Direct Known Subclasses:
TIsU, TSubU, TSuperU

public abstract class TUConstraint extends Object
Subclasses of TUConstraint represent constraints between a type parameter, whose type arguments are being inferred, and the types used to do that inference. These constraints are used by the TASolver to infer arguments.

TU constraints come in the classic form of subtype, supertype, and equality constraints.

  • T <: U -- implies T is a subtype of U, it is represented by TSubU
  • T >: U -- implies T is a supertype of U, it is represented by TSuperU
  • T = U -- implies T is equal to U, it is represented by TIsU

Note, it is important that the type parameter is represented by an AnnotatedTypeVariable because if a use of the type parameter has a primary annotation, then the two types represented in by a TUConstraint are NOT constrained in the hierarchy of that annotation. e.g.

 <T> void method(List<@NonNull T> t1, T t2)
 method(new ArrayList<@NonNull String>(), null);
The above method call would eventually be reduced to constraints: [@NonNull String == @NonNull T, @Nullable null <: T]

In this example, if we did not ignore the first constraint then the type argument would be exactly @NonNull String and the second argument would be invalid. However, the correct inference would be @Nullable String and both arguments would be valid.

  • Field Details

    • typeVariable

      public final AnnotatedTypeMirror.AnnotatedTypeVariable typeVariable
      An AnnotatedTypeVariable representing a target type parameter for which we are inferring a type argument. This is the T in the TUConstraints.
    • relatedType

      public final AnnotatedTypeMirror relatedType
      A type used to infer an argument for the typeVariable T. This would be the U in the TUConstraints.
    • uIsArg

      public final boolean uIsArg
      Whether or not U is a type from an argument to the method.
  • Constructor Details

  • Method Details