issue-58149-generic-signature-builder-keypath-iterable.swift

// RUN: %target-swift-frontend -emit-sil -verify %s

// https://github.com/apple/swift/issues/58149
// Crash while compiling Swift for TensorFlow
//
// This was caused by a bug in GenericSignatureBuilder, similar to one involving
// `CaseIterable`. In this reproducer, `KeyPathIterable` is similar enough to
// `CaseIterable` to have caused the GSB to crash. It was fixed by
// RequirementMachine abstract signatures.

import _Differentiation
@_spi(Reflection)import Swift

structRNNCellInput<Input>:Differentiable{}
structRNNCellOutput<Output>:Differentiable{}

protocolLayer:Differentiable{
associatedtypeInput
associatedtypeOutput:Differentiable

@differentiable(reverse)
func callAsFunction(_ input:Input)->Output
}

publicprotocolKeyPathIterable{
associatedtypeAllKeyPaths:Sequence
where AllKeyPaths.Element ==PartialKeyPath<Self>
}

protocolRecurrentLayerCell:Layer,KeyPathIterable
where
 Input ==RNNCellInput<TimeStepInput>,
 Output ==RNNCellOutput<TimeStepOutput>
{
associatedtypeTimeStepInput
associatedtypeTimeStepOutput:Differentiable
}

structRecurrentLayer<Cell:RecurrentLayerCell>:Layer{
typealiasInput=Cell.TimeStepInput
typealiasOutput=Cell.TimeStepOutput

varcell:Cell

@differentiable(reverse)
func callAsFunction(_ inputs:Cell.TimeStepInput)->Cell.TimeStepOutput{
 // expected-warning @+1 {{function call causes an infinite recursion}}
returnself(inputs)
}
}