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results: document experimental error shortcut, and its gotchas (#168)

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Jacek Sieka 2023-01-20 15:32:34 +01:00 committed by GitHub
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@ -854,7 +854,18 @@ template valueOr*[T: not void, E](self: Result[T, E], def: untyped): T =
## v = Result[int, string].err("hello") ## v = Result[int, string].err("hello")
## x = v.valueOr: 42 # x == 42 now ## x = v.valueOr: 42 # x == 42 now
## y = v.valueOr: raise (ref ValueError)(msg: "v is an error, gasp!") ## y = v.valueOr: raise (ref ValueError)(msg: "v is an error, gasp!")
## # experimental: direct error access using an unqualified `error` symbol
## z = v.valueOr: raise (ref ValueError)(msg: error)
## ``` ## ```
##
## `error` access:
##
## TODO experimental, might change in the future
##
## The template contains a shortcut for accessing the error of the result,
## without specifying the error - it can only be used outside of generic code,
## see https://github.com/status-im/nim-stew/issues/161#issuecomment-1397121386
##
let s = (self) # TODO avoid copy let s = (self) # TODO avoid copy
if s.o: s.v if s.o: s.v
else: else: