public int defineStringLiteral(String lit) {
		if ( stringLiteralToTypeMap.containsKey(lit) ) {
			return stringLiteralToTypeMap.get(lit);
		}
		return defineStringLiteral(lit, getNewTokenType());

	}
Return a new unique integer in the channel value space.
tool/src/org/antlr/v4/tool/Grammar.java