fix: compiler crash on primitive type checking against opaque types

[tanishiking]

fix #3700

It is caused because in isPrimitiveValueType against opaque type, t.widenDealias.typeSymbol isn't ClassSymbol but a TypeSymbol for cmark_event_type. This commit adds an additional check that is the type symbol ClassSymbol before casting.

[WojciechMazur]

Instead of expensive scripted tests, let's define it as quick unit test in nscplugin, for example in this test

scala-native/nscplugin/src/test/scala-3/scala/scalanative/NIRCompilerTest3.scala

Lines 12 to 13 in 8df8dce

	class NIRCompilerTest3 {
	inline def nativeCompilation(source: String): Unit = {

We only need to ensure that is compiles, we don't require linking

[tanishiking]

Thanks! done in 1a3dbcc
(I added clib.cp to Test/ nscplugin / javaOptions since I couldn't find a way to reproduce the compilation crash without using clib.stdio 🤔

[WojciechMazur]

I think you might have problems with that, becouse there are 2 definitions of printf. One is defined as extension here:

scala-native/clib/src/main/scala/scala/scalanative/libc/package.scala

Lines 5 to 8 in ba2bd19

	implicit class StdioHelpers(val _stdio: libc.stdio.type) extends AnyVal {
	def printf(format: CString, args: CVarArg*): CInt =
	Zone { implicit z => stdio.vprintf(format, toCVarArgList(args.toSeq)) }

it's a legacy support from before introduction of better varargs in extern
The second one is standard extern binding

scala-native/clib/src/main/scala/scala/scalanative/libc/stdio.scala

Lines 587 to 589 in ba2bd19

	@blocking def fprintf(stream: Ptr[FILE], format: CString, vargs: Any*): CInt =
	extern

I belive it could have been coused by the clash of the two. It would be great if we could get rid of the dependency. I'd like to remove legacy version in the future.

[tanishiking]

Thanks @WojciechMazur!
I'm not sure the duplication of printf is the problem, I could reproduce it without clib 74fbddd

It seems like we hit the ensureUnboxed -> isPrimitiveType when the argument is for extern method's varargs (e.g. printf's vargs)

scala-native/nscplugin/src/main/scala-3/scala/scalanative/nscplugin/NirGenExpr.scala

Lines 1722 to 1723 in 74fbddd

	if (isVarArg) ensureUnboxed(rawValue, paramTpe.finalResultType)
	else rawValue

With something like def test(t: Any*) = extern, and if I pass the opaque typed value to the test method, we could break the compiler 👍