patch 9.0.1617: charidx() result is not consistent with byteidx()v9.0.1617

Problem:    charidx() and utf16idx() result is not consistent with byteidx().
Solution:   When the index is equal to the length of the text return the
            lenght of the text instead of -1. (Yegappan Lakshmanan,
            closes #12503)

6 files changed, 132 insertions, 52 deletions

diff --git a/runtime/doc/builtin.txt b/runtime/doc/builtin.txt
index 0cbfe21439..5fd401c603 100644
--- a/runtime/doc/builtin.txt
+++ b/runtime/doc/builtin.txt
@@ -1528,11 +1528,13 @@ charidx({string}, {idx} [, {countcc} [, {utf16}]])
 		When {utf16} is present and TRUE, {idx} is used as the UTF-16
 		index in the String {expr} instead of as the byte index.
 
-		Returns -1 if the arguments are invalid or if {idx} is greater
-		than the index of the last byte in {string}.  An error is
-		given if the first argument is not a string, the second
-		argument is not a number or when the third argument is present
-		and is not zero or one.
+		Returns -1 if the arguments are invalid or if there are less
+		than {idx} bytes. If there are exactly {idx} bytes the length
+		of the string in characters is returned.
+
+		An error is given and -1 is returned if the first argument is
+		not a string, the second argument is not a number or when the
+		third argument is present and is not zero or one.
 
 		See |byteidx()| and |byteidxcomp()| for getting the byte index
 		from the character index and |utf16idx()| for getting the
@@ -10119,8 +10121,8 @@ uniq({list} [, {func} [, {dict}]])			*uniq()* *E882*
 <
 							*utf16idx()*
 utf16idx({string}, {idx} [, {countcc} [, {charidx}]])
-		Same as |charidx()| but returns the UTF-16 index of the byte
-		at {idx} in {string} (after converting it to UTF-16).
+		Same as |charidx()| but returns the UTF-16 code unit index of
+		the byte at {idx} in {string} (after converting it to UTF-16).
 
 		When {charidx} is present and TRUE, {idx} is used as the
 		character index in the String {string} instead of as the byte
@@ -10128,6 +10130,10 @@ utf16idx({string}, {idx} [, {countcc} [, {charidx}]])
 		An {idx} in the middle of a UTF-8 sequence is rounded upwards
 		to the end of that sequence.
 
+		Returns -1 if the arguments are invalid or if there are less
+		than {idx} bytes in {string}. If there are exactly {idx} bytes
+		the length of the string in UTF-16 code units is returned.
+
 		See |byteidx()| and |byteidxcomp()| for getting the byte index
 		from the UTF-16 index and |charidx()| for getting the
 		character index from the UTF-16 index.
diff --git a/src/evalfunc.c b/src/evalfunc.c
index 62e9a40624..63ca0486fe 100644
--- a/src/evalfunc.c
+++ b/src/evalfunc.c
@@ -1099,6 +1099,7 @@ static argcheck_T arg3_string_string_number[] = {arg_string, arg_string, arg_num
 static argcheck_T arg4_number_number_string_any[] = {arg_number, arg_number, arg_string, NULL};
 static argcheck_T arg4_string_string_any_string[] = {arg_string, arg_string, NULL, arg_string};
 static argcheck_T arg4_string_string_number_string[] = {arg_string, arg_string, arg_number, arg_string};
+static argcheck_T arg4_string_number_bool_bool[] = {arg_string, arg_number, arg_bool, arg_bool};
 /* Function specific argument types (not covered by the above) */
 static argcheck_T arg15_assert_fails[] = {arg_string_or_nr, arg_string_or_list_any, NULL, arg_number, arg_string};
 static argcheck_T arg34_assert_inrange[] = {arg_float_or_nr, arg_float_or_nr, arg_float_or_nr, arg_string};
@@ -1814,7 +1815,7 @@ static funcentry_T global_functions[] =
 			ret_number,	    f_charclass},
     {"charcol",		1, 2, FEARG_1,	    arg2_string_or_list_number,
 			ret_number,	    f_charcol},
-    {"charidx",		2, 4, FEARG_1,	    arg3_string_number_bool,
+    {"charidx",		2, 4, FEARG_1,	    arg4_string_number_bool_bool,
 			ret_number,	    f_charidx},
     {"chdir",		1, 1, FEARG_1,	    arg1_string,
 			ret_string,	    f_chdir},
@@ -2798,7 +2799,7 @@ static funcentry_T global_functions[] =
 			ret_dict_any,	    f_undotree},
     {"uniq",		1, 3, FEARG_1,	    arg13_sortuniq,
 			ret_first_arg,	    f_uniq},
-    {"utf16idx",	2, 4, FEARG_1,	    arg3_string_number_bool,
+    {"utf16idx",	2, 4, FEARG_1,	    arg4_string_number_bool_bool,
 			ret_number,	    f_utf16idx},
     {"values",		1, 1, FEARG_1,	    arg1_dict_any,
 			ret_list_member,    f_values},
@@ -3630,7 +3631,7 @@ f_copy(typval_T *argvars, typval_T *rettv)
 
 /*
  * Set the cursor position.
- * If 'charcol' is TRUE, then use the column number as a character offset.
+ * If "charcol" is TRUE, then use the column number as a character offset.
  * Otherwise use the column number as a byte offset.
  */
     static void
diff --git a/src/strings.c b/src/strings.c
index 5aa7152bbd..9e2c331bf4 100644
--- a/src/strings.c
+++ b/src/strings.c
@@ -1054,7 +1054,8 @@ byteidx_common(typval_T *argvars, typval_T *rettv, int comp UNUSED)
 
     if (in_vim9script()
 	    && (check_for_string_arg(argvars, 0) == FAIL
-		|| check_for_number_arg(argvars, 1) == FAIL))
+		|| check_for_number_arg(argvars, 1) == FAIL
+		|| check_for_opt_bool_arg(argvars, 2) == FAIL))
 	return;
 
     char_u *str = tv_get_string_chk(&argvars[0]);
@@ -1158,7 +1159,14 @@ f_charidx(typval_T *argvars, typval_T *rettv)
     for (p = str, len = 0; utf16idx ? idx >= 0 : p <= str + idx; len++)
     {
 	if (*p == NUL)
+	{
+	    // If the index is exactly the number of bytes or utf-16 code units
+	    // in the string then return the length of the string in
+	    // characters.
+	    if (utf16idx ? (idx == 0) : (p == (str + idx)))
+		rettv->vval.v_number = len;
 	    return;
+	}
 	if (utf16idx)
 	{
 	    idx--;
@@ -1775,7 +1783,14 @@ f_utf16idx(typval_T *argvars, typval_T *rettv)
     for (p = str, len = 0; charidx ? idx >= 0 : p <= str + idx; len++)
     {
 	if (*p == NUL)
+	{
+	    // If the index is exactly the number of bytes or characters in the
+	    // string then return the length of the string in utf-16 code
+	    // units.
+	    if (charidx ? (idx == 0) : (p == (str + idx)))
+		rettv->vval.v_number = len;
 	    return;
+	}
 	int clen = ptr2len(p);
 	int c = (clen > 1) ? utf_ptr2char(p) : *p;
 	if (c > 0xFFFF)
diff --git a/src/testdir/test_functions.vim b/src/testdir/test_functions.vim
index 715da0b834..d7e7f923ba 100644
--- a/src/testdir/test_functions.vim
+++ b/src/testdir/test_functions.vim
@@ -1395,7 +1395,8 @@ func Test_charidx()
   call assert_equal(1, charidx(a, 3))
   call assert_equal(2, charidx(a, 4))
   call assert_equal(3, charidx(a, 7))
-  call assert_equal(-1, charidx(a, 8))
+  call assert_equal(4, charidx(a, 8))
+  call assert_equal(-1, charidx(a, 9))
   call assert_equal(-1, charidx(a, -1))
 
   " count composing characters
@@ -1403,14 +1404,18 @@ func Test_charidx()
   call assert_equal(2, a->charidx(2, 1))
   call assert_equal(3, a->charidx(4, 1))
   call assert_equal(5, a->charidx(7, 1))
-  call assert_equal(-1, a->charidx(8, 1))
+  call assert_equal(6, a->charidx(8, 1))
+  call assert_equal(-1, a->charidx(9, 1))
 
   " empty string
-  call assert_equal(-1, charidx('', 0))
-  call assert_equal(-1, charidx('', 0, 1))
+  call assert_equal(0, charidx('', 0))
+  call assert_equal(-1, charidx('', 1))
+  call assert_equal(0, charidx('', 0, 1))
+  call assert_equal(-1, charidx('', 1, 1))
 
   " error cases
-  call assert_equal(-1, charidx(test_null_string(), 0))
+  call assert_equal(0, charidx(test_null_string(), 0))
+  call assert_equal(-1, charidx(test_null_string(), 1))
   call assert_fails('let x = charidx([], 1)', 'E1174:')
   call assert_fails('let x = charidx("abc", [])', 'E1210:')
   call assert_fails('let x = charidx("abc", 1, [])', 'E1212:')
@@ -1422,10 +1427,10 @@ endfunc
 func Test_charidx_from_utf16_index()
   " string with single byte characters
   let str = "abc"
-  for i in range(3)
+  for i in range(4)
     call assert_equal(i, charidx(str, i, v:false, v:true))
   endfor
-  call assert_equal(-1, charidx(str, 3, v:false, v:true))
+  call assert_equal(-1, charidx(str, 4, v:false, v:true))
 
   " string with two byte characters
   let str = "a©©b"
@@ -1433,7 +1438,8 @@ func Test_charidx_from_utf16_index()
   call assert_equal(1, charidx(str, 1, v:false, v:true))
   call assert_equal(2, charidx(str, 2, v:false, v:true))
   call assert_equal(3, charidx(str, 3, v:false, v:true))
-  call assert_equal(-1, charidx(str, 4, v:false, v:true))
+  call assert_equal(4, charidx(str, 4, v:false, v:true))
+  call assert_equal(-1, charidx(str, 5, v:false, v:true))
 
   " string with four byte characters
   let str = "a😊😊b"
@@ -1443,38 +1449,48 @@ func Test_charidx_from_utf16_index()
   call assert_equal(2, charidx(str, 3, v:false, v:true))
   call assert_equal(2, charidx(str, 4, v:false, v:true))
   call assert_equal(3, charidx(str, 5, v:false, v:true))
-  call assert_equal(-1, charidx(str, 6, v:false, v:true))
+  call assert_equal(4, charidx(str, 6, v:false, v:true))
+  call assert_equal(-1, charidx(str, 7, v:false, v:true))
 
   " string with composing characters
   let str = '-á-b́'
   for i in str->strcharlen()->range()
     call assert_equal(i, charidx(str, i, v:false, v:true))
   endfor
-  call assert_equal(-1, charidx(str, 4, v:false, v:true))
+  call assert_equal(4, charidx(str, 4, v:false, v:true))
+  call assert_equal(-1, charidx(str, 5, v:false, v:true))
   for i in str->strchars()->range()
     call assert_equal(i, charidx(str, i, v:true, v:true))
   endfor
-  call assert_equal(-1, charidx(str, 6, v:true, v:true))
+  call assert_equal(6, charidx(str, 6, v:true, v:true))
+  call assert_equal(-1, charidx(str, 7, v:true, v:true))
 
   " string with multiple composing characters
   let str = '-ą́-ą́'
   for i in str->strcharlen()->range()
     call assert_equal(i, charidx(str, i, v:false, v:true))
   endfor
-  call assert_equal(-1, charidx(str, 4, v:false, v:true))
+  call assert_equal(4, charidx(str, 4, v:false, v:true))
+  call assert_equal(-1, charidx(str, 5, v:false, v:true))
   for i in str->strchars()->range()
     call assert_equal(i, charidx(str, i, v:true, v:true))
   endfor
-  call assert_equal(-1, charidx(str, 8, v:true, v:true))
+  call assert_equal(8, charidx(str, 8, v:true, v:true))
+  call assert_equal(-1, charidx(str, 9, v:true, v:true))
 
   " empty string
-  call assert_equal(-1, charidx('', 0, v:false, v:true))
-  call assert_equal(-1, charidx('', 0, v:true, v:true))
+  call assert_equal(0, charidx('', 0, v:false, v:true))
+  call assert_equal(-1, charidx('', 1, v:false, v:true))
+  call assert_equal(0, charidx('', 0, v:true, v:true))
+  call assert_equal(-1, charidx('', 1, v:true, v:true))
 
   " error cases
-  call assert_equal(-1, charidx('', 0, v:false, v:true))
-  call assert_equal(-1, charidx('', 0, v:true, v:true))
-  call assert_equal(-1, charidx(test_null_string(), 0, v:false, v:true))
+  call assert_equal(0, charidx('', 0, v:false, v:true))
+  call assert_equal(-1, charidx('', 1, v:false, v:true))
+  call assert_equal(0, charidx('', 0, v:true, v:true))
+  call assert_equal(-1, charidx('', 1, v:true, v:true))
+  call assert_equal(0, charidx(test_null_string(), 0, v:false, v:true))
+  call assert_equal(-1, charidx(test_null_string(), 1, v:false, v:true))
   call assert_fails('let x = charidx("abc", 1, v:false, [])', 'E1212:')
   call assert_fails('let x = charidx("abc", 1, v:true, [])', 'E1212:')
 endfunc
@@ -1483,10 +1499,10 @@ endfunc
 func Test_utf16idx_from_byteidx()
   " UTF-16 index of a string with single byte characters
   let str = "abc"
-  for i in range(3)
+  for i in range(4)
     call assert_equal(i, utf16idx(str, i))
   endfor
-  call assert_equal(-1, utf16idx(str, 3))
+  call assert_equal(-1, utf16idx(str, 4))
 
   " UTF-16 index of a string with two byte characters
   let str = 'a©©b'
@@ -1496,7 +1512,8 @@ func Test_utf16idx_from_byteidx()
   call assert_equal(2, str->utf16idx(3))
   call assert_equal(2, str->utf16idx(4))
   call assert_equal(3, str->utf16idx(5))
-  call assert_equal(-1, str->utf16idx(6))
+  call assert_equal(4, str->utf16idx(6))
+  call assert_equal(-1, str->utf16idx(7))
 
   " UTF-16 index of a string with four byte characters
   let str = 'a😊😊b'
@@ -1510,7 +1527,8 @@ func Test_utf16idx_from_byteidx()
   call assert_equal(4, utf16idx(str, 7))
   call assert_equal(4, utf16idx(str, 8))
   call assert_equal(5, utf16idx(str, 9))
-  call assert_equal(-1, utf16idx(str, 10))
+  call assert_equal(6, utf16idx(str, 10))
+  call assert_equal(-1, utf16idx(str, 11))
 
   " UTF-16 index of a string with composing characters
   let str = '-á-b́'
@@ -1522,7 +1540,8 @@ func Test_utf16idx_from_byteidx()
   call assert_equal(3, utf16idx(str, 5))
   call assert_equal(3, utf16idx(str, 6))
   call assert_equal(3, utf16idx(str, 7))
-  call assert_equal(-1, utf16idx(str, 8))
+  call assert_equal(4, utf16idx(str, 8))
+  call assert_equal(-1, utf16idx(str, 9))
   call assert_equal(0, utf16idx(str, 0, v:true))
   call assert_equal(1, utf16idx(str, 1, v:true))
   call assert_equal(2, utf16idx(str, 2, v:true))
@@ -1531,7 +1550,8 @@ func Test_utf16idx_from_byteidx()
   call assert_equal(4, utf16idx(str, 5, v:true))
   call assert_equal(5, utf16idx(str, 6, v:true))
   call assert_equal(5, utf16idx(str, 7, v:true))
-  call assert_equal(-1, utf16idx(str, 8, v:true))
+  call assert_equal(6, utf16idx(str, 8, v:true))
+  call assert_equal(-1, utf16idx(str, 9, v:true))
 
   " string with multiple composing characters
   let str = '-ą́-ą́'
@@ -1547,7 +1567,8 @@ func Test_utf16idx_from_byteidx()
   call assert_equal(3, utf16idx(str, 9))
   call assert_equal(3, utf16idx(str, 10))
   call assert_equal(3, utf16idx(str, 11))
-  call assert_equal(-1, utf16idx(str, 12))
+  call assert_equal(4, utf16idx(str, 12))
+  call assert_equal(-1, utf16idx(str, 13))
   call assert_equal(0, utf16idx(str, 0, v:true))
   call assert_equal(1, utf16idx(str, 1, v:true))
   call assert_equal(2, utf16idx(str, 2, v:true))
@@ -1560,16 +1581,21 @@ func Test_utf16idx_from_byteidx()
   call assert_equal(6, utf16idx(str, 9, v:true))
   call assert_equal(7, utf16idx(str, 10, v:true))
   call assert_equal(7, utf16idx(str, 11, v:true))
-  call assert_equal(-1, utf16idx(str, 12, v:true))
+  call assert_equal(8, utf16idx(str, 12, v:true))
+  call assert_equal(-1, utf16idx(str, 13, v:true))
 
   " empty string
-  call assert_equal(-1, utf16idx('', 0))
-  call assert_equal(-1, utf16idx('', 0, v:true))
+  call assert_equal(0, utf16idx('', 0))
+  call assert_equal(-1, utf16idx('', 1))
+  call assert_equal(0, utf16idx('', 0, v:true))
+  call assert_equal(-1, utf16idx('', 1, v:true))
 
   " error cases
-  call assert_equal(-1, utf16idx("", 0))
+  call assert_equal(0, utf16idx("", 0))
+  call assert_equal(-1, utf16idx("", 1))
   call assert_equal(-1, utf16idx("abc", -1))
-  call assert_equal(-1, utf16idx(test_null_string(), 0))
+  call assert_equal(0, utf16idx(test_null_string(), 0))
+  call assert_equal(-1, utf16idx(test_null_string(), 1))
   call assert_fails('let l = utf16idx([], 0)', 'E1174:')
   call assert_fails('let l = utf16idx("ab", [])', 'E1210:')
   call assert_fails('let l = utf16idx("ab", 0, [])', 'E1212:')
@@ -1581,14 +1607,16 @@ func Test_utf16idx_from_charidx()
   for i in str->strcharlen()->range()
     call assert_equal(i, utf16idx(str, i, v:false, v:true))
   endfor
-  call assert_equal(-1, utf16idx(str, 3, v:false, v:true))
+  call assert_equal(3, utf16idx(str, 3, v:false, v:true))
+  call assert_equal(-1, utf16idx(str, 4, v:false, v:true))
 
   " UTF-16 index of a string with two byte characters
   let str = "a©©b"
   for i in str->strcharlen()->range()
     call assert_equal(i, utf16idx(str, i, v:false, v:true))
   endfor
-  call assert_equal(-1, utf16idx(str, 4, v:false, v:true))
+  call assert_equal(4, utf16idx(str, 4, v:false, v:true))
+  call assert_equal(-1, utf16idx(str, 5, v:false, v:true))
 
   " UTF-16 index of a string with four byte characters
   let str = "a😊😊b"
@@ -1596,36 +1624,44 @@ func Test_utf16idx_from_charidx()
   call assert_equal(2, utf16idx(str, 1, v:false, v:true))
   call assert_equal(4, utf16idx(str, 2, v:false, v:true))
   call assert_equal(5, utf16idx(str, 3, v:false, v:true))
-  call assert_equal(-1, utf16idx(str, 4, v:false, v:true))
+  call assert_equal(6, utf16idx(str, 4, v:false, v:true))
+  call assert_equal(-1, utf16idx(str, 5, v:false, v:true))
 
   " UTF-16 index of a string with composing characters
   let str = '-á-b́'
   for i in str->strcharlen()->range()
     call assert_equal(i, utf16idx(str, i, v:false, v:true))
   endfor
-  call assert_equal(-1, utf16idx(str, 4, v:false, v:true))
+  call assert_equal(4, utf16idx(str, 4, v:false, v:true))
+  call assert_equal(-1, utf16idx(str, 5, v:false, v:true))
   for i in str->strchars()->range()
     call assert_equal(i, utf16idx(str, i, v:true, v:true))
   endfor
-  call assert_equal(-1, utf16idx(str, 6, v:true, v:true))
+  call assert_equal(6, utf16idx(str, 6, v:true, v:true))
+  call assert_equal(-1, utf16idx(str, 7, v:true, v:true))
 
   " string with multiple composing characters
   let str = '-ą́-ą́'
   for i in str->strcharlen()->range()
     call assert_equal(i, utf16idx(str, i, v:false, v:true))
   endfor
-  call assert_equal(-1, utf16idx(str, 4, v:false, v:true))
+  call assert_equal(4, utf16idx(str, 4, v:false, v:true))
+  call assert_equal(-1, utf16idx(str, 5, v:false, v:true))
   for i in str->strchars()->range()
     call assert_equal(i, utf16idx(str, i, v:true, v:true))
   endfor
-  call assert_equal(-1, utf16idx(str, 8, v:true, v:true))
+  call assert_equal(8, utf16idx(str, 8, v:true, v:true))
+  call assert_equal(-1, utf16idx(str, 9, v:true, v:true))
 
   " empty string
-  call assert_equal(-1, utf16idx('', 0, v:false, v:true))
-  call assert_equal(-1, utf16idx('', 0, v:true, v:true))
+  call assert_equal(0, utf16idx('', 0, v:false, v:true))
+  call assert_equal(-1, utf16idx('', 1, v:false, v:true))
+  call assert_equal(0, utf16idx('', 0, v:true, v:true))
+  call assert_equal(-1, utf16idx('', 1, v:true, v:true))
 
   " error cases
-  call assert_equal(-1, utf16idx(test_null_string(), 0, v:true, v:true))
+  call assert_equal(0, utf16idx(test_null_string(), 0, v:true, v:true))
+  call assert_equal(-1, utf16idx(test_null_string(), 1, v:true, v:true))
   call assert_fails('let l = utf16idx("ab", 0, v:false, [])', 'E1212:')
 endfunc
 
diff --git a/src/testdir/test_vim9_builtin.vim b/src/testdir/test_vim9_builtin.vim
index 8cf16a2cf6..a226bb2cab 100644
--- a/src/testdir/test_vim9_builtin.vim
+++ b/src/testdir/test_vim9_builtin.vim
@@ -460,6 +460,7 @@ enddef
 def Test_byteidx()
   v9.CheckDefAndScriptFailure(['byteidx(1, 2)'], ['E1013: Argument 1: type mismatch, expected string but got number', 'E1174: String required for argument 1'])
   v9.CheckDefAndScriptFailure(['byteidx("a", "b")'], ['E1013: Argument 2: type mismatch, expected number but got string', 'E1210: Number required for argument 2'])
+  v9.CheckDefAndScriptFailure(['byteidx("a", 0, "")'], ['E1013: Argument 3: type mismatch, expected bool but got string', 'E1212: Bool required for argument 3'])
   byteidx('', 0)->assert_equal(0)
   byteidx('', 1)->assert_equal(-1)
 enddef
@@ -467,6 +468,7 @@ enddef
 def Test_byteidxcomp()
   v9.CheckDefAndScriptFailure(['byteidxcomp(1, 2)'], ['E1013: Argument 1: type mismatch, expected string but got number', 'E1174: String required for argument 1'])
   v9.CheckDefAndScriptFailure(['byteidxcomp("a", "b")'], ['E1013: Argument 2: type mismatch, expected number but got string', 'E1210: Number required for argument 2'])
+  v9.CheckDefAndScriptFailure(['byteidxcomp("a", 0, "")'], ['E1013: Argument 3: type mismatch, expected bool but got string', 'E1212: Bool required for argument 3'])
 enddef
 
 def Test_call_call()
@@ -702,7 +704,8 @@ def Test_charidx()
   v9.CheckDefAndScriptFailure(['charidx(0z10, 1)'], ['E1013: Argument 1: type mismatch, expected string but got blob', 'E1174: String required for argument 1'])
   v9.CheckDefAndScriptFailure(['charidx("a", "b")'], ['E1013: Argument 2: type mismatch, expected number but got string', 'E1210: Number required for argument 2'])
   v9.CheckDefAndScriptFailure(['charidx("a", 1, "")'], ['E1013: Argument 3: type mismatch, expected bool but got string', 'E1212: Bool required for argument 3'])
-  charidx('', 0)->assert_equal(-1)
+  v9.CheckDefAndScriptFailure(['charidx("a", 1, 0, "")'], ['E1013: Argument 4: type mismatch, expected bool but got string', 'E1212: Bool required for argument 4'])
+  charidx('', 0)->assert_equal(0)
   charidx('', 1)->assert_equal(-1)
 enddef
 
@@ -4305,6 +4308,14 @@ def Test_strtrans()
   strtrans('')->assert_equal('')
 enddef
 
+def Test_strutf16len()
+  v9.CheckDefAndScriptFailure(['strutf16len([])'], ['E1013: Argument 1: type mismatch, expected string but got list<unknown>', 'E1174: String required for argument 1'])
+  v9.CheckDefAndScriptFailure(['strutf16len("a", "")'], ['E1013: Argument 2: type mismatch, expected bool but got string', 'E1212: Bool required for argument 2'])
+  ""->strutf16len()->assert_equal(0)
+  '-ą́-ą́'->strutf16len(true)->assert_equal(8)
+  '-ą́-ą́'->strutf16len(false)->assert_equal(4)
+enddef
+
 def Test_strwidth()
   v9.CheckDefAndScriptFailure(['strwidth(10)'], ['E1013: Argument 1: type mismatch, expected string but got number', 'E1174: String required for argument 1'])
   assert_equal(4, strwidth('abcd'))
@@ -4727,6 +4738,15 @@ def Test_uniq()
   v9.CheckDefFailure(['var l: list<number> = uniq(["a", "b"])'], 'E1012: Type mismatch; expected list<number> but got list<string>')
 enddef
 
+def Test_utf16idx()
+  v9.CheckDefAndScriptFailure(['utf16idx(0z10, 1)'], ['E1013: Argument 1: type mismatch, expected string but got blob', 'E1174: String required for argument 1'])
+  v9.CheckDefAndScriptFailure(['utf16idx("a", "b")'], ['E1013: Argument 2: type mismatch, expected number but got string', 'E1210: Number required for argument 2'])
+  v9.CheckDefAndScriptFailure(['utf16idx("a", 1, "")'], ['E1013: Argument 3: type mismatch, expected bool but got string', 'E1212: Bool required for argument 3'])
+  v9.CheckDefAndScriptFailure(['utf16idx("a", 1, 0, "")'], ['E1013: Argument 4: type mismatch, expected bool but got string', 'E1212: Bool required for argument 4'])
+  utf16idx('', 0)->assert_equal(0)
+  utf16idx('', 1)->assert_equal(-1)
+enddef
+
 def Test_uniq_const()
   var lines =<< trim END
       const l = [1, 2, 3, 4]
diff --git a/src/version.c b/src/version.c
index e6858c2a2b..a3fc959c5d 100644
--- a/src/version.c
+++ b/src/version.c
@@ -696,6 +696,8 @@ static char *(features[]) =
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1617,
+/**/
     1616,
 /**/
     1615,