typetools / typetools/checker-framework

@RequiresNonNull seems to be forgotten depending on order of initialization

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Dataflow False Positive (false warning or imprecision)
Dominant language
Java
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Description

I would expect the following to check successfully:

MonotonicNonNullConstructorTest.java

import org.checkerframework.checker.nullness.qual.*;

public class MonotonicNonNullConstructorTest {
  static class Data {
    @MonotonicNonNull Object field;
  }

  Data data;
  Object object;

  @RequiresNonNull("#1.field")
  MonotonicNonNullConstructorTest(final Data data) {
    this.data = data;
    this.object = data.field;
  }
}

However I get the following error:

$ java -jar checker.jar -processor org.checkerframework.checker.nullness.NullnessChecker -version MonotonicNonNullConstructorTest.java 
javac 1.8.0-jsr308-1.9.10
MonotonicNonNullConstructorTest.java:14: error: [assignment.type.incompatible] incompatible types in assignment.
    this.object = data.field;
                      ^
  found   : @Initialized @MonotonicNonNull Object
  required: @Initialized @NonNull Object
1 error

However, if the order of the two lines in the constructor are reversed so that 'object' is initialized before 'data', the file checks successfully. Is it possible that the checker is confusing the instance field 'data' with the constructor parameter 'data'? I would expect that because the constructor parameter is final, it shouldn't matter where in the constructor its field is accessed; it must continue to be non-null because of the combination of @RequiresNonNull and @MonotonicNonNull.

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Research direction

Start by reproducing the report with the shown MonotonicNonNullConstructorTest.java and the NullnessChecker command. Trace handling of @RequiresNonNull and @MonotonicNonNull, then verify that both constructor statement orders check successfully without the reported assignment error.

Written by the indexing model from the issue text.

Assessment

Tech stack
java
Domain
devtools
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Clearly specified
Newbie friendliness
35/100

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