Fix for JRUBY-4084: Working with the enumerable methods on arrays containing strings created by splicing can raise a Java Exception

Thanks to RJ Lorimer for the fix!

Author: headius

src/org/jruby/RubyString.java

@@ -6609,7 +6609,7 @@ private IRubyObject each_charCommon18(ThreadContext context, Block block) {
         ByteList val = value.shallowDup();
         while (p < end) {
             int n = StringSupport.length(enc, bytes, p, end);
-            block.yield(context, makeShared19(runtime, val, p, n));
+            block.yield(context, makeShared19(runtime, val, p-val.begin, n));
             p += n;
         }
         return this;
@@ -6635,7 +6635,7 @@ private IRubyObject each_charCommon19(ThreadContext context, Block block) {
         ByteList val = value.shallowDup();
         while (p < end) {
             int n = StringSupport.length(enc, bytes, p, end);
-            block.yield(context, makeShared19(runtime, val, p, n));
+            block.yield(context, makeShared19(runtime, val, p-value.begin, n));
             p += n;
         }
         return this;

test/jruby_index

@@ -55,6 +55,7 @@ test_java_accessible_object
 test_java_extension
 test_java_wrapper_deadlock
 test_jruby_internals
+test_jruby_4084
 compiler/test_jrubyc
 test_launching_by_shell_script
 #test_local_jump_error

test/ruby_1_9_index

@@ -9,3 +9,4 @@ test_loop_1_9
 test_assignment_1_9
 test_regexp_1_9
 test_io_1_9
+test_jruby_4084

test/test_jruby_4084.rb

@@ -0,0 +1,9 @@
+require 'test/unit'
+
+class TestJruby4084 < Test::Unit::TestCase
+  def test_jruby_4084
+    result = ["1"[0..1], "1111111"[5..6]].map{|i| i.each_char.to_a.map{|i| i == "1"}}
+    assert_equal [[true], [true, true]], result
+  end
+end
+