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import org.checkerframework.checker.nullness.qual.*;
public class Polymorphism {
// Test parameters
@PolyNull String identity(@PolyNull String s) {
return s;
}
void testParam() {
// Test without inference
String nullable = null;
@NonNull String nonNull = "m";
// :: error: (assignment.type.incompatible)
nonNull = identity(nullable); // invalid
nonNull = identity(nonNull);
// test flow
nullable = "m";
nonNull = identity(nullable); // valid
}
// Test within a method
@PolyNull String random(@PolyNull String m) {
if (m == "d") {
// :: error: (return.type.incompatible)
return null; // invalid
}
return "m"; // valid
}
public static @PolyNull Object staticIdentity(@PolyNull Object a) {
return a;
}
void testStatic(@Nullable Object nullable, @NonNull Object nonnull) {
@Nullable Object nullable2 = staticIdentity(nullable);
@NonNull Object nonnull2 = staticIdentity(nonnull);
}
}
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