Store RdrName rather than OccName in Holes

In #20472 it was pointed out that you couldn't defer out of scope but
the implementation collapsed a RdrName into an OccName to stuff it into
a Hole. This leads to the error message for a deferred qualified name
dropping the qualification which affects the quality of the error
message.

This commit adds a bit more structure to a hole, so a hole can replace a
RdrName without losing information about what that RdrName was. This is
important when printing error messages.

I also added a test which checks the Template Haskell deferral of out of
scope qualified names works properly.

Fixes #22130

5 files changed, 13 insertions, 4 deletions

diff --git a/testsuite/tests/perf/compiler/hard_hole_fits.stderr b/testsuite/tests/perf/compiler/hard_hole_fits.stderr
index fcdde2ee2d..9d4e926892 100644
--- a/testsuite/tests/perf/compiler/hard_hole_fits.stderr
+++ b/testsuite/tests/perf/compiler/hard_hole_fits.stderr
@@ -22,7 +22,7 @@ hard_hole_fits.hs:15:32: warning: [GHC-88464] [-Wtyped-holes (in -Wdefault)]
     • Found hole: _ :: Int
     • In an equation for ‘testMe’: testMe (HsUnboundVar xuv uv) = _
     • Relevant bindings include
-        uv :: GHC.Types.Name.Occurrence.OccName
+        uv :: GHC.Types.Name.Reader.RdrName
           (bound at hard_hole_fits.hs:15:26)
         xuv :: Language.Haskell.Syntax.Extension.XUnboundVar GhcPs
           (bound at hard_hole_fits.hs:15:22)
diff --git a/testsuite/tests/plugins/hole-fit-plugin/HoleFitPlugin.hs b/testsuite/tests/plugins/hole-fit-plugin/HoleFitPlugin.hs
index e9f504d92d..3e8cd06a52 100644
--- a/testsuite/tests/plugins/hole-fit-plugin/HoleFitPlugin.hs
+++ b/testsuite/tests/plugins/hole-fit-plugin/HoleFitPlugin.hs
@@ -34,7 +34,7 @@ fromModule _ = []
 
 toHoleFitCommand :: TypedHole -> String -> Maybe String
 toHoleFitCommand (TypedHole {th_hole = Just (Hole { hole_occ = h })}) str
-    = stripPrefix ("_" <> str) $ occNameString h
+    = stripPrefix ("_" <> str) $ occNameString (occName h)
 toHoleFitCommand _ _ = Nothing
 
 
diff --git a/testsuite/tests/quotes/T20472_quotes.hs b/testsuite/tests/quotes/T20472_quotes.hs
new file mode 100644
index 0000000000..faebf59a21
--- /dev/null
+++ b/testsuite/tests/quotes/T20472_quotes.hs
@@ -0,0 +1,6 @@
+{-# LANGUAGE TemplateHaskellQuotes #-}
+{-# LANGUAGE NoMonomorphismRestriction #-}
+{-# OPTIONS_GHC -fdefer-out-of-scope-variables #-}
+module T20472_quotes where
+
+foo = [| Prelude.a |]
diff --git a/testsuite/tests/quotes/all.T b/testsuite/tests/quotes/all.T
index ba580ccaf4..4fa5d13d55 100644
--- a/testsuite/tests/quotes/all.T
+++ b/testsuite/tests/quotes/all.T
@@ -41,3 +41,4 @@ test('TH_double_splice', normal, compile_fail, [''])
 test('T20688', normal, compile, ['-Wimplicit-lift -Werror'])
 test('T20893', normal, compile_and_run, [''])
 test('T21619', normal, compile, [''])
+test('T20472_quotes', normal, compile, [''])
diff --git a/testsuite/tests/rename/should_compile/T20472.stderr b/testsuite/tests/rename/should_compile/T20472.stderr
index c1b18c4951..11e4e830d9 100644
--- a/testsuite/tests/rename/should_compile/T20472.stderr
+++ b/testsuite/tests/rename/should_compile/T20472.stderr
@@ -3,7 +3,9 @@ T20472.hs:5:5: warning: [GHC-88464] [-Wdeferred-out-of-scope-variables (in -Wdef
     Variable not in scope: nonexistent
 
 T20472.hs:6:5: warning: [GHC-88464] [-Wdeferred-out-of-scope-variables (in -Wdefault)]
-    Variable not in scope: nonexistent
+    Variable not in scope: Prelude.nonexistent
+    NB: the module ‘Prelude’ does not export ‘nonexistent’.
 
 T20472.hs:8:5: warning: [GHC-88464] [-Wdeferred-out-of-scope-variables (in -Wdefault)]
-    Variable not in scope: x
+    Variable not in scope: Nonexistent.x
+    NB: no module named ‘Nonexistent’ is imported.