Remove unneeded constants and update docs

Author: JonRowe

lib/rspec/support/encoded_string.rb

@@ -5,31 +5,11 @@ class EncodedString
       # Reduce allocations by storing constants.
       UTF_8    = "UTF-8"
       US_ASCII = "US-ASCII"
-      #
-      # In MRI 2.1 'invalid: :replace' changed to also replace an invalid byte sequence
-      # see https://github.com/ruby/ruby/blob/v2_1_0/NEWS#L176
-      # https://www.ruby-forum.com/topic/6861247
-      # https://twitter.com/nalsh/status/553413844685438976
-      #
-      # For example, given:
-      #   "\x80".force_encoding("Emacs-Mule").encode(:invalid => :replace).bytes.to_a
-      #
-      # On MRI 2.1 or above: 63  # '?'
-      # else               : 128 # "\x80"
-      #
+
       # Ruby's default replacement string is:
       #   U+FFFD ("\xEF\xBF\xBD"), for Unicode encoding forms, else
       #   ?      ("\x3F")
       REPLACE = "?"
-      ENCODE_UNCONVERTABLE_BYTES =  {
-        :invalid => :replace,
-        :undef   => :replace,
-        :replace => REPLACE
-      }
-      ENCODE_NO_CONVERTER = {
-        :invalid => :replace,
-        :replace => REPLACE
-      }
 
       def initialize(string, encoding=nil)
         @encoding = encoding
@@ -112,15 +92,25 @@ def matching_encoding(string)
           string = remove_invalid_bytes(string)
           string.encode(@encoding)
         rescue Encoding::UndefinedConversionError, Encoding::InvalidByteSequenceError
-          # ENCODE_UNCONVERTABLE_BYTES inlined here to avoid warnings on Ruby 2.7
-          string.encode(@encoding,
-                        :invalid => :replace,
-                        :undef   => :replace,
-                        :replace => REPLACE)
+          # Originally defined as a constant to avoid uneeded allocations, this hash must
+          # be defined inline (without {}) to avoid warnings on Ruby 2.7
+          #
+          # In MRI 2.1 'invalid: :replace' changed to also replace an invalid byte sequence
+          # see https://github.com/ruby/ruby/blob/v2_1_0/NEWS#L176
+          # https://www.ruby-forum.com/topic/6861247
+          # https://twitter.com/nalsh/status/553413844685438976
+          #
+          # For example, given:
+          #   "\x80".force_encoding("Emacs-Mule").encode(:invalid => :replace).bytes.to_a
+          #
+          # On MRI 2.1 or above: 63  # '?'
+          # else               : 128 # "\x80"
+          #
+          string.encode(@encoding, :invalid => :replace, :undef => :replace, :replace => REPLACE)
         rescue Encoding::ConverterNotFoundError
-          # ENCODE_NO_CONVERTER inlined here to avoid warnings on Ruby 2.7
-          string.dup.force_encoding(@encoding).encode(:invalid => :replace,
-                                                      :replace => REPLACE)
+          # Originally defined as a constant to avoid uneeded allocations, this hash must
+          # be defined inline (without {}) to avoid warnings on Ruby 2.7
+          string.dup.force_encoding(@encoding).encode(:invalid => :replace, :replace => REPLACE)
         end
 
         # Prevents raising ArgumentError