RFR: 8255449: Improve the exception message of MethodHandles::permuteArguments [v2]

[Chris Hegarty]

On Wed, 28 Oct 2020 13:32:19 GMT, Jorn Vernee <jvernee at openjdk.org> wrote:

>>> 
>>> 
>>> Seems like a reasonable change. Is there an already existing test for "bad" permute args that could be expanded to discern the new exception message?
>> 
>> There are several tests for permuteArguments, but none that explicitly test this failure. I'll add some (good idea).
>
> I've added some negative tests that test for the different failure conditions.

Thanks for adding additional test coverage @JornVernee.

Writing a tight implementation of assertThrows is non-trivial - I'm not sure that the version you have will fail if the exception is not thrown?  Either way maybe we can reuse some of the junit machinery for this purpose, e.g.:

static final Class<IllegalArgumentException> IAE = IllegalArgumentException.class;

public void testReorderTypeMismatch() throws Throwable {
    MethodHandle mh = MethodHandles.empty(MethodType.methodType(void.class, int.class, int.class, String.class));
    MethodType newType = MethodType.methodType(void.class, double.class, String.class);
    var exception = expectThrows(IAE, () -> MethodHandles.permuteArguments(mh, newType, 0, 0, 1));
    assertMatches(exception.getMessage(), ".*parameter types do not match after reorder.*");
}

private static void assertMatches(String str, String pattern) {
    if (!str.matches(pattern)) {
        throw new AssertionError("'" + str + "' did not match the pattern '" + pattern + "'.");
    }
}

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PR: https://git.openjdk.java.net/jdk/pull/878