test: reproducer for issue spotbugs#2558

spotbugs-tests/src/test/java/edu/umd/cs/findbugs/detect/Issue2558Test.java

@@ -0,0 +1,24 @@
+package edu.umd.cs.findbugs.detect;
+
+import static edu.umd.cs.findbugs.test.CountMatcher.containsExactly;
+import static org.hamcrest.MatcherAssert.assertThat;
+
+import org.junit.jupiter.api.Test;
+
+import edu.umd.cs.findbugs.AbstractIntegrationTest;
+import edu.umd.cs.findbugs.test.matcher.BugInstanceMatcher;
+import edu.umd.cs.findbugs.test.matcher.BugInstanceMatcherBuilder;
+
+
+public class Issue2558Test extends AbstractIntegrationTest {
+    @Test
+    public void test() {
+        performAnalysis("ghIssues/Issue2558.class");
+
+        BugInstanceMatcher bugTypeMatcher = new BugInstanceMatcherBuilder()
+                .bugType("NP_EQUALS_SHOULD_HANDLE_NULL_ARGUMENT")
+                .build();
+
+        assertThat(getBugCollection(), containsExactly(0, bugTypeMatcher));
+    }
+}

spotbugsTestCases/src/java/ghIssues/Issue2558.java

@@ -0,0 +1,11 @@
+package ghIssues;
+
+public class Issue2558 {
+
+    public boolean equals(@edu.umd.cs.findbugs.annotations.NonNull Object a) { //report a warning, but it is an FP
+        return a.hashCode() == this.hashCode();
+    }
+    public boolean something(Issue2558 a, Issue2558 b) {
+        return a.equals(b);
+    }
+}