Generalise Package Support

This patch pushes through one fundamental change: a module is now
identified by the pair of its package and module name, whereas
previously it was identified by its module name alone.  This means
that now a program can contain multiple modules with the same name, as
long as they belong to different packages.

This is a language change - the Haskell report says nothing about
packages, but it is now necessary to understand packages in order to
understand GHC's module system.  For example, a type T from module M
in package P is different from a type T from module M in package Q.
Previously this wasn't an issue because there could only be a single
module M in the program.

The "module restriction" on combining packages has therefore been
lifted, and a program can contain multiple versions of the same
package.

Note that none of the proposed syntax changes have yet been
implemented, but the architecture is geared towards supporting import
declarations qualified by package name, and that is probably the next
step.

It is now necessary to specify the package name when compiling a
package, using the -package-name flag (which has been un-deprecated).
Fortunately Cabal still uses -package-name.

Certain packages are "wired in".  Currently the wired-in packages are:
base, haskell98, template-haskell and rts, and are always referred to
by these versionless names.  Other packages are referred to with full
package IDs (eg. "network-1.0").  This is because the compiler needs
to refer to entities in the wired-in packages, and we didn't want to
bake the version of these packages into the comiler.  It's conceivable
that someone might want to upgrade the base package independently of
GHC.

Internal changes:

  - There are two module-related types:

        ModuleName      just a FastString, the name of a module
        Module          a pair of a PackageId and ModuleName

    A mapping from ModuleName can be a UniqFM, but a mapping from Module
    must be a FiniteMap (we provide it as ModuleEnv).

  - The "HomeModules" type that was passed around the compiler is now
    gone, replaced in most cases by the current package name which is
    contained in DynFlags.  We can tell whether a Module comes from the
    current package by comparing its package name against the current
    package.

  - While I was here, I changed PrintUnqual to be a little more useful:
    it now returns the ModuleName that the identifier should be qualified
    with according to the current scope, rather than its original
    module.  Also, PrintUnqual tells whether to qualify module names with
    package names (currently unused).

Docs to follow.

1 files changed, 10 insertions, 10 deletions

diff --git a/compiler/codeGen/CgExpr.lhs b/compiler/codeGen/CgExpr.lhs
index 33d72f1608..e36b2ae236 100644
--- a/compiler/codeGen/CgExpr.lhs
+++ b/compiler/codeGen/CgExpr.lhs
@@ -152,8 +152,8 @@ cgExpr (StgOpApp (StgPrimOp TagToEnumOp) [arg] res_ty)
     do	{ (_,amode) <- getArgAmode arg
 	; amode' <- assignTemp amode	-- We're going to use it twice,
 					-- so save in a temp if non-trivial
-	; hmods <- getHomeModules
-	; stmtC (CmmAssign nodeReg (tagToClosure hmods tycon amode'))
+	; this_pkg <- getThisPackage
+	; stmtC (CmmAssign nodeReg (tagToClosure this_pkg tycon amode'))
 	; performReturn (emitAlgReturnCode tycon amode') }
    where
 	  -- If you're reading this code in the attempt to figure
@@ -185,9 +185,9 @@ cgExpr x@(StgOpApp op@(StgPrimOp primop) args res_ty)
   | ReturnsAlg tycon <- result_info, isEnumerationTyCon tycon
 	-- c.f. cgExpr (...TagToEnumOp...)
 	= do tag_reg <- newTemp wordRep
-	     hmods <- getHomeModules
+	     this_pkg <- getThisPackage
 	     cgPrimOp [tag_reg] primop args emptyVarSet
-	     stmtC (CmmAssign nodeReg (tagToClosure hmods tycon (CmmReg tag_reg)))
+	     stmtC (CmmAssign nodeReg (tagToClosure this_pkg tycon (CmmReg tag_reg)))
 	     performReturn (emitAlgReturnCode tycon (CmmReg tag_reg))
   where
 	result_info = getPrimOpResultInfo primop
@@ -282,8 +282,8 @@ cgRhs name (StgRhsCon maybe_cc con args)
 	; returnFC (name, idinfo) }
 
 cgRhs name (StgRhsClosure cc bi fvs upd_flag srt args body)
-  = do hmods <- getHomeModules
-       mkRhsClosure hmods name cc bi srt fvs upd_flag args body
+  = do this_pkg <- getThisPackage
+       mkRhsClosure this_pkg name cc bi srt fvs upd_flag args body
 \end{code}
 
 mkRhsClosure looks for two special forms of the right-hand side:
@@ -306,7 +306,7 @@ form:
 
 
 \begin{code}
-mkRhsClosure	hmods bndr cc bi srt
+mkRhsClosure	this_pkg bndr cc bi srt
 		[the_fv]   		-- Just one free var
 		upd_flag		-- Updatable thunk
 		[]			-- A thunk
@@ -328,7 +328,7 @@ mkRhsClosure	hmods bndr cc bi srt
   where
     lf_info 		  = mkSelectorLFInfo bndr offset_into_int
 				 (isUpdatable upd_flag)
-    (_, params_w_offsets) = layOutDynConstr hmods con (addIdReps params)
+    (_, params_w_offsets) = layOutDynConstr this_pkg con (addIdReps params)
 			-- Just want the layout
     maybe_offset	  = assocMaybe params_w_offsets selectee
     Just the_offset 	  = maybe_offset
@@ -352,7 +352,7 @@ We only generate an Ap thunk if all the free variables are pointers,
 for semi-obvious reasons.
 
 \begin{code}
-mkRhsClosure 	hmods bndr cc bi srt
+mkRhsClosure 	this_pkg bndr cc bi srt
 		fvs
 		upd_flag
 		[]			-- No args; a thunk
@@ -377,7 +377,7 @@ mkRhsClosure 	hmods bndr cc bi srt
 The default case
 ~~~~~~~~~~~~~~~~
 \begin{code}
-mkRhsClosure hmods bndr cc bi srt fvs upd_flag args body
+mkRhsClosure this_pkg bndr cc bi srt fvs upd_flag args body
   = cgRhsClosure bndr cc bi srt fvs upd_flag args body
 \end{code}