Don't raise ArgumentError in when detecting encoding

lib/parser/source/buffer.rb

@@ -66,7 +66,11 @@ def self.recognize_encoding(string)
         return nil if encoding_line.nil? || encoding_line[0] != '#'
 
         if (result = ENCODING_RE.match(encoding_line))
-          Encoding.find(result[3] || result[4] || result[6])
+          begin
+            Encoding.find(result[3] || result[4] || result[6])
+          rescue ArgumentError
+            nil
+          end
         else
           nil
         end

test/test_encoding.rb

@@ -60,20 +60,28 @@ def test_suffix
     assert_equal Encoding::UTF_8, recognize('# coding: utf-8-unix')
     assert_equal Encoding::UTF_8, recognize('# coding: utf-8-mac')
 
-    assert_raises(ArgumentError) do
-      assert_nil recognize('# coding: utf-8-dicks')
-    end
+    assert_nil recognize('# coding: utf-8-dicks')
   end
 
   def test_parse_18_invalid_enc
+    # Ruby 1.8. did not have this magic comment
     ast = Parser::Ruby18.parse("# encoding:feynman-diagram\n1")
-    assert_equal ast, s(:int, 1)
+    encoding = ast.location.expression.source_buffer.source.encoding
+    assert_equal(Encoding::BINARY, encoding)
   end
 
   def test_parse_19_invalid_enc
-    assert_raises(ArgumentError) do
-      Parser::Ruby19.parse("# encoding:feynman-diagram\n1")
-    end
+    # The default encoding for Ruby 1.9 is BINARY
+    ast = Parser::Ruby19.parse("# encoding:feynman-diagram\n1")
+    encoding = ast.location.expression.source_buffer.source.encoding
+    assert_equal(Encoding::BINARY, encoding)
+  end
+
+  def test_parse_20_invalid_enc
+    # Ruby 2.0 changed the default encoding to UTF-8
+    ast = Parser::Ruby20.parse("# encoding:feynman-diagram\n1")
+    encoding = ast.location.expression.source_buffer.source.encoding
+    assert_equal(Encoding::UTF_8, encoding)
   end
 
   def test_ending_comment