Help overriding a derivations runtime Haskell dependencies (reproducible pinned nix file included)

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I was trying to override each package and thinking it would work out. What I really wnated to do was override haskellPackages for this build of the diagrams-builder derivations digrams-builder haskell dependency like this (still compiling… but feel like this will work):

let pkgs = import (fetchTarball "https://github.com/NixOS/nixpkgs-channels/archive/c71518e75bf067fb639d44264fdd8cf80f53d75a.tar.gz") {};
    my-haskell-src-exts =
      pkgs.haskellPackages.callHackageDirect 
        { pkg = "haskell-src-exts";
          ver = "1.22.0";
          sha256 = "0jwp8vhk3ncfxprbmg0jx001g7mh1kyp16973mjkjqz0d60zarwi";
        } {};
    my-haskell-src-exts-simple =
      pkgs.haskellPackages.callHackageDirect 
        { pkg = "haskell-src-exts-simple";
          ver = "1.22.0.0";
          sha256 = "1ixx2bpc7g6lclzrdjrnyf026g581rwm0iji1mn1iv03yzl3y215";
        } {};
    diagrams-postscript = 
      pkgs.haskellPackages.callHackageDirect 
        { pkg = "diagrams-postscript";
          ver = "1.4.1";
          sha256 = "0174y4s6rx6cckkbhph22ybl96h00wjqqkzkrcni7ylxcvgf37bd";
        } {};
    myHaskellPackages = pkgs.haskellPackages.override {
      overrides = self: super: {
        haskell-src-exts = my-haskell-src-exts;
        haskell-src-exts-simple = my-haskell-src-exts-simple;
      };
    };
in pkgs.diagrams-builder.override( {
      diagrams-builder = myHaskellPackages.diagrams-builder;
})