by_requirement = {}
         @iteration_counter = 0
         @parents_of = Hash.new { |h, k| h[k] = [] }
       end
@@ -200,6 +201,10 @@ def resolve
       attr_accessor :states
       private :states
 
+      # @return [Hash{Object => ResolutionState}] states keyed by their requirement
+      attr_accessor :states_by_requirement
+      private :states
+
       private
 
       # Sets up the resolution process
@@ -586,7 +591,7 @@ def requirement_for_existing_name(name)
       #   `requirement`.
       def find_state_for(requirement)
         return nil unless requirement
-        states.find { |i| requirement == i.requirement }
+        states_by_requirement[requirement]
       end
 
       # @param [Object] underlying_error
@@ -755,7 +760,7 @@ def push_state_for_requirements(new_requirements, requires_sort = true, new_acti
         new_requirement = nil
         loop do
           new_requirement = new_requirements.shift
-          break if new_requirement.nil? || states.none? { |s| s.requirement == new_requirement }
+          break if new_requirement.nil? || states_by_requirement[new_requirement].nil?
         end
         new_name = new_requirement ? name_for(new_requirement) : ''.freeze
         possibilities = possibilities_for_requirement(new_requirement)
@@ -831,6 +836,7 @@ def handle_missing_or_push_dependency_state(state)
           state.activated.detach_vertex_named(state.name)
           push_state_for_requirements(state.requirements.dup, false, state.activated)
         else
+          states_by_requirement[state.requirement] = state
           states.push(state).tap { activated.tag(state) }
         end
       end