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  1. JDK
  2. JDK-8048326

18.2: Clarify that some constraints should never be encountered

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    Details

    • Type: Bug
    • Status: Closed
    • Priority: P5
    • Resolution: Fixed
    • Affects Version/s: 8
    • Fix Version/s: 8u40
    • Component/s: specification
    • Labels:

      Description

      For completeness, 18.2 prescribes a "false" result for the reduction of certain constraints that should never be encountered by a compiler. These all involve non-proper types appearing in certain parts of a lambda's or method ref's target type.

      In these cases, a clarifying comment would be useful.

      ---
      18.2.1

      If the lambda expression is implicitly typed and one or more of the function type's parameter types is not a proper type, the constraint reduces to false.

      ***This condition never arises in practice, due to the handling of implicitly-typed lambda expressions in 18.5.1 and the substitution applied to the target type in 18.5.2.***

      ...

      If one or more of the function type's parameter types is not a proper type, the constraint reduces to false.

      ***This condition never arises in practice, due to the handling of inexact method references in 18.5.1 and the substitution applied to the target type in 18.5.2.***

      ---
      18.2.5

      Otherwise, if the lambda expression is implicitly typed, and one or more of the function type's parameter types is not a proper type, the constraint reduces to false.

      Otherwise, if the function type's return type is neither void nor a proper type, the constraint reduces to false.

      ***The previous two conditions never arise in practice, due to the substitution applied to the target type in 18.5.2.***

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            Assignee:
            abuckley Alex Buckley
            Reporter:
            dlsmith Dan Smith
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