patch 8.2.3783: confusing error for using a variable as a function

Problem:    Confusing error for using a variable as a function.
Solution:   If a function is not found but there is a variable, give a more
            useful error. (issue #9310)

src/eval.c

@@ -1988,6 +1988,7 @@ eval_func(
     partial_T	*partial;
     int		ret = OK;
     type_T	*type = NULL;
+    int		found_var = FALSE;
 
     if (!evaluate)
 	check_vars(s, len);
@@ -1995,7 +1996,7 @@ eval_func(
     // If "s" is the name of a variable of type VAR_FUNC
     // use its contents.
     s = deref_func_name(s, &len, &partial,
-				    in_vim9script() ? &type : NULL, !evaluate);
+			in_vim9script() ? &type : NULL, !evaluate, &found_var);
 
     // Need to make a copy, in case evaluating the arguments makes
     // the name invalid.
@@ -2014,6 +2015,7 @@ eval_func(
 	funcexe.partial = partial;
 	funcexe.basetv = basetv;
 	funcexe.check_type = type;
+	funcexe.fe_found_var = found_var;
 	ret = get_func_tv(s, len, rettv, arg, evalarg, &funcexe);
     }
     vim_free(s);

src/proto/userfunc.pro

@@ -4,7 +4,7 @@ hashtab_T *func_tbl_get(void);
 char_u *get_lambda_name(void);
 char_u *register_cfunc(cfunc_T cb, cfunc_free_T cb_free, void *state);
 int get_lambda_tv(char_u **arg, typval_T *rettv, int types_optional, evalarg_T *evalarg);
-char_u *deref_func_name(char_u *name, int *lenp, partial_T **partialp, type_T **type, int no_autoload);
+char_u *deref_func_name(char_u *name, int *lenp, partial_T **partialp, type_T **type, int no_autoload, int *found_var);
 void emsg_funcname(char *ermsg, char_u *name);
 int get_func_tv(char_u *name, int len, typval_T *rettv, char_u **arg, evalarg_T *evalarg, funcexe_T *funcexe);
 char_u *fname_trans_sid(char_u *name, char_u *fname_buf, char_u **tofree, int *error);
@@ -30,7 +30,7 @@ int func_call(char_u *name, typval_T *args, partial_T *partial, dict_T *selfdict
 int get_callback_depth(void);
 int call_callback(callback_T *callback, int len, typval_T *rettv, int argcount, typval_T *argvars);
 varnumber_T call_callback_retnr(callback_T *callback, int argcount, typval_T *argvars);
-void user_func_error(int error, char_u *name);
+void user_func_error(int error, char_u *name, funcexe_T *funcexe);
 int call_func(char_u *funcname, int len, typval_T *rettv, int argcount_in, typval_T *argvars_in, funcexe_T *funcexe);
 char_u *printable_func_name(ufunc_T *fp);
 char_u *trans_function_name(char_u **pp, int *is_global, int skip, int flags, funcdict_T *fdp, partial_T **partial, type_T **type);

src/structs.h

@@ -2001,6 +2001,8 @@ typedef struct {
     dict_T	*selfdict;	// Dictionary for "self"
     typval_T	*basetv;	// base for base->method()
     type_T	*check_type;	// type from funcref or NULL
+    int		fe_found_var;	// if the function is not found then give an
+				// error that a variable is not callable.
 } funcexe_T;
 
 /*

src/testdir/test_functions.vim

@@ -2234,6 +2234,12 @@ func Test_call()
   call call(test_null_partial(), [])
   call assert_fails('call test_null_function()()', 'E1192:')
   call assert_fails('call test_null_partial()()', 'E117:')
+
+  let lines =<< trim END
+      let Time = 'localtime'
+      call Time()
+  END
+  CheckScriptFailure(lines, 'E1085:')
 endfunc
 
 func Test_char2nr()

src/testdir/test_vim9_func.vim

@@ -1459,7 +1459,7 @@ endfunc
 def Test_call_funcref()
   g:SomeFunc('abc')->assert_equal(3)
   assert_fails('NotAFunc()', 'E117:', '', 2, 'Test_call_funcref') # comment after call
-  assert_fails('g:NotAFunc()', 'E117:', '', 3, 'Test_call_funcref')
+  assert_fails('g:NotAFunc()', 'E1085:', '', 3, 'Test_call_funcref')
 
   var lines =<< trim END
     vim9script

src/testdir/test_vim9_script.vim

@@ -1922,6 +1922,15 @@ def Test_script_var_shadows_command()
   CheckDefAndScriptFailure(lines, 'E1207:', 2)
 enddef
 
+def Test_vim9script_call_wrong_type()
+  var lines =<< trim END
+      vim9script
+      var Time = 'localtime'
+      Time()
+  END
+  CheckScriptFailure(lines, 'E1085:')
+enddef
+
 def s:RetSome(): string
   return 'some'
 enddef

src/userfunc.c

@@ -1544,6 +1544,7 @@ errret:
  * "partialp".
  * If "type" is not NULL and a Vim9 script-local variable is found look up the
  * type of the variable.
+ * If "found_var" is not NULL and a variable was found set it to TRUE.
  */
     char_u *
 deref_func_name(
@@ -1551,7 +1552,8 @@ deref_func_name(
 	int	    *lenp,
 	partial_T   **partialp,
 	type_T	    **type,
-	int	    no_autoload)
+	int	    no_autoload,
+	int	    *found_var)
 {
     dictitem_T	*v;
     typval_T	*tv = NULL;
@@ -1609,6 +1611,8 @@ deref_func_name(
 
     if (tv != NULL)
     {
+	if (found_var != NULL)
+	    *found_var = TRUE;
 	if (tv->v_type == VAR_FUNC)
 	{
 	    if (tv->vval.v_string == NULL)
@@ -3199,12 +3203,15 @@ call_callback_retnr(
  * Nothing if "error" is FCERR_NONE.
  */
     void
-user_func_error(int error, char_u *name)
+user_func_error(int error, char_u *name, funcexe_T *funcexe)
 {
     switch (error)
     {
 	case FCERR_UNKNOWN:
-		emsg_funcname(e_unknownfunc, name);
+		if (funcexe->fe_found_var)
+		    semsg(_(e_not_callable_type_str), name);
+		else
+		    emsg_funcname(e_unknownfunc, name);
 		break;
 	case FCERR_NOTMETHOD:
 		emsg_funcname(
@@ -3448,7 +3455,7 @@ theend:
      */
     if (!aborting())
     {
-	user_func_error(error, (name != NULL) ? name : funcname);
+	user_func_error(error, (name != NULL) ? name : funcname, funcexe);
     }
 
     // clear the copies made from the partial
@@ -3677,7 +3684,7 @@ trans_function_name(
     {
 	len = (int)STRLEN(lv.ll_exp_name);
 	name = deref_func_name(lv.ll_exp_name, &len, partial, type,
-						     flags & TFN_NO_AUTOLOAD);
+						flags & TFN_NO_AUTOLOAD, NULL);
 	if (name == lv.ll_exp_name)
 	    name = NULL;
     }
@@ -3685,7 +3692,7 @@ trans_function_name(
     {
 	len = (int)(end - *pp);
 	name = deref_func_name(*pp, &len, partial, type,
-						      flags & TFN_NO_AUTOLOAD);
+						flags & TFN_NO_AUTOLOAD, NULL);
 	if (name == *pp)
 	    name = NULL;
     }
@@ -5004,6 +5011,7 @@ ex_call(exarg_T *eap)
     partial_T	*partial = NULL;
     evalarg_T	evalarg;
     type_T	*type = NULL;
+    int		found_var = FALSE;
 
     fill_evalarg_from_eap(&evalarg, eap, eap->skip);
     if (eap->skip)
@@ -5040,7 +5048,7 @@ ex_call(exarg_T *eap)
     // from trans_function_name().
     len = (int)STRLEN(tofree);
     name = deref_func_name(tofree, &len, partial != NULL ? NULL : &partial,
-			in_vim9script() && type == NULL ? &type : NULL, FALSE);
+	    in_vim9script() && type == NULL ? &type : NULL, FALSE, &found_var);
 
     // Skip white space to allow ":call func ()".  Not good, but required for
     // backward compatibility.
@@ -5096,6 +5104,7 @@ ex_call(exarg_T *eap)
 	funcexe.partial = partial;
 	funcexe.selfdict = fudi.fd_dict;
 	funcexe.check_type = type;
+	funcexe.fe_found_var = found_var;
 	rettv.v_type = VAR_UNKNOWN;	// clear_tv() uses this
 	if (get_func_tv(name, -1, &rettv, &arg, &evalarg, &funcexe) == FAIL)
 	{

src/version.c

@@ -753,6 +753,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    3783,
 /**/
     3782,
 /**/

src/vim9execute.c

@@ -890,7 +890,7 @@ call_ufunc(
 
     if (error != FCERR_NONE)
     {
-	user_func_error(error, ufunc->uf_name);
+	user_func_error(error, ufunc->uf_name, &funcexe);
 	return FAIL;
     }
     if (did_emsg > did_emsg_before)
@@ -2343,7 +2343,8 @@ exec_instructions(ectx_T *ectx)
 		    long	n = 0;
 		    char_u	*s = NULL;
 		    char	*msg;
-		    callback_T	cb = {NULL, NULL, 0};
+		    char_u	numbuf[NUMBUFLEN];
+		    char_u	*tofree = NULL;
 
 		    --ectx->ec_stack.ga_len;
 		    tv = STACK_TV_BOT(0);
@@ -2356,28 +2357,29 @@ exec_instructions(ectx_T *ectx)
 		    else if (iptr->isn_type == ISN_STOREFUNCOPT)
 		    {
 			SOURCING_LNUM = iptr->isn_lnum;
-			cb = get_callback(tv);
+			// If the option can be set to a function reference or
-			if (cb.cb_name == NULL || *cb.cb_name == NUL)
+			// 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);
+			if (s == NULL || *s == NUL)
 			{
 			    clear_tv(tv);
-			    free_callback(&cb);
 			    goto on_error;
 			}
-			s = cb.cb_name;
 		    }
 		    else
 			// must be VAR_NUMBER, CHECKTYPE makes sure
 			n = tv->vval.v_number;
 		    msg = set_option_value(opt_name, n, s, opt_flags);
 		    clear_tv(tv);
+		    vim_free(tofree);
 		    if (msg != NULL)
 		    {
 			SOURCING_LNUM = iptr->isn_lnum;
 			emsg(_(msg));
 			goto on_error;
 		    }
-		    if (cb.cb_name != NULL)
-			free_callback(&cb);
 		}
 		break;