Unicode characters are escaped in pretty-printed `Text` values

[xsebek]

Describe the bug
The format command escapes the Unicode character ∀.

To Reproduce
Type in REPL:

> tydef L a = rec l. a * 1 end
> format {(undefined) : L a}
it : Text = "{undefined : \8704 a. L a}"

Expected behavior
The format command should show the ASCII forall or Unicode ∀.

Additional context
This could be related to escaped characters in strings, like \n.

Discovered while testing #1928 (comment).

[byorgey]

Aha, it turns out the problem is not format, the problem is how we pretty-print Text values:

swarm/src/swarm-lang/Swarm/Language/Pretty.hs

Line 270 in f607470

TText s -> fromString (show s)

Currently we just call show on the underlying Text value, which automatically handles wrapping it in double quotes and turning things like newline characters into escape sequences. But it also turns many non-ASCII characters into escape sequences as well (which is controversial). But in any case it looks like we can probably just use ushow instead.

I don't think I would call this a "bug", exactly; the produced output is valid Swarm code which evaluates to the correct string. But it doesn't look nice and I agree we ought to change it.

[byorgey]

A simpler test case is just:

> "∀"
it0 : Text = "\8704"