Investigate Fishy Record Names in Optimizer Core

[gzm0]

Follow-up form here:

scala-js/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala

Lines 1236 to 1240 in 244fa53

	/* FIXME How come this lookup requires only the `simpleName`?
	* The `recordType` is created at `InlineableClassStructure.recordType`,
	* where it uses an allocator. Something fishy is going on here.
	* (And no, this is not dead code.)
	*/

[gzm0]

I've been playing around with this and so far, I have not actually managed for the optimizer to produce a Record.

Either, the local def system already resolved everything before even creating a record (this is what happened here: #4946 (comment)) or the optimizer cancelled the inlining.

@sjrd how did you determine the piece of code in question is not dead code? I'm starting to suspect that it only triggers for RuntimeLong (where we have more aggressive class inlining policies).

[sjrd]

@sjrd how did you determine the piece of code in question is not dead code? I'm starting to suspect that it only triggers for RuntimeLong (where we have more aggressive class inlining policies).

Replace it by ??? and try testSuite2_12/Test/fastLinkJS. It blows up.

In order for a record to be reified, I believe we need at least an if/else where both branches return an instance of the inline class. Or any other merge point. So that's maybe what we need to add to #4946 (comment)