Ensure that =? works with types that do not have a default value

questionable/binding.nim

@@ -4,15 +4,19 @@ import std/macros
 proc option[T](option: Option[T]): Option[T] =
   option
 
+proc placeholder(T: type): T =
+  discard
+
 template bindLet(name, expression): bool =
   let option = expression.option
-  const default = typeof(option.unsafeGet()).default
+  type T = typeof(option.unsafeGet())
-  let name {.used.} = if option.isSome: option.unsafeGet() else: default
+  let name {.used.} = if option.isSome: option.unsafeGet() else: placeholder(T)
   option.isSome
 
 template bindVar(name, expression): bool =
   let option = expression.option
-  var name {.used.} : typeof(option.unsafeGet())
+  type T = typeof(option.unsafeGet())
+  var name {.used.} : T = placeholder(T)
   if option.isSome:
     name = option.unsafeGet()
   option.isSome

testmodules/nim.cfg

@@ -0,0 +1,2 @@
+--warningAsError[UnsafeDefault]:"on"
+--warningAsError[ProveInit]:"on"

testmodules/options/test.nim

@@ -162,6 +162,20 @@ suite "optionals":
 
     check called
 
+  test "=? works with types that do not have a default value":
+    type NoDefault {.requiresInit.} = distinct int
+    proc `==`(a,b: NoDefault): bool {.borrow.}
+
+    if a =? some NoDefault(42):
+      check a == NoDefault(42)
+    else:
+      fail()
+
+    if var a =? some NoDefault(42):
+      check a == NoDefault(42)
+    else:
+      fail()
+
   test "without statement can be used for early returns":
     proc test1 =
       without a =? 42.some: