Domen Kožar domenkozar

Nix error messaging improvements

The goal is to improve beginner experience in Nix.

Go through Nix issues, move those related to error messages in our new repo.

	{ nixpkgs ? (fetchTarball https://github.com/NixOS/nixpkgs-channels/archive/nixos-19.09.tar.gz)
	, system ? builtins.currentSystem
	}:

	let
	haskellnix = import (builtins.fetchTarball https://github.com/input-output-hk/haskell.nix/archive/master.tar.gz);
	overlay = _: pkgs:
	let
	hnPkgs = pkgs.haskell-nix.stackProject {
	src = ./.;

	{-# LANGUAGE ScopedTypeVariables #-}
	import GHC.Stack
	import Control.Exception
	import Data.Functor

	g :: HasCallStack => IO Bool
	g = throwIO $ SomeException $ userError "foo"

	f :: HasCallStack => IO ()
	f = void $ g

	<!DOCTYPE html>
	<html>
	<head>
	<meta charset="utf-8" />
	<meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1" />
	<meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0">
	</head>
	<body>
	<dev id="pricing-elm"></div>
	<div id="footer-elm"></div>

	services.xserver = {
	enable = true;
	monitorSection = ''
	Option "NODPMS"
	'';
	serverLayoutSection = ''
	Option "BlankTime" "0"
	Option "DPMS" "false"
	'';
	displayManager.auto.user = "guest";

	{ config, pkgs, ... }:

	let
	uuid = "91434e29-edf5-42b7-b339-43d3a1d58359";
	backup = pkgs.writeScript "usb-backup.sh" ''
	#!/bin/sh

	export DISPLAY=:0.0
	SECONDS=0

	#!/usr/bin/env nix-shell
	#!nix-shell -i runhaskell -p "haskellPackages.ghcWithPackages (pkgs: with pkgs; [servant-server servant-auth-server servant-streaming-server ])"
	#!nix-shell -I https://github.com/NixOS/nixpkgs/archive/299814b385d2c1553f60ada8216d3b0af3d8d3c6.tar.gz

	{-# LANGUAGE DataKinds #-}
	{-# LANGUAGE TypeOperators #-}
	{-# LANGUAGE TemplateHaskell #-}
	{-# LANGUAGE QuasiQuotes #-}
	{-# LANGUAGE LambdaCase #-}
	{-# LANGUAGE ScopedTypeVariables #-}

	• No instance for (Servant.Auth.Server.Internal.AddSetCookie.AddSetCookies
	('Servant.Auth.Server.Internal.AddSetCookie.S
	('Servant.Auth.Server.Internal.AddSetCookie.S
	'Servant.Auth.Server.Internal.AddSetCookie.Z))
	(Handler
	(Streaming.Internal.Stream
	(Data.Functor.Of.Of ByteString)
	(Control.Monad.Trans.Resource.Internal.ResourceT IO)
	()))
	(ServerT

	• Could not deduce (ToJSON a0)
	from the context: ToJSON a
	bound by the type of the constructor ‘Remove’:
	forall a. ToJSON a => Operation
	at src/MixPanel/Types/EngageData.hs:20:5-35
	The type variable ‘a0’ is ambiguous
	• In the ambiguity check for ‘Remove’
	To defer the ambiguity check to use sites, enable AllowAmbiguousTypes
	In the definition of data constructor ‘Remove’
	In the data type declaration for ‘Operation’