Enable building Cabal with parsec

Cabal's parser has been rewritten in terms of Parsec (which is not
enabled yet in Cabal-2.0 by default, but can be enabled by a cabal
flag). The plan for Cabal is to drop support for the non-parsec parser,
so we need to prepare GHC to cope with new situation.

However, this means that lib:Cabal requires three new library
dependency submodules,

 - parsec
 - text
 - mtl

What complicates matters is that we need to build `ghc-cabal` early on
during the bootstrap phase which currently needs to invoke `ghc --make`
directly. So these additional dependencies need to be integrated into
the monolithic `ghc --make` invocation which produces the `ghc-cabal`
executable.

Test Plan: `./validate --fast` passed

Reviewers: austin, bgamari

Subscribers: erikd, phadej, rwbarton, thomie

Differential Revision: https://phabricator.haskell.org/D3757

9 files changed, 72 insertions, 7 deletions

diff --git a/configure.ac b/configure.ac
index 00fae0aad0..c11910ea85 100644
--- a/configure.ac
+++ b/configure.ac
@@ -158,8 +158,8 @@ if test "$WithGhc" = ""
 then
     AC_MSG_ERROR([GHC is required.])
 fi
-FP_COMPARE_VERSIONS([$GhcVersion],[-lt],[7.10],
-    [AC_MSG_ERROR([GHC version 7.10 or later is required to compile GHC.])])
+FP_COMPARE_VERSIONS([$GhcVersion],[-lt],[8.0],
+    [AC_MSG_ERROR([GHC version 8.0 or later is required to compile GHC.])])
 
 if test `expr $GhcMinVersion % 2` = "1"
 then
diff --git a/ghc.mk b/ghc.mk
index 4eb1658174..55cc1197c5 100644
--- a/ghc.mk
+++ b/ghc.mk
@@ -430,7 +430,7 @@ else # CLEANING
 # programs such as GHC and ghc-pkg, that we do not assume the stage0
 # compiler already has installed (or up-to-date enough).
 
-PACKAGES_STAGE0 = binary Cabal/Cabal hpc ghc-boot-th ghc-boot transformers template-haskell ghci
+PACKAGES_STAGE0 = binary text transformers mtl parsec Cabal/Cabal hpc ghc-boot-th ghc-boot template-haskell ghci
 ifeq "$(Windows_Host)" "NO"
 PACKAGES_STAGE0 += terminfo
 endif
@@ -457,11 +457,17 @@ PACKAGES_STAGE1 += process
 PACKAGES_STAGE1 += hpc
 PACKAGES_STAGE1 += pretty
 PACKAGES_STAGE1 += binary
+PACKAGES_STAGE1 += text
+PACKAGES_STAGE1 += transformers
+PACKAGES_STAGE1 += mtl
+PACKAGES_STAGE1 += parsec
+# temporary until Cabal switches to parsec mode by default
+libraries/Cabal/Cabal_dist-boot_CONFIGURE_OPTS += --flag parsec
+libraries/Cabal/Cabal_dist-install_CONFIGURE_OPTS += --flag parsec
 PACKAGES_STAGE1 += Cabal/Cabal
 PACKAGES_STAGE1 += ghc-boot-th
 PACKAGES_STAGE1 += ghc-boot
 PACKAGES_STAGE1 += template-haskell
-PACKAGES_STAGE1 += transformers
 PACKAGES_STAGE1 += ghc-compact
 
 ifeq "$(HADDOCK_DOCS)" "YES"
@@ -1264,6 +1270,7 @@ $(eval $(call sdist-ghc-file,compiler,stage2,parser,Parser,y))
 $(eval $(call sdist-ghc-file,utils/hpc,dist-install,,HpcParser,y))
 $(eval $(call sdist-ghc-file,utils/genprimopcode,dist,,Lexer,x))
 $(eval $(call sdist-ghc-file,utils/genprimopcode,dist,,Parser,y))
+$(eval $(call sdist-ghc-file2,libraries/Cabal/Cabal,dist-install,Distribution/Parsec,Lexer,x))
 
 .PHONY: sdist-ghc-prep
 sdist-ghc-prep : sdist-ghc-prep-tree
diff --git a/libraries/mtl b/libraries/mtl
new file mode 160000
+Subproject b4725fe28cba8a535e969e0ddbce3d5e05146cc
diff --git a/libraries/parsec b/libraries/parsec
new file mode 160000
+Subproject d21d86387998614de31697a26fd8fec15d40e62
diff --git a/libraries/text b/libraries/text
new file mode 160000
+Subproject 81f9de11424b79e075d0d22cee23ce9ad90b506
diff --git a/mk/warnings.mk b/mk/warnings.mk
index af5f4f51d9..16d13a28ba 100644
--- a/mk/warnings.mk
+++ b/mk/warnings.mk
@@ -114,6 +114,11 @@ libraries/transformers_dist-install_EXTRA_HC_OPTS += -Wno-unused-matches -Wno-un
 libraries/transformers_dist-install_EXTRA_HC_OPTS += -Wno-redundant-constraints
 libraries/transformers_dist-install_EXTRA_HC_OPTS += -Wno-orphans
 
+# parsec has various warnings
+libraries/parsec_dist-install_EXTRA_HC_OPTS += -Wno-name-shadowing -Wno-unused-matches
+libraries/parsec_dist-install_EXTRA_HC_OPTS += -Wno-unused-do-bind -Wno-missing-signatures
+libraries/parsec_dist-install_EXTRA_HC_OPTS += -Wno-unused-imports -Wno-type-defaults
+
 # Turn of trustworthy-safe warning
 libraries/base_dist-install_EXTRA_HC_OPTS += -Wno-trustworthy-safe
 libraries/ghc-prim_dist-install_EXTRA_HC_OPTS += -Wno-trustworthy-safe
diff --git a/packages b/packages
index 6ee80712f2..a44e31687e 100644
--- a/packages
+++ b/packages
@@ -52,9 +52,12 @@ libraries/directory          -           -                               ssh://g
 libraries/filepath           -           -                               ssh://git@github.com/haskell/filepath.git
 libraries/haskeline          -           -                               https://github.com/judah/haskeline.git
 libraries/hpc                -           -                               -
+libraries/mtl                -           -                               https://github.com/ekmett/mtl.git
+libraries/parsec             -           -                               https://github.com/haskell/parsec.git
 libraries/pretty             -           -                               https://github.com/haskell/pretty.git
 libraries/process            -           -                               ssh://git@github.com/haskell/process.git
 libraries/terminfo           -           -                               https://github.com/judah/terminfo.git
+libraries/text               -           -                               https://github.com/bos/text.git
 libraries/time               -           -                               https://github.com/haskell/time.git
 libraries/transformers       -           -                               https://git.haskell.org/darcs-mirrors/transformers.git
 libraries/unix               -           -                               ssh://git@github.com/haskell/unix.git
diff --git a/rules/sdist-ghc-file.mk b/rules/sdist-ghc-file.mk
index 9ea0b6521a..d6a70e10fb 100644
--- a/rules/sdist-ghc-file.mk
+++ b/rules/sdist-ghc-file.mk
@@ -44,3 +44,34 @@ sdist_$1_$2_$4 : $1/$2/build/$4.hs
 # didn't generate all package-data.mk files.
 $$(eval $$(call hs-suffix-rules-srcdir,$1,$2,$3))
 endef
+
+# -----------------------------------------------------------------------------
+# Variant of sdist-ghc-file whose `$3`-argument is interpreted
+# differently in a more appropriate way for cabal-packages
+
+define sdist-ghc-file2
+# $1 = dir
+# $2 = distdir
+# $3 = moduledir
+# $4 = filename
+# $5 = extension
+
+.PHONY: sdist_$1_$2_$4
+
+# We should do this before creating the `sdist-ghc` tarball, or when just
+# running `make sdist-ghc-prep`.
+sdist-ghc-prep : sdist_$1_$2_$4
+
+# But first create SRC_DIST_GHC_DIR.
+sdist_$1_$2_$4 : sdist-ghc-prep-tree
+
+# Generate the .hs files if they don't exist yet, then do actual copying and
+# moving.
+sdist_$1_$2_$4 : $1/$2/build/$3/$4.hs
+	"$(CP)" $1/$2/build/$3/$4.hs $(SRC_DIST_GHC_DIR)/$1/$3
+	mv $(SRC_DIST_GHC_DIR)/$1/$3/$4.$5 $(SRC_DIST_GHC_DIR)/$1/$3/$4.$5.source
+
+# And make sure the rules for generating the .hs files exist, even when we
+# didn't generate all package-data.mk files.
+$$(eval $$(call hs-suffix-rules-srcdir,$1,$2,$3))
+endef
diff --git a/utils/ghc-cabal/ghc.mk b/utils/ghc-cabal/ghc.mk
index 6250484017..eeae8a715b 100644
--- a/utils/ghc-cabal/ghc.mk
+++ b/utils/ghc-cabal/ghc.mk
@@ -27,9 +27,9 @@ CABAL_CONSTRAINT := --constraint="Cabal == $(CABAL_DOTTED_VERSION)"
 # `cabal_macros_boot.h` also for GHC >= 8 (in which case it becomes a
 # dummy include that doesn't contribute any macro definitions).
 ifeq "$(Windows_Host)" "YES"
-CABAL_BUILD_DEPS := base array time containers bytestring deepseq process pretty directory Win32
+CABAL_BUILD_DEPS := ghc-prim base array transformers time containers bytestring deepseq process pretty directory Win32
 else
-CABAL_BUILD_DEPS := base array time containers bytestring deepseq process pretty directory unix
+CABAL_BUILD_DEPS := ghc-prim base array transformers time containers bytestring deepseq process pretty directory unix
 endif
 
 ghc-cabal_DIST_BINARY_NAME = ghc-cabal$(exeext0)
@@ -40,11 +40,23 @@ ifneq "$(BINDIST)" "YES"
 $(ghc-cabal_INPLACE) : $(ghc-cabal_DIST_BINARY) | $$(dir $$@)/.
 	"$(CP)" $< $@
 
+# Minor hack, since we can't reuse the `hs-suffix-rules-srcdir` macro
+ifneq ($(wildcard libraries/Cabal/Cabal/Distribution/Parsec/Lexer.x),)
+# Lexer.x exists so we have to call Alex ourselves
+CABAL_LEXER_DEP := bootstrapping/Cabal/Distribution/Parsec/Lexer.hs
+
+bootstrapping/Cabal/Distribution/Parsec/Lexer.hs: libraries/Cabal/Cabal/Distribution/Parsec/Lexer.x
+	mkdir -p bootstrapping/Cabal/Distribution/Parsec
+	$(call cmd,ALEX) $< -o $@
+else
+CABAL_LEXER_DEP := libraries/Cabal/Cabal/Distribution/Parsec/Lexer.hs
+endif
+
 $(ghc-cabal_DIST_BINARY): $(wildcard libraries/Cabal/Cabal/Distribution/*/*/*.hs)
 $(ghc-cabal_DIST_BINARY): $(wildcard libraries/Cabal/Cabal/Distribution/*/*.hs)
 $(ghc-cabal_DIST_BINARY): $(wildcard libraries/Cabal/Cabal/Distribution/*.hs)
 
-$(ghc-cabal_DIST_BINARY): utils/ghc-cabal/Main.hs $(TOUCH_DEP) | $$(dir $$@)/. bootstrapping/.
+$(ghc-cabal_DIST_BINARY): $(CABAL_LEXER_DEP) utils/ghc-cabal/Main.hs $(TOUCH_DEP) | $$(dir $$@)/. bootstrapping/.
 	"$(GHC)" $(SRC_HC_OPTS) \
 	       $(addprefix -optc, $(SRC_CC_OPTS) $(CONF_CC_OPTS_STAGE0)) \
 	       $(addprefix -optl, $(SRC_LD_OPTS) $(CONF_GCC_LINKER_OPTS_STAGE0)) \
@@ -54,14 +66,21 @@ $(ghc-cabal_DIST_BINARY): utils/ghc-cabal/Main.hs $(TOUCH_DEP) | $$(dir $$@)/. b
 	       -no-user-$(GHC_PACKAGE_DB_FLAG) \
 	       -Wall -fno-warn-unused-imports -fno-warn-warnings-deprecations \
 	       -DCABAL_VERSION=$(CABAL_VERSION) \
+	       -DCABAL_PARSEC \
 	       -DBOOTSTRAPPING \
 	       -optP-include -optPutils/ghc-cabal/cabal_macros_boot.h \
 	       -odir  bootstrapping \
 	       -hidir bootstrapping \
+	       $(CABAL_LEXER_DEP) \
 	       -ilibraries/Cabal/Cabal \
 	       -ilibraries/binary/src \
 	       -ilibraries/filepath \
 	       -ilibraries/hpc \
+	       -ilibraries/mtl \
+	       -ilibraries/text \
+	       libraries/text/cbits/cbits.c \
+	       -Ilibraries/text/include \
+	       -ilibraries/parsec \
 	       $(utils/ghc-cabal_dist_EXTRA_HC_OPTS) \
 	       $(EXTRA_HC_OPTS)
 	"$(TOUCH_CMD)" $@