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

4 files changed, 8 insertions, 2 deletions

diff --git a/testsuite/tests/driver/dynamicToo/dynamicToo005/A005.hsig b/testsuite/tests/driver/dynamicToo/dynamicToo005/A005.hs-boot
index 75d621cfec..75d621cfec 100644
--- a/testsuite/tests/driver/dynamicToo/dynamicToo005/A005.hsig
+++ b/testsuite/tests/driver/dynamicToo/dynamicToo005/A005.hs-boot
diff --git a/testsuite/tests/driver/dynamicToo/dynamicToo005/Makefile b/testsuite/tests/driver/dynamicToo/dynamicToo005/Makefile
index 617510eec4..a08827a92d 100644
--- a/testsuite/tests/driver/dynamicToo/dynamicToo005/Makefile
+++ b/testsuite/tests/driver/dynamicToo/dynamicToo005/Makefile
@@ -5,11 +5,15 @@ include $(TOP)/mk/test.mk
 checkExists = [ -f $1 ] || echo $1 missing
 
 .PHONY: dynamicToo005
-# Check that "-c -dynamic-too" works with .hsig
+# Check that "-c -dynamic-too" works with signatures
 dynamicToo005:
 	"$(TEST_HC)" $(TEST_HC_OPTS) -dynamic-too -v0 \
                                -sig-of A005=base:Prelude \
-                               -c A005.hsig
+                               -c A005.hs-boot
+	$(call checkExists,A005.o-boot)
+	$(call checkExists,A005.hi-boot)
+	"$(TEST_HC)" $(TEST_HC_OPTS) -dynamic-too -v0 \
+                               --merge-requirements A005
 	$(call checkExists,A005.o)
 	$(call checkExists,A005.hi)
 	$(call checkExists,A005.dyn_o)
diff --git a/testsuite/tests/driver/dynamicToo/dynamicToo006/A.hsig b/testsuite/tests/driver/dynamicToo/dynamicToo006/A.hs-boot
index f79d5d334f..f79d5d334f 100644
--- a/testsuite/tests/driver/dynamicToo/dynamicToo006/A.hsig
+++ b/testsuite/tests/driver/dynamicToo/dynamicToo006/A.hs-boot
diff --git a/testsuite/tests/driver/dynamicToo/dynamicToo006/Makefile b/testsuite/tests/driver/dynamicToo/dynamicToo006/Makefile
index 497f2c0942..6e025f8322 100644
--- a/testsuite/tests/driver/dynamicToo/dynamicToo006/Makefile
+++ b/testsuite/tests/driver/dynamicToo/dynamicToo006/Makefile
@@ -11,8 +11,10 @@ dynamicToo006:
                                -sig-of A=base:Prelude \
                                --make B
 	$(call checkExists,A.o)
+	$(call checkExists,A.o-boot)
 	$(call checkExists,B.o)
 	$(call checkExists,A.hi)
+	$(call checkExists,A.hi-boot)
 	$(call checkExists,B.hi)
 	$(call checkExists,A.dyn_o)
 	$(call checkExists,B.dyn_o)