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3039 :: Error with generic typeclass

• jackpboy (orginal) [2017-07-11T15:17:31+02:00] view original

  This fails to compile:

  type
    Range[T] = object
      start, limit: T
  
  proc fromTo[T: SomeOrdinal](a, b: T;): Range[T] =
    result.start = a
    result.limit = b
  
  echo fromTo("a", "b")
  Run

  But this compiles:

  type
    Range[T: SomeOrdinal] = object
      start, limit: T
  
  proc fromTo[T](a, b: T;): Range[T] =
    result.start = a
    result.limit = b
  
  echo fromTo("a", "b")
  Run

  And this crashes the compiler:

  type
    Range[T: SomeOrdinal] = object
      start, limit: T
  
  proc fromTo[T: SomeOrdinal](a, b: T;): Range[T] =
    result.start = a
    result.limit = b
  
  echo fromTo("a", "b")
  Run

  I'm using Nim version 0.17.0 on Windows. To me, only the first one makes sense. Am I missing something?

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• mashingan (orginal) [2017-07-11T17:23:53+02:00] view original

  For example 1, string is not an Ordinal type.

  From doc,

  type
    SomeOrdinal = int | int8 | int16 | int32 | int64 | bool | enum | uint8 | uint16 | uint32
  Run

  For example 2, I'm not sure too but I never know that you can put type guard in type definition.

  For example 3, I got crash too, Windows too

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