Run linear Lint on the desugarer output (part of #19165)

This addresses points (1a) and (1b) of #19165.

- Move mkFailExpr to HsToCore/Utils, as it can be shared
- Desugar incomplete patterns and holes to an empty case,
  as in Note [Incompleteness and linearity]
- Enable linear linting of desugarer output
- Mark MultConstructor as broken. It fails Lint, but I'd like to fix this
  separately.

Metric Decrease:
    T6048

3 files changed, 10 insertions, 7 deletions

diff --git a/testsuite/tests/linear/should_compile/all.T b/testsuite/tests/linear/should_compile/all.T
index 4869db0f2f..17e04ca94a 100644
--- a/testsuite/tests/linear/should_compile/all.T
+++ b/testsuite/tests/linear/should_compile/all.T
@@ -29,7 +29,7 @@ test('LinearConstructors', normal, compile, [''])
 test('Linear1Rule', normal, compile, [''])
 test('LinearEmptyCase', normal, compile, [''])
 test('Tunboxer', normal, compile, [''])
-test('MultConstructor', normal, compile, [''])
+test('MultConstructor', expect_broken(19165), compile, [''])
 test('LinearLetRec', expect_broken(405), compile, ['-O -dlinear-core-lint'])
 test('LinearTH1', normal, compile, [''])
 test('LinearTH2', normal, compile, [''])
diff --git a/testsuite/tests/simplCore/should_compile/T9400.stderr b/testsuite/tests/simplCore/should_compile/T9400.stderr
index 9e3f4184ea..7825071aea 100644
--- a/testsuite/tests/simplCore/should_compile/T9400.stderr
+++ b/testsuite/tests/simplCore/should_compile/T9400.stderr
@@ -9,7 +9,7 @@ T9400.hs:18:9: warning: [-Woverlapping-patterns (in -Wdefault)]
 
 ==================== Tidy Core ====================
 Result size of Tidy Core
-  = {terms: 37, types: 22, coercions: 0, joins: 0/0}
+  = {terms: 38, types: 22, coercions: 0, joins: 0/0}
 
 -- RHS size: {terms: 1, types: 0, coercions: 0, joins: 0/0}
 $trModule1 :: Addr#
@@ -36,7 +36,7 @@ T9400.$trModule :: Module
 [GblId, Unf=OtherCon []]
 T9400.$trModule = GHC.Types.Module $trModule2 $trModule4
 
--- RHS size: {terms: 22, types: 15, coercions: 0, joins: 0/0}
+-- RHS size: {terms: 23, types: 15, coercions: 0, joins: 0/0}
 main :: IO ()
 [GblId]
 main
@@ -64,8 +64,10 @@ main
                @()
                @()
                (putStrLn (unpackCString# "efg"#))
-               (Control.Exception.Base.patError
-                  @'LiftedRep @(IO ()) "T9400.hs:(17,5)-(18,29)|case"#))))
+               (case Control.Exception.Base.patError
+                       @'LiftedRep @() "T9400.hs:(17,5)-(18,29)|case"#
+                of wild {
+                }))))
 
 
 
diff --git a/testsuite/tests/simplCore/should_compile/spec-inline.stderr b/testsuite/tests/simplCore/should_compile/spec-inline.stderr
index a9da295e8b..a8fa8e58e8 100644
--- a/testsuite/tests/simplCore/should_compile/spec-inline.stderr
+++ b/testsuite/tests/simplCore/should_compile/spec-inline.stderr
@@ -45,10 +45,11 @@ lvl :: GHC.Prim.Addr#
 lvl = "spec-inline.hs:(19,5)-(29,25)|function go"#
 
 -- RHS size: {terms: 2, types: 2, coercions: 0, joins: 0/0}
-Roman.foo3 :: Int
+Roman.foo3 :: ()
 [GblId, Str=b, Cpr=b]
 Roman.foo3
-  = Control.Exception.Base.patError @'GHC.Types.LiftedRep @Int lvl
+  = Control.Exception.Base.patError
+      @'GHC.Types.LiftedRep @() lvl
 
 Rec {
 -- RHS size: {terms: 40, types: 5, coercions: 0, joins: 0/0}