Compilation failure on JDK 8 involving inferred generic type

[Gunnar Morling]

Hi,

I'm investigating a compilation error which I'm seeing when compiling the
Bean Validation TCK using JDK 8 (build 121). The following example shows
the issue:

    public class GenericsTest {

        public class Input<O extends Output<O>> {}

        public class Output<O extends Output<O>> {}

        public class OutputContainer<O extends Output<O>> {}

        public <O extends Output<O>, I extends Input<O>> OutputContainer<O>
process(
                Class<I> inputType) {
            return null;
        }

        public void testProcess() {
            Class<? extends Input> inputType = null;

            //next line compiles with source level 1.7 but fails with
source level 1.8
            OutputContainer<?> outputContainer = process( inputType );
        }
    }

This code used to compile with JDK 7 and it also does with JDK 8, when
using 1.7 as source level. But it fails with source level 1.8, saying:

    "incompatible types: inferred type does not conform to upper bound(s)"

I can make the code compile when declaring the outputContainer variable of
the raw type OutputContainer instead of declaring it with the wildcard
parameter.

Is this an intentional change in JDK 8 or is it some kind of regression? If
it is intentional, maybe the error message should be a bit more
descriptive, mentioning the concerned inferred type and the bounds?

Many thanks,

--Gunnar
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