Unify hsig and hs-boot; add preliminary "hs-boot" merging.

This patch drops the file level distinction between hs-boot and hsig;
we figure out which one we are compiling based on whether or not there
is a corresponding hs file lying around.

To make the "import A" syntax continue to work for bare hs-boot
files, we also introduce hs-boot merging, which takes an A.hi-boot
and converts it to an A.hi when there is no A.hs file in scope.
This will be generalized in Backpack to merge multiple A.hi files together;
which means we can jettison the "load multiple interface files" functionality.

This works automatically for --make, but for one-shot compilation
we need a new mode: ghc --merge-requirements A will generate an A.hi/A.o
from a local A.hi-boot file; Backpack will extend this mechanism further.

Has Haddock submodule update to deal with change in msHsFilePath behavior.

    - This commit drops support for the hsig extension. Can
      we support it?  It's annoying because the finder code is
      written with the assumption that where there's an hs-boot
      file, there's always an hs file too.  To support hsig, you'd
      have to probe two locations.  Easier to just not support it.

    - #10333 affects us, modifying an hs-boot still doesn't trigger
      recomp.

    - See compiler/main/Finder.hs: this diff is very skeevy, but
      it seems to work.

    - This code cunningly doesn't drop hs-boot files from the
      "drop hs-boot files" module graph, if they don't have a
      corresponding hs file.  I have no idea if this actually is useful.

Signed-off-by: Edward Z. Yang <ezyang@cs.stanford.edu>

Test Plan: validate

Reviewers: simonpj, austin, bgamari, spinda

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D1098

1 files changed, 17 insertions, 2 deletions

diff --git a/ghc/Main.hs b/ghc/Main.hs
index e2c7479008..7ca7481fc3 100644
--- a/ghc/Main.hs
+++ b/ghc/Main.hs
@@ -22,7 +22,7 @@ import CmdLineParser
 -- Implementations of the various modes (--show-iface, mkdependHS. etc.)
 import LoadIface        ( showIface )
 import HscMain          ( newHscEnv )
-import DriverPipeline   ( oneShot, compileFile )
+import DriverPipeline   ( oneShot, compileFile, mergeRequirement )
 import DriverMkDepend   ( doMkDependHS )
 #ifdef GHCI
 import InteractiveUI    ( interactiveUI, ghciWelcomeMsg, defaultGhciSettings )
@@ -156,6 +156,7 @@ main' postLoadMode dflags0 args flagWarnings = do
                DoMake          -> (CompManager, dflt_target,    LinkBinary)
                DoMkDependHS    -> (MkDepend,    dflt_target,    LinkBinary)
                DoAbiHash       -> (OneShot,     dflt_target,    LinkBinary)
+               DoMergeRequirements -> (OneShot, dflt_target,    LinkBinary)
                _               -> (OneShot,     dflt_target,    LinkBinary)
 
   let dflags1 = case lang of
@@ -250,6 +251,7 @@ main' postLoadMode dflags0 args flagWarnings = do
        DoInteractive          -> ghciUI srcs Nothing
        DoEval exprs           -> ghciUI srcs $ Just $ reverse exprs
        DoAbiHash              -> abiHash (map fst srcs)
+       DoMergeRequirements           -> doMergeRequirements (map fst srcs)
        ShowPackages           -> liftIO $ showPackages dflags6
 
   liftIO $ dumpFinalStats dflags6
@@ -455,14 +457,16 @@ data PostLoadMode
   | DoEval [String]         -- ghc -e foo -e bar => DoEval ["bar", "foo"]
   | DoAbiHash               -- ghc --abi-hash
   | ShowPackages            -- ghc --show-packages
+  | DoMergeRequirements            -- ghc --merge-requirements
 
 doMkDependHSMode, doMakeMode, doInteractiveMode,
-  doAbiHashMode, showPackagesMode :: Mode
+  doAbiHashMode, showPackagesMode, doMergeRequirementsMode :: Mode
 doMkDependHSMode = mkPostLoadMode DoMkDependHS
 doMakeMode = mkPostLoadMode DoMake
 doInteractiveMode = mkPostLoadMode DoInteractive
 doAbiHashMode = mkPostLoadMode DoAbiHash
 showPackagesMode = mkPostLoadMode ShowPackages
+doMergeRequirementsMode = mkPostLoadMode DoMergeRequirements
 
 showInterfaceMode :: FilePath -> Mode
 showInterfaceMode fp = mkPostLoadMode (ShowInterface fp)
@@ -598,6 +602,7 @@ mode_flags =
   , defFlag "C"            (PassFlag (setMode (stopBeforeMode HCc)))
   , defFlag "S"            (PassFlag (setMode (stopBeforeMode (As False))))
   , defFlag "-make"        (PassFlag (setMode doMakeMode))
+  , defFlag "-merge-requirements" (PassFlag (setMode doMergeRequirementsMode))
   , defFlag "-interactive" (PassFlag (setMode doInteractiveMode))
   , defFlag "-abi-hash"    (PassFlag (setMode doAbiHashMode))
   , defFlag "e"            (SepArg   (\s -> setMode (doEvalMode s) "-e"))
@@ -698,6 +703,16 @@ doMake srcs  = do
     when (failed ok_flag) (liftIO $ exitWith (ExitFailure 1))
     return ()
 
+-- ----------------------------------------------------------------------------
+-- Run --merge-requirements mode
+
+doMergeRequirements :: [String] -> Ghc ()
+doMergeRequirements srcs = mapM_ doMergeRequirement srcs
+
+doMergeRequirement :: String -> Ghc ()
+doMergeRequirement src = do
+    hsc_env <- getSession
+    liftIO $ mergeRequirement hsc_env (mkModuleName src)
 
 -- ---------------------------------------------------------------------------
 -- --show-iface mode