The SIL type lowering logic for AutoDiff gets the substituted generic signature
mixed up with the invocation generic signature, so it tries to ask questions
about DependentMemberTypes in a signature with no requirements. This triggers
assertions when the requirement machine is enabled.
Disable the requirement machine until this is fixed.
`partial_apply` can be rewritten to `thin_to_thick_function` only if the
specialized callee is `@convention(thin)`.
This condition is newly exercised by the differentiation transform:
`{JVP,VJP}Emitter::visitApplyInst` generates argument-less `partial_apply`
with `@convention(method)` callees.
Resolves SR-12732.
Add `Differentiable.withDerivative(_:)`, a "derivative surgery" API.
`Differentiable.withDerivative(_:)` is an identity function returning `self`.
It takes a closure and applies it to the derivative of the return value, in
contexts where the return value is differentiated with respect to.
