Consider the stage of typeable evidence when checking stage restriction

We were considering all Typeable evidence to be "BuiltinInstance"s which
meant the stage restriction was going unchecked. In-fact, typeable has
evidence and so we need to apply the stage restriction.

This is
complicated by the fact we don't generate typeable evidence and the
corresponding DFunIds until after typechecking is concluded so we
introcue a new `InstanceWhat` constructor, BuiltinTypeableInstance which
records whether the evidence is going to be local or not.

Fixes #21547

4 files changed, 30 insertions, 0 deletions

diff --git a/testsuite/tests/th/T21547.hs b/testsuite/tests/th/T21547.hs
new file mode 100644
index 0000000000..99b9992c59
--- /dev/null
+++ b/testsuite/tests/th/T21547.hs
@@ -0,0 +1,11 @@
+{-# LANGUAGE TemplateHaskell #-}
+module T21547 where
+import T21547A
+
+data T a = T a deriving (Show)
+
+main :: IO ()
+main = do
+  let x = $$(foo [|| T () ||])
+  let y = $$(foo [|| F () ||])
+  return ()
diff --git a/testsuite/tests/th/T21547.stderr b/testsuite/tests/th/T21547.stderr
new file mode 100644
index 0000000000..a37b98aa85
--- /dev/null
+++ b/testsuite/tests/th/T21547.stderr
@@ -0,0 +1,9 @@
+
+T21547.hs:9:14: error:
+    • GHC stage restriction:
+        instance for ‘base-4.16.0.0:Data.Typeable.Internal.Typeable
+                        T’ is used in a top-level splice, quasi-quote, or annotation,
+        and must be imported, not defined locally
+    • In the expression: foo [|| T () ||]
+      In the Template Haskell splice $$(foo [|| T () ||])
+      In the expression: $$(foo [|| T () ||])
diff --git a/testsuite/tests/th/T21547A.hs b/testsuite/tests/th/T21547A.hs
new file mode 100644
index 0000000000..19b47f8987
--- /dev/null
+++ b/testsuite/tests/th/T21547A.hs
@@ -0,0 +1,9 @@
+module T21547A where
+
+import Data.Typeable
+import Language.Haskell.TH
+
+foo :: Typeable a => Code Q a -> Code Q ()
+foo = undefined
+
+data F a = F a deriving (Show)
diff --git a/testsuite/tests/th/all.T b/testsuite/tests/th/all.T
index ec79e19249..7147fa4182 100644
--- a/testsuite/tests/th/all.T
+++ b/testsuite/tests/th/all.T
@@ -543,6 +543,7 @@ test('T17820c', normal, compile_fail, [''])
 test('T17820d', normal, compile_fail, [''])
 test('T17820e', normal, compile_fail, [''])
 test('T20454', normal, compile_and_run, [''])
+test('T21547', [extra_files(['T21547A.hs'])], multimod_compile_fail, ['T21547', '-v0'])
 test('T20590', normal, compile, ['-v0 -ddump-splices -dsuppress-uniques'])
 test('T20773', only_ways(['ghci']), ghci_script, ['T20773.script'])
 test('T20884', normal, compile_fail, [''])