From 1105ed95b8b1eaf0346bb3c5aca87d7084b4ddd6 Mon Sep 17 00:00:00 2001
From: Leorize <leorize+oss@disroot.org>
Date: Thu, 11 Nov 2021 17:55:42 -0600
Subject: [PATCH] union: add a way to stringify unions

This will be very helpful for debugging as it hides away implementation
details within union.
---
 tests/tconv.nim | 6 ++++++
 union.nim       | 8 ++++++++
 2 files changed, 14 insertions(+)

diff --git a/tests/tconv.nim b/tests/tconv.nim
index 2beca87..6f5c4d8 100644
--- a/tests/tconv.nim
+++ b/tests/tconv.nim
@@ -79,3 +79,9 @@ suite "Union conversions":
     check (10 as union(int | float)) == (10 as union(int | string))
     check ("string" as union(int | float | string | seq[string])) == ("string" as union(int | string))
     check ("string" as union(int | float | string | seq[string])) != (42 as union(int | string))
+
+  test "Auto string representation for unions":
+    check $(10 as union(int | float)) == "int(10)"
+    check $("string" as union(int | string)) == "string(\"string\")"
+    check $([1, 2] as union(int | array[2, int])) == "array[0..1, int]([1, 2])"
+    check $(@[1, 2] as union(string | seq[int])) == "seq[int](@[1, 2])"
diff --git a/union.nim b/union.nim
index cb638e0..10f6379 100644
--- a/union.nim
+++ b/union.nim
@@ -706,3 +706,11 @@ func `==`*[U, V: Union](a: U, b: V): bool {.inline.} =
           false
   else:
     false
+
+proc `$`*[T: Union](u: T): string =
+  ## Stringify `u` based on its current type in the format `type(value)`.
+  ## Its main purpose is to enable debugging.
+  unpack(u):
+    result = $typeof(it) & "("
+    result.addQuoted it
+    result.add ")"