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  1. JDK
  2. JDK-6640435

inference: propagate >> and == constraints to help uninferred type vars

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    • Enhancement
    • Resolution: Fixed
    • P4
    • 7
    • 7
    • specification
    • None
    • rc
    • generic
    • generic
    • Verified

    Description

      JLS 15.12.2.7 generates but does not use supertype constraints of the form S>>T. Such a constraint arises if a formal parameter uses '? super T'. If T is not inferred by 15.12.2.7, then 15.12.2.8 takes over and (in many cases) generates Object>>T. This is not wrong, but is imprecise. There is no reason why the JLS shouldn't propagate the >> constraints from 15.12.2.7 to 15.12.2.8. Also, as per 6650759, it is desirable to propagate == constraints. 15.12.2.8 could say:

      "Then, a set of initial constraints consisting of:
      - the constraint S >> R'...
      - additional constraints Bi[T1=B(T1)..Tn=B(Tn)] >> Ti, where ...
      ***- for any constraint of the form V >> Ti generated in 15.12.2.7: a constraint V[T1=B(T1)..Tn=B(Tn)] >> Ti***
      ***- for any constraint of the form Ti == V generated in 15.12.2.7: a constraint Ti == V[T1=B(T1)..Tn=B(Tn)]***"

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          relates to

          Bug - A problem which impairs or prevents the functions of the product. JDK-6638712 Inference with wildcard types causes selection of inapplicable method

          • P3 - Major loss of function.
          • Closed

          Bug - A problem which impairs or prevents the functions of the product. JDK-6707034 javac accepts method invocation with actuals that are not subtypes of the formal

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

          Bug - A problem which impairs or prevents the functions of the product. JDK-6476073 Capture using super wildcard of type variables doesn't work

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

          Enhancement - null JDK-6650759 Inference of formal type parameter (unused in formal parameters) is not performed

          • P3 - Major loss of function.
          • Closed

          Bug - A problem which impairs or prevents the functions of the product. JDK-6357966 parameters containing nested generic types avoid recursive calls

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

          Enhancement - null JDK-6811943 inference: javac 1.6 & Eclipse infer more types than JLS (umbrella CR)

          • P3 - Major loss of function.
          • Closed

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              abuckley Alex Buckley
              abuckley Alex Buckley
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