patch 8.2.4138: Vim9: no error for return with argument when invalid

Problem:    Vim9: no error for return with argument when the function does not
            return anything.
Solution:   Give an error for the invalid argument. (issue #9497)

src/testdir/test_vim9_func.vim

@@ -341,6 +341,20 @@ def Test_return_something()
   ReturnString()->assert_equal('string')
   ReturnNumber()->assert_equal(123)
   assert_fails('ReturnGlobal()', 'E1012: Type mismatch; expected number but got string', '', 1, 'ReturnGlobal')
+
+  var lines =<< trim END
+      vim9script
+
+      def Msg()
+          echomsg 'in Msg()...'
+      enddef
+
+      def Func()
+        return Msg()
+      enddef
+      defcompile
+  END
+  CheckScriptFailure(lines, 'E1096:')
 enddef
 
 def Test_check_argument_type()

src/version.c

@@ -750,6 +750,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    4138,
 /**/
     4137,
 /**/

src/vim9cmds.c

@@ -2196,6 +2196,11 @@ compile_return(char_u *arg, int check_return_type, int legacy, cctx_T *cctx)
 
     if (*p != NUL && *p != '|' && *p != '\n')
     {
+	if (cctx->ctx_ufunc->uf_ret_type->tt_type == VAR_VOID)
+	{
+	    emsg(_(e_returning_value_in_function_without_return_type));
+	    return NULL;
+	}
 	if (legacy)
 	{
 	    int save_flags = cmdmod.cmod_flags;
@@ -2231,13 +2236,6 @@ compile_return(char_u *arg, int check_return_type, int legacy, cctx_T *cctx)
 	    }
 	    else
 	    {
-		if (cctx->ctx_ufunc->uf_ret_type->tt_type == VAR_VOID
-			&& stack_type->tt_type != VAR_VOID
-			&& stack_type->tt_type != VAR_UNKNOWN)
-		{
-		    emsg(_(e_returning_value_in_function_without_return_type));
-		    return NULL;
-		}
 		if (need_type(stack_type, cctx->ctx_ufunc->uf_ret_type, -1,
 						0, cctx, FALSE, FALSE) == FAIL)
 		    return NULL;