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4.3.0: BitSet.clear() fails with flowexpr.parse.index.too.big — @SideEffectsOnly("#1") on a no-arg method

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Since Oct 7, 2026.

  • #8326 by @mernst — open

Assessment

Difficulty
2/5
Estimated time
1-3 hours
Newbie friendliness
82/100
Issue type
Bug
Clarity
Clearly specified
Activity status
Active
Tech stack
java
Domain
testing-qa

Research direction

The issue identifies the three clear overloads in annotated-jdk/src/java.base/share/classes/java/util/BitSet.java and provides a reproducer. Read the @SideEffectsOnly annotations and run the supplied Nullness Checker command with the 4.3.0 jars. Done when the no-arg reproducer no longer reports the parameter-index error and the other overloads' annotations reflect receiver mutation.

Written by the indexing model from the issue text.

Description

Problem

Since 4.3.0, any call to the no-arg BitSet.clear() fails the Nullness Checker:

Repro.java:5: error: [flowexpr.parse.index.too.big] the method has no parameter #1 (total 0 parameters)
        bits.clear();
                  ^

It worked on 4.2.2.

Reproduce
import java.util.BitSet;

class Repro {
    void reset(BitSet bits) {
        bits.clear();
    }
}

javac -proc:only \
  -cp checker-qual-4.3.0.jar \
  -processorpath checker-4.3.0.jar:checker-qual-4.3.0.jar \
  -processor org.checkerframework.checker.nullness.NullnessChecker \
  Repro.java

With 4.2.2 jars: no errors. With 4.3.0 jars: the error above.
JDK: 21.0.3.

Cause

4.3.0 added @SideEffectsOnly("#1") to all three clear overloads in annotated-jdk/src/java.base/share/classes/java/util/BitSet.java:

@SideEffectsOnly("#1")
public void clear(@GuardSatisfied BitSet this, @NonNegative int bitIndex);

@SideEffectsOnly("#1")
public void clear(@GuardSatisfied BitSet this, @NonNegative int fromIndex, @NonNegative int toIndex);

@SideEffectsOnly("#1")
public void clear(@GuardSatisfied BitSet this);

On clear(), #1 doesn't exist, which causes the error. On the other two overloads, #1 is an int index, but the method mutates the receiver. So "this" looks like the intended value for all three:

@SideEffectsOnly("this")
Dominant language
Java
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Merged PRs (30d)
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