Implement record dot syntaxwip/joachim/bump-haddock

1 files changed, 26 insertions, 0 deletions

diff --git a/testsuite/tests/parser/should_fail/RecordDotSyntaxFail13.hs b/testsuite/tests/parser/should_fail/RecordDotSyntaxFail13.hs
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+++ b/testsuite/tests/parser/should_fail/RecordDotSyntaxFail13.hs
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+{-# LANGUAGE AllowAmbiguousTypes, FunctionalDependencies, ScopedTypeVariables, PolyKinds, TypeApplications, DataKinds #-}
+{-# LANGUAGE OverloadedRecordDot, OverloadedRecordUpdate #-}
+{-# LANGUAGE RecordWildCards, NamedFieldPuns #-}
+{-# LANGUAGE TypeFamilies #-}
+{-# LANGUAGE UndecidableInstances #-}
+{-# LANGUAGE FlexibleInstances #-}
+{-# LANGUAGE RebindableSyntax #-}
+import Prelude
+
+class HasField x r a | x r -> a where
+  hasField :: r -> (a -> r, a)
+
+getField :: forall x r a . HasField x r a => r -> a
+getField = snd . hasField @x -- Note: a.x = is getField @"x" a.
+
+setField :: forall x r a . HasField x r a => r -> a -> r
+setField = fst . hasField @x -- Note : a{x = b} is setField @"x" a b.
+
+-- 'Foo' has 'foo' field of type 'Int'
+data Foo = Foo { foo :: Int } deriving (Show, Eq)
+instance HasField "foo" Foo Int where
+    hasField r = (\x -> case r of Foo { .. } -> Foo { foo = x, .. }, foo r)
+main = do
+  let a = Foo {foo = 12};
+  -- let foo = 13;
+  print $ a {foo}