diff options
| -rw-r--r-- | changelog.md | 2 | ||||
| -rw-r--r-- | lib/pure/options.nim | 34 |
2 files changed, 17 insertions, 19 deletions
diff --git a/changelog.md b/changelog.md index 6dbfa1a2d..093ea7ae2 100644 --- a/changelog.md +++ b/changelog.md @@ -29,6 +29,8 @@ - `osproc.execProcess` now also takes a `workingDir` parameter. +- `options.UnpackError` is no longer a ref type and inherits from `System.Defect` instead of `System.ValueError`. + #### Breaking changes in the compiler - The compiler now implements the "generic symbol prepass" for `when` statements diff --git a/lib/pure/options.nim b/lib/pure/options.nim index 12e38d8b5..b827e1aa3 100644 --- a/lib/pure/options.nim +++ b/lib/pure/options.nim @@ -39,17 +39,18 @@ ## ## .. code-block:: nim ## -## try: -## assert("abc".find('c').get() == 2) # Immediately extract the value -## except UnpackError: # If there is no value -## assert false # This will not be reached, because the value is present -## +## let found = "abc".find('c') +## assert found.isSome and found.get() == 2 +## ## The ``get`` operation demonstrated above returns the underlying value, or -## raises ``UnpackError`` if there is no value. There is another option for -## obtaining the value: ``unsafeGet``, but you must only use it when you are -## absolutely sure the value is present (e.g. after checking ``isSome``). If -## you do not care about the tiny overhead that ``get`` causes, you should -## simply never use ``unsafeGet``. +## raises ``UnpackError`` if there is no value. Note that ``UnpackError`` inherits +## from ``system.Defect``, and should therefore never be catched. Instead, rely on +## checking if the option contains a value with ``isSome`` and ``isNone``. +## +## There is another option for obtaining the value: ``unsafeGet``, but you must +## only use it when you are absolutely sure the value is present (e.g. after +## checking ``isSome``). If you do not care about the tiny overhead that ``get`` +## causes, you should simply never use ``unsafeGet``. ## ## How to deal with an absence of a value: ## @@ -61,12 +62,7 @@ ## assert(result == none(int)) ## # It has no value: ## assert(result.isNone) -## -## try: -## echo result.get() -## assert(false) # This will not be reached -## except UnpackError: # Because an exception is raised -## discard + import typetraits type @@ -81,7 +77,7 @@ type val: T has: bool - UnpackError* = ref object of ValueError + UnpackError* = object of Defect proc some*[T](val: T): Option[T] = ## Returns a ``Option`` that has this value. @@ -129,7 +125,7 @@ proc get*[T](self: Option[T]): T = ## Returns contents of the Option. If it is none, then an exception is ## thrown. if self.isNone: - raise UnpackError(msg: "Can't obtain a value from a `none`") + raise newException(UnpackError, "Can't obtain a value from a `none`") self.val proc get*[T](self: Option[T], otherwise: T): T = @@ -143,7 +139,7 @@ proc get*[T](self: var Option[T]): var T = ## Returns contents of the Option. If it is none, then an exception is ## thrown. if self.isNone: - raise UnpackError(msg: "Can't obtain a value from a `none`") + raise newException(UnpackError, "Can't obtain a value from a `none`") return self.val proc map*[T](self: Option[T], callback: proc (input: T)) = |