typetools / typetools/checker-framework

false negative when using ternary operator

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#6,849 0 comments 0 reactions 1 assignee View on GitHub

@smillst is already working on this.

Since Oct 8, 2024.

False Negative (missing warning or unsoundness)
Dominant language
Java
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Description

Command
javac -J--add-exports=jdk.compiler/com.sun.tools.javac.api=ALL-UNNAMED \
  -J--add-exports=jdk.compiler/com.sun.tools.javac.code=ALL-UNNAMED \
  -J--add-exports=jdk.compiler/com.sun.tools.javac.file=ALL-UNNAMED \
  -J--add-exports=jdk.compiler/com.sun.tools.javac.main=ALL-UNNAMED \
  -J--add-exports=jdk.compiler/com.sun.tools.javac.model=ALL-UNNAMED \
  -J--add-exports=jdk.compiler/com.sun.tools.javac.processing=ALL-UNNAMED \
  -J--add-exports=jdk.compiler/com.sun.tools.javac.tree=ALL-UNNAMED \
  -J--add-exports=jdk.compiler/com.sun.tools.javac.util=ALL-UNNAMED \
  -J--add-opens=jdk.compiler/com.sun.tools.javac.comp=ALL-UNNAMED \
-processor org.checkerframework.checker.nullness.NullnessChecker \
-cp checker-framework/checker/dist/checker.jar Test.java
File
import org.checkerframework.checker.nullness.qual.*;
import java.util.*;

public class Test {

  public static <T> T m(List<T> lst) { return lst.get(0); }

  public static void main(String[] args) {
      List<@Nullable Integer> lst = new LinkedList<>();
      lst.add(null);
      int y = ((true) ? Test.<@Nullable Integer>m(lst) : 10);
  }
}
Actual behavior

The code passes the checks, but there's NPE

Exception in thread "main" java.lang.NullPointerException: Cannot invoke "java.lang.Integer.intValue()" because the return value of "Test.m(java.util.List)" is null
        at Test.main(Test.java:12)

Expected behavior

The code should have been rejected with

Test.java:12: error: [unboxing.of.nullable] unboxing a possibly-null reference Test.<@Nullable Integer>m(lst)
      int y = ((true) ? Test.<@Nullable Integer>m(lst) : 10);
                                                 ^
1 error

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