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  1. JDK
  2. JDK-7035413

JDK6: generics statement fails to compile in one line, compiles in two lines

    Details

    • Type: Bug
    • Status: Closed
    • Priority: P4
    • Resolution: Duplicate
    • Affects Version/s: 6u24
    • Fix Version/s: None
    • Component/s: tools
    • Labels:
    • Subcomponent:
    • CPU:
      x86
    • OS:
      linux_ubuntu

      Description

      FULL PRODUCT VERSION :
      java version "1.6.0_24"
      Java(TM) SE Runtime Environment (build 1.6.0_24-b07)
      Java HotSpot(TM) 64-Bit Server VM (build 19.1-b02, mixed mode)

      ADDITIONAL OS VERSION INFORMATION :
      Linux work-laptop 2.6.35-27-generic #48-Ubuntu SMP Tue Feb 22 20:25:46 UTC 2011 x86_64 GNU/Linux

      A DESCRIPTION OF THE PROBLEM :
      This is my third try reporting this bug. Last time, it was marked as a duplicate of a bug that was a regression in JDK7, but this is a BUG in JDK6!!

      The provided source code won't compile as is, but by splitting one statement into two, it works fine. The compiler seems to infer the wrong type when the whole thing is in one statement.

      STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
      Compile the given source code.

      EXPECTED VERSUS ACTUAL BEHAVIOR :
      EXPECTED -
      Success
      ACTUAL -
      Failure--see error message

      ERROR MESSAGES/STACK TRACES THAT OCCUR :
      <T>contains(java.util.List<T>,T) in com.foo.Foo cannot be applied to (java.util.List<java.util.Comparator<? super java.lang.Object>>,com.foo.Foo.SomeComparator<java.lang.String>)

      REPRODUCIBILITY :
      This bug can be reproduced always.

      ---------- BEGIN SOURCE ----------
      import java.util.Arrays;
      import java.util.Comparator;
      import java.util.List;

      public class Foo {
          public static void main(String[] args) {
              boolean b = contains(
                      buildList(new SomeComparator<String>("bar")),
                      new SomeComparator<String>("x"));
              System.out.println(b);
          }

          public static <T> boolean contains(List<T> objects, T customer ) {
              return objects.contains( customer );
          }

          public static <T> List<Comparator<? super T>> buildList(Comparator<? super T>... comparator) {
              return Arrays.asList(comparator);
          }

          private static class SomeComparator<T> implements Comparator<T> {
              public SomeComparator(T arg) {}
              public int compare(T o1, T o2) { return 0; }
          }
      }
      ---------- END SOURCE ----------

      CUSTOMER SUBMITTED WORKAROUND :
      "Help" the compiler recognize the correct type by splitting the problem line (first line of the main method) into two lines, like so:
              List<Comparator<? super String>> list = buildList(new SomeComparator<String>("bar"));
              boolean b = contains(
                      list,
                      new SomeComparator<String>("x"));

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              • Assignee:
                Unassigned
                Reporter:
                webbuggrp Webbug Group
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                • Created:
                  Updated:
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