patch 8.2.3751: cannot assign a lambda to an option that takes a functionv8.2.3751

Problem:    Cannot assign a lambda to an option that takes a function.
Solution:   Automatically convert the lambda to a string. (Yegappan
            Lakshmanan, closes #9286)

18 files changed, 344 insertions, 85 deletions

diff --git a/runtime/doc/options.txt b/runtime/doc/options.txt
index ee03570ba8..c49b608247 100644
--- a/runtime/doc/options.txt
+++ b/runtime/doc/options.txt
@@ -376,7 +376,8 @@ Note: In the future more global options can be made global-local.  Using
 						*option-value-function*
 Some options ('completefunc', 'imactivatefunc', 'imstatusfunc', 'omnifunc',
 'operatorfunc', 'quickfixtextfunc', 'tagfunc' and 'thesaurusfunc') are set to
-a function name or a function reference or a lambda function.  Examples:
+a function name or a function reference or a lambda function.  When using a
+lambda it will be converted to the name, e.g. "<lambda>123".  Examples:
 >
 	set opfunc=MyOpFunc
 	set opfunc=function('MyOpFunc')
@@ -386,10 +387,10 @@ a function name or a function reference or a lambda function.  Examples:
 	let Fn = function('MyTagFunc')
 	let &tagfunc = string(Fn)
 	" set using a lambda expression
-	let &tagfunc = "{t -> MyTagFunc(t)}"
+	let &tagfunc = {t -> MyTagFunc(t)}
 	" set using a variable with lambda expression
 	let L = {a, b, c -> MyTagFunc(a, b , c)}
-	let &tagfunc = string(L)
+	let &tagfunc = L
 <
 
 Setting the filetype
diff --git a/src/eval.c b/src/eval.c
index bebe2f0ad5..bc4db2906c 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -6281,23 +6281,23 @@ ex_execute(exarg_T *eap)
  * after the option name.
  */
     char_u *
-find_option_end(char_u **arg, int *opt_flags)
+find_option_end(char_u **arg, int *scope)
 {
     char_u	*p = *arg;
 
     ++p;
     if (*p == 'g' && p[1] == ':')
     {
-	*opt_flags = OPT_GLOBAL;
+	*scope = OPT_GLOBAL;
 	p += 2;
     }
     else if (*p == 'l' && p[1] == ':')
     {
-	*opt_flags = OPT_LOCAL;
+	*scope = OPT_LOCAL;
 	p += 2;
     }
     else
-	*opt_flags = 0;
+	*scope = 0;
 
     if (!ASCII_ISALPHA(*p))
 	return NULL;
diff --git a/src/evalvars.c b/src/evalvars.c
index 4342100312..f5465cfb74 100644
--- a/src/evalvars.c
+++ b/src/evalvars.c
@@ -1367,7 +1367,7 @@ ex_let_option(
     char_u	*op)
 {
     char_u	*p;
-    int		opt_flags;
+    int		scope;
     char_u	*arg_end = NULL;
 
     if ((flags & (ASSIGN_CONST | ASSIGN_FINAL))
@@ -1378,7 +1378,7 @@ ex_let_option(
     }
 
     // Find the end of the name.
-    p = find_option_end(&arg, &opt_flags);
+    p = find_option_end(&arg, &scope);
     if (p == NULL || (endchars != NULL
 			       && vim_strchr(endchars, *skipwhite(p)) == NULL))
 	emsg(_(e_unexpected_characters_in_let));
@@ -1391,11 +1391,14 @@ ex_let_option(
 	char_u	    *stringval = NULL;
 	char_u	    *s = NULL;
 	int	    failed = FALSE;
+	int	    opt_p_flags;
+	char_u	    *tofree = NULL;
 
 	c1 = *p;
 	*p = NUL;
 
-	opt_type = get_option_value(arg, &numval, &stringval, opt_flags);
+	opt_type = get_option_value(arg, &numval, &stringval, &opt_p_flags,
+									scope);
 	if ((opt_type == gov_bool
 		    || opt_type == gov_number
 		    || opt_type == gov_hidden_bool
@@ -1410,9 +1413,20 @@ ex_let_option(
 		n = (long)tv_get_number(tv);
 	}
 
+	if (opt_p_flags & P_FUNC && (tv->v_type == VAR_PARTIAL
+						|| tv->v_type == VAR_FUNC))
+	{
+	    char_u	numbuf[NUMBUFLEN];
+
+	    // If the option can be set to a function reference or a lambda
+	    // and the passed value is a function reference, then convert it to
+	    // the name (string) of the function reference.
+
+	    s = tv2string(tv, &tofree, numbuf, 0);
+	}
 	// Avoid setting a string option to the text "v:false" or similar.
 	// In Vim9 script also don't convert a number to string.
-	if (tv->v_type != VAR_BOOL && tv->v_type != VAR_SPECIAL
+	else if (tv->v_type != VAR_BOOL && tv->v_type != VAR_SPECIAL
 			 && (!in_vim9script() || tv->v_type != VAR_NUMBER))
 	    s = tv_get_string_chk(tv);
 
@@ -1458,7 +1472,7 @@ ex_let_option(
 	{
 	    if (opt_type != gov_string || s != NULL)
 	    {
-		set_option_value(arg, n, s, opt_flags);
+		set_option_value(arg, n, s, scope);
 		arg_end = p;
 	    }
 	    else
@@ -1466,6 +1480,7 @@ ex_let_option(
 	}
 	*p = c1;
 	vim_free(stringval);
+	vim_free(tofree);
     }
     return arg_end;
 }
diff --git a/src/if_mzsch.c b/src/if_mzsch.c
index 57b593a19e..41b6d0006f 100644
--- a/src/if_mzsch.c
+++ b/src/if_mzsch.c
@@ -1715,7 +1715,7 @@ get_option(void *data, int argc, Scheme_Object **argv)
     getoption_T	    rc;
     Scheme_Object   *rval = NULL;
     Scheme_Object   *name = NULL;
-    int		    opt_flags = 0;
+    int		    scope = 0;
     buf_T	    *save_curb = curbuf;
     win_T	    *save_curw = curwin;
 
@@ -1736,11 +1736,11 @@ get_option(void *data, int argc, Scheme_Object **argv)
 	}
 
 	if (argv[1] == M_global)
-	    opt_flags = OPT_GLOBAL;
+	    scope = OPT_GLOBAL;
 	else if (SCHEME_VIMBUFFERP(argv[1]))
 	{
 	    curbuf = get_valid_buffer(argv[1]);
-	    opt_flags = OPT_LOCAL;
+	    scope = OPT_LOCAL;
 	}
 	else if (SCHEME_VIMWINDOWP(argv[1]))
 	{
@@ -1748,14 +1748,14 @@ get_option(void *data, int argc, Scheme_Object **argv)
 
 	    curwin = win;
 	    curbuf = win->w_buffer;
-	    opt_flags = OPT_LOCAL;
+	    scope = OPT_LOCAL;
 	}
 	else
 	    scheme_wrong_type(prim->name, "vim-buffer/window", 1, argc, argv);
     }
 
     rc = get_option_value(BYTE_STRING_VALUE(name), &value, (char_u **)&strval,
-								    opt_flags);
+								  NULL, scope);
     curbuf = save_curb;
     curwin = save_curw;
 
@@ -1793,7 +1793,7 @@ get_option(void *data, int argc, Scheme_Object **argv)
 set_option(void *data, int argc, Scheme_Object **argv)
 {
     char_u	*command = NULL;
-    int		opt_flags = 0;
+    int		scope = 0;
     buf_T	*save_curb = curbuf;
     win_T	*save_curw = curwin;
     Vim_Prim	*prim = (Vim_Prim *)data;
@@ -1814,18 +1814,18 @@ set_option(void *data, int argc, Scheme_Object **argv)
 	}
 
 	if (argv[1] == M_global)
-	    opt_flags = OPT_GLOBAL;
+	    scope = OPT_GLOBAL;
 	else if (SCHEME_VIMBUFFERP(argv[1]))
 	{
 	    curbuf = get_valid_buffer(argv[1]);
-	    opt_flags = OPT_LOCAL;
+	    scope = OPT_LOCAL;
 	}
 	else if (SCHEME_VIMWINDOWP(argv[1]))
 	{
 	    win_T *win = get_valid_window(argv[1]);
 	    curwin = win;
 	    curbuf = win->w_buffer;
-	    opt_flags = OPT_LOCAL;
+	    scope = OPT_LOCAL;
 	}
 	else
 	    scheme_wrong_type(prim->name, "vim-buffer/window", 1, argc, argv);
@@ -1834,7 +1834,7 @@ set_option(void *data, int argc, Scheme_Object **argv)
     // do_set can modify cmd, make copy
     command = vim_strsave(BYTE_STRING_VALUE(cmd));
     MZ_GC_UNREG();
-    do_set(command, opt_flags);
+    do_set(command, scope);
     vim_free(command);
     update_screen(NOT_VALID);
     curbuf = save_curb;
diff --git a/src/if_ruby.c b/src/if_ruby.c
index 5098468e6a..0d7eaf2e89 100644
--- a/src/if_ruby.c
+++ b/src/if_ruby.c
@@ -875,7 +875,7 @@ vim_str2rb_enc_str(const char *s)
     char_u *sval;
     rb_encoding *enc;
 
-    if (get_option_value((char_u *)"enc", &lval, &sval, 0) == gov_string)
+    if (get_option_value((char_u *)"enc", &lval, &sval, NULL, 0) == gov_string)
     {
 	enc = rb_enc_find((char *)sval);
 	vim_free(sval);
@@ -895,7 +895,7 @@ eval_enc_string_protect(const char *str, int *state)
     rb_encoding *enc;
     VALUE v;
 
-    if (get_option_value((char_u *)"enc", &lval, &sval, 0) == gov_string)
+    if (get_option_value((char_u *)"enc", &lval, &sval, NULL, 0) == gov_string)
     {
 	enc = rb_enc_find((char *)sval);
 	vim_free(sval);
diff --git a/src/if_tcl.c b/src/if_tcl.c
index 4838e31976..75fa858e8e 100644
--- a/src/if_tcl.c
+++ b/src/if_tcl.c
@@ -1308,7 +1308,7 @@ tclsetoption(
 
     option = (char_u *)Tcl_GetStringFromObj(objv[objn], NULL);
     ++objn;
-    gov = get_option_value(option, &lval, &sval, 0);
+    gov = get_option_value(option, &lval, &sval, NULL, 0);
     err = TCL_OK;
     switch (gov)
     {
diff --git a/src/option.c b/src/option.c
index c6230c4027..8d950b1770 100644
--- a/src/option.c
+++ b/src/option.c
@@ -56,10 +56,10 @@ static int put_setstring(FILE *fd, char *cmd, char *name, char_u **valuep, long_
 static int put_setnum(FILE *fd, char *cmd, char *name, long *valuep);
 static int put_setbool(FILE *fd, char *cmd, char *name, int value);
 static int istermoption(struct vimoption *p);
-static char_u *get_varp_scope(struct vimoption *p, int opt_flags);
+static char_u *get_varp_scope(struct vimoption *p, int scope);
 static char_u *get_varp(struct vimoption *);
 static void check_win_options(win_T *win);
-static void option_value2string(struct vimoption *, int opt_flags);
+static void option_value2string(struct vimoption *, int scope);
 static void check_winopt(winopt_T *wop);
 static int wc_use_keyname(char_u *varp, long *wcp);
 static void paste_option_changed(void);
@@ -3937,13 +3937,16 @@ findoption(char_u *arg)
  * Hidden Toggle option: gov_hidden_bool.
  * Hidden String option: gov_hidden_string.
  * Unknown option: gov_unknown.
+ *
+ * "flagsp" (if not NULL) is set to the option flags (P_xxxx).
  */
     getoption_T
 get_option_value(
     char_u	*name,
     long	*numval,
     char_u	**stringval,	    // NULL when only checking existence
-    int		opt_flags)
+    int		*flagsp,
+    int		scope)
 {
     int		opt_idx;
     char_u	*varp;
@@ -3981,7 +3984,11 @@ get_option_value(
 	return gov_unknown;
     }
 
-    varp = get_varp_scope(&(options[opt_idx]), opt_flags);
+    varp = get_varp_scope(&(options[opt_idx]), scope);
+
+    if (flagsp != NULL)
+	// Return the P_xxxx option flags.
+	*flagsp = options[opt_idx].flags;
 
     if (options[opt_idx].flags & P_STRING)
     {
@@ -5179,17 +5186,18 @@ unset_global_local_option(char_u *name, void *from)
 
 /*
  * Get pointer to option variable, depending on local or global scope.
+ * "scope" can be OPT_LOCAL, OPT_GLOBAL or a combination.
  */
     static char_u *
-get_varp_scope(struct vimoption *p, int opt_flags)
+get_varp_scope(struct vimoption *p, int scope)
 {
-    if ((opt_flags & OPT_GLOBAL) && p->indir != PV_NONE)
+    if ((scope & OPT_GLOBAL) && p->indir != PV_NONE)
     {
 	if (p->var == VAR_WIN)
 	    return (char_u *)GLOBAL_WO(get_varp(p));
 	return p->var;
     }
-    if ((opt_flags & OPT_LOCAL) && ((int)p->indir & PV_BOTH))
+    if ((scope & OPT_LOCAL) && ((int)p->indir & PV_BOTH))
     {
 	switch ((int)p->indir)
 	{
@@ -5248,9 +5256,9 @@ get_varp_scope(struct vimoption *p, int opt_flags)
  * scope.
  */
     char_u *
-get_option_varp_scope(int opt_idx, int opt_flags)
+get_option_varp_scope(int opt_idx, int scope)
 {
-    return get_varp_scope(&(options[opt_idx]), opt_flags);
+    return get_varp_scope(&(options[opt_idx]), scope);
 }
 
 /*
@@ -6618,11 +6626,11 @@ ExpandOldSetting(int *num_file, char_u ***file)
     static void
 option_value2string(
     struct vimoption	*opp,
-    int			opt_flags)	// OPT_GLOBAL and/or OPT_LOCAL
+    int			scope)	// OPT_GLOBAL and/or OPT_LOCAL
 {
     char_u	*varp;
 
-    varp = get_varp_scope(opp, opt_flags);
+    varp = get_varp_scope(opp, scope);
 
     if (opp->flags & P_NUM)
     {
diff --git a/src/option.h b/src/option.h
index 080d90d5c0..fc8124543e 100644
--- a/src/option.h
+++ b/src/option.h
@@ -59,6 +59,7 @@
 #define P_NDNAME      0x8000000L // only normal dir name chars allowed
 #define P_RWINONLY   0x10000000L // only redraw current window
 #define P_MLE	     0x20000000L // under control of 'modelineexpr'
+#define P_FUNC	     0x40000000L // accept a function reference or a lambda
 
 // Returned by get_option_value().
 typedef enum {
diff --git a/src/optiondefs.h b/src/optiondefs.h
index 5a9a674537..6a96a9f2fc 100644
--- a/src/optiondefs.h
+++ b/src/optiondefs.h
@@ -684,7 +684,7 @@ static struct vimoption options[] =
 #endif
 			    {(char_u *)0L, (char_u *)0L}
 			    SCTX_INIT},
-    {"completefunc", "cfu", P_STRING|P_ALLOCED|P_VI_DEF|P_SECURE,
+    {"completefunc", "cfu", P_STRING|P_ALLOCED|P_VI_DEF|P_SECURE|P_FUNC,
 #ifdef FEAT_COMPL_FUNC
 			    (char_u *)&p_cfu, PV_CFU,
 			    {(char_u *)"", (char_u *)0L}
@@ -1321,7 +1321,7 @@ static struct vimoption options[] =
     {"ignorecase",  "ic",   P_BOOL|P_VI_DEF,
 			    (char_u *)&p_ic, PV_NONE,
 			    {(char_u *)FALSE, (char_u *)0L} SCTX_INIT},
-    {"imactivatefunc","imaf",P_STRING|P_VI_DEF|P_SECURE,
+    {"imactivatefunc","imaf",P_STRING|P_VI_DEF|P_SECURE|P_FUNC,
 #if defined(FEAT_EVAL)
 			    (char_u *)&p_imaf, PV_NONE,
 			    {(char_u *)"", (char_u *)NULL}
@@ -1356,7 +1356,7 @@ static struct vimoption options[] =
 			    (char_u *)&p_imsearch, PV_IMS,
 			    {(char_u *)B_IMODE_USE_INSERT, (char_u *)0L}
 			    SCTX_INIT},
-    {"imstatusfunc","imsf",P_STRING|P_VI_DEF|P_SECURE,
+    {"imstatusfunc","imsf",P_STRING|P_VI_DEF|P_SECURE|P_FUNC,
 #if defined(FEAT_EVAL)
 			    (char_u *)&p_imsf, PV_NONE,
 			    {(char_u *)"", (char_u *)NULL}
@@ -1822,7 +1822,7 @@ static struct vimoption options[] =
 			    (char_u *)NULL, PV_NONE,
 #endif
 			    {(char_u *)8L, (char_u *)4L} SCTX_INIT},
-    {"omnifunc",    "ofu",  P_STRING|P_ALLOCED|P_VI_DEF|P_SECURE,
+    {"omnifunc",    "ofu",  P_STRING|P_ALLOCED|P_VI_DEF|P_SECURE|P_FUNC,
 #ifdef FEAT_COMPL_FUNC
 			    (char_u *)&p_ofu, PV_OFU,
 			    {(char_u *)"", (char_u *)0L}
@@ -1842,7 +1842,7 @@ static struct vimoption options[] =
 #endif
 			    {(char_u *)FALSE, (char_u *)FALSE}
 			    SCTX_INIT},
-    {"operatorfunc", "opfunc", P_STRING|P_VI_DEF|P_SECURE,
+    {"operatorfunc", "opfunc", P_STRING|P_VI_DEF|P_SECURE|P_FUNC,
 			    (char_u *)&p_opfunc, PV_NONE,
 			    {(char_u *)"", (char_u *)0L} SCTX_INIT},
     {"optimize",    "opt",  P_BOOL|P_VI_DEF,
@@ -2055,7 +2055,7 @@ static struct vimoption options[] =
 #endif
 			    {(char_u *)DEFAULT_PYTHON_VER, (char_u *)0L}
 			    SCTX_INIT},
-    {"quickfixtextfunc", "qftf", P_STRING|P_ALLOCED|P_VI_DEF|P_VIM|P_SECURE,
+    {"quickfixtextfunc", "qftf", P_STRING|P_ALLOCED|P_VI_DEF|P_VIM|P_SECURE|P_FUNC,
 #if defined(FEAT_QUICKFIX) && defined(FEAT_EVAL)
 			    (char_u *)&p_qftf, PV_NONE,
 			    {(char_u *)"", (char_u *)0L}
@@ -2507,7 +2507,7 @@ static struct vimoption options[] =
     {"tagcase",	    "tc",   P_STRING|P_VIM,
 			    (char_u *)&p_tc, PV_TC,
 			    {(char_u *)"followic", (char_u *)"followic"} SCTX_INIT},
-    {"tagfunc",    "tfu",   P_STRING|P_ALLOCED|P_VI_DEF|P_SECURE,
+    {"tagfunc",    "tfu",   P_STRING|P_ALLOCED|P_VI_DEF|P_SECURE|P_FUNC,
 #ifdef FEAT_EVAL
 			    (char_u *)&p_tfu, PV_TFU,
 			    {(char_u *)"", (char_u *)0L}
@@ -2624,7 +2624,7 @@ static struct vimoption options[] =
     {"thesaurus",   "tsr",  P_STRING|P_EXPAND|P_VI_DEF|P_ONECOMMA|P_NODUP|P_NDNAME,
 			    (char_u *)&p_tsr, PV_TSR,
 			    {(char_u *)"", (char_u *)0L} SCTX_INIT},
-    {"thesaurusfunc", "tsrfu",  P_STRING|P_ALLOCED|P_VI_DEF|P_SECURE,
+    {"thesaurusfunc", "tsrfu",  P_STRING|P_ALLOCED|P_VI_DEF|P_SECURE|P_FUNC,
 #ifdef FEAT_COMPL_FUNC
 			    (char_u *)&p_tsrfu, PV_TSRFU,
 			    {(char_u *)"", (char_u *)0L}
diff --git a/src/proto/eval.pro b/src/proto/eval.pro
index 96a2c6d1e6..45b559de52 100644
--- a/src/proto/eval.pro
+++ b/src/proto/eval.pro
@@ -73,7 +73,7 @@ void ex_echo(exarg_T *eap);
 void ex_echohl(exarg_T *eap);
 int get_echo_attr(void);
 void ex_execute(exarg_T *eap);
-char_u *find_option_end(char_u **arg, int *opt_flags);
+char_u *find_option_end(char_u **arg, int *scope);
 void last_set_msg(sctx_T script_ctx);
 char_u *do_string_sub(char_u *str, char_u *pat, char_u *sub, typval_T *expr, char_u *flags);
 /* vim: set ft=c : */
diff --git a/src/proto/option.pro b/src/proto/option.pro
index ea6baa7e4f..2390f58776 100644
--- a/src/proto/option.pro
+++ b/src/proto/option.pro
@@ -25,7 +25,7 @@ void set_option_sctx_idx(int opt_idx, int opt_flags, sctx_T script_ctx);
 void set_term_option_sctx_idx(char *name, int opt_idx);
 void check_redraw(long_u flags);
 int findoption(char_u *arg);
-getoption_T get_option_value(char_u *name, long *numval, char_u **stringval, int opt_flags);
+getoption_T get_option_value(char_u *name, long *numval, char_u **stringval, int *flagsp, int scope);
 int get_option_value_strict(char_u *name, long *numval, char_u **stringval, int opt_type, void *from);
 char_u *option_iter_next(void **option, int opt_type);
 long_u get_option_flags(int opt_idx);
@@ -48,7 +48,7 @@ void free_one_termoption(char_u *var);
 void set_term_defaults(void);
 int istermoption_idx(int opt_idx);
 void unset_global_local_option(char_u *name, void *from);
-char_u *get_option_varp_scope(int opt_idx, int opt_flags);
+char_u *get_option_varp_scope(int opt_idx, int scope);
 char_u *get_option_var(int opt_idx);
 char_u *get_option_fullname(int opt_idx);
 char_u *get_equalprg(void);
diff --git a/src/spell.c b/src/spell.c
index f472f99326..9b2d3e89f6 100644
--- a/src/spell.c
+++ b/src/spell.c
@@ -3830,7 +3830,7 @@ ex_spelldump(exarg_T *eap)
 
     if (no_spell_checking(curwin))
 	return;
-    (void)get_option_value((char_u*)"spl", &dummy, &spl, OPT_LOCAL);
+    (void)get_option_value((char_u*)"spl", &dummy, &spl, NULL, OPT_LOCAL);
 
     // Create a new empty buffer in a new window.
     do_cmdline_cmd((char_u *)"new");
diff --git a/src/testdir/test_iminsert.vim b/src/testdir/test_iminsert.vim
index 14063f9d89..c3c4725a1e 100644
--- a/src/testdir/test_iminsert.vim
+++ b/src/testdir/test_iminsert.vim
@@ -130,12 +130,15 @@ func Test_imactivatefunc_imstatusfunc_callback()
 
   " Using a funcref variable to set 'completefunc'
   let Fn1 = function('IMactivatefunc1')
-  let &imactivatefunc = string(Fn1)
+  let &imactivatefunc = Fn1
   let Fn2 = function('IMstatusfunc1')
+  let &imstatusfunc = Fn2
+  normal! i
+
+  " Using a string(funcref variable) to set 'completefunc'
+  let &imactivatefunc = string(Fn1)
   let &imstatusfunc = string(Fn2)
   normal! i
-  call assert_fails('let &imactivatefunc = Fn1', 'E729:')
-  call assert_fails('let &imstatusfunc = Fn2', 'E729:')
 
   " Test for using a funcref()
   set imactivatefunc=funcref('IMactivatefunc1')
@@ -144,12 +147,15 @@ func Test_imactivatefunc_imstatusfunc_callback()
 
   " Using a funcref variable to set 'imactivatefunc'
   let Fn1 = funcref('IMactivatefunc1')
-  let &imactivatefunc = string(Fn1)
+  let &imactivatefunc = Fn1
   let Fn2 = funcref('IMstatusfunc1')
+  let &imstatusfunc = Fn2
+  normal! i
+
+  " Using a string(funcref variable) to set 'imactivatefunc'
+  let &imactivatefunc = string(Fn1)
   let &imstatusfunc = string(Fn2)
   normal! i
-  call assert_fails('let &imactivatefunc = Fn1', 'E729:')
-  call assert_fails('let &imstatusfunc = Fn2', 'E729:')
 
   " Test for using a lambda function
   set imactivatefunc={a\ ->\ IMactivatefunc1(a)}
@@ -157,6 +163,11 @@ func Test_imactivatefunc_imstatusfunc_callback()
   normal! i
 
   " Set 'imactivatefunc' and 'imstatusfunc' to a lambda expression
+  let &imactivatefunc = {a -> IMactivatefunc1(a)}
+  let &imstatusfunc = { -> IMstatusfunc1()}
+  normal! i
+
+  " Set 'imactivatefunc' and 'imstatusfunc' to a string(lambda expression)
   let &imactivatefunc = '{a -> IMactivatefunc1(a)}'
   let &imstatusfunc = '{ -> IMstatusfunc1()}'
   normal! i
@@ -164,11 +175,15 @@ func Test_imactivatefunc_imstatusfunc_callback()
   " Set 'imactivatefunc' 'imstatusfunc' to a variable with a lambda expression
   let Lambda1 = {a -> IMactivatefunc1(a)}
   let Lambda2 = { -> IMstatusfunc1()}
+  let &imactivatefunc = Lambda1
+  let &imstatusfunc = Lambda2
+  normal! i
+
+  " Set 'imactivatefunc' 'imstatusfunc' to a string(variable with a lambda
+  " expression)
   let &imactivatefunc = string(Lambda1)
   let &imstatusfunc = string(Lambda2)
   normal! i
-  call assert_fails('let &imactivatefunc = Lambda1', 'E729:')
-  call assert_fails('let &imstatusfunc = Lambda2', 'E729:')
 
   " Test for clearing the 'completefunc' option
   set imactivatefunc='' imstatusfunc=''
@@ -179,8 +194,8 @@ func Test_imactivatefunc_imstatusfunc_callback()
   call assert_fails("set imactivatefunc=funcref('abc')", "E700:")
   call assert_fails("set imstatusfunc=funcref('abc')", "E700:")
 
-  call assert_equal(7, g:IMactivatefunc_called)
-  call assert_equal(14, g:IMstatusfunc_called)
+  call assert_equal(11, g:IMactivatefunc_called)
+  call assert_equal(22, g:IMstatusfunc_called)
 
   " Vim9 tests
   let lines =<< trim END
@@ -216,12 +231,17 @@ func Test_imactivatefunc_imstatusfunc_callback()
            g:IMstatusfunc_called += 1
            return 1
         }
+    &imactivatefunc = Fn1
+    &imstatusfunc = Fn2
+    normal! i
+
+    # Test for using a string(variable with a lambda expression)
     &imactivatefunc = string(Fn1)
     &imstatusfunc = string(Fn2)
     normal! i
 
-    assert_equal(3, g:IMactivatefunc_called)
-    assert_equal(6, g:IMstatusfunc_called)
+    assert_equal(4, g:IMactivatefunc_called)
+    assert_equal(8, g:IMstatusfunc_called)
 
     set iminsert=0
     set imactivatefunc=
diff --git a/src/testdir/test_ins_complete.vim b/src/testdir/test_ins_complete.vim
index d39acf4270..d508ba087f 100644
--- a/src/testdir/test_ins_complete.vim
+++ b/src/testdir/test_ins_complete.vim
@@ -885,13 +885,22 @@ func Test_completefunc_callback()
 
   " Using a funcref variable to set 'completefunc'
   let Fn = function('MycompleteFunc1')
+  let &completefunc = Fn
+  new | only
+  call setline(1, 'two')
+  let g:MycompleteFunc1_args = []
+  call feedkeys("A\<C-X>\<C-U>\<Esc>", 'x')
+  call assert_equal([[1, ''], [0, 'two']], g:MycompleteFunc1_args)
+  bw!
+
+  " Using string(funcref_variable) to set 'completefunc'
+  let Fn = function('MycompleteFunc1')
   let &completefunc = string(Fn)
   new | only
   call setline(1, 'two')
   let g:MycompleteFunc1_args = []
   call feedkeys("A\<C-X>\<C-U>\<Esc>", 'x')
   call assert_equal([[1, ''], [0, 'two']], g:MycompleteFunc1_args)
-  call assert_fails('let &completefunc = Fn', 'E729:')
   bw!
 
   " Test for using a funcref()
@@ -909,13 +918,22 @@ func Test_completefunc_callback()
 
   " Using a funcref variable to set 'completefunc'
   let Fn = funcref('MycompleteFunc2')
+  let &completefunc = Fn
+  new | only
+  call setline(1, 'four')
+  let g:MycompleteFunc2_args = []
+  call feedkeys("A\<C-X>\<C-U>\<Esc>", 'x')
+  call assert_equal([[1, ''], [0, 'four']], g:MycompleteFunc2_args)
+  bw!
+
+  " Using a string(funcref_variable) to set 'completefunc'
+  let Fn = funcref('MycompleteFunc2')
   let &completefunc = string(Fn)
   new | only
   call setline(1, 'four')
   let g:MycompleteFunc2_args = []
   call feedkeys("A\<C-X>\<C-U>\<Esc>", 'x')
   call assert_equal([[1, ''], [0, 'four']], g:MycompleteFunc2_args)
-  call assert_fails('let &completefunc = Fn', 'E729:')
   bw!
 
   " Test for using a lambda function
@@ -932,6 +950,15 @@ func Test_completefunc_callback()
   bw!
 
   " Set 'completefunc' to a lambda expression
+  let &completefunc = {a, b -> MycompleteFunc3(a, b)}
+  new | only
+  call setline(1, 'six')
+  let g:MycompleteFunc3_args = []
+  call feedkeys("A\<C-X>\<C-U>\<Esc>", 'x')
+  call assert_equal([[1, ''], [0, 'six']], g:MycompleteFunc3_args)
+  bw!
+
+  " Set 'completefunc' to string(lambda_expression)
   let &completefunc = '{a, b -> MycompleteFunc3(a, b)}'
   new | only
   call setline(1, 'six')
@@ -942,18 +969,27 @@ func Test_completefunc_callback()
 
   " Set 'completefunc' to a variable with a lambda expression
   let Lambda = {a, b -> MycompleteFunc3(a, b)}
+  let &completefunc = Lambda
+  new | only
+  call setline(1, 'seven')
+  let g:MycompleteFunc3_args = []
+  call feedkeys("A\<C-X>\<C-U>\<Esc>", 'x')
+  call assert_equal([[1, ''], [0, 'seven']], g:MycompleteFunc3_args)
+  bw!
+
+  " Set 'completefunc' to a string(variable with a lambda expression)
+  let Lambda = {a, b -> MycompleteFunc3(a, b)}
   let &completefunc = string(Lambda)
   new | only
   call setline(1, 'seven')
   let g:MycompleteFunc3_args = []
   call feedkeys("A\<C-X>\<C-U>\<Esc>", 'x')
   call assert_equal([[1, ''], [0, 'seven']], g:MycompleteFunc3_args)
-  call assert_fails('let &completefunc = Lambda', 'E729:')
   bw!
 
   " Test for using a lambda function with incorrect return value
   let Lambda = {s -> strlen(s)}
-  let &completefunc = string(Lambda)
+  let &completefunc = Lambda
   new | only
   call setline(1, 'eight')
   call feedkeys("A\<C-X>\<C-U>\<Esc>", 'x')
@@ -965,7 +1001,7 @@ func Test_completefunc_callback()
 
   call assert_fails("set completefunc=function('abc')", "E700:")
   call assert_fails("set completefunc=funcref('abc')", "E700:")
-  let &completefunc = "{a -> 'abc'}"
+  let &completefunc = {a -> 'abc'}
   call feedkeys("A\<C-X>\<C-U>\<Esc>", 'x')
 
   " Vim9 tests
@@ -990,6 +1026,15 @@ func Test_completefunc_callback()
       add(g:LambdaComplete1_args, [findstart, base])
       return findstart ? 0 : []
     enddef
+    &completefunc = (a, b) => LambdaComplete1(a, b)
+    new | only
+    setline(1, 'two')
+    g:LambdaComplete1_args = []
+    feedkeys("A\<C-X>\<C-U>\<Esc>", 'x')
+    assert_equal([[1, ''], [0, 'two']], g:LambdaComplete1_args)
+    bw!
+
+    # Test for using a string(lambda)
     &completefunc = '(a, b) => LambdaComplete1(a, b)'
     new | only
     setline(1, 'two')
@@ -1003,6 +1048,15 @@ func Test_completefunc_callback()
             add(g:LambdaComplete2_args, [findstart, base])
             return findstart ? 0 : []
         }
+    &completefunc = Fn
+    new | only
+    setline(1, 'three')
+    g:LambdaComplete2_args = []
+    feedkeys("A\<C-X>\<C-U>\<Esc>", 'x')
+    assert_equal([[1, ''], [0, 'three']], g:LambdaComplete2_args)
+    bw!
+
+    # Test for using a string(variable with a lambda expression)
     &completefunc = string(Fn)
     new | only
     setline(1, 'three')
@@ -1045,13 +1099,22 @@ func Test_omnifunc_callback()
 
   " Using a funcref variable to set 'omnifunc'
   let Fn = function('MyomniFunc1')
+  let &omnifunc = Fn
+  new | only
+  call setline(1, 'two')
+  let g:MyomniFunc1_args = []
+  call feedkeys("A\<C-X>\<C-O>\<Esc>", 'x')
+  call assert_equal([[1, ''], [0, 'two']], g:MyomniFunc1_args)
+  bw!
+
+  " Using a string(funcref_variable) to set 'omnifunc'
+  let Fn = function('MyomniFunc1')
   let &omnifunc = string(Fn)
   new | only
   call setline(1, 'two')
   let g:MyomniFunc1_args = []
   call feedkeys("A\<C-X>\<C-O>\<Esc>", 'x')
   call assert_equal([[1, ''], [0, 'two']], g:MyomniFunc1_args)
-  call assert_fails('let &omnifunc = Fn', 'E729:')
   bw!
 
   " Test for using a funcref()
@@ -1069,13 +1132,22 @@ func Test_omnifunc_callback()
 
   " Using a funcref variable to set 'omnifunc'
   let Fn = funcref('MyomniFunc2')
+  let &omnifunc = Fn
+  new | only
+  call setline(1, 'four')
+  let g:MyomniFunc2_args = []
+  call feedkeys("A\<C-X>\<C-O>\<Esc>", 'x')
+  call assert_equal([[1, ''], [0, 'four']], g:MyomniFunc2_args)
+  bw!
+
+  " Using a string(funcref_variable) to set 'omnifunc'
+  let Fn = funcref('MyomniFunc2')
   let &omnifunc = string(Fn)
   new | only
   call setline(1, 'four')
   let g:MyomniFunc2_args = []
   call feedkeys("A\<C-X>\<C-O>\<Esc>", 'x')
   call assert_equal([[1, ''], [0, 'four']], g:MyomniFunc2_args)
-  call assert_fails('let &omnifunc = Fn', 'E729:')
   bw!
 
   " Test for using a lambda function
@@ -1092,6 +1164,15 @@ func Test_omnifunc_callback()
   bw!
 
   " Set 'omnifunc' to a lambda expression
+  let &omnifunc = {a, b -> MyomniFunc3(a, b)}
+  new | only
+  call setline(1, 'six')
+  let g:MyomniFunc3_args = []
+  call feedkeys("A\<C-X>\<C-O>\<Esc>", 'x')
+  call assert_equal([[1, ''], [0, 'six']], g:MyomniFunc3_args)
+  bw!
+
+  " Set 'omnifunc' to a string(lambda_expression)
   let &omnifunc = '{a, b -> MyomniFunc3(a, b)}'
   new | only
   call setline(1, 'six')
@@ -1102,18 +1183,27 @@ func Test_omnifunc_callback()
 
   " Set 'omnifunc' to a variable with a lambda expression
   let Lambda = {a, b -> MyomniFunc3(a, b)}
+  let &omnifunc = Lambda
+  new | only
+  call setline(1, 'seven')
+  let g:MyomniFunc3_args = []
+  call feedkeys("A\<C-X>\<C-O>\<Esc>", 'x')
+  call assert_equal([[1, ''], [0, 'seven']], g:MyomniFunc3_args)
+  bw!
+
+  " Set 'omnifunc' to a string(variable with a lambda expression)
+  let Lambda = {a, b -> MyomniFunc3(a, b)}
   let &omnifunc = string(Lambda)
   new | only
   call setline(1, 'seven')
   let g:MyomniFunc3_args = []
   call feedkeys("A\<C-X>\<C-O>\<Esc>", 'x')
   call assert_equal([[1, ''], [0, 'seven']], g:MyomniFunc3_args)
-  call assert_fails('let &omnifunc = Lambda', 'E729:')
   bw!
 
   " Test for using a lambda function with incorrect return value
   let Lambda = {s -> strlen(s)}
-  let &omnifunc = string(Lambda)
+  let &omnifunc = Lambda
   new | only
   call setline(1, 'eight')
   call feedkeys("A\<C-X>\<C-O>\<Esc>", 'x')
@@ -1125,7 +1215,7 @@ func Test_omnifunc_callback()
 
   call assert_fails("set omnifunc=function('abc')", "E700:")
   call assert_fails("set omnifunc=funcref('abc')", "E700:")
-  let &omnifunc = "{a -> 'abc'}"
+  let &omnifunc = {a -> 'abc'}
   call feedkeys("A\<C-X>\<C-O>\<Esc>", 'x')
 
   " Vim9 tests
@@ -1150,6 +1240,15 @@ func Test_omnifunc_callback()
       add(g:MyomniFunc2_args, [findstart, base])
       return findstart ? 0 : []
     enddef
+    &omnifunc = (a, b) => MyomniFunc2(a, b)
+    new | only
+    setline(1, 'two')
+    g:MyomniFunc2_args = []
+    feedkeys("A\<C-X>\<C-O>\<Esc>", 'x')
+    assert_equal([[1, ''], [0, 'two']], g:MyomniFunc2_args)
+    bw!
+
+    # Test for using a string(lambda)
     &omnifunc = '(a, b) => MyomniFunc2(a, b)'
     new | only
     setline(1, 'two')
@@ -1160,6 +1259,15 @@ func Test_omnifunc_callback()
 
     # Test for using a variable with a lambda expression
     var Fn: func = (a, b) => MyomniFunc2(a, b)
+    &omnifunc = Fn
+    new | only
+    setline(1, 'three')
+    g:MyomniFunc2_args = []
+    feedkeys("A\<C-X>\<C-O>\<Esc>", 'x')
+    assert_equal([[1, ''], [0, 'three']], g:MyomniFunc2_args)
+    bw!
+
+    # Test for using a string(variable with a lambda expression)
     &omnifunc = string(Fn)
     new | only
     setline(1, 'three')
@@ -1202,13 +1310,22 @@ func Test_thesaurusfunc_callback()
 
   " Using a funcref variable to set 'thesaurusfunc'
   let Fn = function('MytsrFunc1')
+  let &thesaurusfunc = Fn
+  new | only
+  call setline(1, 'two')
+  let g:MytsrFunc1_args = []
+  call feedkeys("A\<C-X>\<C-T>\<Esc>", 'x')
+  call assert_equal([[1, ''], [0, 'two']], g:MytsrFunc1_args)
+  bw!
+
+  " Using a string(funcref_variable) to set 'thesaurusfunc'
+  let Fn = function('MytsrFunc1')
   let &thesaurusfunc = string(Fn)
   new | only
   call setline(1, 'two')
   let g:MytsrFunc1_args = []
   call feedkeys("A\<C-X>\<C-T>\<Esc>", 'x')
   call assert_equal([[1, ''], [0, 'two']], g:MytsrFunc1_args)
-  call assert_fails('let &thesaurusfunc = Fn', 'E729:')
   bw!
 
   " Test for using a funcref()
@@ -1226,13 +1343,22 @@ func Test_thesaurusfunc_callback()
 
   " Using a funcref variable to set 'thesaurusfunc'