From bb0c8c6bb89d384023935e87ebdd1239ed6d242c Mon Sep 17 00:00:00 2001
From: Sergei Trofimovich <slyich@gmail.com>
Date: Fri, 12 Jan 2024 10:05:41 +0000
Subject: [PATCH] dmd: improve eval failure on `pkgsLLVM` package set

`dmd` requires `libgcc` to be able to run `dmd` binary. As a result
`pkgsLLVM.dmd` fails the eval as:

    $ nix build -f. pkgsLLVM.dmd
       error: attribute 'libgcc' missing

       at pkgs/development/compilers/dmd/binary.nix:31:5:

           30|     glibc
           31|     stdenv.cc.cc.libgcc
             |     ^

Such reference to non-existent attributes is an unrecoverable exception.
The change turns it into recoverable `assert`:

    $ nix build --no-link -f. pkgsLLVM.dmd
       error: assertion '((hostPlatform).isLinux -> (((stdenv).cc.cc) ? libgcc))' failed

       at pkgs/development/compilers/dmd/binary.nix:12:1:

           11| # and can't build `dmd`.
           12| assert hostPlatform.isLinux -> (stdenv.cc.cc ? libgcc);
             | ^
---
 pkgs/development/compilers/dmd/binary.nix | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/pkgs/development/compilers/dmd/binary.nix b/pkgs/development/compilers/dmd/binary.nix
index 6a99d42eff72..3a5d6b76cec8 100644
--- a/pkgs/development/compilers/dmd/binary.nix
+++ b/pkgs/development/compilers/dmd/binary.nix
@@ -5,7 +5,12 @@ let
   inherit (stdenv) hostPlatform;
   OS = if hostPlatform.isDarwin then "osx" else hostPlatform.parsed.kernel.name;
   MODEL = toString hostPlatform.parsed.cpu.bits;
-in stdenv.mkDerivation {
+in
+
+# On linux pargets like `pkgsLLVM.dmd` `cc` does not expose `libgcc`
+# and can't build `dmd`.
+assert hostPlatform.isLinux -> (stdenv.cc.cc ? libgcc);
+stdenv.mkDerivation {
   pname = "dmd-bootstrap";
   inherit version;