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  1. JDK
  2. JDK-8141613

Compiler fails to infer generic type

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    • Subcomponent:
    • Resolved In Build:
      b93
    • CPU:
      x86
    • OS:
      windows_8
    • Verification:
      Verified

      Description

      FULL PRODUCT VERSION :
      java version "1.9.0-ea"
      Java(TM) SE Runtime Environment (build 1.9.0-ea-b90)
      Java HotSpot(TM) Client VM (build 1.9.0-ea-b90, mixed mode)

      FULL OS VERSION :
      Windows 10, 64bit
      RHEL 7.1, 64bit

      A DESCRIPTION OF THE PROBLEM :
      Compiler fails to infer generic type when using combination of wildcard and inherited generic types.



      REGRESSION. Last worked in version 8u66

      STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
      Try to compile the attached sources and compile will fail.
      Or grab reproducer from https://github.com/ctomc/jdk9-compiler
      and run mvn clean install.
      it fails on jdk9u90
      but works just fine on jdk8

      EXPECTED VERSUS ACTUAL BEHAVIOR :
      Compile should work as it does on JDK8.
      But fails with:

      /C:/development/java/jdk9-compiler/src/main/java/InfinispanSessionManagerFactory.java:[27,44] incompatible types: cannot infer type arguments for InfinispanSessionFactory<>
          reason: inference variable V has incompatible equality constraints capture#1 of ?,capture#2 of ?
      REPRODUCIBILITY :
      This bug can be reproduced always.

      ---------- BEGIN SOURCE ----------

      public class InfinispanSessionFactory<V, L> implements SessionFactory<List<L>, V, L> {

          public InfinispanSessionFactory(SessionAttributesFactory<V> attributesFactory) {

          }
      }

      public interface SessionAttributesFactory<V> {

      }

      public interface SessionAttributesFactory<V> {

      }

      public interface SessionFactory<MV, AV, L> {

      }

      public class InfinispanSessionManagerFactory {

          private <L> SessionFactory<?, ?, L> createSessionFactory() {
              return new InfinispanSessionFactory<>(this.createSessionAttributesFactory());
          }

          private <L> SessionAttributesFactory<?> createSessionAttributesFactory() {
              return null;
          }
      }
      ---------- END SOURCE ----------

      CUSTOMER SUBMITTED WORKAROUND :
      Problem can be workaround by explicitly casting result of createSessionAttributesFactory()

      so that method call looks like:
      return new InfinispanSessionFactory<>((SessionAttributesFactory<Object>) this.createSessionAttributesFactory());


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              Assignee:
              mcimadamore Maurizio Cimadamore
              Reporter:
              webbuggrp Webbug Group
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                Created:
                Updated:
                Resolved: