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authorJoey Hess2019-07-01 18:27:48 -0400
committerJoey Hess2019-07-01 22:06:21 -0400
commitde21ef26861db458b0dfb0212cf501f9f8ed459b (patch)
tree474b1e9ae6874368d5489c0906ae05d28eb077e7 /src/Propellor/Types
parent14f6ae30809d8bbdb10b91cc59757e865a365df8 (diff)
optionally use type-errors to detect stuckness
Use the type-errors library to detect when the type checker gets stuck unable to reduce type-level operations on MetaTypes, and avoid displaying massive error messages in such a case. But, since type-errors is a new library not available in eg Debian yet, added a WithTypeErrors build flag. When the library is not available, cabal will automatically disable that build flag, and it will build without the type-errors library. This is most often used when combining properties of different types. If the MetaTypes don't have an OS in common, the error message used to be "Property " followed by pages of MetaTypes operations. Now it looks like this: • Cannot combine Properties: Property <unknown> Property HasInfo + Debian + Buntish + ArchLinux + FreeBSD (Property <unknown> is often due to a partially applied Property constructor, or due to passing the wrong type to a Property constructor.) Also it's used in ensureProperty to detect a case where the outer MetaTypes need to be inferred in order to check if the inner MetaTypes match, but the type checker is unable to infer it: • ensureProperty outer Property type is not able to be inferred here. Consider adding a type annotation. • When checking the inferred type writeConfig :: forall (outer :: [Propellor.Types.MetaTypes.MetaType]) t. And it's used in tightenTargets to detect when ghc is unable to infer the desired type of Property: • Unable to infer desired Property type in this use of tightenTargets. Consider adding a type annotation. • When checking the inferred type mk :: forall (tightened :: [Propellor.Types.MetaTypes.MetaType]).
Diffstat (limited to 'src/Propellor/Types')
-rw-r--r--src/Propellor/Types/MetaTypes.hs54
1 files changed, 40 insertions, 14 deletions
diff --git a/src/Propellor/Types/MetaTypes.hs b/src/Propellor/Types/MetaTypes.hs
index beb9ff61..567f533a 100644
--- a/src/Propellor/Types/MetaTypes.hs
+++ b/src/Propellor/Types/MetaTypes.hs
@@ -1,4 +1,5 @@
{-# LANGUAGE TypeOperators, PolyKinds, DataKinds, TypeFamilies, UndecidableInstances, FlexibleInstances, GADTs #-}
+{-# LANGUAGE CPP #-}
module Propellor.Types.MetaTypes (
MetaType(..),
@@ -28,6 +29,7 @@ module Propellor.Types.MetaTypes (
Union,
Intersect,
Difference,
+ IfStuck,
) where
import Propellor.Types.Singletons
@@ -36,6 +38,13 @@ import Propellor.Types.OS
import GHC.TypeLits hiding (type (+))
import Data.Type.Bool
+#ifdef WITH_TYPE_ERRORS
+import Type.Errors
+#else
+type family IfStuck (expr :: k) (b :: k1) (c :: k1) :: k1 where
+ IfStuck expr b c = c
+#endif
+
data MetaType
= Targeting TargetOS -- ^ A target OS of a Property
| WithInfo -- ^ Indicates that a Property has associated Info
@@ -141,28 +150,45 @@ type family CheckCombinable (list1 :: [a]) (list2 :: [a]) :: Bool where
CheckCombinable list1 list2 =
If (IsCombinable list1 list2)
'True
- ( TypeError (CannotCombine list1 list2)
- )
+ (CannotCombine list1 list2 'Nothing)
-- | Allows providing an additional note.
type family CheckCombinableNote (list1 :: [a]) (list2 :: [a]) (note :: ErrorMessage) :: Bool where
CheckCombinableNote list1 list2 note =
If (IsCombinable list1 list2)
'True
- ( TypeError
- ( CannotCombine list1 list2
- ':$$: 'Text "("
- ':<>: note
- ':<>: 'Text ")"
- )
+ (CannotCombine list1 list2
+ ('Just ('Text "(" ':<>: note ':<>: 'Text ")"))
+ )
+
+-- Checking IfStuck is to avoid massive and useless error message leaking
+-- type families from this module.
+type family CannotCombine (list1 :: [a]) (list2 :: [a]) (note :: Maybe ErrorMessage) :: Bool where
+ CannotCombine list1 list2 note =
+ IfStuck list1
+ (IfStuck list2
+ (TypeError (CannotCombineMessage UnknownType UnknownType UnknownTypeNote))
+ (TypeError (CannotCombineMessage UnknownType (PrettyPrintMetaTypes list2) UnknownTypeNote))
)
+ (IfStuck list2
+ (TypeError (CannotCombineMessage (PrettyPrintMetaTypes list1) UnknownType UnknownTypeNote))
+ (TypeError (CannotCombineMessage (PrettyPrintMetaTypes list1) (PrettyPrintMetaTypes list2) note))
+ )
+
+type family UnknownType :: ErrorMessage where
+ UnknownType = 'Text "<unknown>"
+
+type family UnknownTypeNote :: Maybe ErrorMessage where
+ UnknownTypeNote = 'Just ('Text "(Property <unknown> is often due to a partially applied Property constructor, or due to passing the wrong type to a Property constructor.)")
-type family CannotCombine (list1 :: [a]) (list2 :: [a]) :: ErrorMessage where
- CannotCombine list1 list2 =
- 'Text "Cannot combine properties with MetaTypes"
- ':$$: ('Text " " ':<>: PrettyPrintMetaTypes list1)
- ':$$: 'Text " vs"
- ':$$: ('Text " " ':<>: PrettyPrintMetaTypes list2)
+type family CannotCombineMessage (a :: ErrorMessage) (b :: ErrorMessage) (note :: Maybe ErrorMessage) :: ErrorMessage where
+ CannotCombineMessage a b ('Just note) =
+ CannotCombineMessage a b 'Nothing
+ ':$$: note
+ CannotCombineMessage a b 'Nothing =
+ 'Text "Cannot combine Properties:"
+ ':$$: ('Text " Property " ':<>: a)
+ ':$$: ('Text " Property " ':<>: b)
type family IsTarget (a :: t) :: Bool where
IsTarget ('Targeting a) = 'True