Make Kernel#{Pathname,BigDecimal,Complex} return argument if given correct type

This is how Kernel#{Array,String,Float,Integer,Hash,Rational} work.
BigDecimal and Complex instances are always frozen, so this should
not cause backwards compatibility issues for those.  Pathname
instances are not frozen, so potentially this could cause backwards
compatibility issues by not returning a new object.

Based on a patch from Joshua Ballanco, some minor changes by me.

Fixes [Bug #7522]

1 files changed, 5 insertions, 0 deletions

diff --git a/test/bigdecimal/test_bigdecimal.rb b/test/bigdecimal/test_bigdecimal.rb
index e4f14449a1..b3368b4f4b 100644
--- a/test/bigdecimal/test_bigdecimal.rb
+++ b/test/bigdecimal/test_bigdecimal.rb
@@ -54,6 +54,11 @@ class TestBigDecimal < Test::Unit::TestCase
     assert_equal(111, BigDecimal("1_1_1_"))
     assert_equal(10**(-1), BigDecimal("1E-1"), '#4825')
     assert_equal(1234, BigDecimal(" \t\n\r \r1234 \t\n\r \r"))
+    bd = BigDecimal.new("1.12", 1)
+    assert_same(bd, BigDecimal(bd))
+    assert_same(bd, BigDecimal(bd, exception: false))
+    assert_not_same(bd, BigDecimal(bd, 1))
+    assert_not_same(bd, BigDecimal(bd, 1, exception: false))
 
     assert_raise(ArgumentError) { BigDecimal("1", -1) }
     assert_raise_with_message(ArgumentError, /"1__1_1"/) { BigDecimal("1__1_1") }