Merge pull request #550 from iij/pr-string-slice-boundary-error

fix the issue String#slice with Range may return broken String.

src/range.c

@@ -286,7 +286,7 @@ mrb_range_beg_len(mrb_state *mrb, mrb_value range, mrb_int *begp, mrb_int *lenp,
     if (end > len) end = len;
   }
   if (end < 0) end += len;
-  if (!r->excl) end++;  /* include end point */
+  if (!r->excl && end < len) end++;  /* include end point */
   len = end - beg;
   if (len < 0) len = 0;
 

test/t/string.rb

@@ -61,6 +61,32 @@ assert('String#[]', '15.2.10.5.6') do
     a3 == 'bc' and b3 == nil
 end
 
+assert('String#[] with Range') do
+  a1 = 'abc'[1..0]
+  b1 = 'abc'[1..1]
+  c1 = 'abc'[1..2]
+  d1 = 'abc'[1..3]
+  e1 = 'abc'[1..4]
+  f1 = 'abc'[0..-2]
+  g1 = 'abc'[-2..3]
+  h1 = 'abc'[3..4]
+  i1 = 'abc'[4..5]
+  a2 = 'abc'[1...0]
+  b2 = 'abc'[1...1]
+  c2 = 'abc'[1...2]
+  d2 = 'abc'[1...3]
+  e2 = 'abc'[1...4]
+  f2 = 'abc'[0...-2]
+  g2 = 'abc'[-2...3]
+  h2 = 'abc'[3...4]
+  i2 = 'abc'[4...5]
+
+  a1 == ''   and b1 == 'b'  and c1 == 'bc' and d1 == 'bc' and e1 == 'bc' and
+  f1 == 'ab' and g1 == 'bc' and h1 == ''   and i2 == nil  and
+  a2 == ''   and b2 == ''   and c2 == 'b'  and d2 == 'bc' and e2 == 'bc' and
+  f2 == 'a'  and g2 == 'bc' and h2 == ''   and i2 == nil
+end
+
 assert('String#capitalize', '15.2.10.5.7') do
   a = 'abc'
   a.capitalize