Add instance Lift (Expr s a) #1119
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This allows Exprs to be lifted in template-haskell. This is useful to build a [dhall||] quasiquoter
| {-# LANGUAGE OverloadedStrings #-} | ||
| {-# LANGUAGE TemplateHaskell #-} |
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Actually, even if it were, we could guard this behind a cabal configure flag so that users can compile out Template Haskell support if necessary. But let's still confirm whether or not we even need to do so
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It wouldn't be hard to remove it from this file.
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Oh, if it's easy to do, then go ahead. The real issue here is that I just don't really understand what are the exact requirements for Dhall to be easy-to-cross-compile. For example, it's not clear to me if depending on th-lift-instances matters or not for the original use case @vmchale had in mind.
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This can actually get away with just TemplateHaskellQuotes, which is cross-compilation friendly.
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I've changed this to TemplateHaskellQuotes, I hadn't even heard of that extension!
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Sorry for the merge conflicts, @ocharles! :/ |
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No problem! I have a little more work to do anyway, should be easy to fix up. |
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Anyone got any ideas on the build failure? Is this Cabal messing up? It seems to be in the "Preprocessing" stage. |
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FWIW, when I built your branch with stack just now, I got the same error, and added |
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Oh, that's a slightly different error but I do probably need to fix the |
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I have a feeling that even though |
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@ocharles: I think the only option is to guard all of the |
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Cabal actually doesn't care - that list is only relevant for |
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@quasicomputational are you sure? Because this extension has existed since 7.4, yet the build is failing on 7.10 |
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GHC's manual says new in 8.0, so actually, yeah, this won't work without either conditionally exposing the |
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Huh. This says since 7.2.1 |
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I guess this was a bug and the documentation has been fixed in HEAD? |
Right: https://gitlab.haskell.org/ghc/ghc/commit/1ad3c8245cc114c3f862633d027361700fba3e50 |
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Ok, I've taken a different approach using the default instance for |
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@ocharles: It looks like we might need to replace |
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Yea I saw. Sorry, I'm traveling a lot this weekend so I'm just pushing
commits out when I get a few minutes spare.
…On Sun, 21 Jul 2019, 3:46 pm Gabriel Gonzalez, ***@***.***> wrote:
@ocharles <https://github.com/ocharles>: It looks like we might need to
replace TemplateHaskellQuotes with another extension for older GHC
versions
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Thank you! 🙂 |
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Oh good, I finally got all CI systems happy! |
This allows Exprs to be lifted in template-haskell. This is useful to build a
[dhall| ... |]quasiquoter