From 9414202d53fac99a0b1af33acac816ff9236e6d0 Mon Sep 17 00:00:00 2001
From: Jacek Sieka <jacek@status.im>
Date: Fri, 3 Apr 2020 13:33:24 +0200
Subject: [PATCH] result: `and` can deal with heterogenous values

---
 stew/result.nim       | 2 +-
 tests/test_result.nim | 3 +++
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/stew/result.nim b/stew/result.nim
index 6d95eb3..9e04c6f 100644
--- a/stew/result.nim
+++ b/stew/result.nim
@@ -266,7 +266,7 @@ func mapCast*[T0, E0](
   if self.isOk: result.ok(cast[T1](self.v))
   else: result.err(self.e)
 
-template `and`*[T, E](self, other: Result[T, E]): Result[T, E] =
+template `and`*[T0, E, T1](self: Result[T0, E], other: Result[T1, E]): Result[T1, E] =
   ## Evaluate `other` iff self.isOk, else return error
   ## fail-fast - will not evaluate other if a is an error
   ##
diff --git a/tests/test_result.nim b/tests/test_result.nim
index d9a8d03..40706c6 100644
--- a/tests/test_result.nim
+++ b/tests/test_result.nim
@@ -32,6 +32,9 @@ doAssert (rErr and rOk).isErr
 doAssert (rOk or rErr).isOk
 doAssert (rErr or rOk).isOk
 
+# `and` heterogenous types
+doAssert (rOk and rOk.map(proc(x: auto): auto = $x))[] == $(rOk[])
+
 # Exception on access
 let va = try: discard rOk.error; false except: true
 doAssert va, "not an error, should raise"