public static String getRangeEscapedString(int codePointStart, int codePointEnd) {
		return codePointStart != codePointEnd
				? getANTLRCharLiteralForChar(codePointStart) + ".." + getANTLRCharLiteralForChar(codePointEnd)
				: getANTLRCharLiteralForChar(codePointStart);
	}
Given char x or \\t or \\u1234 return the char value;
 Unnecessary escapes like '\{' yield -1.
tool/src/org/antlr/v4/misc/CharSupport.java