Detected at #14341.
Affects PR #14364

(Documentation)

Test.java

import java.util.ArrayList;
import java.util.List;

public class Test {
  List a = new ArrayList<> (); // violation expected
}

config.xml

<?xml version="1.0"?>
<!DOCTYPE module PUBLIC
        "-//Checkstyle//DTD Checkstyle Configuration 1.3//EN"
        "https://checkstyle.org/dtds/configuration_1_3.dtd">
<module name="Checker">
  <module name="TreeWalker">
    <module name="GenericWhitespace"/>
  </module>
</module>

Actual:

java -jar checkstyle-10.12.7-all.jar -c config.xml Test.java
Starting audit...
Audit done.

Expected: violation on line 5.
Test.java:5:26: '>' is followed by whitespace. [GenericWhitespace]

Explanation:

• As per the documentation, right angle bracket (>) should not be followed by whitespace for diamond operators and when preceding method name or constructor.
• In List a = new ArrayList<> (); the right angle bracket (>) precedes the constructor, and is also part of the diamond operator (<>), hence shouldn't be followed by the whitespace.
• The exact example is provided provided in the documentation, showcasing that it is incorrect style and should throw a violation, but this is ignored by the Check. (Also evident in the referenced PR)