Unclosed string literal error on regex string

Issue にある簡略化された Java 再現コードから始め、文書化されている java -jar コマンドで google-java-format 1.26.0 を実行します。フォーマッタが regex のバックスラッシュを含む文字列リテラルをどのように解析するかを追跡し、有効なソースが未閉鎖の文字列リテラルとして報告される理由を特定します。再現コードがそのエラーなしでフォーマットされれば完了です。

Hello, I found this issue when updating the formatter version in googleapis/java-spanner

package com.example;

final class Test {
  // Error: unclosed string literal
  String breaks = "'\\d{2}):(\\d{2}):(\\d{2})(\\.\\d{1,9})?)([Zz]|([+-])(\\d{2}):(\\d{2})))|(READ_TIMESTAMP)[\\t";
  // Works
  String fix =    "'\\d{2}):(\\d{2}):(\\d{2})(\\.\\d{1,9})?)([Zz]|([+-])(\\d{2}):(\\d{2})))|(READ_TIMESTAMP)[\u005Ct";
}

Produces the following error:

hi on] diegomarquezp:java-spanner$ java -jar ~/.library_generation/google-java-format.jar --version 
google-java-format: Version 1.26.0
[hi on] diegomarquezp:java-spanner$ java -jar ~/.library_generation/google-java-format.jar test.java 
test.java:7:13: error: unclosed string literal
  String fix = "'((STRONG)|(MIN_READ_TIMESTAMP)[\\t ]+((\\d{4})-(\\d{2})-(\\d{2})([Tt](\\d{2}):(\\d{2}):(\\d{2})(\\.\\d{1,9})?)([Zz]|([+-])(\\d{2}):(\\d{2})))|(READ_TIMESTAMP)[\u005Ct ]+((\\d{4})-(\\d{2})-(\\d{2})([Tt](\\d{2}):(\\d{2}):(    \\d{2})(\\.\\d{1,9})?)([Zz]|([+-])(\\d{2}):(\\d{2})))|(MAX_STALENESS)[\u005Ct ]+((\\d{1,19})(s|ms|us|ns))|(EXACT_STALENESS)[\\t ]+((\\d{1,19})(s|ms|us|ns)))'";
            ^
[hi on] diegomarquezp:java-spanner$ 

Note that String fix doesn't have the error after replacing these two specific double backslashes \\ with the hexcode version \u0005C.

update: simplified reproducer code.