raisingfutures.nim

{.push raises: [].}

import pkg/chronos

type
  MyError = object of CatchableError
  Handle1 = Future[void].Raising([CancelledError])
  Handle2 = Future[void].Raising([CancelledError, MyError])

  SomeType = object
    name: string
    handle1: Handle1
    handle2: Handle2

proc `$`(t: SomeType): string =
  t.name

# The key to understand the failures is by reading this from
# .nimble/pkgs2/chronos-4.0.4-455802a90204d8ad6b31d53f2efff8ebfe4c834a/chronos/internal/
# raisesfutures.nim
# type
#   InternalRaisesFuture*[T, E] = ref object of Future[T]
#     ## Future with a tuple of possible exception types
#     ## eg InternalRaisesFuture[void, (ValueError, OSError)]
#     ##
#     ## This type gets injected by `async: (raises: ...)` and similar utilities
#     ## and should not be used manually as the internal exception representation
#     ## is subject to change in future chronos versions.
#     # TODO https://github.com/nim-lang/Nim/issues/23418
#     # TODO https://github.com/nim-lang/Nim/issues/23419
#     when E is void:
#       dummy: E
#     else:
#       dummy: array[0, E]

let t = SomeType(
  name: "example1",
  # both fail
  # type mismatch: got 'Future[system.void]' for '
  # newFutureImpl(srcLocImpl("", (filename: "raisingfutures.nim", line: 44,
  # column: 26).filename, (filename: "raisingfutures.nim", line: 44, 
  # column: 26).line), {})' but expected 'Handle1 = InternalRaisesFuture[system.void, 
  # (CancelledError,)]'
  # handle1: newFuture[void](),
  # type mismatch: got 'Future[system.void]' for '
  # newFutureImpl(srcLocImpl("", (filename: "raisingfutures.nim", line: 50,
  # column: 26).filename, (filename: "raisingfutures.nim", line: 50,
  # column: 26).line), {})' but expected 'Handle2 = InternalRaisesFuture[system.void, 
  # (CancelledError, MyError)]'
  # handle2: newFuture[void](),
)

proc getHandle1(): Future[void] {.async: (raw: true, raises: [CancelledError]).} =
  ## Add an event for a block
  ##
  let t = SomeType(
    name: "example2",
    handle1: newFuture[void](),
    # handle2 does not compile:
    # type mismatch: got 'Handle1' for '
    # newInternalRaisesFutureImpl(srcLocImpl("", (filename: "raisingfutures.nim",
    # line: 66, column: 28).filename, (filename: "raisingfutures.nim",
    # line: 66, column: 28).line), {})' but expected 
    # 'Handle2 = InternalRaisesFuture[system.void,
    # (CancelledError, MyError)]'
    # handle2: newFuture[void](),
  )

  echo t

  t.handle1


proc getHandle2(): Future[void] {.async: (raw: true, raises: [CancelledError, MyError]).} =
  ## Add an event for a block
  ##
  let t = SomeType(
    name: "example3",
    # handle1 does not compile:
    # type mismatch: got 'Handle2' for '
    # newInternalRaisesFutureImpl(srcLocImpl("", (filename: "raisingfutures.nim",
    # line: 85, column: 28).filename, (filename: "raisingfutures.nim",
    # line: 85, column: 28).line), {})' but expected 
    # 'Handle1 = InternalRaisesFuture[system.void, (CancelledError,)]'
    # handle1: newFuture[void](),
    handle2: newFuture[void](),
  )

  echo t

  t.handle2

proc newSomeType(): SomeType =
  ## Add an event for a block
  ##
  let t = SomeType(
    name: "example4",
    # both does not compile
    # type mismatch: got 'Future[system.void]' for '
    # newFutureImpl(srcLocImpl("", (filename: "raisingfutures.nim", line: 104, 
    # column: 28). filename, (filename: "raising.nim", line: 104, column: 28).line),
    # {})' but expected 'Handle1 = InternalRaisesFuture[system.void,
    # (CancelledError,)]'
    # handle1: newFuture[void](),
    # type mismatch: got 'Future[system.void]' for '
    # newFutureImpl(srcLocImpl("", (filename: "raisingfutures.nim", line: 110,
    # column: 28). filename, (filename: "raising.nim", line: 110, column: 28).line),
    # {})' but expected 'Handle2 = InternalRaisesFuture[system.void,
    # (CancelledError, MyError)]'
    # handle2: newFuture[void](),
  )

  t

echo t
discard getHandle1()
discard getHandle2()
echo newSomeType()