checker/tests/nullness/CastsNullness.java

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

public class CastsNullness {

  void test(String nonNullParam) {
    Object lc1 = (Object) nonNullParam;
    lc1.toString();

    String nullable = null;
    Object lc2 = (Object) nullable;
    // :: error: (dereference.of.nullable)
    lc2.toString(); // error
  }

  void testBoxing() {
    Integer b = null;
    // :: error: (unboxing.of.nullable)
    int i = b;
    // no error, because there was already a nullpointer exception
    Object o = (int) b;
  }

  void testUnsafeCast(@Nullable Object x) {
    // :: warning: (cast.unsafe)
    @NonNull Object y = (@NonNull Object) x;
    y.toString();
  }

  void testUnsafeCastArray1(@Nullable Object[] x) {
    // Warning only with -AcheckCastElementType.
    // TODO:: warning: (cast.unsafe)
    @NonNull Object[] y = (@NonNull Object[]) x;
    y[0].toString();
  }

  void testUnsafeCastArray2(@NonNull Object x) {
    // We don't know about the component type of x -> warn
    // Warning only with -AcheckCastElementType.
    // TODO:: warning: (cast.unsafe)
    @NonNull Object[] y = (@NonNull Object[]) x;
    y[0].toString();
  }

  void testUnsafeCastList1(java.util.ArrayList<@Nullable Object> x) {
    // Warning only with -AcheckCastElementType.
    // TODO:: warning: (cast.unsafe)
    java.util.List<@NonNull Object> y = (java.util.List<@NonNull Object>) x;
    y.get(0).toString();
    // TODO:: warning: (cast.unsafe)
    java.util.List<@NonNull Object> y2 = (java.util.ArrayList<@NonNull Object>) x;
    java.util.List<@Nullable Object> y3 = (java.util.List<@Nullable Object>) x;
  }

  void testUnsafeCastList2(java.util.List<@Nullable Object> x) {
    java.util.List<@Nullable Object> y = (java.util.ArrayList<@Nullable Object>) x;
    // Warning only with -AcheckCastElementType.
    // TODO:: warning: (cast.unsafe)
    java.util.List<@NonNull Object> y2 = (java.util.ArrayList<@NonNull Object>) x;
  }

  void testUnsafeCastList3(@NonNull Object x) {
    // Warning only with -AcheckCastElementType.
    // TODO:: warning: (cast.unsafe)
    // :: warning: [unchecked] unchecked cast
    java.util.List<@Nullable Object> y = (java.util.List<@Nullable Object>) x;
    // TODO:: warning: (cast.unsafe)
    // :: warning: [unchecked] unchecked cast
    java.util.List<@NonNull Object> y2 = (java.util.ArrayList<@NonNull Object>) x;
  }

  void testSuppression(@Nullable Object x) {
    // :: error: (assignment)
    @NonNull String s1 = (String) x;
    @SuppressWarnings("nullness")
    @NonNull String s2 = (String) x;
  }

  class Generics<T extends Object> {
    T t;
    @Nullable T nt;

    Generics(T t) {
      this.t = t;
      this.nt = t;
    }

    void m() {
      // :: error: (assignment)
      t = (@Nullable T) null;
      nt = (@Nullable T) null;
      // :: warning: (cast.unsafe)
      t = (T) null;
      // :: warning: (cast.unsafe)
      nt = (T) null;
    }
  }

  void testSafeCasts() {
    // :: error: (nullness.on.primitive)
    Integer x = (@Nullable int) 1;
  }
}