patch 8.2.4499: Vim9: at the script level declarations leak to next block

Problem:    Vim9: at the script level declarations leak from try block to
            catch and finally block.
Solution:   End the block and start a new one. (closes #9883)

src/ex_eval.c

@@ -1827,6 +1827,16 @@ ex_catch(exarg_T *eap)
 	    cstack->cs_flags[idx] |= CSF_ACTIVE | CSF_CAUGHT;
 	    did_emsg = got_int = did_throw = FALSE;
 	    catch_exception((except_T *)cstack->cs_exception[idx]);
+
+	    if (cstack->cs_idx >= 0
+			       && (cstack->cs_flags[cstack->cs_idx] & CSF_TRY))
+	    {
+		// Variables declared in the previous block can no longer be
+		// used.
+		leave_block(cstack);
+		enter_block(cstack);
+	    }
+
 	    // It's mandatory that the current exception is stored in the cstack
 	    // so that it can be discarded at the next ":catch", ":finally", or
 	    // ":endtry" or when the catch clause is left by a ":continue",
@@ -1930,6 +1940,15 @@ ex_finally(exarg_T *eap)
 	     */
 	    cleanup_conditionals(cstack, CSF_TRY, FALSE);
 
+	    if (cstack->cs_idx >= 0
+			       && (cstack->cs_flags[cstack->cs_idx] & CSF_TRY))
+	    {
+		// Variables declared in the previous block can no longer be
+		// used.
+		leave_block(cstack);
+		enter_block(cstack);
+	    }
+
 	    /*
 	     * Make did_emsg, got_int, did_throw pending.  If set, they overrule
 	     * a pending ":continue", ":break", ":return", or ":finish".  Then

src/testdir/test_vim9_script.vim

@@ -763,6 +763,30 @@ def Test_try_catch_throw()
   v9.CheckDefAndScriptSuccess(lines)
 enddef
 
+def Test_try_var_decl()
+  var lines =<< trim END
+      vim9script
+      try
+        var in_try = 1
+        assert_equal(1, get(s:, 'in_try', -1))
+        throw "getout"
+      catch
+        var in_catch = 2
+        assert_equal(-1, get(s:, 'in_try', -1))
+        assert_equal(2, get(s:, 'in_catch', -1))
+      finally
+        var in_finally = 3
+        assert_equal(-1, get(s:, 'in_try', -1))
+        assert_equal(-1, get(s:, 'in_catch', -1))
+        assert_equal(3, get(s:, 'in_finally', -1))
+      endtry
+      assert_equal(-1, get(s:, 'in_try', -1))
+      assert_equal(-1, get(s:, 'in_catch', -1))
+      assert_equal(-1, get(s:, 'in_finally', -1))
+  END
+  v9.CheckScriptSuccess(lines)
+enddef
+
 def Test_try_ends_in_return()
   var lines =<< trim END
       vim9script

src/version.c

@@ -754,6 +754,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    4499,
 /**/
     4498,
 /**/