patch 8.2.2660: Vim9: no error for declaration with trailing text

Problem:    Vim9: no error for declaration with trailing text.
Solution:   Give an error. (closes #8014)

src/evalvars.c

@@ -789,8 +789,11 @@ ex_let(exarg_T *eap)
 	{
 	    if (vim9script)
 	    {
-		// Vim9 declaration ":var name: type"
+		if (!ends_excmd2(eap->cmd, skipwhite(argend)))
-		arg = vim9_declare_scriptvar(eap, arg);
+		    semsg(_(e_trailing_arg), argend);
+		else
+		    // Vim9 declaration ":var name: type"
+		    arg = vim9_declare_scriptvar(eap, arg);
 	    }
 	    else
 	    {

src/testdir/test_vim9_assign.vim

@@ -1290,6 +1290,8 @@ def Test_var_declaration()
     other = 1234
     g:other_var = other
 
+    var xyz: string  # comment
+
     # type is inferred
     var s:dict = {['a']: 222}
     def GetDictVal(key: any)
@@ -1365,7 +1367,7 @@ def Test_var_declaration_fails()
     vim9script
     var 9var: string
   END
-  CheckScriptFailure(lines, 'E475:')
+  CheckScriptFailure(lines, 'E488:')
 
   CheckDefFailure(['var foo.bar = 2'], 'E1087:')
   CheckDefFailure(['var foo[3] = 2'], 'E1087:')
@@ -1617,6 +1619,11 @@ def Test_expr_error_no_assign()
       echo x
   END
   CheckScriptFailureList(lines, ['E1154:', 'E121:'])
+
+  lines =<< trim END
+      var x: string  'string'
+  END
+  CheckDefAndScriptFailure(lines, 'E488:')
 enddef
 
 

src/version.c

@@ -750,6 +750,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    2660,
 /**/
     2659,
 /**/