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andersioandersio
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Improved error messages of the inhabitable type guards.
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‎CHANGELOG.md‎

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# master
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*Please add new entries at the top.*
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1. When composing `Signal` and `SignalProducer` of inhabitable types, e.g. `Never` or `NoError`, ReactiveSwift now warns about operators that are illogical to use, and traps at runtime when such operators attempt to instantiate an instance. (#429, kudos to @andersio)
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1. N-ary `SignalProducer` operators are now generic and accept any type that can be expressed as `SignalProducer`. (#410, kudos to @andersio)
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Types may conform to `SignalProducerConvertible` to be an eligible operand.
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‎Sources/InhabitableTypeGuards.swift‎

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@@ -3,100 +3,105 @@ import Result
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// Observation
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extension SignalProducer where Value == Never {
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@discardableResult
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@available(*, deprecated, message:"`success` event is never delivered.")
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public func startWithResult(_ action: @escaping (Result<Value, Error>) -> Void) -> Disposable { fatalError() }
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@available(*, deprecated, message:"`Result.success` is never delivered - `Value` is inhabitable (Instantiation at runtime would trap)")
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public func startWithResult(_ action: @escaping (Result<Value, Error>) -> Void) -> Disposable { observingInhabitableTypeError() }
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@discardableResult
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@available(*, deprecated, message:"The observer is never invoked.")
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public func startWithValues(_ action: @escaping (Value) -> Void) -> Disposable { fatalError() }
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@available(*, deprecated, message:"Observer is never called - `Value` is inhabitable (Instantiation at runtime would trap)")
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public func startWithValues(_ action: @escaping (Value) -> Void) -> Disposable { observingInhabitableTypeError() }
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}
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extension SignalProducer where Value == Never, Error == NoError {
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@discardableResult
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@available(*, deprecated, message:"The observer is never invoked.")
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public func startWithResult(_ action: @escaping (Result<Value, Error>) -> Void) -> Disposable { fatalError() }
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@available(*, deprecated, message:"Observer is never called - `Value` and `Error` are inhabitable (Instantiation at runtime would trap)")
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public func startWithResult(_ action: @escaping (Result<Value, Error>) -> Void) -> Disposable { observingInhabitableTypeError() }
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}
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extension SignalProducer where Error == NoError {
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@discardableResult
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@available(*, deprecated, message:"The observer is never invoked.")
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public func startWithFailed(_ action: @escaping (Error) -> Void) -> Disposable { fatalError() }
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@available(*, deprecated, message:"`Error` is inhabitable so the observer is never called (Instantiation at runtime would trap)")
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public func startWithFailed(_ action: @escaping (Error) -> Void) -> Disposable { observingInhabitableTypeError() }
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}
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extension Signal where Value == Never {
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@discardableResult
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@available(*, deprecated, message:"`success` event is never delivered.")
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public func observeResult(_ action: @escaping (Result<Value, Error>) -> Void) -> Disposable { fatalError() }
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@available(*, deprecated, message:"`Result.success` is never delivered - `Value` is inhabitable (Instantiation at runtime would trap)")
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public func observeResult(_ action: @escaping (Result<Value, Error>) -> Void) -> Disposable? { observingInhabitableTypeError() }
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@discardableResult
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@available(*, deprecated, message:"The observer is never invoked.")
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public func observeValues(_ action: @escaping (Value) -> Void) -> Disposable { fatalError() }
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@available(*, deprecated, message:"Observer is never called - `Value` is inhabitable (Instantiation at runtime would trap)")
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public func observeValues(_ action: @escaping (Value) -> Void) -> Disposable? { observingInhabitableTypeError() }
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}
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extension Signal where Value == Never, Error == NoError {
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@discardableResult
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@available(*, deprecated, message:"The observer is never invoked.")
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public func observeResult(_ action: @escaping (Result<Value, Error>) -> Void) -> Disposable { fatalError() }
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@available(*, deprecated, message:"Observer is never called - `Value` and `Error` are inhabitable (Instantiation at runtime would trap)")
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public func observeResult(_ action: @escaping (Result<Value, Error>) -> Void) -> Disposable? { observingInhabitableTypeError() }
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}
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extension Signal where Error == NoError {
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@discardableResult
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@available(*, deprecated, message:"The observer is never invoked.")
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public func observeFailed(_ action: @escaping (Error) -> Void) -> Disposable { fatalError() }
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@available(*, deprecated, message:"Observer is never invoked - `Error` is inhabitable (Instantiation at runtime would trap)")
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public func observeFailed(_ action: @escaping (Error) -> Void) -> Disposable? { observingInhabitableTypeError() }
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}
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// flatMap
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extension SignalProducer where Value == Never {
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@discardableResult
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@available(*, deprecated, message:"Use `promoteValue` instead.")
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public func flatMap<Inner: SignalProducerConvertible>(_ strategy: FlattenStrategy, _ transform: @escaping (Value) -> Inner) -> SignalProducer<Inner.Value, Error> where Inner.Error == Error { fatalError() }
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@available(*, deprecated, message:"Use `promoteValue` instead - `Value` is inhabitable (Instantiation at runtime would trap)")
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public func flatMap<Inner: SignalProducerConvertible>(_ strategy: FlattenStrategy, _ transform: @escaping (Value) -> Inner) -> SignalProducer<Inner.Value, Error> where Inner.Error == Error { observingInhabitableTypeError() }
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@discardableResult
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@available(*, deprecated, message:"Use `promoteValue` instead.")
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public func flatMap<Inner: SignalProducerConvertible>(_ strategy: FlattenStrategy, _ transform: @escaping (Value) -> Inner) -> SignalProducer<Inner.Value, Error> where Inner.Error == NoError { fatalError() }
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@available(*, deprecated, message:"Use `promoteValue` instead - `Value` is inhabitable (Instantiation at runtime would trap)")
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public func flatMap<Inner: SignalProducerConvertible>(_ strategy: FlattenStrategy, _ transform: @escaping (Value) -> Inner) -> SignalProducer<Inner.Value, Error> where Inner.Error == NoError { observingInhabitableTypeError() }
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}
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extension SignalProducer where Value == Never, Error == NoError {
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@discardableResult
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@available(*, deprecated, message:"Use `promoteValue` instead.")
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public func flatMap<Inner: SignalProducerConvertible>(_ strategy: FlattenStrategy, _ transform: @escaping (Value) -> Inner) -> SignalProducer<Inner.Value, Inner.Error> { fatalError() }
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@available(*, deprecated, message:"Use `promoteValue` instead - `Value` and `Error` are inhabitable (Instantiation at runtime would trap)")
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public func flatMap<Inner: SignalProducerConvertible>(_ strategy: FlattenStrategy, _ transform: @escaping (Value) -> Inner) -> SignalProducer<Inner.Value, Inner.Error> { observingInhabitableTypeError() }
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@discardableResult
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@available(*, deprecated, message:"Use `promoteValue` instead.")
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public func flatMap<Inner: SignalProducerConvertible>(_ strategy: FlattenStrategy, _ transform: @escaping (Value) -> Inner) -> SignalProducer<Inner.Value, Inner.Error> where Inner.Error == Error { fatalError() }
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@available(*, deprecated, message:"Use `promoteValue` instead - `Value` and `Error` are inhabitable (Instantiation at runtime would trap)")
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public func flatMap<Inner: SignalProducerConvertible>(_ strategy: FlattenStrategy, _ transform: @escaping (Value) -> Inner) -> SignalProducer<Inner.Value, Inner.Error> where Inner.Error == Error { observingInhabitableTypeError() }
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}
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extension SignalProducer where Error == NoError {
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@discardableResult
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@available(*, deprecated, message:"Use `promoteError` instead.")
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public func flatMapError<NewError>(_ transform: @escaping (Error) -> SignalProducer<Value, NewError>) -> SignalProducer<Value, NewError> { fatalError() }
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@available(*, deprecated, message:"Use `promoteError` instead - `Error` is inhabitable (Instantiation at runtime would trap)")
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public func flatMapError<NewError>(_ transform: @escaping (Error) -> SignalProducer<Value, NewError>) -> SignalProducer<Value, NewError> { observingInhabitableTypeError() }
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}
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extension Signal where Value == Never {
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@discardableResult
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@available(*, deprecated, message:"Use `promoteValue` instead.")
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public func flatMap<Inner: SignalProducerConvertible>(_ strategy: FlattenStrategy, _ transform: @escaping (Value) -> Inner) -> Signal<Inner.Value, Error> where Inner.Error == Error { fatalError() }
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@available(*, deprecated, message:"Use `promoteValue` instead - `Value` is inhabitable (Instantiation at runtime would trap)")
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public func flatMap<Inner: SignalProducerConvertible>(_ strategy: FlattenStrategy, _ transform: @escaping (Value) -> Inner) -> Signal<Inner.Value, Error> where Inner.Error == Error { observingInhabitableTypeError() }
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@discardableResult
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@available(*, deprecated, message:"Use `promoteValue` instead.")
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public func flatMap<Inner: SignalProducerConvertible>(_ strategy: FlattenStrategy, _ transform: @escaping (Value) -> Inner) -> Signal<Inner.Value, Error> where Inner.Error == NoError { fatalError() }
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@available(*, deprecated, message:"Use `promoteValue` instead - `Value` is inhabitable (Instantiation at runtime would trap)")
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public func flatMap<Inner: SignalProducerConvertible>(_ strategy: FlattenStrategy, _ transform: @escaping (Value) -> Inner) -> Signal<Inner.Value, Error> where Inner.Error == NoError { observingInhabitableTypeError() }
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}
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extension Signal where Value == Never, Error == NoError {
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@discardableResult
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@available(*, deprecated, message:"Use `promoteValue` instead.")
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public func flatMap<Inner: SignalProducerConvertible>(_ strategy: FlattenStrategy, _ transform: @escaping (Value) -> Inner) -> Signal<Inner.Value, Inner.Error> { fatalError() }
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@available(*, deprecated, message:"Use `promoteValue` instead - `Value` and `Error` are inhabitable (Instantiation at runtime would trap)")
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public func flatMap<Inner: SignalProducerConvertible>(_ strategy: FlattenStrategy, _ transform: @escaping (Value) -> Inner) -> Signal<Inner.Value, Inner.Error> { observingInhabitableTypeError() }
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@discardableResult
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@available(*, deprecated, message:"Use `promoteValue` instead.")
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public func flatMap<Inner: SignalProducerConvertible>(_ strategy: FlattenStrategy, _ transform: @escaping (Value) -> Inner) -> Signal<Inner.Value, Inner.Error> where Inner.Error == Error { fatalError() }
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@available(*, deprecated, message:"Use `promoteValue` instead - `Value` and `Error` are inhabitable (Instantiation at runtime would trap)")
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public func flatMap<Inner: SignalProducerConvertible>(_ strategy: FlattenStrategy, _ transform: @escaping (Value) -> Inner) -> Signal<Inner.Value, Inner.Error> where Inner.Error == Error { observingInhabitableTypeError() }
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}
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extension Signal where Error == NoError {
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@discardableResult
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@available(*, deprecated, message:"Use `promoteError` instead.")
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public func flatMapError<NewError>(_ transform: @escaping (Error) -> SignalProducer<Value, NewError>) -> Signal<Value, NewError> { fatalError() }
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@available(*, deprecated, message:"Use `promoteError` instead - `Error` is inhabitable (Instantiation at runtime would trap)")
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public func flatMapError<NewError>(_ transform: @escaping (Error) -> SignalProducer<Value, NewError>) -> Signal<Value, NewError> { observingInhabitableTypeError() }
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}
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@inline(never)
103+
private func observingInhabitableTypeError() -> Never {
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fatalError("Detected an attempt to instantiate a `Signal` or `SignalProducer` that observes an inhabitable type, e.g. `Never` or `NoError`. This is considered a logical error, and appropriate operators should be used instead. Please refer to the warnings raised by the compiler.")
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}
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/*

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