JDK-8167966 : MethodHandles.iteratedLoop fails with IAE in the case of correct arguments
  • Type: Bug
  • Component: core-libs
  • Sub-Component: java.lang.invoke
  • Affected Version: 9
  • Priority: P2
  • Status: Closed
  • Resolution: Fixed
  • Submitted: 2016-10-13
  • Updated: 2017-07-13
  • Resolved: 2016-11-02
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JDK 9
9 b143Fixed
Related Reports
Relates :  
JDK-8151179 - address issues raised by JCK team on JEP 274 API
Description
Please, observe MethodHandles.iteratedLoop(...) constraints for iterator, init and body.

According to these constraints, three MethodHandle with following signatures should be accepted in abovementioned method :
iterator=()Iterator
init=()I
body=(I,Object,I)I

Let's look on their types. First I is locals state, Object is T, and second I  is single loop argument. Init's parameter list should be effectively identical to loop parameter list (it is 'I'). The same requirements for iterator handle. However, following exception occurs:
>> Exception in thread "main" java.lang.IllegalArgumentException: inferred first loop argument must be an array or inherit from Iterable: int

Observing last constraint you can find  constraint (first argument must be Iterable or array) in the case iterator=null. Here iterator is not null, so it is inapplicable.
You can find complete code in Example0.java


Was found on jdk9b140
Comments
I think there is a bug in MethodHandles.iteratedLoopChecks: Class<?> iterableType = outerList.isEmpty() ? null : outerList.get(0); if (iterableType != null && !Iterable.class.isAssignableFrom(iterableType) && !iterableType.isArray()) { throw newIllegalArgumentException( "inferred first loop argument must be an array or inherit from Iterable: " + iterableType); } return iterableType; // help the caller a bit It probably requires: if (iterator == null && iterableType != null ... )
29-10-2016
Testsuite: JCK9/b47 OS: Solaris 12 x64 Tested JDK: JDK 9 140 RULE "api/java_lang/invoke/MethodHandles/index_IteratedLoopTests" Exception java.lang.ClassCastException: Cannot cast [Ljava.lang.String; to java.lang.Iterable RULE "api/java_lang/invoke/MethodHandles/index_IteratedLoopTests" Exception java.lang.IllegalArgumentException: inferred first loop argument must be an array or inherit from Iterable: class java.lang.Integer RULE "api/java_lang/invoke/MethodHandles/index_IteratedLoopTests" Exception java.lang.IllegalArgumentException: inferred first loop argument must be an array or inherit from Iterable: int RULE "api/java_lang/invoke/MethodHandles/index_IteratedLoopTests" TestCase [testIteratorDefinesExternalParameterList] test cases: 54; passed: 9; failed: 45 Matches: RULE "api/java_lang/invoke/MethodHandles/index_IteratedLoopTests" TestCase [testResultIsLastLocalState] test cases: 24; passed: 18; failed: 6
20-10-2016
Corresponding tests are excluded: api/java_lang/invoke/MethodHandles/index.html#IteratedLoopTests[testBodyDefinesExternalParameterList] api/java_lang/invoke/MethodHandles/index.html#IteratedLoopTests[testHandlesConformingEachOther] api/java_lang/invoke/MethodHandles/index.html#IteratedLoopTests[testHandlesReturnType] api/java_lang/invoke/MethodHandles/index.html#IteratedLoopTests[testIteratorDefinesExternalParameterList]
13-10-2016