add injTagged

src/Data/Functor/Variant.purs

@@ -1,6 +1,7 @@
 module Data.Functor.Variant
   ( VariantF
   , inj
+  , class VariantInjTagged, injTagged
   , prj
   , on
   , onMatch
@@ -35,6 +36,7 @@ import Data.Variant.Internal (class Contractable, class VariantFMatchCases, clas
 import Partial.Unsafe (unsafeCrashWith)
 import Prim.Row as R
 import Prim.RowList as RL
+import Record (get)
 import Type.Equality (class TypeEquals)
 import Type.Proxy (Proxy(..))
 import Unsafe.Coerce (unsafeCoerce)
@@ -135,6 +137,24 @@ inj p value = coerceV $ VariantFRep { type: reflectSymbol p, value, map }
   coerceV ∷ VariantFRep f a → VariantF r2 a
   coerceV = unsafeCoerce
 
+class VariantInjTagged a f b | a → f, a → b where
+  -- | Injects value from a single field of record into variant
+  -- |
+  -- | ```purescript
+  -- | maybeAtFoo :: forall r. Variant (foo :: FProxy Maybe | r) Int
+  -- | maybeAtFoo = injTagged { foo: Just 42 }
+  -- | ```
+  injTagged ∷ Record a → VariantF f b
+
+instance variantInjTagged ∷
+  ( RL.RowToList r1 (RL.Cons sym (f a) RL.Nil)
+  , R.Cons sym (f a) () r1
+  , R.Cons sym (FProxy f) rx r2
+  , Functor f
+  , IsSymbol sym
+  ) ⇒ VariantInjTagged r1 r2 a where
+  injTagged = inj (SProxy ∷ SProxy sym) <<< get (SProxy ∷ SProxy sym)
+
 -- | Attempt to read a variant at a given label.
 -- | ```purescript
 -- | case prj (SProxy :: SProxy "foo") maybeAtFoo of

src/Data/Variant.purs

@@ -1,6 +1,7 @@
 module Data.Variant
   ( Variant
   , inj
+  , class VariantInjTagged, injTagged
   , prj
   , on
   , onMatch
@@ -34,6 +35,7 @@ import Data.Variant.Internal (class Contractable, class VariantMatchCases, class
 import Partial.Unsafe (unsafeCrashWith)
 import Prim.Row as R
 import Prim.RowList as RL
+import Record (get)
 import Unsafe.Coerce (unsafeCoerce)
 
 foreign import data Variant ∷ # Type → Type
@@ -55,6 +57,23 @@ inj p value = coerceV $ VariantRep { type: reflectSymbol p, value }
   coerceV ∷ VariantRep a → Variant r2
   coerceV = unsafeCoerce
 
+class VariantInjTagged a b | a → b where
+  -- | Injects value from a single field of record into variant
+  -- |
+  -- | ```purescript
+  -- | intAtFoo :: forall r. Variant (foo :: Int | r)
+  -- | intAtFoo = injTagged { foo: 42 }
+  -- | ```
+  injTagged ∷ Record a → Variant b
+
+instance variantInjTagged ∷
+  ( RL.RowToList r1 (RL.Cons sym a RL.Nil)
+  , R.Cons sym a () r1
+  , R.Cons sym a rx r2
+  , IsSymbol sym
+  ) ⇒ VariantInjTagged r1 r2 where
+  injTagged = inj (SProxy ∷ SProxy sym) <<< get (SProxy ∷ SProxy sym)
+
 -- | Attempt to read a variant at a given label.
 -- | ```purescript
 -- | case prj (SProxy :: SProxy "foo") intAtFoo of

test/Variant.purs

@@ -5,7 +5,7 @@ import Prelude
 import Data.List as L
 import Data.Maybe (Maybe(..), isJust)
 import Data.Symbol (reflectSymbol)
-import Data.Variant (Variant, on, onMatch, case_, default, inj, prj, SProxy(..), match, contract, Unvariant(..), unvariant, revariant)
+import Data.Variant (Variant, on, onMatch, case_, default, inj, prj, SProxy(..), match, contract, Unvariant(..), unvariant, revariant, injTagged)
 import Record.Builder (build, modify, Builder())
 import Test.Assert (assert')
 import Effect (Effect)
@@ -26,7 +26,7 @@ _baz ∷ SProxy "baz"
 _baz = SProxy
 
 foo ∷ ∀ r. Variant (foo ∷ Int | r)
-foo = inj _foo 42
+foo = injTagged { foo: 42 }
 
 bar ∷ ∀ r. Variant (bar ∷ String | r)
 bar = inj _bar "bar"

test/VariantF.purs

@@ -3,7 +3,7 @@ module Test.VariantF where
 import Prelude
 
 import Data.Either (Either(..))
-import Data.Functor.Variant (FProxy, SProxy(..), VariantF, case_, contract, default, inj, match, on, onMatch, prj, revariantF, unvariantF)
+import Data.Functor.Variant (FProxy, SProxy(..), VariantF, case_, contract, default, inj, match, on, onMatch, prj, revariantF, unvariantF, injTagged)
 import Data.List as L
 import Data.Maybe (Maybe(..), isJust)
 import Data.Tuple (Tuple(..))
@@ -26,7 +26,7 @@ _baz ∷ SProxy "baz"
 _baz = SProxy
 
 foo ∷ ∀ r. VariantF (foo ∷ FProxy Maybe | r) Int
-foo = inj _foo (Just 42)
+foo = injTagged { foo: Just 42 }
 
 bar ∷ ∀ r. VariantF (bar ∷ FProxy (Tuple String) | r) Int
 bar = inj _bar (Tuple "bar" 42)