Consolidate to_matcher definitions in one place

lib/mocha/parameter_matchers/base.rb

@@ -2,11 +2,6 @@ module Mocha
   module ParameterMatchers
     # @abstract Subclass and implement +#matches?+ and +#mocha_inspect+ to define a custom matcher. Also add a suitably named instance method to {ParameterMatchers} to build an instance of the new matcher c.f. {#equals}.
     class Base
-      # @private
-      def to_matcher(_expectation = nil, _top_level = false)
-        self
-      end
-
       # A shorthand way of combining two matchers when both must match.
       #
       # Returns a new {AllOf} parameter matcher combining two matchers using a logical AND.

lib/mocha/parameter_matchers/instance_methods.rb

@@ -1,3 +1,4 @@
+require 'mocha/parameter_matchers/base'
 require 'mocha/parameter_matchers/equals'
 require 'mocha/parameter_matchers/positional_or_keyword_hash'
 
@@ -7,7 +8,9 @@ module ParameterMatchers
     module InstanceMethods
       # @private
       def to_matcher(expectation = nil, top_level = false)
-        if is_a?(Hash) && top_level
+        if is_a?(Base)
+          self
+        elsif is_a?(Hash) && top_level
           Mocha::ParameterMatchers::PositionalOrKeywordHash.new(self, expectation)
         else
           Mocha::ParameterMatchers::Equals.new(self)