False positive: parameter must be non-null in inner class constructor

[ahubold]

Spotbugs 3.1.6 shows an issue for rule findbugs:NP_PARAMETER_MUST_BE_NONNULL_BUT_MARKED_AS_NULLABLE that an inner class constructor parameter must be non-null, even if the parameter is already annotated as NonNull. Code example:

package com.example;

import edu.umd.cs.findbugs.annotations.NonNull;
import edu.umd.cs.findbugs.annotations.Nullable;

public class NonNullParameterOfInnerClassConstructor {

  private class Inner {
    private final String a;
    private final Object b;

    Inner(@NonNull String a, @Nullable Object b) {
      this.a = a.toLowerCase(); // <--- false positive: a must be non-null but is marked as nullable
      this.b = b;
    }
  }
}

[ahubold]

Pull request with reproducer for this issue: #773

(Not sure if this is the correct way to write test cases for issues, so please have a look)

I detected this bug by using sonar-findbugs and opened an issue there that is caused by this one: spotbugs/sonar-findbugs#213

[KengoTODA]

@ahubold Thanks for your nice report and reproduction! I've fixed it, we'll release patched version in the next January.