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  1. JDK
  2. JDK-5052943

4.10.4: Improve lub for lower-bounded wildcards and variables

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Details

    • Fix Understood
    • generic
    • generic

    Description

      In:

        static <T> T choose(boolean b, T trueValue, T falseValue) {
          return b ? trueValue : falseValue;
        }
        boolean b = false;
        List<? super Number> s = null;
        s = b ? s : s;
        s = choose(b, s, s);

      Inference can't handle lower/super bounded wildcards leading to errors like:

      Choose.java:10: incompatible types
      found : java.util.List<capture of ? extends java.lang.Object>
      required: java.util.List<? super java.lang.Number>
              s = b ? s : s;
                    ^
      Choose.java:11: incompatible types
      found : java.util.List<capture of ? extends java.lang.Object>
      required: java.util.List<? super java.lang.Number>
              s = choose(b, s, s);
                        ^

      See the attached file Choose.java

      ###@###.### 2004-05-25

      Attachments

        Issue Links

          duplicates

          Bug - A problem which impairs or prevents the functions of the product. JDK-6573446 javac infers a type bound where none should exist

          • P4 - Minor loss of function, or other problem where easy workaround is present.
          • Closed
          relates to

          Bug - A problem which impairs or prevents the functions of the product. JDK-8059898 4.10.4: lub incorrect for '? extends T', '? super T' combination

          • P4 - Minor loss of function, or other problem where easy workaround is present.
          • Closed

          Enhancement - null JDK-8068542 18.4: Improve resolution where lub is incompatible with an upper bound

          • P5 - Cosmetic problem like misspelt words or misaligned text.
          • Open

          Enhancement - null JDK-6480391 Unbounded wildcard '?' means '? extends Object'

          • P5 - Cosmetic problem like misspelt words or misaligned text.
          • Closed

          Bug - A problem which impairs or prevents the functions of the product. JDK-8073129 The result of lub(C<U>, C<? super V>) is incorrect

          • P4 - Minor loss of function, or other problem where easy workaround is present.
          • Open

          Enhancement - null JDK-8061427 Type variables should have lower/super bounds

          • P5 - Cosmetic problem like misspelt words or misaligned text.
          • Closed

          Activity

            People

              dlsmith Dan Smith
              ahe Peter Ahe
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                Updated:
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