patch 8.2.4024: confusing error message if imported name is used directly

Problem:    Confusing error message if imported name is used directly.
Solution:   Give a better error message.

src/eval.c

@@ -3481,6 +3481,7 @@ eval7(
 				      && (evalarg->eval_flags & EVAL_EVALUATE);
     int		len;
     char_u	*s;
+    char_u	*name_start = NULL;
     char_u	*start_leader, *end_leader;
     int		ret = OK;
     char_u	*alias;
@@ -3713,8 +3714,11 @@ eval7(
 		    ret = OK;
 		}
 		else
+		{
+		    name_start = s;
 		    ret = eval_variable(s, len, 0, rettv, NULL,
 					   EVAL_VAR_VERBOSE + EVAL_VAR_IMPORT);
+		}
 	    }
 	    else
 	    {
@@ -3729,7 +3733,7 @@ eval7(
     // Handle following '[', '(' and '.' for expr[expr], expr.name,
     // expr(expr), expr->name(expr)
     if (ret == OK)
-	ret = handle_subscript(arg, rettv, evalarg, TRUE);
+	ret = handle_subscript(arg, name_start, rettv, evalarg, TRUE);
 
     /*
      * Apply logical NOT and unary '-', from right to left, ignore '+'.
@@ -5891,10 +5895,12 @@ eval_isdictc(int c)
  * - method call: var->method()
  *
  * Can all be combined in any order: dict.func(expr)[idx]['func'](expr)->len()
+ * "name_start" points to a variable before the subscript or is NULL.
  */
     int
 handle_subscript(
     char_u	**arg,
+    char_u	*name_start,
     typval_T	*rettv,
     evalarg_T	*evalarg,
     int		verbose)	// give error messages
@@ -5936,7 +5942,8 @@ handle_subscript(
 	    if (**arg != '.')
 	    {
 		if (verbose)
-		    semsg(_(e_expected_str_but_got_str), "'.'", *arg);
+		    semsg(_(e_expected_dot_after_name_str),
+					name_start != NULL ? name_start: *arg);
 		ret = FAIL;
 		break;
 	    }

src/evalvars.c

@@ -1239,8 +1239,8 @@ list_arg_vars(exarg_T *eap, char_u *arg, int *first)
 		{
 		    // handle d.key, l[idx], f(expr)
 		    arg_subsc = arg;
-		    if (handle_subscript(&arg, &tv, &EVALARG_EVALUATE, TRUE)
+		    if (handle_subscript(&arg, name_start, &tv,
-								       == FAIL)
+					      &EVALARG_EVALUATE, TRUE) == FAIL)
 			error = TRUE;
 		    else
 		    {
@@ -3955,7 +3955,8 @@ var_exists(char_u *var)
 	{
 	    // handle d.key, l[idx], f(expr)
 	    arg = skipwhite(arg);
-	    n = (handle_subscript(&arg, &tv, &EVALARG_EVALUATE, FALSE) == OK);
+	    n = (handle_subscript(&arg, name, &tv, &EVALARG_EVALUATE,
+								 FALSE) == OK);
 	    if (n)
 		clear_tv(&tv);
 	}

src/proto/eval.pro

@@ -70,7 +70,7 @@ char_u *find_name_end(char_u *arg, char_u **expr_start, char_u **expr_end, int f
 int eval_isnamec(int c);
 int eval_isnamec1(int c);
 int eval_isdictc(int c);
-int handle_subscript(char_u **arg, typval_T *rettv, evalarg_T *evalarg, int verbose);
+int handle_subscript(char_u **arg, char_u *name_start, typval_T *rettv, evalarg_T *evalarg, int verbose);
 int item_copy(typval_T *from, typval_T *to, int deep, int copyID);
 void echo_one(typval_T *rettv, int with_space, int *atstart, int *needclr);
 void ex_echo(exarg_T *eap);

src/testdir/test_vim9_script.vim

@@ -1265,6 +1265,26 @@ def Test_vim9_import_export()
   unlet g:imported_func
   delete('Ximport_lbr.vim')
 
+  var line_break_before_dot =<< trim END
+    vim9script
+    import './Xexport.vim' as expo
+    g:exported = expo
+                  .exported
+  END
+  writefile(line_break_before_dot, 'Ximport_lbr_before_dot.vim')
+  assert_fails('source Ximport_lbr_before_dot.vim', 'E1060:', '', 3)
+  delete('Ximport_lbr_before_dot.vim')
+
+  var line_break_after_dot =<< trim END
+    vim9script
+    import './Xexport.vim' as expo
+    g:exported = expo.
+                  exported
+  END
+  writefile(line_break_after_dot, 'Ximport_lbr_after_dot.vim')
+  assert_fails('source Ximport_lbr_after_dot.vim', 'E1074:', '', 3)
+  delete('Ximport_lbr_after_dot.vim')
+
   var import_star_as_lines =<< trim END
     vim9script
     import './Xexport.vim' as Export
@@ -1333,7 +1353,7 @@ def Test_vim9_import_export()
     g:imported_script = Export exported
   END
   writefile(import_star_as_lines_script_no_dot, 'Ximport.vim')
-  assert_fails('source Ximport.vim', 'E1029:')
+  assert_fails('source Ximport.vim', 'E1060: Expected dot after name: Export exported')
 
   var import_star_as_lines_script_space_after_dot =<< trim END
     vim9script
@@ -1519,7 +1539,7 @@ def Test_import_star_fails()
       import './Xfoo.vim' as foo
       var that = foo
   END
-  CheckScriptFailure(lines, 'E1029: Expected ''.''')
+  CheckScriptFailure(lines, 'E1060: Expected dot after name: foo')
 
   lines =<< trim END
       vim9script

src/userfunc.c

@@ -5170,7 +5170,7 @@ ex_call(exarg_T *eap)
 	    dbg_check_breakpoint(eap);
 
 	// Handle a function returning a Funcref, Dictionary or List.
-	if (handle_subscript(&arg, &rettv,
+	if (handle_subscript(&arg, NULL, &rettv,
 			   eap->skip ? NULL : &EVALARG_EVALUATE, TRUE) == FAIL)
 	{
 	    failed = TRUE;

src/version.c

@@ -750,6 +750,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    4024,
 /**/
     4023,
 /**/