Fix String#lines for multibyte characters

Author: chrisseaton

CHANGELOG.md

@@ -1,3 +1,10 @@
+# 1.0 RC 12
+
+Bug fixes:
+
+* Fixed a bug with `String#lines` and similar methods with multibyte
+  characters (#1543).
+
 # 1.0 RC 11
 
 New features:

spec/tags/core/string/each_line_tags.txt

@@ -934,7 +934,7 @@ def each_line(sep=$/, chomp: false)
       sep = "\n\n"
       data = bytes
 
-      while pos < size
+      while pos < bytesize
         nxt = Truffle.invoke_primitive(:find_string, self, sep, pos)
         break unless nxt
 
@@ -964,10 +964,10 @@ def each_line(sep=$/, chomp: false)
     else
 
       # This is the normal case.
-      pat_size = sep.size
+      pat_size = sep.bytesize
       unmodified_self = clone
 
-      while pos < size
+      while pos < bytesize
         nxt = Truffle.invoke_primitive(:find_string, unmodified_self, sep, pos)
         break unless nxt