Add prop variant using VTA

Author: amesgen

CHANGELOG.md

@@ -7,6 +7,7 @@ Notable changes to this project are documented in this file. The format is based
 Breaking changes:
 
 New features:
+- Added a variant of `prop` in `Data.Lens.Record.VTA` that supplies the `Symbol` via VTA (visible type application) instead of via `Proxy` (#145 by @amesgen)
 
 Bugfixes:
 

src/Data/Lens/Record/VTA.purs

@@ -0,0 +1,27 @@
+module Data.Lens.Record.VTA (prop) where
+
+import Data.Lens (Lens)
+import Data.Symbol (class IsSymbol)
+import Prim.Row as Row
+import Type.Proxy (Proxy(..))
+import Data.Lens.Record as Data.Lens.Record
+
+-- | Construct a (type-changing) lens for a record property, by providing a
+-- | `Symbol` via VTA (visible type application) which corresponds to the
+-- | property label.
+-- |
+-- | The lens is polymorphic in the rest of the row of property labels.
+-- |
+-- | For example:
+-- |
+-- | ```purescript
+-- | prop @"foo"
+-- |   :: forall a b r. Lens { foo :: a | r } { foo :: b | r } a b
+-- | ```
+prop
+  :: forall @l r1 r2 r a b
+   . IsSymbol l
+  => Row.Cons l a r r1
+  => Row.Cons l b r r2
+  => Lens (Record r1) (Record r2) a b
+prop = Data.Lens.Record.prop (Proxy @l)

test/Main.purs

@@ -12,6 +12,7 @@ import Data.Lens.Index (ix)
 import Data.Lens.Indexed (itraversed, reindexed)
 import Data.Lens.Lens (IndexedLens, cloneIndexedLens, ilens)
 import Data.Lens.Record (prop)
+import Data.Lens.Record.VTA as VTA
 import Data.Lens.Setter (iover)
 import Data.Lens.Traversal (cloneTraversal)
 import Data.Lens.Zoom (ATraversal', IndexedTraversal', Lens, Lens', Traversal, Traversal', zoom)
@@ -28,6 +29,12 @@ foo = prop (Proxy :: Proxy "foo")
 bar :: forall a b r. Lens { bar :: a | r } { bar :: b | r } a b
 bar = prop (Proxy :: Proxy "bar")
 
+foo' :: forall a b r. Lens { foo :: a | r } { foo :: b | r } a b
+foo' = VTA.prop @"foo"
+
+bar' :: forall a b r. Lens { bar :: a | r } { bar :: b | r } a b
+bar' = VTA.prop @"bar"
+
 barAndFoo :: forall a b r. Getter' { bar :: a, foo :: b | r } (Tuple a b)
 barAndFoo = takeBoth bar foo