[SR-13627] Derivative registration doesn't work on rethrowing functions #56062
Description
| Previous ID | SR-13627 |
| Radar | rdar://problem/69733357 |
| Original Reporter | @rxwei |
| Type | Bug |
Additional Detail from JIRA
| Votes | 0 |
| Component/s | Compiler |
| Labels | Bug, AutoDiff |
| Assignee | None |
| Priority | Medium |
md5: dd36f68f8af4408fe46600b0524f8839
blocks:
- SR-13624
??is not differentiable
Issue Description:
When I try to register a derivative for a function that rethrows with a derivative that also rethrows, the type checker is unable to match the expected candidate.
Failure:
The nil-coalescing operator ?? needs a derivative in order to be differentiable. Defining the following derivative will show that the type checker has disregarded the rethrowing-ness of the derivative function, causing it to think that no candidate original functions match.
@derivative(of: ??, wrt: optional)
@usableFromInline
func _derivativeOfNilCoalescing<T: Differentiable>(
optional: T?,
defaultValue: @autoclosure () throws -> T
) rethrows -> (
value: T,
pullback: (T.TangentVector) -> Optional<T>.TangentVector
) {
fatalError()
}/home/rxwei/Development/Swift/swift-source/swift/stdlib/public/Differentiation/OptionalDifferentiation.swift:85:17: error: referenced declaration '??' could not be resolved
@derivative(of: ??, wrt: optional)
^
Swift.??:1:13: note: candidate operator function does not have type equal to or less constrained than '<T where T : Differentiable> (optional: T?, defaultValue: @autoclosure () throws -> T) -> T?'
public func ?? <T>(optional: T?, defaultValue: @autoclosure () throws -> T) rethrows -> T
^
Swift.??:1:13: note: candidate operator function does not have type equal to or less constrained than '<T where T : Differentiable> (optional: T?, defaultValue: @autoclosure () throws -> T) -> T?'
public func ?? <T>(optional: T?, defaultValue: @autoclosure () throws -> T?) rethrows -> T?
^For context, unlike rethrowing functions, throwing functions are okay:
func foo(x: Float) throws -> Float { x }
@derivative(of: foo)
func foo(x: Float) throws -> (value: Float, pullback: (Float) -> Float) {
fatalError()
}