`def-conversion` sometimes breaks when AOT-compiled

[DerGuteMoritz]

Repro: https://github.com/bevuta/byte-streams-def-conversion-aot-issue

Essentially the same issue as #34 but with tools.deps and tools.build instead of Leiningen. The resulting error is the same:

Execution error (ClassCastException) at clj_commons.byte_streams.graph.ConversionGraph/assoc_conversion (graph.clj:117).
class clj_commons.byte_streams.graph.Type cannot be cast to class clj_commons.byte_streams.graph.Type (clj_commons.byte_streams.graph.Type is in unnamed module of loader 'app'; clj_commons.byte_streams.graph.Type is in unnamed module of loader clojure.lang.DynamicClassLoader @650a1aff)

It's very likely caused by https://clojure.atlassian.net/browse/CLJ-1741, i.e. when first AOT-compiling a namespace which depends on another namespace which contains a def-conversion call, and then AOT-compiling that namespace itself.

[KingMob]

Update for posterity: it's probably not the same as CLJ-1741, even if it's related. 1741 is a duplicate of of CLJ-1650, but that was fixed in Clojure 1.8, so the timing seems wrong.

[KingMob]

Re-opening, because the problem isn't really fixed, we just removed the type hints.

But it's interfering with Eastwood, CircleCI, and automatic deploys.

[KingMob]

Update. Now it's flat-out breaking the new HTTP/2 code. What's going on?

[DerGuteMoritz]

Ouch! Do you have a repro case to look at somewhere?

[KingMob]

No, I think I was confused. I don't think it's AOT-related now.

I think the issue is loading byte-streams in Netty threads that use their own classloader. It gives me a ClassCastException even when Netty finds the class because class identity is tied to classloader.

It just looked a bit like the AOT errors we've gotten in the past.

Right now I'm biting the bullet and trying to decide how best to insert the clj loader into Netty threads. It's become more of an issue with the way ALPN and http2 multiplexing work; we have to do more work in Netty than we did for http1, and that runs a greater risk of needing the clj loader.