patch 9.0.1355: no error when declaring a class twice

Problem:    No error when declaring a class twice. (Ernie Rael)
Solution:   Pass different flags when declaring the class. (closes #12057)
diff --git a/src/testdir/test_vim9_class.vim b/src/testdir/test_vim9_class.vim
index c268dde..87c1d4a 100644
--- a/src/testdir/test_vim9_class.vim
+++ b/src/testdir/test_vim9_class.vim
@@ -164,6 +164,28 @@
   v9.CheckScriptSuccess(lines)
 enddef
 
+def Test_class_defined_twice()
+  # class defined twice should fail
+  var lines =<< trim END
+      vim9script
+      class There
+      endclass
+      class There
+      endclass
+  END
+  v9.CheckScriptFailure(lines, 'E1041: Redefining script item: "There"')
+
+  # one class, reload same script twice is OK
+  lines =<< trim END
+      vim9script
+      class There
+      endclass
+  END
+  writefile(lines, 'XclassTwice.vim', 'D')
+  source XclassTwice.vim
+  source XclassTwice.vim
+enddef
+
 def Test_class_interface_wrong_end()
   var lines =<< trim END
       vim9script
@@ -1012,14 +1034,13 @@
         this.member: string
       endinterface
 
-      class SomeImpl implements Some, Another
+      class AnotherImpl implements Some, Another
         this.member = 'abc'
         static count: number
         def Method(nr: number)
           echo nr
         enddef
       endclass
-
   END
   v9.CheckScriptSuccess(lines)
 
diff --git a/src/version.c b/src/version.c
index 315f91e..785f76e 100644
--- a/src/version.c
+++ b/src/version.c
@@ -696,6 +696,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1355,
+/**/
     1354,
 /**/
     1353,
diff --git a/src/vim9class.c b/src/vim9class.c
index 4431640..a2b186e 100644
--- a/src/vim9class.c
+++ b/src/vim9class.c
@@ -230,7 +230,8 @@
     void
 ex_class(exarg_T *eap)
 {
-    int is_class = eap->cmdidx == CMD_class;  // FALSE for :interface
+    int	    is_class = eap->cmdidx == CMD_class;  // FALSE for :interface
+    long    start_lnum = SOURCING_LNUM;
 
     char_u *arg = eap->arg;
     int is_abstract = eap->cmdidx == CMD_abstract;
@@ -1097,8 +1098,9 @@
 	tv.v_type = VAR_CLASS;
 	tv.vval.v_class = cl;
 	is_export = class_export;
+	SOURCING_LNUM = start_lnum;
 	set_var_const(cl->class_name, current_sctx.sc_sid,
-					     NULL, &tv, FALSE, ASSIGN_DECL, 0);
+						       NULL, &tv, FALSE, 0, 0);
 	return;
     }