patch 7.4.1782

Problem:    strcharpart() does not work properly with some multi-byte
            characters.
Solution:   Use mb_cptr2len() instead of mb_char2len(). (Hirohito Higashi)

src/eval.c

@@ -19764,7 +19764,7 @@ f_strcharpart(typval_T *argvars, typval_T *rettv)
 	if (nchar > 0)
 	    while (nchar > 0 && nbyte < slen)
 	    {
-		nbyte += mb_char2len(p[nbyte]);
+		nbyte += mb_cptr2len(p + nbyte);
 		--nchar;
 	    }
 	else
@@ -19779,7 +19779,7 @@ f_strcharpart(typval_T *argvars, typval_T *rettv)
 		if (off < 0)
 		    len += 1;
 		else
-		    len += mb_char2len(p[off]);
+		    len += mb_cptr2len(p + off);
 		--charlen;
 	    }
 	}

src/testdir/test_expr_utf8.vim

@@ -23,6 +23,16 @@ func Test_strcharpart()
   call assert_equal('á', strcharpart('áxb', 0, 1))
   call assert_equal('x', strcharpart('áxb', 1, 1))
 
+  call assert_equal('いうeお', strcharpart('あいうeお', 1))
+  call assert_equal('い', strcharpart('あいうeお', 1, 1))
+  call assert_equal('いう', strcharpart('あいうeお', 1, 2))
+  call assert_equal('いうe', strcharpart('あいうeお', 1, 3))
+  call assert_equal('いうeお', strcharpart('あいうeお', 1, 4))
+  call assert_equal('eお', strcharpart('あいうeお', 3))
+  call assert_equal('e', strcharpart('あいうeお', 3, 1))
+
+  call assert_equal('あ', strcharpart('あいうeお', -3, 4))
+
   call assert_equal('a', strcharpart('àxb', 0, 1))
   call assert_equal('̀', strcharpart('àxb', 1, 1))
   call assert_equal('x', strcharpart('àxb', 2, 1))

src/version.c

@@ -753,6 +753,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1782,
 /**/
     1781,
 /**/