The Backpack patch.

Summary:
This patch implements Backpack for GHC.  It's a big patch but I've tried quite
hard to keep things, by-in-large, self-contained.

The user facing specification for Backpack can be found at:

    https://github.com/ezyang/ghc-proposals/blob/backpack/proposals/0000-backpack.rst

A guide to the implementation can be found at:

    https://github.com/ezyang/ghc-proposals/blob/backpack-impl/proposals/0000-backpack-impl.rst

Has a submodule update for Cabal, as well as a submodule update
for filepath to handle more strict checking of cabal-version.

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

Test Plan: validate

Reviewers: simonpj, austin, simonmar, bgamari, goldfire

Subscribers: thomie, mpickering

Differential Revision: https://phabricator.haskell.org/D1482

1 files changed, 10 insertions, 13 deletions

diff --git a/compiler/main/PackageConfig.hs b/compiler/main/PackageConfig.hs
index cda8f7f12c..f16c902a7e 100644
--- a/compiler/main/PackageConfig.hs
+++ b/compiler/main/PackageConfig.hs
@@ -1,4 +1,4 @@
-{-# LANGUAGE CPP, RecordWildCards, MultiParamTypeClasses #-}
+{-# LANGUAGE CPP, RecordWildCards, FlexibleInstances, MultiParamTypeClasses #-}
 
 -- |
 -- Package configuration information: essentially the interface to Cabal, with
@@ -11,6 +11,7 @@ module PackageConfig (
 
         -- * UnitId
         packageConfigId,
+        expandedPackageConfigId,
 
         -- * The PackageConfig type: information about a package
         PackageConfig,
@@ -40,9 +41,11 @@ import Unique
 -- which is similar to a subset of the InstalledPackageInfo type from Cabal.
 
 type PackageConfig = InstalledPackageInfo
+                       ComponentId
                        SourcePackageId
                        PackageName
                        Module.UnitId
+                       Module.UnitId
                        Module.ModuleName
                        Module.Module
 
@@ -50,14 +53,9 @@ type PackageConfig = InstalledPackageInfo
 --       feature, but ghc doesn't currently have convenient support for any
 --       other compact string types, e.g. plain ByteString or Text.
 
-newtype ComponentId = ComponentId FastString deriving (Eq, Ord)
 newtype SourcePackageId    = SourcePackageId    FastString deriving (Eq, Ord)
 newtype PackageName        = PackageName        FastString deriving (Eq, Ord)
 
-instance BinaryStringRep ComponentId where
-  fromStringRep = ComponentId . mkFastStringByteString
-  toStringRep (ComponentId s) = fastStringToByteString s
-
 instance BinaryStringRep SourcePackageId where
   fromStringRep = SourcePackageId . mkFastStringByteString
   toStringRep (SourcePackageId s) = fastStringToByteString s
@@ -66,18 +64,12 @@ instance BinaryStringRep PackageName where
   fromStringRep = PackageName . mkFastStringByteString
   toStringRep (PackageName s) = fastStringToByteString s
 
-instance Uniquable ComponentId where
-  getUnique (ComponentId n) = getUnique n
-
 instance Uniquable SourcePackageId where
   getUnique (SourcePackageId n) = getUnique n
 
 instance Uniquable PackageName where
   getUnique (PackageName n) = getUnique n
 
-instance Outputable ComponentId where
-  ppr (ComponentId str) = ftext str
-
 instance Outputable SourcePackageId where
   ppr (SourcePackageId str) = ftext str
 
@@ -125,7 +117,6 @@ pprPackageConfig InstalledPackageInfo {..} =
   where
     field name body = text name <> colon <+> nest 4 body
 
-
 -- -----------------------------------------------------------------------------
 -- UnitId (package names, versions and dep hash)
 
@@ -140,3 +131,9 @@ pprPackageConfig InstalledPackageInfo {..} =
 -- | Get the GHC 'UnitId' right out of a Cabalish 'PackageConfig'
 packageConfigId :: PackageConfig -> UnitId
 packageConfigId = unitId
+
+expandedPackageConfigId :: PackageConfig -> UnitId
+expandedPackageConfigId p =
+    case instantiatedWith p of
+        [] -> packageConfigId p
+        _ -> newUnitId (unitIdComponentId (packageConfigId p)) (instantiatedWith p)