R6: Fix null pointer crash in tokenDelete function

Units/parser-r6class.r/r6-null-pointer-regression.d/args.ctags

@@ -0,0 +1,4 @@
+--sort=no
+--fields=+ilaKSe{extras}
+--extras=-p
+

Units/parser-r6class.r/r6-null-pointer-regression.d/expected.tags

@@ -0,0 +1,3 @@
+TestCase1	input.r	/^TestCase1 <- R6::SomethingElse("TestCase1")$/;"	globalVar	language:R	end:6
+TestCase2	input.r	/^TestCase2 <- R6::$/;"	globalVar	language:R	end:10
+TestCase3	input.r	/^TestCase3 <- R6::R6Clas("TestCase3")$/;"	globalVar	language:R	end:12

Units/parser-r6class.r/r6-null-pointer-regression.d/input.r

@@ -0,0 +1,13 @@
+# Test case for R6 parser null pointer regression
+# This triggers the error path in r6ReadRightSideSymbol that was causing
+# tokenDelete to be called with NULL pointers
+
+# Case 1: R6:: followed by something other than R6Class
+TestCase1 <- R6::SomethingElse("TestCase1")
+
+# Case 2: Incomplete R6 namespace reference
+TestCase2 <- R6::
+
+# Case 3: R6 followed by :: but with syntax error
+TestCase3 <- R6::R6Clas("TestCase3")
+

main/tokeninfo.c

@@ -91,7 +91,8 @@ void  flashTokenBacklog (struct tokenInfoClass *klass)
 
 void tokenDelete (tokenInfo *token)
 {
-	objPoolPut (token->klass->pool, token);
+	if (token != NULL)
+		objPoolPut (token->klass->pool, token);
 }
 
 

parsers/r-r6class.c

@@ -219,14 +219,14 @@ static int r6ReadRightSideSymbol (rSubparser *s,
 	tokenInfo * token1 = NULL;
 	if (strcmp (tokenString (token), "R6") == 0)
 	{
-		tokenInfo * token0 = rNewToken ();
+		token0 = rNewToken ();
 		tokenRead (token0);
 		if (!tokenIsType (token0, R_SCOPE))
 			goto reject;
 		if (strcmp (tokenString (token0), "::"))
 			goto reject;
 
-		tokenInfo * token1 = rNewToken ();
+		token1 = rNewToken ();
 		tokenRead (token1);
 		if (!tokenIsType (token1, R_SYMBOL))
 			goto reject;
@@ -252,11 +252,12 @@ static int r6ReadRightSideSymbol (rSubparser *s,
 	}
 	return CORK_NIL;
  reject:
-	if (token1)
+	/* For incomplete "R6::" cases, we don't want to unread the "::" token
+	   as the main R parser may not handle it well. */
+	if (token1 && tokenIsType(token1, R_SYMBOL)) {
 		tokenUnread (token1);
-	if (token0)
-		tokenUnread (token0);
-	/* tokenDelete accepts NULL. */
+	}
+	/* Don't unread token0 (::) to prevent main parser confusion */
 	tokenDelete (token1);
 	tokenDelete (token0);