results: work around nim codegen bug (#192)

https://github.com/nim-lang/Nim/issues/22049

stew/results.nim

@@ -865,6 +865,10 @@ template tryGet*[E](self: Result[void, E]) = self.tryValue()
 template unsafeGet*[T: not void, E](self: Result[T, E]): T = self.unsafeValue()
 template unsafeGet*[E](self: Result[void, E]) = self.unsafeValue()
 
+# `var` overloads should not be needed but result in invalid codegen (!):
+# TODO https://github.com/nim-lang/Nim/issues/22049
+func get*[T: not void, E](self: var Result[T, E]): var T = self.value()
+
 func get*[T, E](self: Result[T, E], otherwise: T): T {.inline.} =
   ## Fetch value of result if set, or return the value `otherwise`
   ## See `valueOr` for a template version that avoids evaluating `otherwise`

tests/test_results.nim

@@ -482,3 +482,13 @@ block: # Constants
   proc checkIt(v: WithOpt) =
     doAssert v.opt.isNone()
   checkIt(noneWithOpt)
+
+  block: # TODO https://github.com/nim-lang/Nim/issues/22049
+    var v: Result[(seq[int], seq[int]), int]
+    v.ok((@[1], @[2]))
+    let (a, b) = v.get()
+    doAssert a == [1] and b == [2]
+    let (c, d) = v.tryGet()
+    doAssert c == [1] and d == [2]
+    let (e, f) = v.unsafeGet()
+    doAssert e == [1] and f == [2]