patch 8.2.4774: crash when using a number for lambda name

Problem:    Crash when using a number for lambda name.
Solution:   Check the type of the lambda reference.

src/errors.h

@@ -3259,3 +3259,7 @@ EXTERN char e_nfa_regexp_missing_value_in_chr[]
 	INIT(= N_("E1273: (NFA regexp) missing value in '\\%%%c'"));
 EXTERN char e_no_script_file_name_to_substitute_for_script[]
 	INIT(= N_("E1274: No script file name to substitute for \"<script>\""));
+#ifdef FEAT_EVAL
+EXTERN char e_string_or_function_required_for_arrow_parens_expr[]
+	INIT(= N_("E1275: String or function required for ->(expr)"));
+#endif

src/eval.c

@@ -4102,19 +4102,23 @@ eval_lambda(
 	++*arg;
 	ret = eval1(arg, rettv, evalarg);
 	*arg = skipwhite_and_linebreak(*arg, evalarg);
-	if (**arg == ')')
+	if (**arg != ')')
-	{
-	    ++*arg;
-	}
-	else
 	{
 	    emsg(_(e_missing_closing_paren));
-	    ret = FAIL;
+	    return FAIL;
 	}
+	if (rettv->v_type != VAR_STRING && rettv->v_type != VAR_FUNC
+					       && rettv->v_type != VAR_PARTIAL)
+	{
+	    emsg(_(e_string_or_function_required_for_arrow_parens_expr));
+	    return FAIL;
+	}
+	++*arg;
     }
     if (ret != OK)
 	return FAIL;
-    else if (**arg != '(')
+
+    if (**arg != '(')
     {
 	if (verbose)
 	{

src/testdir/test_lambda.vim

@@ -66,6 +66,10 @@ function Test_lambda_fails()
   echo assert_fails('echo 10->{a -> a + 2}', 'E107:')
 
   call assert_fails('eval 0->(', "E110: Missing ')'")
+  call assert_fails('eval 0->(3)()', "E1275:")
+  call assert_fails('eval 0->([3])()', "E1275:")
+  call assert_fails('eval 0->({"a": 3})()', "E1275:")
+  call assert_fails('eval 0->(xxx)()', "E121:")
 endfunc
 
 func Test_not_lamda()

src/version.c

@@ -746,6 +746,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    4774,
 /**/
     4773,
 /**/