From de21ef26861db458b0dfb0212cf501f9f8ed459b Mon Sep 17 00:00:00 2001 From: Joey Hess Date: Mon, 1 Jul 2019 18:27:48 -0400 Subject: 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 Property HasInfo + Debian + Buntish + ArchLinux + FreeBSD (Property 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]). --- propellor.cabal | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'propellor.cabal') diff --git a/propellor.cabal b/propellor.cabal index 300313c0..71d3c578 100644 --- a/propellor.cabal +++ b/propellor.cabal @@ -35,6 +35,9 @@ Description: . It is configured using haskell. +Flag WithTypeErrors + Description: Build with type-errors library for better error messages + Library Default-Language: Haskell98 GHC-Options: -Wall -fno-warn-tabs -O0 @@ -47,6 +50,9 @@ Library directory, filepath, IfElse, process, bytestring, hslogger, split, unix, unix-compat, ansi-terminal, containers (>= 0.5), network, async, time, mtl, transformers, exceptions (>= 0.6), stm, text, hashable + if flag(WithTypeErrors) + Build-Depends: type-errors + CPP-Options: -DWITH_TYPE_ERRORS Exposed-Modules: Propellor -- cgit v1.2.3