@sarahzrf How can I reproduce the problem that this PR fixes? And then, how can I run ihaskell to make sure that the problem is fixed with this patch?

Try using nix-shell in a directory with the following shell.nix:

{ nixpkgs ? import <nixpkgs> {}, compiler ? "ghc883" }:
let unbreak = nixpkgs.haskell.lib.markUnbroken;
    hs = nixpkgs.haskell.packages.${compiler}.override {overrides = self: super: {
      ihaskell = unbreak super.ihaskell;
      ihaskell-blaze = unbreak super.ihaskell-blaze;
      ihaskell-display = unbreak super.ihaskell-display;
      ihaskell-diagrams = unbreak super.ihaskell-diagrams;
    };};
    packages = hp: with hp; [];
    ihaskell = nixpkgs.ihaskell.override {inherit (hs) ghcWithPackages; inherit packages;};
in nixpkgs.stdenv.mkDerivation {
  name = "env";
  buildInputs = [nixpkgs.glibcLocales ihaskell];
}

Then attempt to run ihaskell-notebook, and you should see an error like

/nix/store/8g24wvk11y9ycly9p2g5xjm98ffzqkpk-ihaskell-with-packages/bin/.ihaskell-notebook-wrapped: line 3: unexpected EOF while looking for matching `"'
/nix/store/8g24wvk11y9ycly9p2g5xjm98ffzqkpk-ihaskell-with-packages/bin/.ihaskell-notebook-wrapped: line 5: syntax error: unexpected end of file

The breakage seems to have been introduced in e20f308, although the single quotes around the : in PATH seem to have been there since 43a62b6. Still, I'm pretty sure the latter is wrong too.

@sarahzrf Do you want to unbreak the various ihaskell packages in this PR as well? If so, can you rebase this on the haskell-updates branch?

I'm not entirely confident in how actually non-broken they are—I've had all kinds of horrible issues trying to get various ihaskell things working before :\

As long as they all build and you're able to successfully run them, that should be enough for now.

If someone comes along and figures out that there is some bug with them, then we can potentially mark them as broken again, but until that time I think marking them as unbroken is probably the way to go.