use hierarchical namespace for all modules

src/Protolude/Error.hs

@@ -0,0 +1,45 @@
+{-# LANGUAGE CPP #-}
+{-# LANGUAGE MagicHash #-}
+{-# LANGUAGE PolyKinds #-}
+{-# LANGUAGE ImplicitParams #-}
+{-# LANGUAGE ExistentialQuantification #-}
+
+#if MIN_VERSION_base(4,9,0)
+{-# OPTIONS_GHC -fno-warn-redundant-constraints #-}
+#endif
+
+module Protolude.Error
+( error
+) where
+
+import GHC.Prim
+import Data.Text (Text, unpack)
+
+#if MIN_VERSION_base(4,9,0)
+-- Full stack trace.
+
+import GHC.Types (RuntimeRep)
+import Protolude.CallStack (HasCallStack)
+import GHC.Exception (errorCallWithCallStackException)
+
+error :: forall (r :: RuntimeRep) . forall (a :: TYPE r) . HasCallStack => Text -> a
+error s = raise# (errorCallWithCallStackException (unpack s) ?callstack)
+
+#elif MIN_VERSION_base(4,7,0)
+-- Basic Call Stack with callsite.
+
+import GHC.Exception (errorCallException)
+
+error :: Text -> a
+error s = raise# (errorCallException (unpack s))
+
+#else
+
+-- No exception tracing.
+import GHC.Types
+import GHC.Exception
+
+error :: Text -> a
+error s = throw (ErrorCall (unpack s))
+
+#endif