Fix deprecation warning when deprecated identifier is from another module

A stray 'Just' was being printed in the deprecation message.

Fixes #23573

(cherry picked from commit 2be99b7)

Author: mpickering

compiler/GHC/Tc/Errors/Ppr.hs

@@ -1100,8 +1100,11 @@ instance Diagnostic TcRnMessage where
           , pprWarningTxtForMsg pragma_warning_msg ]
           where
             impMsg  = text "imported from" <+> ppr pragma_warning_import_mod <> extra
-            extra | maybe True (pragma_warning_import_mod ==) pragma_warning_defined_mod = empty
-                  | otherwise = text ", but defined in" <+> ppr pragma_warning_defined_mod
+            extra = case pragma_warning_defined_mod of
+                      Just def_mod
+                        | def_mod /= pragma_warning_import_mod
+                          -> text ", but defined in" <+> ppr def_mod
+                      _ -> empty
     TcRnDifferentExportWarnings name locs
       -> mkSimpleDecorated $ vcat [quotes (ppr name) <+> text "exported with different error messages",
                                    text "at" <+> vcat (map ppr $ sortBy leftmost_smallest $ NE.toList locs)]

testsuite/tests/warnings/should_compile/T23573.hs

@@ -0,0 +1,5 @@
+module T23573 where
+
+import T23573A
+
+foo = deprec

testsuite/tests/warnings/should_compile/T23573.stderr

@@ -0,0 +1,5 @@
+
+T23573.hs:5:7: warning: [GHC-68441] [-Wdeprecations (in -Wextended-warnings)]
+    In the use of ‘deprec’
+    (imported from T23573A, but defined in T23573B):
+    Deprecated: "deprec"

testsuite/tests/warnings/should_compile/T23573A.hs

@@ -0,0 +1,5 @@
+module T23573A(module T23573B) where
+
+import T23573B
+
+

testsuite/tests/warnings/should_compile/T23573B.hs

@@ -0,0 +1,4 @@
+module T23573B where
+
+{-# DEPRECATED deprec "deprec" #-}
+deprec = ()

testsuite/tests/warnings/should_compile/all.T

@@ -65,3 +65,4 @@ test('DodgyImports_hiding', normal, compile, ['-Wdodgy-imports'])
 test('T22702a', normal, compile, [''])
 test('T22702b', normal, compile, [''])
 test('T22826', normal, compile, [''])
+test('T23573', [extra_files(["T23573.hs", "T23573A.hs", "T23573B.hs"])], multimod_compile, ['T23573', '-v0'])