Merge pull request #217 in G/truffleruby from io-read-fix to master

* commit 'a336dd6969c7f488bd9167b941138c920a1ae2eb':
  Handle IO.read with length and options but no offset.

spec/ruby/core/io/read_spec.rb

@@ -27,6 +27,10 @@
     IO.read(@fname, {}).should == @contents
   end
 
+  it "accepts a length, and empty options Hash" do
+    IO.read(@fname, 3, {}).should == @contents[0, 3]
+  end
+
   it "accepts a length, offset, and empty options Hash" do
     IO.read(@fname, 3, 0, {}).should == @contents[0, 3]
   end

src/main/ruby/core/io.rb

@@ -635,8 +635,13 @@ def self.read(name, length_or_options=undefined, offset=0, options=nil)
       offset = 0
       options = length_or_options
     elsif length_or_options
-      offset = Truffle::Type.coerce_to_int(offset || 0)
-      raise Errno::EINVAL, 'offset must not be negative' if offset < 0
+      if Truffle::Type.object_kind_of? offset, Hash
+        options = offset
+        offset = 0
+      else
+        offset = Truffle::Type.coerce_to_int(offset || 0)
+        raise Errno::EINVAL, 'offset must not be negative' if offset < 0
+      end
 
       length = Truffle::Type.coerce_to_int(length_or_options)
       raise ArgumentError, 'length must not be negative' if length < 0