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authorProfpatsch <mail@profpatsch.de>2024-05-13T14·02+0200
committerclbot <clbot@tvl.fyi>2024-05-13T16·09+0000
commit5ea5dff59780c019d67f0863c6d856d42dbf31b0 (patch)
tree16518497094e630bbbe41323a3835064d46cc3b4 /users/Profpatsch/my-prelude/src/Arg.hs
parent53163de836deb795f725995a4e52b81739a1c5eb (diff)
feat(users/Profpatsch/MyPrelude): add Arg r/8137
Change-Id: I218562c924489ff9cba783dc88ecb8e777c8aac3
Reviewed-on: https://cl.tvl.fyi/c/depot/+/11656
Reviewed-by: Profpatsch <mail@profpatsch.de>
Autosubmit: Profpatsch <mail@profpatsch.de>
Tested-by: BuildkiteCI
Diffstat (limited to 'users/Profpatsch/my-prelude/src/Arg.hs')
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+module Arg where
+
+import Data.String (IsString)
+import GHC.Exts (IsList)
+import GHC.TypeLits (Symbol)
+
+-- | Wrap a function argument into this helper to give it a better description for the caller without disturbing the callsite too much.
+--
+-- This has instances for IsString and Num, meaning if the caller is usually a string or number literal, it should Just Work.
+--
+-- e.g.
+--
+-- @
+-- myFoo :: Arg "used as the name in error message" Text -> IO ()
+-- myFoo (Arg name) = …
+-- @
+--
+-- Will display the description in the inferred type of the callsite.
+--
+-- Due to IsString you can call @myFoo@ like
+--
+-- @myFoo "name in error"@
+--
+-- This is mostly intended for literals, if you want to wrap arbitrary data, use @Label@.
+newtype Arg (description :: Symbol) a = Arg {unArg :: a}
+  deriving newtype
+    ( Show,
+      Eq,
+      IsString,
+      IsList,
+      Num,
+      Monoid,
+      Semigroup
+    )