Matchers.anyOf: inference variable has incompatible bounds with Java >8

The following code sample works with OpenJDK 8 but does not compile with OpenJDK 11:

public class SimpleTest {
	@Test
	public void test() {
		List<String> list = new ArrayList<>();
		assertThat(list, anyOf(hasItem("a"), hasItem("b")));
	}
}

Compiling with Java 11 fails with

    [javac]     method Assert.<T#1>assertThat(String,T#1,Matcher<? super T#1>) is not applicable
    [javac]       (cannot infer type-variable(s) T#1
    [javac]         (actual and formal argument lists differ in length))
    [javac]     method Assert.<T#2>assertThat(T#2,Matcher<? super T#2>) is not applicable
    [javac]       (inference variable T#3 has incompatible bounds
    [javac]         lower bounds: String,Object
    [javac]         lower bounds: String,Object)
    [javac]   where T#1,T#2,T#3 are type-variables:
    [javac]     T#1 extends Object declared in method <T#1>assertThat(String,T#1,Matcher<? super T#1>)
    [javac]     T#2 extends Object declared in method <T#2>assertThat(T#2,Matcher<? super T#2>)
    [javac]     T#3 extends Object declared in method <T#3>hasItem(T#3)

If the first argument of the Matchers.anyOf methods would be changed from Matcher to Matcher<? super T> (like in Matchers.allOf), it would work.

Even after applying #257, building hamcrest with OpenJDK 12.0.1 fails with

./org/hamcrest/core/AnyOf.java:44: error: no suitable method found for anyOf(List<Matcher<? super T#1>>)
        return anyOf(Arrays.asList(matchers));
               ^
    method AnyOf.<T#2>anyOf(Iterable<Matcher<? super T#2>>) is not applicable
      (inference variable T#3 has incompatible bounds
        equality constraints: Matcher<? super CAP#1>
        lower bounds: Matcher<? super T#1>)
    method AnyOf.<T#1>anyOf(Matcher<? super T#1>...) is not applicable
      (cannot infer type-variable(s) T#1
        (varargs mismatch; no instance(s) of type variable(s) T#3 exist so that List<T#3> conforms to Matcher<? super T#1>))
  where T#1,T#2,T#3 are type-variables:
    T#1 extends Object declared in method <T#1>anyOf(Matcher<? super T#1>...)
    T#2 extends Object declared in method <T#2>anyOf(Iterable<Matcher<? super T#2>>)
    T#3 extends Object declared in method <T#3>asList(T#3...)
  where CAP#1 is a fresh type-variable:
    CAP#1 extends Object super: T#1 from capture of ? super T#1
./org/hamcrest/core/CombinableMatcher.java:60: error: incompatible types: Matcher<CAP#1> cannot be converted to Matcher<? super CAP#2>
      return new CombinableMatcher<>(first).and(other);
                                                ^
  where X is a type-variable:
    X extends Object declared in class CombinableBothMatcher
  where CAP#1,CAP#2 are fresh type-variables:
    CAP#1 extends Object super: X from capture of ? super X
    CAP#2 extends Object super: X from capture of ? super X
./org/hamcrest/core/CombinableMatcher.java:79: error: incompatible types: Matcher<CAP#1> cannot be converted to Matcher<? super CAP#2>
      return new CombinableMatcher<>(first).or(other);
                                               ^
  where X is a type-variable:
    X extends Object declared in class CombinableEitherMatcher
  where CAP#1,CAP#2 are fresh type-variables:
    CAP#1 extends Object super: X from capture of ? super X
    CAP#2 extends Object super: X from capture of ? super X
./org/hamcrest/text/IsEqualCompressingWhiteSpace.java:52: warning: [dep-ann] deprecated item is not annotated with @Deprecated
    public static Matcher<String> equalToIgnoringWhiteSpace(String expectedString) {
                                  ^
./org/hamcrest/core/AllOf.java:54: error: no suitable method found for allOf(List<Matcher<? super T#1>>)
        return allOf(Arrays.asList(matchers));
               ^
    method AllOf.<T#2>allOf(Iterable<Matcher<? super T#2>>) is not applicable
      (inference variable T#3 has incompatible bounds
        equality constraints: Matcher<? super CAP#1>
        lower bounds: Matcher<? super T#1>)
    method AllOf.<T#1>allOf(Matcher<? super T#1>...) is not applicable
      (cannot infer type-variable(s) T#1
        (varargs mismatch; no instance(s) of type variable(s) T#3 exist so that List<T#3> conforms to Matcher<? super T#1>))
  where T#1,T#2,T#3 are type-variables:
    T#1 extends Object declared in method <T#1>allOf(Matcher<? super T#1>...)
    T#2 extends Object declared in method <T#2>allOf(Iterable<Matcher<? super T#2>>)
    T#3 extends Object declared in method <T#3>asList(T#3...)
  where CAP#1 is a fresh type-variable:
    CAP#1 extends Object super: T#1 from capture of ? super T#1
./org/hamcrest/core/IsCollectionContaining.java:42: warning: [dep-ann] deprecated item is not annotated with @Deprecated
    public static <T> Matcher<Iterable<? super T>> hasItem(Matcher<? super T> itemMatcher) {
                                                   ^
./org/hamcrest/core/IsCollectionContaining.java:59: warning: [dep-ann] deprecated item is not annotated with @Deprecated
    public static <T> Matcher<Iterable<? super T>> hasItem(T item) {
                                                   ^
./org/hamcrest/core/IsCollectionContaining.java:78: warning: [dep-ann] deprecated item is not annotated with @Deprecated
    public static <T> Matcher<Iterable<T>> hasItems(Matcher<? super T>... itemMatchers) {
                                           ^
./org/hamcrest/core/IsCollectionContaining.java:96: warning: [dep-ann] deprecated item is not annotated with @Deprecated
    public static <T> Matcher<Iterable<T>> hasItems(T... items) {
                                           ^
./org/hamcrest/Matchers.java:1204: warning: [dep-ann] deprecated item is not annotated with @Deprecated
  public static <T> org.hamcrest.Matcher<T> isIn(java.util.Collection<T> collection) {
                                            ^
./org/hamcrest/Matchers.java:1219: warning: [dep-ann] deprecated item is not annotated with @Deprecated
  public static <T> org.hamcrest.Matcher<T> isIn(T[] elements) {
                                            ^
./org/hamcrest/Matchers.java:1235: warning: [dep-ann] deprecated item is not annotated with @Deprecated
  public static <T> org.hamcrest.Matcher<T> isOneOf(T... elements) {
                                            ^
./org/hamcrest/Matchers.java:1380: warning: [dep-ann] deprecated item is not annotated with @Deprecated
  public static Matcher<java.lang.String> equalToIgnoringWhiteSpace(java.lang.String expectedString) {
                                          ^
./org/hamcrest/Matchers.java:1430: warning: [dep-ann] deprecated item is not annotated with @Deprecated
  public static Matcher<java.lang.String> isEmptyOrNullString() {
                                          ^
./org/hamcrest/Matchers.java:1442: warning: [dep-ann] deprecated item is not annotated with @Deprecated
  public static Matcher<java.lang.String> isEmptyString() {
                                          ^
./org/hamcrest/collection/IsArrayContainingInOrder.java:54: warning: [dep-ann] deprecated item is not annotated with @Deprecated
    public static <E> Matcher<E[]> arrayContaining(E... items) {
                                   ^
./org/hamcrest/collection/IsArrayContainingInOrder.java:75: warning: [dep-ann] deprecated item is not annotated with @Deprecated
    public static <E> Matcher<E[]> arrayContaining(Matcher<? super E>... itemMatchers) {
                                   ^
./org/hamcrest/collection/IsArrayContainingInOrder.java:76: error: incompatible types: inference variable E#1 has incompatible bounds
        return arrayContaining(asList(itemMatchers));
                              ^
    equality constraints: E#2
    lower bounds: List<T>
  where E#1,E#2,T are type-variables:
    E#1 extends Object declared in method <E#1>arrayContaining(E#1...)
    E#2 extends Object declared in method <E#2>arrayContaining(Matcher<? super E#2>...)
    T extends Object declared in method <T>asList(T...)
./org/hamcrest/collection/IsArrayContainingInOrder.java:92: warning: [dep-ann] deprecated item is not annotated with @Deprecated
    public static <E> Matcher<E[]> arrayContaining(List<Matcher<? super E>> itemMatchers) {
                                   ^
./org/hamcrest/collection/IsArrayContainingInOrder.java:17: warning: [dep-ann] deprecated item is not annotated with @Deprecated
public class IsArrayContainingInOrder<E> extends TypeSafeMatcher<E[]> {
       ^
./org/hamcrest/collection/ArrayMatching.java:70: error: incompatible types: inference variable E#1 has incompatible bounds
      return arrayContainingInAnyOrder(asList(itemMatchers));
                                      ^
    equality constraints: E#2
    lower bounds: List<T>
  where E#1,E#2,T are type-variables:
    E#1 extends Object declared in method <E#1>arrayContainingInAnyOrder(E#1...)
    E#2 extends Object declared in method <E#2>arrayContainingInAnyOrder(Matcher<? super E#2>...)
    T extends Object declared in method <T>asList(T...)
./org/hamcrest/collection/IsArrayContainingInAnyOrder.java:61: warning: [dep-ann] deprecated item is not annotated with @Deprecated
    public static <E> Matcher<E[]> arrayContainingInAnyOrder(Matcher<? super E>... itemMatchers) {
                                   ^
./org/hamcrest/collection/IsArrayContainingInAnyOrder.java:62: error: incompatible types: inference variable E#1 has incompatible bounds
        return arrayContainingInAnyOrder(Arrays.asList(itemMatchers));
                                        ^
    equality constraints: E#2
    lower bounds: List<T>
  where E#1,E#2,T are type-variables:
    E#1 extends Object declared in method <E#1>arrayContainingInAnyOrder(E#1...)
    E#2 extends Object declared in method <E#2>arrayContainingInAnyOrder(Matcher<? super E#2>...)
    T extends Object declared in method <T>asList(T...)
./org/hamcrest/collection/IsArrayContainingInAnyOrder.java:83: warning: [dep-ann] deprecated item is not annotated with @Deprecated
    public static <E> Matcher<E[]> arrayContainingInAnyOrder(Collection<Matcher<? super E>> itemMatchers) {
                                   ^
./org/hamcrest/collection/IsArrayContainingInAnyOrder.java:105: warning: [dep-ann] deprecated item is not annotated with @Deprecated
    public static <E> Matcher<E[]> arrayContainingInAnyOrder(E... items) {
                                   ^
./org/hamcrest/collection/IsIterableContainingInAnyOrder.java:101: error: incompatible types: inference variable T#1 has incompatible bounds
        return containsInAnyOrder(Arrays.asList(itemMatchers));
                                 ^
    equality constraints: T#2
    lower bounds: List<T#3>
  where T#1,T#2,T#3 are type-variables:
    T#1 extends Object declared in method <T#1>containsInAnyOrder(T#1...)
    T#2 extends Object declared in method <T#2>containsInAnyOrder(Matcher<? super T#2>...)
    T#3 extends Object declared in method <T#3>asList(T#3...)
./org/hamcrest/collection/IsIterableContainingInRelativeOrder.java:102: error: incompatible types: inference variable E#1 has incompatible bounds
        return containsInRelativeOrder(asList(itemMatchers));
                                      ^
    equality constraints: E#2
    lower bounds: List<T>
  where E#1,E#2,T are type-variables:
    E#1 extends Object declared in method <E#1>containsInRelativeOrder(E#1...)
    E#2 extends Object declared in method <E#2>containsInRelativeOrder(Matcher<? super E#2>...)
    T extends Object declared in method <T>asList(T...)
Note: Some input files use unchecked or unsafe operations.
Note: Recompile with -Xlint:unchecked for details.
Note: Some messages have been simplified; recompile with -Xdiags:verbose to get full output
9 errors
18 warnings

Use "<? super T>" for all arguments of anyOf

The intention was to make it possible to use anyOf from Java 11 code and not to make Hamcrest compilable with Java 11.

Gentoo has a patch making it compile even with jdk 17.

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Matchers.anyOf: inference variable has incompatible bounds with Java >8 #256

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Matchers.anyOf: inference variable has incompatible bounds with Java >8 #256

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berolinux commented on May 5, 2019

vaukai commented on Jul 5, 2022

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