Malformed expression on `@non_differentiable` with splatting operator

[dfdx]

On Julia v1.5.0 and ChainRulesCore v0.9.36:

julia> using ChainRulesCore

julia> @non_differentiable Core.print(::Any...)
ERROR: syntax: malformed expression
Stacktrace:
 [1] top-level scope at REPL[2]:1

This essentially breaks precompilation of ChainRules >= v.0.7.35.

Is it a know issue?

[dfdx]

After dissecting the package versions I see that the first failing version is 0.9.35, the most likely sources of the error are changes in _nondiff_frule_expr() or _nondiff_rrule_expr(). Perhaps it's the deepest thing I can dig myself.

Fixing ChainRulesCore at version v0.9.34 fixes precompilation of ChainRules:

(@v1.5) pkg> add ChainRulesCore@v0.9.34
   Updating registry at `~/.julia/registries/General`
######################################################################## 100,0%
  Resolving package versions...
No Changes to `~/.julia/environments/v1.5/Project.toml`
No Changes to `~/.julia/environments/v1.5/Manifest.toml`

(@v1.5) pkg> add ChainRules
  Resolving package versions...
No Changes to `~/.julia/environments/v1.5/Project.toml`
No Changes to `~/.julia/environments/v1.5/Manifest.toml`

julia> using ChainRules
[ Info: Precompiling ChainRules [082447d4-558c-5d27-93f4-14fc19e9eca2]

[devmotion]

I can reproduce the error with Julia 1.5.0 and 1.5.1, but 1.5.2, 1.5.3, 1.5.4 and also (some) earlier versions such as 1.4.0 work.

We perform integration tests for ChainRules but they use the latest Julia versions and hence the problem did not show up.

[devmotion]

Probably JuliaLang/julia#37134, which was fixed in Julia 1.5.2 (JuliaLang/julia#37181).

[simeonschaub]

Yes, there's not much we can do here. Julia 1.5.0 is not officially supported anymore.

[devmotion]

The problem is fixed in ChainRulesCore 0.9.37 which will be available soon (PR to the registry: JuliaRegistries/General#33480).