patch 8.2.4872: Vim9: no error for using an expression only

Problem:    Vim9: no error for using an expression only at the script level
            when followed by an empty line.
Solution:   Do not check the line number but whether something follows.
            (closes #10357)

src/ex_eval.c

@@ -940,8 +940,14 @@ ex_eval(exarg_T *eap)
     if (eval0(eap->arg, &tv, eap, &evalarg) == OK)
     {
 	clear_tv(&tv);
-	if (in_vim9script() && name_only && lnum == SOURCING_LNUM)
+	if (in_vim9script() && name_only
+		&& (evalarg.eval_tofree == NULL
+		    || ends_excmd2(evalarg.eval_tofree,
+					      skipwhite(evalarg.eval_tofree))))
+	{
+	    SOURCING_LNUM = lnum;
 	    semsg(_(e_expression_without_effect_str), eap->arg);
+	}
     }
 
     clear_evalarg(&evalarg, eap);

src/testdir/test_vim9_cmd.vim

@@ -650,6 +650,20 @@ def Test_use_register()
   END
   v9.CheckDefAndScriptFailure(lines, 'E1207:', 2)
 
+  lines =<< trim END
+      @a = 'echo "text"'
+      @a
+
+  END
+  v9.CheckDefAndScriptFailure(lines, 'E1207:', 2)
+
+  lines =<< trim END
+      @a = 'echo "text"'
+      @a
+          # comment
+  END
+  v9.CheckDefAndScriptFailure(lines, 'E1207:', 2)
+
   lines =<< trim END
       @/ = 'pattern'
       @/

src/version.c

@@ -746,6 +746,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    4872,
 /**/
     4871,
 /**/