[Git][ghc/ghc][master] Fix bootstrap with ghc-9.0

[Marge Bot (@marge-bot)]

Marge Bot pushed to branch master at Glasgow Haskell Compiler / GHC


Commits:
7f527f01 by Matthew Pickering at 2022-09-01T12:01:56-04:00
Fix bootstrap with ghc-9.0

It turns out Solo is a very recent addition to base, so for older GHC
versions we just defined it inline here the one place we use it in the
compiler.

- - - - -


1 changed file:

- compiler/GHC/Core/Opt/SpecConstr.hs


Changes:

=====================================
compiler/GHC/Core/Opt/SpecConstr.hs
=====================================
@@ -1,3 +1,4 @@
+{-# LANGUAGE CPP #-}
 {-
 ToDo [Oct 2013]
 ~~~~~~~~~~~~~~~
@@ -974,6 +975,14 @@ lookupHowBound env id = lookupVarEnv (sc_how_bound env) id
 scSubstId :: ScEnv -> InId -> OutExpr
 scSubstId env v = lookupIdSubst (sc_subst env) v
 
+
+-- Solo is only defined in base starting from ghc-9.2
+#if !(MIN_VERSION_base(4, 16, 0))
+
+data Solo a = Solo a
+
+#endif
+
 -- The !subst ensures that we force the selection `(sc_subst env)`, which avoids
 -- retaining all of `env` when we only need `subst`.  The `Solo` means that the
 -- substitution itself is lazy, because that type is often discarded.



View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/7f527f01c8b4b61047fa87905750ee962f527e36

-- 
View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/7f527f01c8b4b61047fa87905750ee962f527e36
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