Method equal

common/src/main/java/com/google/auto/common/MoreTypes.java:321–346

(
      @Nullable TypeMirror a, @Nullable TypeMirror b, Set<ComparedElements> visiting)

  }

  @SuppressWarnings("TypeEquals")
  private static boolean equal(
      @Nullable TypeMirror a, @Nullable TypeMirror b, Set<ComparedElements> visiting) {
    if (a == b) {
      return true;
    }
    if (a == null || b == null) {
      return false;
    }
    // TypeMirror.equals is not guaranteed to return true for types that are equal, but we can
    // assume that if it does return true then the types are equal. This check also avoids getting
    // stuck in infinite recursion when Eclipse decrees that the upper bound of the second K in
    // <K extends Comparable<K>> is a distinct but equal K.
    // The javac implementation of ExecutableType, at least in some versions, does not take thrown
    // exceptions into account in its equals implementation, so avoid this optimization for
    // ExecutableType.
    @SuppressWarnings("TypesEquals")
    boolean equal = a.equals(b);
    if (equal && a.getKind() != TypeKind.EXECUTABLE) {
      return true;
    }
    EqualVisitorParam p = new EqualVisitorParam();
    p.type = b;
    p.visiting = visiting;
    return a.accept(EqualVisitor.INSTANCE, p);
  }

  /**
   * Returns the type of the innermost enclosing instance, or null if there is none. This is the