Add failing TemplateHaskell test

test/Spec/TemplateHaskell.failing

@@ -0,0 +1,6 @@
+main: test/Spec/TemplateHaskell/TH.hs:22:1: threeQ
+main: test/Spec/TemplateHaskell/TH.hs:25:1: intQQ
+main: test/Spec/TemplateHaskell/TH.hs:33:1: zero1
+main: test/Spec/TemplateHaskell/TH.hs:36:1: zero2
+main: test/Spec/TemplateHaskell/TH.hs:39:1: zero3
+main: test/Spec/TemplateHaskell/TH.hs:42:1: zero4

test/Spec/TemplateHaskell.toml

@@ -0,0 +1,7 @@
+roots = [ "Spec.TemplateHaskell.User.root" ]
+
+type-class-roots = false
+
+unused-types = false
+
+root-instances = []

test/Spec/TemplateHaskell/TH.hs

@@ -0,0 +1,42 @@
+module Spec.TemplateHaskell.TH (intQQ, oneQ, twoQ, two, three, threeQ) where
+
+import Language.Haskell.TH
+import Language.Haskell.TH.Quote
+
+oneQ :: Q Exp
+oneQ = pure . LitE $ IntegerL one
+
+one :: Integer
+one = 1
+
+two :: Int
+two = 2
+
+twoQ :: Q Exp
+twoQ = pure . VarE $ mkName "two"
+
+three :: Int
+three = 3
+
+threeQ :: Q [Dec]
+threeQ = pure [ValD (VarP $ mkName "three'") (NormalB . VarE $ mkName "three") []]
+
+intQQ :: QuasiQuoter
+intQQ = QuasiQuoter 
+  { quoteExp = pure . LitE . IntegerL . (zero1 +) . read
+  , quotePat = pure . LitP . IntegerL . (zero2 +) . read
+  , quoteType = pure . LitT . NumTyLit . (zero3 +) . read
+  , quoteDec = pure . pure . (\i -> ValD (VarP $ mkName "quote") (NormalB $ LitE $ IntegerL i) []) . (zero4 +) . read
+  }
+
+zero1 :: Integer
+zero1 = 0
+
+zero2 :: Integer
+zero2 = 0
+
+zero3 :: Integer
+zero3 = 0
+
+zero4 :: Integer
+zero4 = 0

test/Spec/TemplateHaskell/User.hs

@@ -0,0 +1,22 @@
+{-# LANGUAGE TemplateHaskell #-}
+{-# LANGUAGE QuasiQuotes #-}
+{-# LANGUAGE DataKinds #-}
+{-# LANGUAGE KindSignatures #-}
+
+module Spec.TemplateHaskell.User where
+
+import Spec.TemplateHaskell.TH
+import GHC.TypeLits (Nat)
+
+$(threeQ)
+
+newtype T (a :: Nat) = T Int
+
+root :: T [intQQ|1|]
+root = T $ $(oneQ) + [intQQ|1|] + quote + f (1 :: Int) + $(twoQ) + three'
+  where
+    f [intQQ|1|] = 1
+    f _ = 1
+
+quote :: Int
+[intQQ|2|]

weeder.cabal

@@ -76,6 +76,7 @@ test-suite weeder-test
     , tasty
     , tasty-hunit-compat
     , tasty-golden
+    , template-haskell
     , text
     , toml-reader
     , weeder
@@ -107,6 +108,8 @@ test-suite weeder-test
     Spec.RangeEnum.RangeEnum
     Spec.RootClasses.RootClasses
     Spec.StandaloneDeriving.StandaloneDeriving
+    Spec.TemplateHaskell.TH
+    Spec.TemplateHaskell.User
     Spec.TypeAliasGADT.TypeAliasGADT
     Spec.TypeDataDecl.TypeDataDecl
     Spec.Types.Types