make Raising compatible with 2.0

See nim-lang/Nim#23432

chronos/internal/raisesfutures.nim

@@ -53,17 +53,32 @@ proc members(tup: NimNode): seq[NimNode] {.compileTime.} =
 macro hasException(raises: typedesc, ident: static string): bool =
  newLit(raises.members.anyIt(it.eqIdent(ident)))
 
-macro Raising*[T](F: typedesc[Future[T]], E: varargs[typedesc]): untyped =
+macro Raising*[T](F: typedesc[Future[T]], E: typed): untyped =
  ## Given a Future type instance, return a type storing `{.raises.}`
  ## information
  ##
  ## Note; this type may change in the future
- E.expectKind(nnkBracket)
 
- let raises = if E.len == 0:
+ # An earlier version used `E: varargs[typedesc]` here but this is buggyt/no
+ # longer supported in 2.0 in certain cases:
+ # https://github.com/nim-lang/Nim/issues/23432
+ let
+ e =
+ case E.getTypeInst().typeKind()
+ of ntyTypeDesc: @[E]
+ of ntyArray:
+ for x in E:
+ if x.getTypeInst().typeKind != ntyTypeDesc:
+ error("Expected typedesc, got " & repr(x), x)
+ E.mapIt(it)
+ else:
+ error("Expected typedesc, got " & repr(E), E)
+ @[]
+
+ let raises = if e.len == 0:
  makeNoRaises()
  else:
- nnkTupleConstr.newTree(E.mapIt(it))
+ nnkTupleConstr.newTree(e)
  nnkBracketExpr.newTree(
  ident "InternalRaisesFuture",
  nnkDotExpr.newTree(F, ident"T"),

tests/testfut.nim

@@ -2047,9 +2047,27 @@ suite "Future[T] behavior test suite":
  check:
  future1.cancelled() == true
  future2.cancelled() == true
+
  test "Sink with literals":
  # https://github.com/nim-lang/Nim/issues/22175
  let fut = newFuture[string]()
  fut.complete("test")
  check:
  fut.value() == "test"
+
+ test "Raising type matching":
+ type X[E] = Future[void].Raising(E)
+
+ proc f(x: X) = discard
+
+ var v: Future[void].Raising([ValueError])
+ f(v)
+
+ type Object = object
+ field: Future[void].Raising([ValueError])
+
+ discard Object(field: v)
+
+ check:
+ not compiles(Future[void].Raising([42]))
+ not compiles(Future[void].Raising(42))