adjust the big-decimal fix

Author: mkristian

core/src/main/java/org/jruby/ext/bigdecimal/RubyBigDecimal.java

@@ -562,7 +562,7 @@ public static RubyBigDecimal newInstance(IRubyObject recv, IRubyObject[] args) {
                     return new RubyBigDecimal(runtime, (RubyClass)recv, new BigDecimal(((RubyFixnum)args[0]).getLongValue(), context));
                 } else if (args[0] instanceof RubyBignum) {
                     return new RubyBigDecimal(runtime, (RubyClass)recv, new BigDecimal(((RubyBignum)args[0]).getBigIntegerValue(), context));
-                } else {
+                } else if (!runtime.is1_8()) {
                     context = MathContext.UNLIMITED;
                 }
                 // fall through to String coercion below

test/test_big_decimal.rb

@@ -262,5 +262,10 @@ def test_div_by_float_precision_gh648
       b = BigDecimal.new(1.05, 10)/1.48
       assert (b.to_f - 0.7094594594594595) < Float::EPSILON
     end
+
+    def test_GH_2650
+      assert_equal(BigDecimal.new("10.91231", 1).to_f, 10.91231)
+      assert_equal(BigDecimal.new("10.9", 2).to_f, 10.9)
+    end
   end
 end

test/test_bignum.rb

@@ -1,5 +1,4 @@
 require 'test/unit'
-require 'bigdecimal'
 
 class TestBignum < Test::Unit::TestCase
   # others tested in FixnumBignumAutoconversion test
@@ -42,11 +41,6 @@ def test_bignum_should_respond_to_array_operator
   def test_bignum_aref_with_bignum_arg_no_exception
     assert_equal(0, (2**64)[2**32])
   end
-
-  def test_GH_2650
-    assert_equal(BigDecimal.new("10.91231", 1).to_f, 10.91231)
-    assert_equal(BigDecimal.new("10.9", 2).to_f, 10.9)
-  end
   # more to come
 
 end