Range#size returns nil for (.."a") and (nil..)

Fixes [Bug #18983]

range.c

@@ -816,7 +816,9 @@ range_size(VALUE range)
         }
     }
     else if (NIL_P(b)) {
-        return DBL2NUM(HUGE_VAL);
+        if (rb_obj_is_kind_of(e, rb_cNumeric)) {
+            return DBL2NUM(HUGE_VAL);
+        }
     }
 
     return Qnil;

spec/ruby/core/range/size_spec.rb

@@ -34,11 +34,28 @@ describe "Range#size" do
     eval("([]...)").size.should == nil
   end
 
-  it 'returns Float::INFINITY for all beginless ranges' do
-    (..1).size.should == Float::INFINITY
-    (...0.5).size.should == Float::INFINITY
-    (..nil).size.should == Float::INFINITY
-    (...'o').size.should == Float::INFINITY
+  ruby_version_is ""..."3.2" do
+    it 'returns Float::INFINITY for all beginless ranges' do
+      (..1).size.should == Float::INFINITY
+      (...0.5).size.should == Float::INFINITY
+      (..nil).size.should == Float::INFINITY
+      (...'o').size.should == Float::INFINITY
+    end
+  end
+
+  ruby_version_is "3.2" do
+    it 'returns Float::INFINITY for all beginless ranges if the start is numeric' do
+      (..1).size.should == Float::INFINITY
+      (...0.5).size.should == Float::INFINITY
+    end
+
+    it 'returns nil for all beginless ranges if the start is numeric' do
+      (...'o').size.should == nil
+    end
+
+    it 'returns nil if the start and the end is both nil' do
+      (nil..nil).size.should == nil
+    end
   end
 
   it "returns nil if first and last are not Numeric" do

test/ruby/test_range.rb

@@ -777,6 +777,9 @@ class TestRange < Test::Unit::TestCase
     assert_equal 5, (1.1...6).size
     assert_equal 42, (1..42).each.size
     assert_nil ("a"..."z").size
+    assert_nil ("a"...).size
+    assert_nil (..."z").size    # [Bug #18983]
+    assert_nil (nil...nil).size # [Bug #18983]
 
     assert_equal Float::INFINITY, (1...).size
     assert_equal Float::INFINITY, (1.0...).size