Desugar modules compiled with -fno-code

Previously modules with hscTarget == HscNothing were not desugared.
This patch changes behavior so that all modules HsSrcFile Modules except GHC.Prim
are desugared. Modules with hscTarget == HscNothing are not simplified.

Warnings and errors produced by the desugarer will now be produced when
compiling with -fno-code.

HscMain.finishTypecheckingOnly is removed, HscMain.hscIncrementalCompile is
simplified a bit, and HscMain.finish takes in the removed logic. I think this
is easier to follow.

Updates haddock submodule.

Tests T8101, T8101b, T10600 are no longer expect_broken.

Reviewers: ezyang, austin, bgamari

Subscribers: rwbarton, thomie

GHC Trac Issues: #10600

Differential Revision: https://phabricator.haskell.org/D3542

4 files changed, 52 insertions, 53 deletions

diff --git a/compiler/main/HscMain.hs b/compiler/main/HscMain.hs
index 69d4031fbe..f4ca3a8b34 100644
--- a/compiler/main/HscMain.hs
+++ b/compiler/main/HscMain.hs
@@ -137,6 +137,7 @@ import FamInstEnv
 import Fingerprint      ( Fingerprint )
 import Hooks
 import TcEnv
+import PrelNames
 
 import DynFlags
 import ErrUtils
@@ -657,8 +658,6 @@ hscIncrementalCompile always_do_basic_recompilation_check m_tc_result
     -- to get those warnings too. (But we'll always exit at that point
     -- because the desugarer runs ioMsgMaybe.)
     runHsc hsc_env $ do
-    let dflags = hsc_dflags hsc_env
-
     e <- hscIncrementalFrontend always_do_basic_recompilation_check m_tc_result mHscMessage
             mod_summary source_modified mb_old_iface mod_index
     case e of
@@ -686,61 +685,58 @@ hscIncrementalCompile always_do_basic_recompilation_check m_tc_result
         -- the interface that existed on disk; it's possible we had
         -- to retypecheck but the resulting interface is exactly
         -- the same.)
-        Right (FrontendTypecheck tc_result, mb_old_hash) -> do
-            (status, hmi, no_change)
-                <- case ms_hsc_src mod_summary of
-                        HsSrcFile | hscTarget dflags /= HscNothing ->
-                            finish              hsc_env mod_summary tc_result mb_old_hash
-                        _ ->
-                            finishTypecheckOnly hsc_env mod_summary tc_result mb_old_hash
-            liftIO $ hscMaybeWriteIface dflags (hm_iface hmi) no_change mod_summary
-            return (status, hmi)
-
--- Generates and writes out the final interface for a typecheck.
-finishTypecheckOnly :: HscEnv
-              -> ModSummary
-              -> TcGblEnv
-              -> Maybe Fingerprint
-              -> Hsc (HscStatus, HomeModInfo, Bool)
-finishTypecheckOnly hsc_env summary tc_result mb_old_hash = do
-    let dflags = hsc_dflags hsc_env
-    (iface, changed, details) <- liftIO $ hscSimpleIface hsc_env tc_result mb_old_hash
-    let hsc_status =
-          case (hscTarget dflags, ms_hsc_src summary) of
-            (HscNothing, _) -> HscNotGeneratingCode
-            (_, HsBootFile) -> HscUpdateBoot
-            (_, HsigFile) -> HscUpdateSig
-            _ -> panic "finishTypecheckOnly"
-    return (hsc_status,
-            HomeModInfo{ hm_details  = details,
-                         hm_iface    = iface,
-                         hm_linkable = Nothing },
-            changed)
+        Right (FrontendTypecheck tc_result, mb_old_hash) ->
+            finish hsc_env mod_summary tc_result mb_old_hash
 
 -- Runs the post-typechecking frontend (desugar and simplify),
 -- and then generates and writes out the final interface. We want
 -- to write the interface AFTER simplification so we can get
 -- as up-to-date and good unfoldings and other info as possible
--- in the interface file.  This is only ever run for HsSrcFile,
--- and NOT for HscNothing.
+-- in the interface file.
 finish :: HscEnv
        -> ModSummary
        -> TcGblEnv
        -> Maybe Fingerprint
-       -> Hsc (HscStatus, HomeModInfo, Bool)
+       -> Hsc (HscStatus, HomeModInfo)
 finish hsc_env summary tc_result mb_old_hash = do
-    let dflags = hsc_dflags hsc_env
-    MASSERT( ms_hsc_src summary == HsSrcFile )
-    MASSERT( hscTarget dflags /= HscNothing )
-    guts0 <- hscDesugar' (ms_location summary) tc_result
-    guts <- hscSimplify' guts0
-    (iface, changed, details, cgguts) <- liftIO $ hscNormalIface hsc_env guts mb_old_hash
-
-    return (HscRecomp cgguts summary,
-            HomeModInfo{ hm_details  = details,
-                         hm_iface    = iface,
-                         hm_linkable = Nothing },
-            changed)
+  let dflags = hsc_dflags hsc_env
+      target = hscTarget dflags
+      hsc_src = ms_hsc_src summary
+      should_desugar =
+        ms_mod summary /= gHC_PRIM && hsc_src == HsSrcFile
+      mk_simple_iface = do
+        let hsc_status =
+              case (target, hsc_src) of
+                (HscNothing, _) -> HscNotGeneratingCode
+                (_, HsBootFile) -> HscUpdateBoot
+                (_, HsigFile) -> HscUpdateSig
+                _ -> panic "finish"
+        (iface, changed, details) <- liftIO $
+          hscSimpleIface hsc_env tc_result mb_old_hash
+        return (iface, changed, details, hsc_status)
+  (iface, changed, details, hsc_status) <-
+    -- we usually desugar even when we are not generating code, otherwise
+    -- we would miss errors thrown by the desugaring (see #10600). The only
+    -- exceptions are when the Module is Ghc.Prim or when
+    -- it is not a HsSrcFile Module.
+    if should_desugar
+      then do
+        desugared_guts0 <- hscDesugar' (ms_location summary) tc_result
+        if target == HscNothing
+          -- We are not generating code, so we can skip simplification
+          -- and generate a simple interface.
+          then mk_simple_iface
+          else do
+            desugared_guts <- hscSimplify' desugared_guts0
+            (iface, changed, details, cgguts) <-
+              liftIO $ hscNormalIface hsc_env desugared_guts mb_old_hash
+            return (iface, changed, details, HscRecomp cgguts summary)
+      else mk_simple_iface
+  liftIO $ hscMaybeWriteIface dflags iface changed summary
+  return
+    ( hsc_status
+    , HomeModInfo
+      {hm_details = details, hm_iface = iface, hm_linkable = Nothing})
 
 hscMaybeWriteIface :: DynFlags -> ModIface -> Bool -> ModSummary -> IO ()
 hscMaybeWriteIface dflags iface changed summary =
diff --git a/testsuite/tests/driver/all.T b/testsuite/tests/driver/all.T
index 7971d46cb3..ddea9ccda8 100644
--- a/testsuite/tests/driver/all.T
+++ b/testsuite/tests/driver/all.T
@@ -200,10 +200,10 @@ test('T8959a',
 
 test('T703', normal, run_command, ['$MAKE -s --no-print-directory T703'])
 test('T2182', normal, run_command, ['$MAKE -s --no-print-directory T2182'])
-test('T8101', expect_broken(10600), compile, ['-Wall -fno-code'])
-test('T8101b', expect_broken(10600), multimod_compile,
+test('T8101', normal, compile, ['-Wall -fno-code'])
+test('T8101b', normal, multimod_compile,
      ['T8101b', '-Wall -fno-code'])
-test('T10600', expect_broken(10600), compile_fail, ['-fno-code'])
+test('T10600', normal, compile_fail, ['-fno-code'])
 
 # Should not panic when compiling cmm file together with -outputdir.
 test('T9050', cmm_src, compile, ['-outputdir=.'])
diff --git a/testsuite/tests/perf/haddock/all.T b/testsuite/tests/perf/haddock/all.T
index 57e4591661..47421ce846 100644
--- a/testsuite/tests/perf/haddock/all.T
+++ b/testsuite/tests/perf/haddock/all.T
@@ -9,7 +9,7 @@ test('haddock.base',
           [(platform('x86_64-unknown-mingw32'), 24286343184, 5)
             # 2017-02-19                        24286343184 (x64/Windows) - Generalize kind of (->)
 
-          ,(wordsize(64), 25592972912, 5)
+          ,(wordsize(64), 27868466432, 5)
             # 2012-08-14:  5920822352 (amd64/Linux)
             # 2012-09-20:  5829972376 (amd64/Linux)
             # 2012-10-08:  5902601224 (amd64/Linux)
@@ -39,6 +39,7 @@ test('haddock.base',
             # 2017-02-16: 32695562088 Better Lint for join points
             # 2017-02-17: 38425793776 (x86_64/Linux) - Generalize kind of (->)
             # 2017-02-12: 25592972912 (x86_64/Linux) - Type-indexed Typeable
+            # 2017-06-05: 27868466432 (x86_64/Linux) - Desugar modules compiled with -fno-code
 
           ,(platform('i386-unknown-mingw32'), 2885173512, 5)
             # 2013-02-10:                     3358693084 (x86/Windows)
@@ -65,7 +66,7 @@ test('haddock.Cabal',
      [extra_files(['../../../../libraries/Cabal/Cabal/dist-install/haddock.t']),
       unless(in_tree_compiler(), skip), req_haddock
      ,stats_num_field('bytes allocated',
-          [(wordsize(64), 18269309128, 5)
+          [(wordsize(64), 22294859000, 5)
             # 2012-08-14:  3255435248 (amd64/Linux)
             # 2012-08-29:  3324606664 (amd64/Linux, new codegen)
             # 2012-10-08:  3373401360 (amd64/Linux)
@@ -111,6 +112,7 @@ test('haddock.Cabal',
             # 2017-02-17: 27784875792 (amd64/Linux) - Generalize kind of (->)
             # 2017-02-12: 18865432648 (amd64/Linux) - Type-indexed Typeable
             # 2017-05-31: 18269309128 (amd64/Linux) - Faster checkFamInstConsistency
+            # 2017-06-05: 22294859000 (amd64/Linux) - Desugar modules compiled with -fno-code
 
           ,(platform('i386-unknown-mingw32'), 3293415576, 5)
             # 2012-10-30:                     1733638168 (x86/Windows)
@@ -134,7 +136,7 @@ test('haddock.compiler',
      [extra_files(['../../../../compiler/stage2/haddock.t']),
       unless(in_tree_compiler(), skip), req_haddock
      ,stats_num_field('bytes allocated',
-          [(wordsize(64), 52762752968, 10)
+          [(wordsize(64), 65378619232, 10)
             # 2012-08-14: 26070600504 (amd64/Linux)
             # 2012-08-29: 26353100288 (amd64/Linux, new CG)
             # 2012-09-18: 26882813032 (amd64/Linux)
@@ -153,6 +155,7 @@ test('haddock.compiler',
             # 2017-02-11: 62070477608 (amd64/Linux) OccurAnal / One-Shot  (#13227) (and others)
             # 2017-02-25: 55777283352 (amd64/Linux) Early inline patch
             # 2017-05-31: 52762752968 (amd64/Linux) Faster checkFamInstConsistency
+            # 2017-06-05: 65378619232 (amd64/Linux) Desugar modules compiled with -fno-code
 
           ,(platform('i386-unknown-mingw32'),   367546388, 10)
             # 2012-10-30:                     13773051312 (x86/Windows)
diff --git a/utils/haddock b/utils/haddock
-Subproject b7d7b7acd42cbe424afde3c8a5a59a070644534
+Subproject a1b57146c5678b32eb5ac37021e93a81a4b7300