From 9a8850aea97840dca1cc1087447ed89dbfe183dc Mon Sep 17 00:00:00 2001
From: Gabriella Gonzalez <Gabriel439@gmail.com>
Date: Sat, 21 Aug 2021 19:25:01 -0700
Subject: [PATCH] dhallToNix: Permit inputs referring to derivations (#134459)
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Fixes https://github.com/dhall-lang/dhall-haskell/issues/2267

`pkgs.dhallToNix` currently fails when a Dhall package is
interpolated into the input source code, like this:

```nix
let
  pkgs = import <nixpkgs> { };

  f = { buildDhallPackage }: buildDhallPackage {
    name = "not";
    code = "λ(x : Bool) → x == False";
    source = true;
  };

  not = pkgs.dhallPackages.callPackage f {};

in
  pkgs.dhallToNix "${not}/source.dhall True"
```

This is because `dhallToNix` was using `builtins.toFile`, which
does not permit inputs with interpolated derivations.  However,
`pkgs.writeText` does not have this limitation, so we can switch
to using that instead.
---
 pkgs/build-support/dhall-to-nix.nix | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/pkgs/build-support/dhall-to-nix.nix b/pkgs/build-support/dhall-to-nix.nix
index 3805656dfa0e..96cc16e16f36 100644
--- a/pkgs/build-support/dhall-to-nix.nix
+++ b/pkgs/build-support/dhall-to-nix.nix
@@ -15,12 +15,12 @@
     Note that this uses "import from derivation", meaning that Nix will perform
     a build during the evaluation phase if you use this `dhallToNix` utility
 */
-{ stdenv, dhall-nix }:
+{ stdenv, dhall-nix, writeText }:
 
 let
   dhallToNix = code :
     let
-      file = builtins.toFile "dhall-expression" code;
+      file = writeText "dhall-expression" code;
 
       drv = stdenv.mkDerivation {
         name = "dhall-compiled.nix";