Simplify custom version scheme handling

Library/Homebrew/formula_support.rb

@@ -52,13 +52,11 @@ class SoftwareSpec
   end
 
   def version val=nil
-    @version ||= case val
-      when nil then Version.parse(@url)
-      when Hash
-        key, value = val.shift
-        scheme = VersionSchemeDetector.new(value).detect
-        scheme.new(key)
-      else Version.new(val)
+    @version ||=
+      case val
+      when nil  then Version.parse(@url)
+      when Hash then Version.new_with_scheme(*val.shift)
+      else           Version.new(val)
       end
   end
 

Library/Homebrew/version.rb

@@ -146,6 +146,14 @@ class Version
     end
   end
 
+  def self.new_with_scheme(value, scheme)
+    if Class === scheme && scheme.ancestors.include?(Version)
+      scheme.new(value)
+    else
+      raise TypeError, "Unknown version scheme #{scheme.inspect}"
+    end
+  end
+
   def initialize(val, detected=false)
     @version = val.to_s
     @detected_from_url = detected
@@ -295,24 +303,3 @@ class Version
     return m.captures.first unless m.nil?
   end
 end
-
-class VersionSchemeDetector
-  def initialize scheme
-    @scheme = scheme
-  end
-
-  def detect
-    if @scheme.is_a? Class and @scheme.ancestors.include? Version
-      @scheme
-    elsif @scheme.is_a? Symbol then detect_from_symbol
-    else
-      raise "Unknown version scheme #{@scheme} was requested."
-    end
-  end
-
-  private
-
-  def detect_from_symbol
-    raise "Unknown version scheme #{@scheme} was requested."
-  end
-end