patch 8.2.4395: some code lines not covered by tests

Problem:    Some code lines not covered by tests.
Solution:   Add a few more test cases.  Fix getting more than one error for
            invalid assignment.

src/errors.h

@@ -2788,7 +2788,8 @@ EXTERN char e_missing_argument_type_for_str[]
 	INIT(= N_("E1077: Missing argument type for %s"));
 // E1078 unused
 // E1079 unused
-// E1080 unused
+EXTERN char e_invalid_assignment[]
+	INIT(= N_("E1080: Invalid assignment"));
 EXTERN char e_cannot_unlet_str[]
 	INIT(= N_("E1081: Cannot unlet %s"));
 #endif

src/evalvars.c

@@ -1107,7 +1107,8 @@ skip_var_list(
 	    {
 		if (*semicolon == 1)
 		{
-		    emsg(_(e_double_semicolon_in_list_of_variables));
+		    if (!silent)
+			emsg(_(e_double_semicolon_in_list_of_variables));
 		    return NULL;
 		}
 		*semicolon = 1;

src/testdir/test_vim9_assign.vim

@@ -1359,7 +1359,8 @@ def Test_assignment_failure()
   v9.CheckDefFailure(['var null = 1'], 'E1034:')
   v9.CheckDefFailure(['var this = 1'], 'E1034:')
 
-  v9.CheckDefFailure(['[a; b; c] = g:list'], 'E452:')
+  v9.CheckDefFailure(['[a; b; c] = g:list'], 'E1001:')
+  v9.CheckDefFailure(['var [a; b; c] = g:list'], 'E1080:')
   v9.CheckDefExecFailure(['var a: number',
                        '[a] = test_null_list()'], 'E1093:')
   v9.CheckDefExecFailure(['var a: number',

src/testdir/test_vim9_cmd.vim

@@ -1354,6 +1354,13 @@ def Test_command_not_recognized()
   END
   v9.CheckDefFailure(lines, 'E1146:', 1)
 
+  lines =<< trim END
+    if 0
+      d.key = 'asdf'
+    endif
+  END
+  v9.CheckDefSuccess(lines)
+
   lines =<< trim END
     d['key'] = 'asdf'
   END
@@ -1621,6 +1628,11 @@ def Test_substitute_expr()
   s/text/\=['aaa', 'bbb', 'ccc']/
   assert_equal(['some aaa', 'bbb', 'ccc', ' here'], getline(1, '$'))
   bwipe!
+
+  # inside "if 0" substitute is ignored
+  if 0
+    s/a/\=nothing/ and | some more
+  endif
 enddef
 
 def Test_redir_to_var()
@@ -1663,6 +1675,12 @@ def Test_redir_to_var()
   END
   v9.CheckDefFailure(lines, 'E1089:')
 
+  lines =<< trim END
+    var text: string
+    redir => text
+  END
+  v9.CheckDefFailure(lines, 'E1185:')
+
   lines =<< trim END
     var ls = 'asdf'
     redir => ls[1]

src/testdir/test_vim9_func.vim

@@ -3762,7 +3762,15 @@ def Test_go_beyond_end_of_cmd()
   v9.CheckScriptFailure(lines, 'E476:')
 enddef
 
+" The following messes up syntax highlight, keep near the end.
 if has('python3')
+  def Test_python3_command()
+    py3 import vim
+    py3 vim.command("let g:done = 'yes'")
+    assert_equal('yes', g:done)
+    unlet g:done
+  enddef
+
   def Test_python3_heredoc()
     py3 << trim EOF
       import vim
@@ -3778,7 +3786,6 @@ if has('python3')
   enddef
 endif
 
-" This messes up syntax highlight, keep near the end.
 if has('lua')
   def Test_lua_heredoc()
     g:d = {}

src/version.c

@@ -750,6 +750,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    4395,
 /**/
     4394,
 /**/

src/vim9compile.c

@@ -2420,7 +2420,7 @@ may_compile_assignment(exarg_T *eap, char_u **line, cctx_T *cctx)
 
     if (*eap->cmd == '[')
     {
-	// [var, var] = expr
+	// might be "[var, var] = expr"
 	*line = compile_assignment(eap->cmd, eap, CMD_SIZE, cctx);
 	if (*line == NULL)
 	    return FAIL;
@@ -2958,7 +2958,10 @@ compile_def_function(
 	    case CMD_decrement:
 		    line = compile_assignment(p, &ea, ea.cmdidx, &cctx);
 		    if (line == p)
+		    {
+			emsg(_(e_invalid_assignment));
 			line = NULL;
+		    }
 		    break;
 
 	    case CMD_unlet: