| This error is triggered by calls to regex-accepting methods with invalid string |
| literals. These calls would cause a PatternSyntaxException at runtime. |
| |
| We deliberately do not check `java.util.regex.Pattern#compile` as many of its |
| users are deliberately testing the regex compiler or using a vacuously true |
| regex. |
| |
| `"."` is also discouraged, as it is a valid regex but is easy to mistake for |
| `"\\."`. Instead of e.g. `str.replaceAll(".", "x")`, prefer `Strings.repeat("x", |
| str.length())` or `CharMatcher.ANY.replaceFrom(str, "x")`. |
