Update String#split to raise TypeError when false is given

Author: bjfish

CHANGELOG.md

@@ -33,6 +33,7 @@ Compatibility:
 * Do not call `IO#flush` dynamically from `IO#close` (#2594, @gogainda).
 * Implement `rb_str_new_static` for C extensions that use it (@aardvark179).
 * Rewrote `ArrayEachIteratorNode` and re-introduced `each` specs for MRI parity when mutating arrays whilst iterating, rather than crashing (#2587, @MattAlp)
+* Update `String#split` to raise `TypeError` when false is given (#2606, @bjfish).
 
 Performance:
 

spec/ruby/core/string/split_spec.rb

@@ -589,4 +589,11 @@
       end
     end
   end
+
+  it "raises a TypeError when not called with nil, String, or Regexp" do
+    -> { "hello".split(42) }.should raise_error(TypeError)
+    -> { "hello".split(:ll) }.should raise_error(TypeError)
+    -> { "hello".split(false) }.should raise_error(TypeError)
+    -> { "hello".split(Object.new) }.should raise_error(TypeError)
+  end
 end

src/main/ruby/truffleruby/core/splitter.rb

@@ -61,7 +61,9 @@ def split(string, pattern, limit, &orig_block)
           return orig_block ? dup_string : result
         end
 
-        pattern ||= ($; || DEFAULT_PATTERN)
+        if Primitive.nil?(pattern)
+          pattern = ($; || DEFAULT_PATTERN)
+        end
 
         if pattern == DEFAULT_PATTERN
           awk_limit = limit < 0 ? -1 : limit