Converts diagnostics for two errors in Ghc.Tc.Module (#19926)

This adds constructors to TcRnMessage to replace use of
TcRnUnknownMessage in Ghc.Tc.Module.
Adds a test case for the UnsafeDueToPlugin warning.

Closes #19926

9 files changed, 52 insertions, 7 deletions

diff --git a/compiler/GHC/Tc/Errors/Ppr.hs b/compiler/GHC/Tc/Errors/Ppr.hs
index d538862e50..578c182a7d 100644
--- a/compiler/GHC/Tc/Errors/Ppr.hs
+++ b/compiler/GHC/Tc/Errors/Ppr.hs
@@ -38,6 +38,10 @@ instance Diagnostic TcRnMessage where
       -> mkDecorated [ text "The import item" <+> quotes (ppr ie) <+>
                        text "does not have an explicit import list"
                      ]
+    TcRnUnsafeDueToPlugin
+      -> mkDecorated [text "Use of plugins makes the module unsafe"]
+    TcRnModMissingRealSrcSpan mod
+      -> mkDecorated [text "Module does not have a RealSrcSpan:" <+> ppr mod]
 
   diagnosticReason = \case
     TcRnUnknownMessage m
@@ -54,6 +58,10 @@ instance Diagnostic TcRnMessage where
       -> WarningWithFlag Opt_WarnDodgyExports
     TcRnMissingImportList{}
       -> WarningWithFlag Opt_WarnMissingImportList
+    TcRnUnsafeDueToPlugin{}
+      -> WarningWithoutFlag
+    TcRnModMissingRealSrcSpan{}
+      -> ErrorWithoutFlag
 
   diagnosticHints = \case
     TcRnUnknownMessage m
@@ -70,6 +78,10 @@ instance Diagnostic TcRnMessage where
       -> noHints
     TcRnMissingImportList{}
       -> noHints
+    TcRnUnsafeDueToPlugin{}
+      -> noHints
+    TcRnModMissingRealSrcSpan{}
+      -> noHints
 
 dodgy_msg :: (Outputable a, Outputable b) => SDoc -> a -> b -> SDoc
 dodgy_msg kind tc ie
diff --git a/compiler/GHC/Tc/Errors/Types.hs b/compiler/GHC/Tc/Errors/Types.hs
index b0deeaaf2c..4e9d233a67 100644
--- a/compiler/GHC/Tc/Errors/Types.hs
+++ b/compiler/GHC/Tc/Errors/Types.hs
@@ -11,6 +11,7 @@ import GHC.Hs
 import GHC.Types.Error
 import GHC.Types.Name (Name)
 import GHC.Types.Name.Reader
+import GHC.Unit.Types (Module)
 import GHC.Utils.Outputable
 import Data.Typeable
 import GHC.Core.Type (Type, Var)
@@ -88,6 +89,16 @@ data TcRnMessage where
      Test cases: rename/should_compile/T4489
   -}
   TcRnMissingImportList :: IE GhcPs -> TcRnMessage
+  {-| When a module marked trustworthy or unsafe (using -XTrustworthy or -XUnsafe) is compiled
+      with a plugin, the TcRnUnsafeDueToPlugin warning (controlled by -Wunsafe) is used as the
+      reason the module was inferred to be unsafe. This warning is not raised if the
+      -fplugin-trustworthy flag is passed.
+  -}
+  TcRnUnsafeDueToPlugin :: TcRnMessage
+  {-| TcRnModMissingRealSrcSpan is an error that occurrs when compiling a module that lacks
+      an associated 'RealSrcSpan'.
+  -}
+  TcRnModMissingRealSrcSpan :: Module -> TcRnMessage
 
 
 -- | Where the levity checking for the input type originated
diff --git a/compiler/GHC/Tc/Module.hs b/compiler/GHC/Tc/Module.hs
index 56c3071ea5..08d082ba32 100644
--- a/compiler/GHC/Tc/Module.hs
+++ b/compiler/GHC/Tc/Module.hs
@@ -214,8 +214,7 @@ tcRnModule hsc_env mod_sum save_rn_syntax
     logger  = hsc_logger hsc_env
     home_unit = hsc_home_unit hsc_env
     err_msg = mkPlainErrorMsgEnvelope loc $
-              TcRnUnknownMessage $ mkPlainError noHints $
-                text "Module does not have a RealSrcSpan:" <+> ppr this_mod
+              TcRnModMissingRealSrcSpan this_mod
 
     pair :: (Module, SrcSpan)
     pair@(this_mod,_)
@@ -3151,10 +3150,6 @@ mark_plugin_unsafe :: DynFlags -> TcM ()
 mark_plugin_unsafe dflags = unless (gopt Opt_PluginTrustworthy dflags) $
   recordUnsafeInfer pluginUnsafe
   where
-    unsafeText = "Use of plugins makes the module unsafe"
     pluginUnsafe =
       singleMessage $
-      mkPlainMsgEnvelope dflags noSrcSpan $
-      TcRnUnknownMessage $
-      mkPlainDiagnostic WarningWithoutFlag noHints $
-      Outputable.text unsafeText
+      mkPlainMsgEnvelope dflags noSrcSpan TcRnUnsafeDueToPlugin
diff --git a/testsuite/tests/plugins/Makefile b/testsuite/tests/plugins/Makefile
index 46ef8cb3eb..2ae8aadae2 100644
--- a/testsuite/tests/plugins/Makefile
+++ b/testsuite/tests/plugins/Makefile
@@ -131,6 +131,11 @@ T16260:
 	"$(TEST_HC)" $(TEST_HC_OPTS) $(ghcPluginWayFlags) -v0 T16260.hs -package-db simple-plugin/pkg.T16260/local.package.conf -fplugin Simple.TrustworthyPlugin
 	"$(TEST_HC)" $(TEST_HC_OPTS) $(ghcPluginWayFlags) -v0 T16260.hs -package-db simple-plugin/pkg.T16260/local.package.conf -fplugin Simple.TrustworthyPlugin -fplugin-trustworthy
 
+.PHONY: T19926
+T19926:
+	"$(TEST_HC)" $(TEST_HC_OPTS) $(ghcPluginWayFlags) -v0 T19926.hs -package-db simple-plugin/pkg.T19926/local.package.conf -fplugin Simple.DefaultPlugin
+	"$(TEST_HC)" $(TEST_HC_OPTS) $(ghcPluginWayFlags) -v0 T19926.hs -package-db simple-plugin/pkg.T19926/local.package.conf -fplugin Simple.DefaultPlugin -fplugin-trustworthy
+
 .PHONY: HoleFitPlugin
 HoleFitPlugin:
 	"$(TEST_HC)" $(TEST_HC_OPTS) $(ghcPluginWayFlags) -v0 HoleFitPlugin.hs -package-db hole-fit-plugin/pkg.hole-fit-plugin/local.package.conf
diff --git a/testsuite/tests/plugins/T19926.hs b/testsuite/tests/plugins/T19926.hs
new file mode 100644
index 0000000000..059611be05
--- /dev/null
+++ b/testsuite/tests/plugins/T19926.hs
@@ -0,0 +1,5 @@
+{-# LANGUAGE Haskell2010 #-}
+{-# LANGUAGE Trustworthy #-}
+{-# OPTIONS_GHC -Wunsafe #-}
+module T19926 where
+-- Trustworthy module compiled with plugin should warn if -fplugin-trustworthy is not set
diff --git a/testsuite/tests/plugins/T19926.stderr b/testsuite/tests/plugins/T19926.stderr
new file mode 100644
index 0000000000..e943a7ffba
--- /dev/null
+++ b/testsuite/tests/plugins/T19926.stderr
@@ -0,0 +1,5 @@
+
+T19926.hs:3:17: warning: [-Wunsafe]
+    ‘T19926’ has been inferred as unsafe!
+    Reason:
+        <no location info>: warning: Use of plugins makes the module unsafe
diff --git a/testsuite/tests/plugins/all.T b/testsuite/tests/plugins/all.T
index 12aba63022..7e8dbb52ef 100644
--- a/testsuite/tests/plugins/all.T
+++ b/testsuite/tests/plugins/all.T
@@ -208,6 +208,12 @@ test('T16260',
       ],
      makefile_test, [])
 
+test('T19926',
+     [extra_files(['simple-plugin/']),
+      pre_cmd('$MAKE -s --no-print-directory -C simple-plugin package.T19926 TOP={top}')
+      ],
+     makefile_test, [])
+
 test('test-hole-plugin',
      [extra_files(['hole-fit-plugin/']),
       pre_cmd('$MAKE -s --no-print-directory -C hole-fit-plugin package.hole-fit-plugin TOP={top}'),
diff --git a/testsuite/tests/plugins/simple-plugin/Simple/DefaultPlugin.hs b/testsuite/tests/plugins/simple-plugin/Simple/DefaultPlugin.hs
new file mode 100644
index 0000000000..6edf122376
--- /dev/null
+++ b/testsuite/tests/plugins/simple-plugin/Simple/DefaultPlugin.hs
@@ -0,0 +1,5 @@
+module Simple.DefaultPlugin (plugin) where
+import GHC.Driver.Plugins (Plugin, defaultPlugin)
+
+plugin :: Plugin
+plugin = defaultPlugin
diff --git a/testsuite/tests/plugins/simple-plugin/simple-plugin.cabal b/testsuite/tests/plugins/simple-plugin/simple-plugin.cabal
index e6f367100c..af68c5ca3b 100644
--- a/testsuite/tests/plugins/simple-plugin/simple-plugin.cabal
+++ b/testsuite/tests/plugins/simple-plugin/simple-plugin.cabal
@@ -21,3 +21,4 @@ Library
         Simple.SourcePlugin
         Simple.RemovePlugin
         Simple.TrustworthyPlugin
+        Simple.DefaultPlugin