From 9a9444bdc00e2a738fb0aa7cac4afa8a123d679b Mon Sep 17 00:00:00 2001
From: Ryo Nihei <nihei.dev@gmail.com>
Date: Sat, 16 Apr 2022 01:44:33 +0900
Subject: Prohibit using the same element multiple times in the #ast directive

---
 grammar/grammar_test.go | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

(limited to 'grammar/grammar_test.go')

diff --git a/grammar/grammar_test.go b/grammar/grammar_test.go
index a90ee8b..2bb2358 100644
--- a/grammar/grammar_test.go
+++ b/grammar/grammar_test.go
@@ -771,6 +771,34 @@ bar
 `,
 			errs: []*SemanticError{semErrDirInvalidParam},
 		},
+		{
+			caption: "a symbol can appear in the `#ast` directive only once",
+			specSrc: `
+%name test
+
+s
+    : foo #ast foo foo
+    ;
+
+foo
+    : 'foo';
+`,
+			errs: []*SemanticError{semErrDuplicateElem},
+		},
+		{
+			caption: "a symbol can appear in the `#ast` directive only once, even if the symbol has a label",
+			specSrc: `
+%name test
+
+s
+    : foo@x #ast foo x
+    ;
+
+foo
+    : 'foo';
+`,
+			errs: []*SemanticError{semErrDuplicateElem},
+		},
 		{
 			caption: "the expansion operator cannot be applied to a terminal symbol",
 			specSrc: `
-- 
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