fix happy bounds #565
fix happy bounds #565
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| @@ -52,7 +52,10 @@ executable ghc-lib-gen | |||
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| executable ghc-lib-build-tool | |||
| import: base | |||
| build-tool-depends: alex:alex, happy:happy < 2.0 | |||
| if impl (ghc > 9.12.0) | |||
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Should this bound instead check for 9.8?
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no, it's a bit subtle. this choice affects the happy that we'll use in ghc-lib-gen that invokes the GHC configure stage in order to compute the modules that go into each of ghc-lib-parser and ghc-lib, not the happy build-tool-depends of those packages (building these packages does not involve configure and generally don't fail with happy-2.0.2, i.e. the point raised in #563 ). except on the current HEAD of the GHC source tree, configure will fail with happy > 1.20 (the change that admits happy 2.0.2 only went on master 2 weeks ago {see the referenced commit above}). so this checks that the GHC compiler we are working with is at least > ghc-9.12.1 (equivalently, the minimum ghc-lib-parser flavor is > ghc-9.12.1) so we can be sure that before enabling 2.0.2 for happy for the purposes of ghc-lib-gen, configure won't fail. in all other cases, 1.20.* works and will pass configure just fine so in tl;dr, this is what we want.
motivation for this change discussed in #563. for >=9.8 flavors, allow happy-2.0.2 in ghc-lib-parser build-tool-depends.
m4/fptools_happy.m4 informs configure which as of https://gitlab.haskell.org/ghc/ghc/-/commit/0029ca91c845dd4530eb2c4606ad5bd59775cec2 allows ==1.20.* || >= 2.0.2 && < 2.1