cabal-install: Fix non-reinstallable package set

In #9064 we discovered that `ghc-boot` was added to the
non-reinstallable package set due to #8051 despite there being no
reason why it can't be built from its source distribution. This
revealed the fact that there is quite some ambiguity around what
constitutes a non-reinstallable package.

In #9064 we worked out a hopefully-more-clear picture of
non-reinstallability. Here we update the commentary to describe this
concept and update the lists to reflect the new definition.

Closes #9064.

Author: bgamari

cabal-install/src/Distribution/Client/Dependency.hs

@@ -456,19 +456,34 @@ dontUpgradeNonUpgradeablePackages params =
         . InstalledPackageIndex.lookupPackageName
           (depResolverInstalledPkgIndex params)
 
--- NOTE: the lists of non-upgradable and non-installable packages used to be
+-- | The set of non-reinstallable packages includes those which cannot be
+-- rebuilt using a GHC installation and Hackage-published source distribution.
+-- There are a few reasons why this might be true:
+--
+--  * the package overrides its unit ID (e.g. with ghc's @-this-unit-id@ flag),
+--    which can result in multiple indistinguishable packages (having potentially
+--    different ABIs) with the same unit ID.
+--
+--  * the package contains definitions of wired-in declarations which tie
+--    it to a particular compiler (e.g. we can't build link against
+--    @base-4.18.0.0@ using GHC 9.6.1).
+--
+--  * the package does not have a complete (that is, buildable) source distribution.
+--    For instance, some packages provided by GHC rely on files outside of the
+--    source tree generated by GHC's build system.
+--
+-- Note: the list of non-upgradable/non-installable packages used to be
 -- respectively in this module and in `Distribution.Solver.Modular.Solver`.
 -- Since they were kept synced, they are now combined in the following list.
 --
--- See: https://github.com/haskell/cabal/issues/8581
+-- See: https://github.com/haskell/cabal/issues/8581 and
+-- https://github.com/haskell/cabal/issues/9064.
 nonUpgradeablePackages :: [PackageName]
 nonUpgradeablePackages =
   [ mkPackageName "base"
   , mkPackageName "ghc-bignum"
   , mkPackageName "ghc-prim"
-  , mkPackageName "ghc-boot"
   , mkPackageName "ghc"
-  , mkPackageName "ghci"
   , mkPackageName "integer-gmp"
   , mkPackageName "integer-simple"
   , mkPackageName "template-haskell"