From 93f5c919fb88c58226609aa388862a8f9514f3f1 Mon Sep 17 00:00:00 2001
From: Mark Spanbroek <mark@spanbroek.net>
Date: Mon, 31 May 2021 16:24:21 +0200
Subject: [PATCH] Ensure that optional binding works with closures

---
 questionable/binding.nim     |  3 ++-
 questionable/results.nim     |  5 ++++-
 testmodules/options/test.nim | 14 ++++++++++++++
 testmodules/result/test.nim  | 14 ++++++++++++++
 4 files changed, 34 insertions(+), 2 deletions(-)

diff --git a/questionable/binding.nim b/questionable/binding.nim
index 357e683..bc927bd 100644
--- a/questionable/binding.nim
+++ b/questionable/binding.nim
@@ -6,7 +6,8 @@ proc option[T](option: Option[T]): Option[T] =
 
 template bindLet(name, expression): bool =
   let option = expression.option
-  template name: auto {.used.} = option.unsafeGet()
+  const default = typeof(option.unsafeGet()).default
+  let name = if option.isSome: option.unsafeGet() else: default
   option.isSome
 
 template bindVar(name, expression): bool =
diff --git a/questionable/results.nim b/questionable/results.nim
index 4dc0de5..763d2e9 100644
--- a/questionable/results.nim
+++ b/questionable/results.nim
@@ -80,7 +80,10 @@ template `|?`*[T,E](value: Result[T,E], fallback: T): T =
 
 proc option*[T,E](value: Result[T,E]): ?T =
   if value.isOk:
-    value.unsafeGet.some
+    try: # workaround for erroneouos exception tracking when T is a closure
+      value.unsafeGet.some
+    except Exception as exception:
+      raise newException(Defect, exception.msg, exception)
   else:
     T.none
 
diff --git a/testmodules/options/test.nim b/testmodules/options/test.nim
index 6f7683f..3733169 100644
--- a/testmodules/options/test.nim
+++ b/testmodules/options/test.nim
@@ -148,6 +148,20 @@ suite "optionals":
     check 42.some.toString == "42"
     check int.none.toString == "none"
 
+  test "=? works with closures":
+    var called = false
+    let closure = some(proc () = called = true)
+
+    if a =? none(proc ()):
+      a()
+
+    check not called
+
+    if a =? closure:
+      a()
+
+    check called
+
   test "without statement can be used for early returns":
     proc test1 =
       without a =? 42.some:
diff --git a/testmodules/result/test.nim b/testmodules/result/test.nim
index 07b1f97..367baa4 100644
--- a/testmodules/result/test.nim
+++ b/testmodules/result/test.nim
@@ -151,6 +151,20 @@ suite "result":
     check 42.success.toString == "42"
     check int.failure(error).toString == "error"
 
+  test "=? works with closures":
+    var called = false
+    let closure = success(proc () = called = true)
+
+    if a =? failure(proc (), error):
+      a()
+
+    check not called
+
+    if a =? closure:
+      a()
+
+    check called
+
   test "without statement works for results":
     proc test1 =
       without a =? 42.success: