Open Radar

 
Summary:
If a generic function parameter T is declared in such a way, that it must inherit from a generic class (e.g. "T: GenericClass<U>"), this information is lost when the variable is used inside the function

Steps to Reproduce:
Open the sample project and try to compile it

Expected Results:
The project should compile fine as it is obvious from the signature of the method OperationChain.chain that O must inherit from ResultOperation<T> and that therefore newOperation is of type ResultOperaiton<T>

Actual Results:
The information that the class of newOperation inherits from ResultOperation<T> is lost and Xcode complains that it "Cannot convert value of type 'O' to expected argument type 'ResultOperation<_>'"

Version:
Xcode 7.0 (7A218) and 7.1 beta (7B75)

Notes:
The issue can be circumvented by explicitly casting newOperation to ResultOperaiton<T>, i.e. by replacing the constructor argument "newOperation" in main.swift:25 by "newOperation as! ResultOperation<T>"

Configuration:
If ResultOperation is not a generic class, the code compiles fine.

Attachments:
'SampleProject.zip' was successfully uploaded.
This contains the following file:


protocol ChainableOperation {
	typealias InputType
	func setInput(input: InputType)
}

class ResultOperation<ReturnType> {
}

class OperationChain<LastReturnType> {
	private var lastOperation: ResultOperation<LastReturnType>
	
	init(_ operation: ResultOperation<LastReturnType>) {
		lastOperation = operation;
	}
	
	func chain<T, O: ResultOperation<T> where O: ChainableOperation>(newOperation: O) -> OperationChain<T> {
		let newChainItem = OperationChain<T>(newOperation as! ResultOperation<T>)
		
		return newChainItem
	}
}