result: add `Opt.some` / `Opt.none` (#117)

stew/results.nim

@@ -884,6 +884,24 @@ func filter*[T](
 
 # Options compatibility
 
+template some*[T](O: type Opt, v: T): Opt[T] =
+  ## Create an `Opt` set to a value
+  ##
+  ## ```
+  ## let o = Opt.some(42)
+  ## assert o.isSome and o.get() == 42
+  ## ```
+  Opt[T].ok(v)
+
+template none*(O: type Opt, T: type): Opt[T] =
+  ## Create an `Opt` set to none
+  ##
+  ## ```
+  ## let o = Opt.none(int)
+  ## assert o.isNone
+  ## ```
+  Opt[T].err()
+
 template isSome*(o: Opt): bool =
   ## Alias for `isOk`
   isOk o

tests/test_results.nim

@@ -351,6 +351,9 @@ block: # Result[T, void] aka `Opt`
   doAssert oOk.filter(proc(x: int): bool = false).isErr()
   doAssert oErr.filter(proc(x: int): bool = true) == oErr
 
+  doAssert Opt.some(42).get() == 42
+  doAssert Opt.none(int).isNone()
+
 block: # `cstring` dangling reference protection
   type CSRes = Result[void, cstring]
 
@@ -398,4 +401,3 @@ block: # Experiments
     counter2 += 1
 
   doAssert counter2 == 1, "one-item collection when set"
-