UnnecessarilyFullyQualified still applies to package-info.java on Windows

[PhilippWendler]

Description of the problem:

The same bug as #1652 still occurs when compiling on Windows: Error Prone warns about unnecessary fully qualified imports in package-info.java and recommends imports instead.

Output:

[javac] C:\projects\java-common-lib\src\org\sosy_lab\common\annotations\package-info.java:10: warning: [UnnecessarilyFullyQualified] This fully qualified name is unambiguous to the compiler if imported.
[javac] @com.google.errorprone.annotations.CheckReturnValue
[javac]                                   ^
[javac]     (see https://errorprone.info/bugpattern/UnnecessarilyFullyQualified)
[javac]   Did you mean '@CheckReturnValue'?
[javac] C:\projects\java-common-lib\src\org\sosy_lab\common\annotations\package-info.java:11: warning: [UnnecessarilyFullyQualified] This fully qualified name is unambiguous to the compiler if imported.
[javac] @javax.annotation.ParametersAreNonnullByDefault
[javac]                  ^
[javac]     (see https://errorprone.info/bugpattern/UnnecessarilyFullyQualified)
[javac]   Did you mean '@ParametersAreNonnullByDefault'?

(full log)

When looking at ea312c9 (the fix for #1652) the problem seems clear: the code in UnnecessarilyFullyQualified.isPackageInfo() of this commit only works if / is used as file-name separator, but in my build \ is used as can be seen from the error message. The code should probably either use File.separatorChar, or allow both / and \, or even better use proper file-name handling methods. Something like name.endsWith("package-info.java") might also be good enough in practice.

Bugs: what's the simplest, easiest way to reproduce this bug? Please provide a minimal example if possible.

Should be possible to reproduce by just using Windows and the same reproducer as in #1652.

What version of Error Prone are you using?

2.5.1

[PhilippWendler]

Was fixed by #2404, thanks!