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  1. Swift
  2. SR-2176

Add warning for ambiguous enum value assignment

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    Details

    • Type: Improvement
    • Status: Open
    • Priority: Medium
    • Resolution: Unresolved
    • Component/s: Compiler
    • Labels:
    • Environment:

      Description

      I've been caught off-guard by the value that's chosen by the compiler when inferring the type to assign to an enum value. This can be especially surprising because nil is shorthand for Optional.none.

      For example, if I have this enum:

      enum Coverage {
    case all      ///< everything is covered
    case partial  ///< only partially covered
    case none     ///< nothing is covered
}

let myCoverageA: Coverage? = .all
let myCoverageB: Coverage? = .none

      Because myCoverageA gets a value of .some(.all), you might expect the value of myCoverageB to be .some(.none), but in fact it is .none.

      I think this would also come up in a double-Optional. For example:

      let str: String?? = nil
// is it `.none` or `.some(.none)`?

      Expect

      I think it would be nice to have a compiler warning in ambiguous cases like this.

      Notes

      I wrote up a slightly more detailed example of this here: http://kelan.io/2016/type-inferior-ence/

        Attachments

          Issue Links

          is duplicated by

          Improvement - An improvement or enhancement to an existing feature or task. SR-6044 We need an ambiguity warning for assigning .none to an optional enum where .none is a valid case.

          • Medium - Has the potential to affect progress.
          • Resolved

          Bug - A problem which impairs or prevents the functions of the product. SR-8283 Enum cases named "none" can cause ambiguity with Optional's "none"

          • Medium - Has the potential to affect progress.
          • Resolved

          Bug - A problem which impairs or prevents the functions of the product. SR-8451 Swift's optional lifting/promotion is overzealous

          • Medium - Has the potential to affect progress.
          • Resolved

          Bug - A problem which impairs or prevents the functions of the product. SR-8515 Compiler should show error for ambiguous enum cases with implicit casting

          • Medium - Has the potential to affect progress.
          • Resolved

          Improvement - An improvement or enhancement to an existing feature or task. SR-3711 Make .member lookups in Optional<T> context ambiguous if member can be found in both Optional and T

          • Medium - Has the potential to affect progress.
          • Closed
          relates to

          Improvement - An improvement or enhancement to an existing feature or task. SR-3711 Make .member lookups in Optional<T> context ambiguous if member can be found in both Optional and T

          • Medium - Has the potential to affect progress.
          • Closed

            Activity

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              • Assignee:
                Unassigned
                Reporter:
                kelan Kelan Champagne
              • Votes:
                2 Vote for this issue
                Watchers:
                11 Start watching this issue

                Dates

                • Created:
                  Updated: