`SVGP` deprecation not exact

[st--]

SVGP simply redirects to SparseVariationalApproximation, but the SVGP default (and only implementation) was Centered representation, whereas SparseVariationalApproximation defaults to NonCentered. So it was actually a breaking change. Is there some way we can fix this?

Originally posted by @st-- in #64 (comment)

[st--]

I think it'd be better to remove the @deprecate and instead have a stub

SVGP(args...) = error(
    "`SVGP(...)` is deprecated; use `SparseVariationalApproximation(Centered(), ...)` "*
    "for retaining previous behaviour, or consider if you want to use "*
    "NonCentered() [new default] instead."
)

[theogf]

But isn't it an issue now that this is a bug and that should be solved before the next breaking release (your solution is nice but would be breaking

[st--]

My solution would be fixing a bug - the change from SVGP to SparseVariationalApproximation was already declared breaking. If anyone is actually using SVGP, and they rely on @deprecate preserving the behaviour, their code might give them wrong answers (without realising). An explicit error message that tells them how to fix it would be much preferable, no?

[theogf]

@deprecate should keep things working but alarm the users that they are going to change.
The real bug fix would be to have @deprecate SVGP(args...) SparseVariationalApproximation(Centered(), args...) not sure what the correct syntax is though

[st--]

You can write

@deprecate SVGP(fz, q) SparseVariationalApproximation(Centered(), fz, q)

but then that won't add a deprecation for the struct, so also wouldn't be backwards compatible.

Moreover, @deprecate as of julia 1.5 doesn't by default print any warnings, so in practice users are likely to miss it.

[devmotion]

Moreover, @deprecate as of julia 1.5 doesn't by default print any warnings, so in practice users are likely to miss it.

AFAIK this is on purpose since deprecatipn warmings slow down code massively. Eg, deprecations in a Turing model make it basically impossible to sample with the model if warnings are enabled.

[st--]

Actually, the type doesn't get aliased anyways, so doesn't make a difference. See #95. (Though personally I'd still prefer an explicit error()!)

[devmotion]

@deprecate_binding can be used to deprecate types.

[st--]

@deprecate_binding can be used to deprecate types.

it doesn't work together with the constructor @deprecate though...